Water Supply Compilation of Reports

GROUP 1 – WATER SUPPLY Chapter 1-2 INTRODUCTION TO SEWERAGE AND WATER SUPPLY

I. Environmental Engineering II. Sources Of Environmental Contaminants

III. Water Supply IV. Sewerage V. Interrelationship Of Environmental Problems

VI. Quantity of Water and Sewerage a. Relation of Quantity and Population

Population Estimation Water Use For Different Purposes

Factors Affecting Water Use

Variation in Water Use b. Fire Demand

VII. Design Periods For Water Supply Components VIII. Sewage

a. Source b. Sewage in Relation to Water Supply c. Design Periods for Sewerage Systems

I. ENVIRONMENTAL ENGINEERING

Definition: Environmental Engineering involves the application of technology to minimize unfavorable impacts of both humans on the environment and of the environment on humans. Advantages of Technology:

Control the spread of many communicable disease

Expanded the agricultural production Greatly improved the quality of our lives

Disadvantages of Technology:

Produced air and water pollution

Radioactive and hazardous wastes

Modified the climate of the world

Responsibility of An Environmental Engineer: To reduce or eliminate the unfavorable impacts of our activ ities while enhancing or at least preserv ing its favorable results. Environmental Engineering: This course includes the design, construction and operation of systems for the treatment and supply of potable water and for the collection, treatment and disposal of waste water. II. SOURCES OF ENVIRONMENTAL CONTAMINANTS Contaminants: can be defined as constituents of the air, water, or soil which render them unsuitable for their intended use.

Natural contaminants of water:

Viruses

Bacteria Dissolved mineral species

Organic and inorganic suspended solids III. WATER SUPPLY

Inadequate water supplies Aqueducts were used to convey water from distant sources.

Pipes that can withstand significant pressures were not available until 17th century.

Pipes made of wood, clay or lead was used. Development of cast-iron pipes and of improved pumps driven by steam

Water Treatment a. 2000 B.C.: Coagulants and Filtration b. 1906: Slow Sand Filters c. 1906: Disinfection with Chlorine d.

IV. SEWERAGE Definition: Sewers were primarily intended to carry storm water, but, since refuse was deposited in the streets, these sewers often carried organic materials as well.

Waste water discharged to the nearest surface water

Became source of disease to downstream users Development and application of Waste Treatment Techniques

Classification of Streams:

Effluent Limited: Suitable for their highest intended use. Quality Limited: Not suitable for their highest intended use.

Waste load allocation: allowable waste load allocated to each discharge point. National Pollution Discharge Elimination System (NPDES): they regulates the waste discharges. V. INTERRELATIONSHIP OF ENVIRONMENTAL PROBLEMS The removal of a contaminant from one region of the environment will result in its being put somewhere else – where its effects may be undesirable as in the original location. Disposal of solid and hazardous wastes in the past has become a long-term sources of env ironmental contamination which will continue to cause problems for many years. Incineration of Solid wastes which can cause air pollution. Environmental Engineers must consider very carefully all the effects of their actions so that pollutants are not simply hidden or transferred from one place to another. VI. QUANTITY OF WATER AND SEWERAGE Population Estimation:

• Arithmetic Method • Uniform Percentage Method • Curv ilinear Method • Logistic Method • Declining Growth Method • Ratio Method

Water Use For Different Purpose:

• Domestic • Commercial and Industrial • Public Use • Loss and Waste

Factors Affecting Water Use:

• Size of the City • Industry and Commerce • Commercial • Characteristics of the Population • Metering • Miscellaneous factors

VII. Design Periods for Water Supply Components

Dam

Treatment Plant Distribution

The Economic Design Period Of The Components Of A Water Supply System Depends On:

Their life

First cost/initial cost The ease with which they can be expanded

Technological advances Pipelines From The Source: Generally designed for a period of 25 years or more. Water Treatment Plant: Are commonly designed for a period of 10 to 15 years. Pumping Plant: Are generally designed for a period of about 10 years. Storage: Design of such structures are closely linked to design of the pumping plant. Distribution System: Design period is indefinite and the capacity is based on the development of the area served. VIII.SEWAGE Definition: Sewage is a water-carried waste that is intended to be removed from a community which is also known as wastewater. Sources:

A. Sanitary or Domestic Sewage: From residences and institutions, carry ing body wastes (primarily feces and urine), washing water, food preparation wastes, laundry wastes.

B. Industrial waste: Wastes that result from an industrial processes such as the production or manufacture of goods are classified as industrial wastewater.

C. Infiltration, Inflow, Storm Sewage: Infiltration are drawn from the soil and may occur even in dry weather.

D. Inflow: is associated with runoff events like rainfall. E. Storm sewage or storm water: is runoff from precipitation that is collected in a system of

pipes or open channels.

Sewage and its Relation to Water Use: sanitary sewage and industrial wastes are derived principally from the water supply . Design Periods for Sewerage System:

Sewers: These are designed for an indefinite period since, like the water distribution system. Sewage Pumping: These are designed for the period of not exceeding 10 years. Sewage Treatment: These are generally designed to be adequate for a period of 15 to 20

years. GROUP 2 – WATER SUPPLY

Chapter 6 AQUEDUCTS AND WATER PIPES I. Introduction II. Aqueducts III. Pipes

i. Stresses in Pipes and Pipeline ii. Standard Pipe Beddings iii. Types of Pipes

a) Iron Pipes

b) Steel Pipes c) Concrete Pipes d) Asbestos-Concrete Pipes e) Plastic Pipes

iv . Valves v . Water Distribution Appurtenances v i. Effects of Pipes and Water Quality v ii. Corrosion and its Prevention

Chapter 7 COLLECTION AND DISTRIBUTION OF WATER

I. Intakes II. Methods of Distribution

III. Storage IV. Flow Estimation V. Pressure Regulation in Distribution Systems

CHAPTER 6: AQUEDUCTS AND WATER PIPES OBJECTIVE:

To be able to identify the different types of conduits and the materials used in conveying and distributing water

To be able to identify and familiarize with the different materials used in water conveyance II. AQUEDUCTS

Definition: Aqueducts are conduits constructed of masonry and built at a certain hydraulic gradient. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose. Usage: Aqueducts are built only for the conveyance of water. It can also be used as means of transportation and as source of energy and electricity Types of Modern Aqueducts:

A. Open Channels: a conduit in which liquid is open to the atmosphere. The simplest aqueducts are small ditches cut into the earth, like the irrigation canals in farms. A major factor in the design of all open channels is its gradient. A higher gradient allows a smaller channel to carry the same amount of water as a larger channel with a lower gradient, but increases the potential of the water to damage the aqueduct's structure. Example: Central Arizona Project, 7.3m wide open channels, coveys water from Colorado River to central Arizona

B. Underground Water Tunnels: are underground tunnels used to transport water to areas with large population Example: Smart Tunnel (Storm water Management And Road Tunnel) in Kuala Lumpur Malaysia, 4KM long, completed in November 2007

C. Pipes: Closed conduits are mostly used to carry treated/clean water. It is also used to transport sewage water to water treatment plants for sanitation and to avoid the risk of leaking contaminants from used water. Pipelines are useful for transporting water over long distances when it needs to move over hills, or where open channels are poor choices due to considerations of evaporation, freezing, pollution, or env ironmental impact. Example: Tinupur Water System, India, completed on 2006 , 55-km pipeline that carries water form 25 different reservoir, carries 185 million liters of water and delivers 30 million liters of wastewater to water treatment plants

III. PIPES Definition: A Pipe is tubular section or a hollow cy linder but not necessarily f circular cross-section used to convey flowing substances. Technically , pipes only refer to those with circular cross-section, while, tubes are for those that are non-circular in cross-section Stresses in Pipes:

A. Static Water Pressure: the pressure exerted by a static fluid depends only upon the depth of the fluid, the density of the fluid, and the acceleration of grav ity .

B. Centrifugal Force Caused by Changes on Direction: The force exerted by flowing water in pipes when direction changes.

C. External Loads: stresses caused by the environment. While static and centrifugal force damages pipes from the inside, external loads damages pipes from the outside, like v ibration from nearby establishment like construction sites , vertical load from passing vehicles, horizontal load which is soil induced (when pipe is situated underground, and other live loads.

D. Changes in Temperature: change in temperature depending on the current weather which causes drastic changes in the pipe depending on what material it is made from.

E. Water Hammer: is a pressure surge or wave caused when a fluid (usually a liquid but sometimes also a gas) in motion is forced to stop or change direction suddenly (momentum change).

Weak Point in Pipes: Joints are considered the weakest point in pipes. Measures against Stress:

A. Buttressing: Buttress is installed along where pipes connect to prevent displacement or separations of pipes.

B. Embedding Underground: The ideal location for pipes are underground in order to protect them from surface loads and to keep out of the way of sub-surface structures.

C. Bedding: supports the pipe within the trench against the total external load on the pipeline. The type of bedding, depend on pipe size, type of sub-soil, the load on the surface of the trench, the cover depth and trench width. Also, you must use the right bedding or else, the bedding itself will add more stress to the pipe. It is recommended to uses granular uniformly sized aggregates as bedding and not backfill because backfill tend sot hav e irregular shaped aggregates and is inconsistent that it may not be able to support the weight of the pipe

D. Stress Relievers: Used to relieve stress inside the pipes to maintain a stable or consistent internal pressure

For low points: use pressure reliev ing devices like blow-off valves

For high points: use pressure inducing devices to resist vacuum pressure which tends to prevent water supply form continuously flow and buckle the pipe

Factors in Selection of Pipes:

A. Capacity – the amount of discharge the pipe is designed to carry B. Durability – depends upon the material and its compatibility with the physical env ironment C. Maintenance Cost – the cost of maintaining the pipes in good condition to avoid further

expenses by replacement D. Initial Cost – the amount of the purchase of materials, labor, cost of installation and

reinforcements A. IRON PIPES Properties: Iron Pipes are manufactured by casting iron alloy in sand molds with solid patterns or core boxes. It has been used for 300 year in piping systems and construction. Kinds of Iron Pipes:

A. Ductile Iron: consist of an alloy of iron, carbon, silica, manganese, phosphorus, and graphite which gives its flex ibility and strength. It can bend without breaking, less corrosive than cast iron, flex ible

B. Cast Iron: consists of an alloy of iron, carbon, and silica which gives it strength but tends to be brittle.

Advantages:

Flex ible Strong and Durable

Cheap and Abundant

Resistance to external Corrosion - Since iron pipes are manufactured w/ relative thickness, corrosion from the outside is much likely neglected because it doesn’t affect the hydraulic capacity of iron pipes unless corrosion has reached inside

Disadvantages:

Highly Corrosive in the Inside - Iron Pipes tend to corrode easily specially on the inside because of its exposure to water which is a major cause of corrosion. Internal corrosion in pipes are called Tuberculation, that causes the pipe to lose 70% of its original hydraulic capacity

Iron Pipe Connections: A. Bell and Spigot; Push-On: max. deflection is 5 degrees, cannot resist longitudinal forces B. Mechanical: max. deflection is 8 degrees C. Flanged: is done by threading the pipe ends and screwing them with flanges; doesn’t permit

defections D. Ball: max. deflection is 15 degrees; ideal to use when large deformation is anticipated E. Threaded: used in large pipes in large-scale pipeline systems because of its durability and

strong hold of connection F. Victaulic Coupling: can be used as substitute to flanged joints in residential pipes because it

is much cheaper G. Dresser Coupling: permits rotation and misalignment of the pipe centerlines, also accommodates longitudinal motions

B. STEEL PIPES

Properties: Steel Pipes is ideal to use where large diameter and high pressure is required. It is also ideal to use steel rather than iron, aluminum or brass pipes when weight concerned. Its average lifespan is up to 50 years. Usage/Application: Steel pipes can be used in water conveyance and distribution systems, in sewerage, in oil & gas pipelines and in the structural and industrial industry . You can see steel pipes being used in the Maynilad Water Distribution System, also in Petroleum and Oil Plants where high pressure and large capacity is concerned. Advantages:

Lightweight High Strength

Easy installation and assemblage Cheaper than Iron by weight

Can resist high pressure conditions Disadvantages

Buckles easily due to its suppressed flex ibility and relativ e thinness

Highly Corrosive

High Treatment/Coating Cost - Steel can be covered in tar or bituminous enamel inside and out to delay corrosion. Though covering steel pipes with cement mortar is the best remedy to corrosion, plus it increases the pipe resistance to buckling, thus increasing the lifespan of steel pipes.

High Maintenance Cost -Steel Pipe coating loses its elasticity and adhesion over time so it is required to have regular intervals for recoating, which also cost a lot than of iron pipes. If not recoated, the coating itself might start contributing to the corrosion of the steel pipe. Also steel pipes are costly to handle once coated because you must avoid scratching/abrasion in the coating.

C. CONCRETE PIPES Properties: Concrete Pipes are frequently used to convey water and wastewater.

Concrete Pipes are manufactured by centrifugally placing cement mortar on a steel cy linder mold then wrapping it with high-tensile wire or pre-stressing wire (wire is wounded tightly to pre-stress the mortar core) then covered with another concrete coating. Concrete Pipes are produced in lengths 3.7-4.9 m. or 12-16 ft. and can resist pressure gauging to 270 kPa. It can last for up to 75 years. Kinds of Concrete Pipes:

A. Reinforced Concrete Pipe: has a tensile or pre-stressing wire embedded in it, B. Unreinforced Concrete Pipe: does not have a reinforcement embedded in it:

Concrete Pipe Connections: Concrete Pipe Fittings consists of concentric rings which are welded to each other to develop enough thrust resistance from sudden jolts of water pressure during storm or flooding to avoid pipe misalignment) Though concrete pipes are very rigid, it can still be deflected along adjoining sections to permit gradual curvature since pipe line systems are not all straight line, or you can simple order specially made sections which are curved already for the purpose of deflection can be ordered. Maximum deflection of concrete pipes is 5 degrees. Usage/Application: Concrete Pipes can be used in water drainage systems, sewer and storm water canals Advantages:

Low Cost

Readily Available Easy to produce

Easy to install Low Maintenance Cost

Disadvantages:

Very Rigid, thus, it cannot be readily suspended Heavy Weight

Low resistance to abrasion Low resistance to v ibration unless reinforced

D. ASBESTOS-CEMENT PIPE Properties: Asbestos-Cement Pipes is composed of mixture of Portland cement and asbestos fiber which is manufactured using a rotating steel mandrel then compacted with steel rollers. It has been used worldwide for over 60 years because of its high hydraulic capacity ; high discharge capacity and relatively low coefficient of friction. Asbestos-Cement Pipe Connections: Iron Fittings are used to connect asbestos-cement pipes. Joints consists of cy lindrical sleeves that fit over adjoining sections. Both fittings and pipe section ends are covered with rubber rings that serve as gaskets to avoid leaks. Maximum deflection of Asbestos-cement pipes are 12 degrees.

Usage/Application: Gas Pipelines, Petroleum Pipelines, Liquid Nitrogen and Oxygen Pipe Systems in Industrial Plants Advantages:

High Hydraulic Capacity Disadvantages:

Costly

Cannot be used in water conveyance due to health threatening properties - Asbestos-cement pipes releases carcinogens which can cause intestinal cancer when inhaled/consumed. Acidic waters tends to corrode concrete thus asbestos leaches out and is exposed to the environment. Standard Rules and Regulations in using Asbestos-cement pipe have been established in 1989

E. PLASTIC PIPES Properties: is made of solid and fiber-reinforced materials. Kinds of Plastic Pipes:

A. ABS (acrylonitrile butadiene styrene) pipes: ABS is used for the conveyance of potable water, slurries and chemicals. Most commonly used for DWV (drain-waste-vent) applications

B. UPVC (unplasticized polyvinyl chloride) and CPVC (post chlorinated polyvinyl chloride) pipes: UPVC has excellent chemical resistance across its operating temperature range, with a broad band of operating pressures. Due to its long-term strength characteristics, high stiffness and cost effectiveness, UPVC systems account for a large proportion of plastic piping installations.

C. PB-1 (polybutylene) pipes: PB-1 is used in pressure piping systems for hot and cold potable water, pre-insulated district heating networks, and surface heating and cooling systems.

D. PP (polypropylene) pipes: Polypropylene is suitable for use with foodstuffs, potable and ultra-pure waters, as well as within the pharmaceutical and chemical industries.

E. PE (polyethylene) pipes: Polyethy lene has been successfully used for the safe conveyance of potable and waste water, hazardous waste, and compressed gases.

F. PVDF (polyvinylidene fluoride) pipes: PVDF has excellent chemical resistance which means that it is widely used in the chemical industry as a piping system for aggressive liquids.

Plastic Pipe Connections: Small diameter Plastic pipes are connected through solvent welding in cy lindrical sleeves. Large Plastic Pipes are connected thru bell-and-spigot or push-on connections with cast iron fittings Usage/Application: It is widely used in domestic plumbing and in water distribution systems. Advantages:

Light weight Easy to handle and install

Cheaper than iron and concrete pipes Disavantages:

Low resistance to heat and chemicals in comparison to iron/steel/concrete pipes

Very Flex ible Health risks

Low resistance to stress and pressure

IV. VALVES Definition: A Valve is a device for controlling the passage of fluid through a pipe or duct, especially an automatic device allowing movement in one direction only . Valves must be designed to resist wear and are often given with hydraulic or electric operator. Large water distribution systems have their valves electrically operated so breaks can be isolated quickly , though when electric operation failed to operate, valves must still have their manual switch so they can be operated even without electricity . Kinds of Valves:

A. Gate Valve: most commonly used for on-off serv ice since they are relatively inexpensive and offer a relatively positive shut-off. Gate Valves are the most common valve used in the water distribution system not only because it is cheap but also because it is easy to operate. They are located throughout the distribution system so that if any break in the system it can be isolated quickly by shutting close the valves near the break, thus, avoiding too much water loss. Valves are usually found in manholes for accessibility , smaller valves may be buried prov ided it is within a valve box made of iron or plastic. Gate Valves are manufactured with threaded, flanged, bell-&-spigot, or combination ends.

B. By-Pass Valve: valves which reduces pressure from main valve to reduce occurrence of water hammer; helps decrease pressure within valves when operating, since opening and closing of valves tends to make water flow produces water hammer or jolts of water pressure due to sudden changes in the flow. Water Hammer can damage pipes and even the valve itself)

C. Check Valves or Foot Valves: prevents reversal of flow when pumps are shut off. Prevents water to go to the reverse direction once the pump sustaining its flow stop operating. It is usually found at the end of the suction line of pumping line. It is also placed on the side of discharge pumps to reduce water hammer forces during pumping operations.

D. Globe and Angle Valves: are seldom used in water distribution systems because their primary use is in household plumbing because of their poor hydraulic capacity .

E. Plug Valves: are valves with cy lindrical or conical tapered plugs inside which is rotated to control water flow flowing through the valve

F. Butterfly Valves: can be used in both high and low pressure applications, although only purely liquid substances can be accommodated by butterfly valves. They are substantially , cheaper, more compact and easier to operate but only if the liquid doesn’t not contain any solid material which can block the valve.

G. Air-Vacuum and Air-Relief valves: attached to long pipeline to permit release of air which accumulates at high points and also to prevent negative pressure when lines are drained. These valves automatically operate once installed; It sucks out or pumps in air so as not to disturb the rate of flow of water in the pipe and ensure it continues to flow whether it is down below or high up in location

H. Pressure Regulating Valves: Automatically reduce pressure on the downstream side to the desired level throttle. (Pressure is increased or decreased by tightening or loosening the opening of the valve until desired pressure is reached)

I. Backflow Preventers: Valves designed to automatically prevent reversal of flows with additional margin of safety against water hammer. It prevents flow reversal by preventing unfavorable pressure gradients/irregularities of pressure within the pipeline.

V, APPURTENANCES IN WATER DISTRIBUTION SYSTEM Definition: Appurtenances are all accessories used in the water distribution system that have a direct affect to the water supply in terms of flow, direction, velocity , pressure and etc. Examples of Appurtenances in Water Distribution System:

A. Fire Hydrants: consists of a cast iron barrel with bell of flange at the bottom which is connected to water line branch which is part of the fire protection measures in any structure.

B. Fittings : connect straight pipe or tubing sections, to adapt to different sizes or shapes, and for other purposes, such as regulating or measuring fluid flow.

C. Valve Boxes: are prov ided so that valves above ground or below ground are protected from external damage and for easy access and maintenance of valve.

VI. EFFECTS OF PIPE MATERIALS ON WATER QUALITY The quality of water can be greatly affected depending on the pipe materials through which it flows. Water which is acidic and low in dissolved solids is likely to attack cement or any metals that comes in contact. Dissolve materials in pipes are found to be harmful to health, aside from just hav ing the water it contaminates undesirable to consume. Common Substances That Contaminate Water Supply:

A. Iron: when dissolved from iron or steel pipes can produce a red color and also the cause as

to why sometimes water from our faucets may taste or smell metallic. Excessive Iron intake can lead to Hemochromatosis or Iron-overload Disease

B. Lead: maybe dissolved from lead pipelines, soldered joints in pipes or from copper pipeline. It can lead to Lead Poisoning if considerably enough amount of lead spread out in the water distribution system

C. Organic Matters: concrete or plastic pipes, under some circumstances, may permit organic materials to pass through its wall and contaminate the water being conveyed. Organic Matter includes fungi, bacteria, worms, etc.

D. Carcinogens: can come not only from asbestos-cement pipes but other plastic pipes as

well.

VII. CORROSION AND ITS PREVENTION

Definition: Corrosion may be define as the conversion of a metal to a salt or ox ide with a loss of desirable properties such as mechanical strength. Corrosion Process: In all types of corrosion, an electron transfer must occur either between dissimilar metals or between different areas on a single material.

Anodic: a zone which releases electrons (in most cases, this is the metal surface) Cathodic: a zone which accepts the electrons from Anodic (this is the ox idizing agent, like air

or water) Kinds of Corrosion: (Kinds of Corrosion are based on how the destructive process of Corrosion affects the metal)

Uniform Corrosion: reaction starts at the surface and proceeds uniformly Localized Corrosion: Portions of metal is being eaten away and damage tends to bore a

hole in the metal while the rest of the affected surface is slightly affected or not at all

Wide Pitting Corrosion: causes localized or uneven scarring Intregranular Corrosion: corrosion is unnoticeable from the outside since corrosion starts at

grain boundaries inside the metal

Transgranular or Intragranular Corrosion: Corrosion occurs within metal material grains while retaining grain boundaries

Galvanice Corrosion: Corrosion in crev ices or cracks in the metal surface/ contact surface where two metal come in contact with each other

Selective Corrosion: corrosion only attacks one element of the metal alloy, example for an alloy of cooper and silver , only copper elements are subjected to corrosion)

Exfoliation Corrosion: Corrosion follows fiber orientation Interfacial Corrosion: Occurs in water-air interfaces

Processes That Prevents Or Delay Corrosion:

A. Impressed Current/ Cathodic Protection: protects metal from corrosion by apply ing DC Voltage to the metal making its molecular behavior act like cathodes instead of anodes This process makes the metal electrons flow at a rate the same as it does during the ox idation process of corrosion, thus, forbidding the electrons to transfer when an anode is present nearby. If voltage used is greater than what is required, it can lead to a more rapid corrosion. Too much voltage applied may break the polarized film of every metal surface, making it anodic against the rest of the surface along the process, thus, it will be the reason for an extremely rapid corrosion

B. Galvanizing:is the process of apply ing zinc coating to steel or iron pipes. Non-corrosive zinc will serve as the sacrifice anode during ox idation, in this process the zinc coating will receive the effects of corrosion, thus protecting the delicate metal within it. Magnesium and Aluminum can also be used in galvanizing. These coatings can be applied by hot dipping, metal spray ing, cladding, vapor deposition, electroplating, metalliding and mechanical plating to form a film 0.0002 to 5.0 mm thick. (The coating may serve as the final cover but in some instances wherein the environment is too corrosive, another coating may be applied so the galvanizing coat may only act as the base coat.)

C. Chemical Coating: include paints, coal tar preparations, asphalt, epoxy materials and even cement. Once coated, these coating will isolate the materials from the

environment thus prov iding a protective coating against the elements that may inhibit corrosion.

D. Inhibition: the removal or binding of molecules or particles in the surface of metals with the use of chemicals such as include, chromate, nitrate, phosphates, silicates and benzoates. Such coating is effective to reduce or delay corrosion against neutral or alkaline solution, metals are treated with these chemical so it will not be reactive to cathodic substances.

E. Inert Materials: is the substitution of other materials to replace the corrosive metal or iron pipes.

CHAPTER 7: COLLECTION AND DISTRIBUTION OF WATER OBJECTIVES:

To be familiar with the different methods and facilities used in water collection To be able to identify the different methods of distributing water

To be able to estimate flow rate and pressure required in the design of water conveyance system

I. INTAKES: Definition Intakes or Intake Structures are structures wherein water will initially enter from its source such as different bodies of water to be collected and distributed. Intakes must be able to resist natural fluctuations such as wide variations of flow, temperature, quality of water, and other natural forces etc. They are usually built within dams. Factors to Consider in the Site-Selection for Building Intakes:

Water Level: When building intake structures, one must consider the water level both maximum and minimum before designing an intake structure.

Navigation Requirements: the manner of operation and control over the intake structure. Local Currents: the type and magnitude of flow, how often or intervals between flow

variations.

Sediment Deposition Pattern: engineers should be aware of the processes and outcomes when disrupting sediment depositions on bodies of water before planning and building intakes. Disturbing sediment depositions may affect the quality of water to be collected, it may also pose serious environmental issues and may be a hindrance in building the foundation and stability of the structure when building over sediment-filled areas.

Variation of Water Quality: water quality varies with depth and location. Water quality is not uniform all throughout a body of water so it is necessary to determine at what depth and location the desired quality of water to intake to locate where to build the intake structure, avoid depths wherein organic matter is abundant and low in dissolved oxygen.

Quantity and Type of Floating Debris: natural bodies of water bears different kinds of debris. It Is necessary to separate it from the water intake.

Kinds of Intake Structures:

A. Lake Intakes: Since saltwater is much tedious to treat, most intakes are built near lakes where there is freshwater. Lake intakes should be placed as far as possible from sources of

pollution. When designing Lake Intakes, consider the wind and direction of the current to avoid collecting many contaminants in the water. If Intakes is located on shallow waters or near the bottom, sediments may stir up from the bottom and be carried along in the intake.

B. Submerged Cribs: Intake structures that consist of an inlet with a screen that is submerged with its opening facing upward. This kind of intake is often used by small communities. Multiple pipe inlets maybe used which is connected to a much larger single pipe to reduce inlet velocities when pumping water in

C. River Intakes: River version of lake intakes. Opening for this kind of intakes should be place slightly below water surface to avoid floating debris at water surface and sediment suspension at the bottom of the river. Some river may accommodate traffic, so it is also recommended to place the opening of the intake or inlet far off the river bank. This may be far off the bank, or on the shore. Screens must be prov ide to avoid fish/any aquatic animals from entering the inlet.

II. METHODS OF WATER DISTRIBUTION Design Purpose:

For domestic use – residential areas, households, apartments, condominiums

For commercial use – establishments like mall, company buildings, museums, hospitals, school

For industrial use – factories, power plants, chemical or petroleum plant, construction sites etc

For Fire-Fighting purposes – This purpose must be applied on all kinds of design, because fire is dangerous in most every kind of community and we must take safety measures for it

Methods of Water Distribution:

A. Gravity Distribution: using grav ity to push water to its intended destination by manipulating conduits into a certain gradient from the source/reservoir to its intended users. This is only possible only when the water supply is substantially located above city level. This is considered the most dependable technique of distribution because it doesn’t require pumps or motors which only run if there is electricity , prov ided that conduits carry ing the water is well protected and well-sealed from outside contaminants. Motor pumps must be prov ided when water from this system will be used in fire-fighting.

B. Pumping without Storage: considered the least desirable of all methods because it has no reserve flows, varied rate of flows, vary ing water pressure, and consistent amount of water supply .

C. Pumping with a Storage: is the most common method of distribution by using elevated

storage tanks to store water and to distribute it by grav ity or pump to its destination. This kind of water distribution ensures reliability when power fails. Motor pumps must be prov ided when water from this system will be used in fire-fighting.

Patterns of Distribution Systems:

A. Branching Pattern: similar to the branching of the tree. It consists of (1) Main (trunk) line, (2) Sub-mains and, (3) Branches.

Main line is the main source of water supply . There is no water distribution to consumers from trunk line.

Sub-mains are connected to the main line and they are along the main roads.

Branches are connected to the sub-mains and they are along the streets

Advantages:

It is a very simple method of water distribution. Calculations are easy and simple to do.

The required dimensions of the pipes are economical.

This method requires comparatively less number of cut-off valves. Disadvantages:

The area receiv ing water from a pipe under repair is without water until the work is completed.

Frequent sedimentation inside pipes and growth of organic matter. Drain Valves must be prov ided for every dead ends. In this system, there are large number of dead ends where water does not circulate but remains static. Sediments accumulate due to stagnation of the dead end and bacterial growth may occur at these points. To overcome this problem drain valves are prov ided at dead ends and stagnant water is drained out by periodically opening these valves but a large amount of water is wasted.

Water available for fire-fighting will be limited since it is being supplied by only one water main source.

The pressure at the end of the line may become undesirably low as additional areas are connected to the water supply system.

B. Grid Pattern: In grid pattern, all the pipes are interconnected with no dead-ends. In such system, water can reach any point from more than one direction. Advantages:

No water stagnation and bacteria growth - Since water in the supply system is free to flow in more than one direction, stagnation does not occur as readily as in the branching pattern.

Continuous Water Supply - In case of repair or break down in a pipe, the area connected to that pipe will continue to receive water, as water will flow to that area from the other side.

Water reaches all points with minimum head loss. Efficient for fire-fighting purposes -At the time of fires, by manipulating the cut-off

valves, plenty of water supply may be diverted and concentrated for fire-fighting Disadvantages:

Cost of pipe lay ing is more because relatively more length of pipes is required.

More number of valves are required.

The calculation of pipe sizes are more complicated.

C. Grid Pattern with Loops: Loops are prov ided in a grid pattern to improve water pressure in portions of a city (industrial, business and commercial areas). Loops should be strategically located so that as the city develops the water pressure should be sustained. The advantages and disadvantages of this pattern are the same as those of the grid pattern

III. STORAGE Water is stored to equalize pumping rates in the short term, to equalize supply and demand in long term and to prepare water for emergencies. Water is stored so pumps will avoid dealing with unstable water currents when pumping directly from a body of water, also water is stored to cater demand and to prov ide a continuous water supply and lastly for emergencies like fire or loss of pumping capacity .

Storage may be made of metal, earth, concrete and shall be considered as reservoirs. They are usually located on high ground or simply elevated higher than the outlets Types of Water Storage:

A. Natural – existing water pockets or reservoirs although some have little man-made structures in it. (For example, reservoir, ponds, groundwater, example: La Mesa) Natural reservoirs tends to be bigger than Artificial Ones.

B. Artificial – man-made water storages. (For example, dam , tanks)

IV. FLOW ESTIMATION: Water distributions system requires accurate estimation of flow to each section of community . Thus, an engineer must predict a pattern of distribution to cater all demands such as industrial, commercial, public, and residential demands without or little failure.

Industrial Use: 20 L/m -day or 21 gal/acre-day

Commercial use: 330 L/m -day or 350,000 gal/acre-day Office and Retail Sales Facilities: 90 L/m -day or 100,000 gal/acre-day

Commercially Developed Areas: 40 L/m -day or 45,000 gal/acre-day Residential Areas: depends upon population densities which can be determined by surveying average water consumption per head. Designing and estimating water flow systems does not extend to the degree of detail in which indiv idual connections are considered. When designing and estimating water flows, the design only extend to the branches in the street. Beyond that, indiv idual distributions systems called system of nodes are series of pipes branching from the main street line to each indiv idual house having many faucets or outlets. Also, estimation of water supply should include fire protection water allowance since in reality , you will be designing to prov ide water for industrial, commercial and residential area using only one large-scale water distribution design pattern/system.

Fire Protection: For large communities- Max Flow: 45.4 m/min or 12,000 gal/min

For small communities/residential areas- Minimum Flow: 1.9 m/min or 500 gal/min; Max. Flow: 9.5 m/min or 2500 gal/min

Fire hydrants must be place throughout the city every 3720 m , thus, spacing between hydrants must be 60m to 150 m. and should be place at street intersections so hose can run in different directions. High-value district must have extra fire-hydrants. V. Pressure Required Residential Districts with 4-Storey Structures: 150-300 kPa or 20-40 lbs/sq. inch Commercial Districts: 400-500 kPa or 60-75 lbs/sq. inch Areas with 10-Storey Structures: 400-500 kPa or 60-75 lbs/sq. inch or greater High-Value districts have a separate water supply system, one for domestic use of water and other for fire-protection. Example is the area of Global City . Fire Protection (in High-value districts): 2,100 kPa or 300 lbs/sq. inch

This method or system is not applicable to city wide distribution systems because it is very expensive. As substitute, city government must prov ide motor pump trucks to boost pressure to the level necessary specially when dealing fire in high-rise structures. Very tall and private buildings must prov ide their own fire protection system by installing internal pumping systems and standpipes which are connected to external fire hydrants. GROUP 3 – WATER SUPPLY Chapter 7 COLLECTON AND DISTRIBUTION OF WATER

I. Pipe System II. Design of Water Distribution Systems

Chapter 8 QUALITY OF WATER SUPPLIES I. Definition of Terms II. Water and its Impurities

i. Common Water Impurities ii. Waterborne Diseases iii. Organic and Inorganic Contaminants

III. Quality of Water Supply

I. THE PIPE SYSTEM Primary or Arterial Mains: form the basic structure of the system and carry flow the pumping station to and from elevated storage tanks and to the various district of the city .

Secondary lines: form smaller loops within the primary mains and run from primary line to another. Small Distribution Mains: form a grid over the entire serv ice area-supply ing water to every user and to the fire hydrants. II. DESIGN OF WATER DISTRIBUTION SYSTEMS A plumbing system is a long-term investment and should be designed so that it does not become outdated and need replacement while its major parts are still serv iceable. This requires careful estimation of current and future demand so that the correct capacity can be specified. -Cleaning -Leak Surveys -Hydrants -Disinfection -Valves - Thawing CHAPTER 8 – QUALITY OF WATER SUPPLY I. DEFINITION OF TERMS Water : known as “life” for it has no alternative : Essential for the sustenance of liv ing organisms (plants, animals, and man) : Potable Water: safe to drink, pleasant in taste, and suitable for domestic

purposes. : Contaminated or Polluted Water: contains suspended or dissolved material

which makes it unsuitable for its intended use. Waterborne Diseases: caused by pathogenic microorganisms that most commonly are transmitted in contaminated fresh water. Inorganic Contaminants: means "material such as sand, salt, iron, calcium salts and other mineral materials. Inorganic substances are of mineral origin. Organic Contaminants: substances that come from animal or plant sources. Organic substances always contain carbon. Environmental Protection Agency (EPA): is an agency which was created for the purpose of protecting human health and the environment by writing and enforcing regulations based on laws passed by Congress. Maximum Contaminant Level (MCL): are standards that are set by the United States Environmental Protection Agency (EPA) for drinking water quality Recommended Contaminant Level (RCL): a secondary standard set by EPA for few contaminants which do not have chronic or tox ic health impacts II. WATER AND ITS IMPURITIES Impurity: a thing or constituent that impairs the purity of something. Water is the universal solvent and in nature, it is never totally pure. No matter how isolated it is from sources of contamination, it will always have some chemicals. Gases or minerals in the air, soil, or rock

are dissolved by the water. Some dissolved materials give water its characteristic taste, and “pure water” is generally considered to be flat and tasteless. Classification of Water Impurities:

- Liv ing organisms and solid - Dissolved organics and inorganics

i. Common Water Impurities Table: Impurities in Fresh Water

Constituent Chemical Formula

Difficulties Caused Means of Treatment

Ox y gen O2 corrosion of w ater lines, heat ex change

equipment, boilers, return lines, etc.

De-aeration; sodium sulfite;

corrosion inhibitors

Ammonia NH3 corrosion of copper and zinc alloys by

formation of complex soluble ion

Cat ion ex change with hydrogen

zeolite; chlorination; de-aeration

Sodium Na+ adds to solids content of w ater: when combined w ith OH-, causes corrosion in boilers under certain conditions

demineralization, reverse osmosis, electro-dialysis, ev aporation

Carbon

Diox ide

CO2 corrosion in w ater lines, particularly steam

and condensate lines

aeration, de-aeration,

neutralization w ith alkalies

Turbidity non-expressed in analysis as units

imparts unsightly appearance to water; deposits in water lines, process equipment, etc.; interferes with most process uses

coagulation, settling, and filtration

Hardness calcium and magnesium salts, expressed as CaCO3

chief source of scale in heat exchange equipment, boilers, pipe lines, etc.; forms curds with soap, interferes with dyeing, etc.

softening; demineralization; internal boiler water treatment; surface active agents

Alkalinity bicarbonate(HCO3-), carbonate (CO32-), and hydrox ide(OH -), expressed as CaCO3

foam and carryover of solids with steam; embrittlement of boiler steel; bicarbonate and carbonate produce CO2 in steam, a source of corrosion in condensate lines

lime and lime-soda softening; acid treatment; hydrogen zeolite softening; demineralization dealkalization by anion exchange

Free Mineral Acid

H2SO4 , HCI. etc., expressed as CaCO3

corrosion neutralization with alkalies

ii. Waterborne Diseases Table: Protozoal Diseases

Disease and Transmission

Microbial Agent Sources of Agent in Water

Supply General Symptoms

Amoebiasis (hand-to-mouth)

Protozoan (Entamoeba histolytica) (Cyst-like appearance)

Sewage, non-treated drinking water, flies in water supply

Abdominal discomfort, fatigue, weight loss, diarrhea, bloating, fever

Cryptosporidiosis (oral)

Protozoan (Cryptosporidium parvum)

Collects on water filters and membranes that cannot be disinfected, animal manure, seasonal runoff of water.

Flu-like symptoms, watery diarrhea, loss of appetite, substantial loss of weight, bloating, increased gas, nausea

Cyclosporiasis Protozoan parasite (Cyclospora cayetanensis)

Sewage, non-treated drinking water

cramps, nausea, vomiting, muscle aches, fever, and fatigue

Giardiasis (fecal-oral) (hand-to-mouth)

Protozoan (Giardia lamblia) Most common intestinal parasite

Untreated water, poor disinfection, pipe breaks, leaks, groundwater contamination, campgrounds where humans and wildlife use same source of water.

Diarrhea, abdominal discomfort, bloating, and flatulence

iii.a. Inorganic Contaminants

A. Suspended Materials: alters color, taste and odor of water B. Dissolved Substances: Aluminum, Arsenic, Barium, Cadmium, Chromium, Fluoride

iii.b. Organic Contaminants: Taste and Odors in water may be produce by either organic or inorganic materials.

- Humic and fulvic acids encompass a group of acidic randomly polymerized macromolecules which constitute the major organic constituent of natural waters.

- Pesticides which enter water supplies from either agricultural or domestic use are, in general, quite resistant to removal by ordinary water techniques.

III. WATER QUALITY Environmental Protection Agency: (EPA) sets the international standards for the quality of water for commercial and domestic use. Regulation of Water Quality: 1. Liabilities for Unsafe Water: liability for health or other problems of the users 2. Characterization of Waterborne Epidemics: outbreaks of waterborne disease in the past have been associated with use of untreated water. 3. Watershed and Reservoir Protection: impounding reservoirs and their watershed are should be protected to the degree necessary to ensure that the water supply is not contaminated 4. Groundwater and Well Protection: ground water supplies and indiv idual wells may be contaminated by surface water during floods and by percolation of waste material through the soil 5. Protection within the Treatment and Distribution Systems: careful design, regulation and maintenance of water treatment system and facilities GROUP 4 and 5 – WATER SUPPLY Chapter 9 SEWAGE AND WATER TREATMENT

I. Water Clarification II. Water Filtration

i. Types of Filtration Methods ii. Types of Filters and Media Used in Filtration iii. The Underdrain System iv . The Backwash Process v . Operating Difficulties v i. Clear Well and Plant Capacity v ii. Other Filtration Processes

III. Treatment of Brackish and Saline Water

i. Stabilization ii. Reverse Osmosis iii. Freezing iv . Ion Exchange v. Electro-dialysis

IV. Water Treatment Wastes V. Miscellaneous Water Treatment Techniques V. General Considerations in Sewerage

CHAPTER 9 - WATER TREATMENT I. WATER CLARIFICATION Purpose:

Water is essential in life.

Water is treated for a variety of purposes. Water Clarification Process:

1. Screening: are used at surface water intakes to prevent the entrance of materials 2. Coagulation: is the destabilization of colloids by addition of chemicals that neutralize the

negative charges. Coagulation is essentially a chemical process.

Water is added with a chemical called alum. Alum produces positive charges to neutralize the negative charges on the particles. Then the particles can stick together, forming larger particles which are more easily removed.

3. Flocculation: is a physical and chemical process which is used for the removal of the v isible sediments and material from water which makes it a colloidal solution

. 4. Settling or Sedimentation: is a physical water treatment process using grav ity to

remove suspended solids from water. • Settling- a unit operation in which solids are drawn toward a source of attraction. The

particular type of settling that will be discussed in this section is grav itational settling. It should be noted that settling is different from sedimentation. Types of Settling:

- Type I: Discrete particle settling - Particles settle indiv idually without interaction with neighboring particles.

- Type II: Flocculent Particles – Flocculation causes the particles to increase in mass and settle at a faster rate

- Type III: Hindered or Zone settling –The mass of particles tends to settle as a unit with indiv idual particles remaining in fixed positions with respect to each other.

- Type IV: Compression – The concentration of particles is so high that sedimentation can only occur through compaction of the structure.

Types of Settling Basin: - Rectangular Basin: are commonly found in large-scale water treatment

plants; are basins that are rectangular in plans and cross sections. In plan, the length may vary from two to four times the width. The length may also vary from ten to 20 times the depth. The depth of the basin may vary from 2 to 6 m. The influent is introduced at one end and allowed to flow through the length of the clarifier toward the other end Rectangular tanks are popular as they tend to have:

• High tolerance to shock overload • Predictable performance • Cost effectiveness due to lower construction cost • Lower maintenance • Minimal short circuiting

- Circular Basin: are frequently referred to as clarifiers.These basins share some of the performance advantages of the rectangular basins, but are generally more prone to short circuiting and particle removal problems.

- Square Basin: For square tanks the design engineer must be certain that some type of sludge removal equipment for the corners is installed.

• Sedimentation- The condition whereby the solids are already at the bottom and in the process of sedimenting. Settling is not yet sedimenting, but the particles are falling down the water column in response to grav ity . Of course, as soon as the solids reach the bottom, they begin sedimenting. In the physical treatment of water and wastewater, settling is normally carried out in settling or sedimentation basins.

Advantages of Clarification Process:

• Simplest technologies • Little energy input • Relatively inexpensive to install and operate • No specialized operational skills • Easily incorporated into new or ex isting facilities

Disadvantages of Clarification Process:

• Low hydraulic loading rates • Poor removal of small suspended solids • Large floor space requirements • Re-suspension of solids and leeching

II. WATER FILTRATION Definition:

- Water Filtration: is required because settling does not eradicate all flocs in the contaminated water. Filtration prov ides the additional opportunity for separation of small flocs or particles Filtration is used to separate non-settle able solids from water and wastewater by passing it through a porous medium.

The most common system is filtration through a layered bed of granular media, usually a coarse anthracite coal underlain by finer sand.

- Filter Controls: The original rapid filter designs incorporated rate of flow controllers to maintain constant filtration rates despite variations in head loss within the filter during a run. The designer must recognize that filter systems are not likely to be operated at a constant rate from the beginning to the end of a filter run. Classification of Filter Control Systems: • Constant head loss: constant head systems employ weirs at the fiber entrances which

prov ide equal flow to each unit.

• Variable head loss - Uniform flow systems split the incoming flow uniformly among the filters in

operation. - Declining flow systems prov ide a common head on all filters and in their

common supply structure. - Turbidity Sensors: commonly connected to an alarm system which is triggered

by increase beyond 1 ntu. - Flow Meter: Should be prov ided for the total influent and effluent flow.

i. TYPES OF FILTRATION

A. Mechanical Straining B. Physical Adsorption

C. Slow Sand Filtration: The early filtration units developed in Great Britain used a process in

which the hydraulic loading rate is relatively low. Grav ity is the driv ing force. Water filters through a layer of sand with gravel base. Figure: Slow Sand Filter Schematic Diagram

***Water Filter Systems consists of a layer called Schmutzdecke. The schmutzdecke consumes and adsorbs/absorbs organic contaminants. ***Layers of sand strain out particulate contaminants due to the small pores created by fine sand particles.

D. Rapid Filtration: Water from the settling basins enters the filter and seeps through the sand and gravel bed, through a false floor, and out into a clear well that stores the finished water. Rapid sand filtration is the flow of water through a bed of granular media, normally following settling basins in conventional water treatment trains. Theory of Filtration in Rapid Filters: the overall removal of impurities from the water in rapid filtration is brought about by a combination of several different processes. The most important are straining, sedimentation, adsorption, and bacterial and biochemical processes. In rapid filtration, however, the filter bed material is much coarser and the filtration rate much higher (up to 50 times higher than in slow sand filtration). These factors completely alter the relative importance of the various purification processes

Solid Removal Mechanism in Filtration:

a. Straining: the most important mechanism which takes place in the first few centimeters of the filter medium. Only large enough particles are removed through the pores

b. Sedimentation: Particles do streamline and settle on the sand grain. It does not follow the fluid flow direction.

c. Interception: occurs when there are too large particles that follow the streamline but get caught by the sand grains in the process

d. Diffusion: occurs when the random movement of particles collide with the sand grains by chance

ii. FILTER MEDIA An Ideal Medium Filter: - Such a size that it will prov ide a satisfactory effluent

- Retain a maximum quantity of solids with minimum head loss - Be readily cleaned with a minimum quality of water. ***The size and uniformity of filter media are specified by the effective size and the uniformity coefficient. Important Considerations in Selecting Media:

Too fine - surface straining which results in high head loss and short filter runs. Too coarse - poor filtrate quality , high backwash flow required.

Types of Filter:

Single–media filters: (mono-media) these have one type of media, usually sand or crushed anthracite coal.

Dual–media filters: These have two types of media, usually crushed anthracite coal and sand.

Multi–media filters: These have three types of media, usually crushed anthracite coal, sand, and garnet.

Types of Filter Media

Sand - normally the cheapest filter medium. Anthracite – used as a substitute for sand in mono medium filters. Garnet sand and Ilmenite –used as a component of multimedia filters.

iii. THE UNDERDRAIN SYSTEM The filter medium in rapid filters is underdrain by a system which serves as a support, as a collector of filtered water, and as a distributor of backwash flow. Gravel, when used as a part of the collection and backwash distribution system, it is normally placed in five or six layers, with the finest material on top. iv. THE BACKWASH PROCESS This refers to pumping water backwards through the filter media, sometimes including intermittent use of compressed air during the process. Backwashing is a form of preventive maintenance so that the filter media can be reused.

v. OPERATING DIFFICULTIES - The turbidity of the effluent from rapid filters at the beginning of a run, like that from slow

sand filters, is usually higher than that obtained after the filter has before some time. - The most common method of handling the initial poor quality is to filter to waste, that is,

discharge the filtrate to a sewer for the first period operation. - Slow start – as an alternative to wasting the initial flow, one may operate the filter at a lower

rate. - Air binding – can best be controlled by adjustment of pretreatment to permit deeper

penetration of floc into the filter.

vi. CLEAR WELL AND PLANT CAPACITY - The maximum capacity of a filter plant depends on the water consumption rate and the

storage available for treated water. - Selecting the number and the size of indiv idual filter units also involves balancing cost and

ease of operation. - It is generally not desirable to build much excess capacity , since expansion is comparatively

easy. vii. OTHER FILTRATION PROCESSES

• Activated Carbon – effective filtration medium insofar as removal of turbidity is concerned. • Coal and Metallic Aluminum – used as a filter medium without a prev ious coagulation step

or the addition of any coagulant aids. • In-line Filtration– which employ either single or two stage filtration without prior treatment

other than addition of a coagulant in the influent line have been used successfully on waters of low turbidity .

• Pressure Filters – are rapid filters contained in a pressure vessel. • Diatomaceous Earth Filters (DE) - were developed by the army for water treatment under

combat conditions. It contains fossil-like skeletons of microscopic water plants called diatoms, which are a type of algae.

• Upflow Filters – the direction of flow is the same as that of the backwash, hence the water is filtered by progressively finer layers as it passes through the bed.

• Biflow Filter - The larger proportion of flow is upwards from the base of the filter bed, while the smaller proportion is downwards from the top of the filter bed. The two flows meet a short way down the bed where there is an outlet grid across the bed.

III. TREATMENT OF BRACKISH AND SALINE WATER Increasing water consumption and depletion of ex isting water resources has led to considerable interest in conversion of saline and brackish waters. Desalination systems can be separated into those which employ a phase change, like distillation or freezing, and those which separate water and dissolved minerals within the aqueous phase, like ion exchange, electro dialysis, and reverse osmosis.

i.. Stabilization Stabilization it is the adjustment of the ionic condition of water so that it will neither corrode the pipes through which it passes nor deposit encrusting films (generally of calcium carbonate). Some waters are naturally corrosive, while other becomes corrosive through pH reduction occasioned by addition of metallic coagulants or chlorine. The marble test for measuring stability is a practical method which clearly indicates the condition of water. A water of known alkalinity is placed in contact with powdered calcium carbonate for 24 hours and the alkalinity is measured.

ii. Reverse Osmosis The principle of osmosis can be readily understood by considering a semi permeable membrane separating two bodies of water which contain differing salt concentrations. Reverse osmosis is the best-demonstrated technology for saline water conversion. This process is particularly useful in coastal communities. Reverse osmosis systems consist of the membrane, a support structure, a pressure vessel, and a pump. The optimum membrane configuration is a hollow fiber which has an area to volume ratio of up to 30,000 (compared to 300 to 3,000 for other designs), requires no support structure, and has reasonable water flux rates. iii. Freezing Freezing for desalination is effected by application of vacuum processes in which evaporation of a portion of the water or of a miscible secondary refrigerant freezes the flow. Freezing for desalination is effected by application of vacuum processes in which evaporation of a portion of the water or of a miscible secondary refrigerant freezes the flow. iv. Ion Exchange Ion exchange has been applied to desalting by using the hydrogen- and hydroxy l- base resins. Ion – exchange systems are simple to operate and have moderate capital costs and few operating problems, but they require costly regenerants and produce troublesome waste streams. v. Electro Dialysis Electro-dialysis employs electrical energy to drive dissolved ionized solids across semipermeable membranes. The system consists of cathodic and anionic semipermeable membranes and two electrodes. vi. Fluoridation and Defluoridation It has been established that fluoride is helpful in reducing the incidence of dental caries and that modest amounts of this ion in drinking water will prov ide the degree of protection which is desirable. Fluoride is added in the form of sodium fluoride, sodium silicofluoride, or hydrofluosilicic acid. Sodium silicofluoride (Na2SiF6) is the least expensive of the chemicals used in fluoridation but is somewhat difficult to dissolve. Waters which naturally contain fluoride in excess of the recommended concentration may be treated for its removal. Fluoride is removed by adsorption on or coprecipitation with magnesium hydrox ide.

IV. WATER TREATMENT WASTES

• Filter Backwash: similarly , contains all those materials retained by or produced with the bed. Filter backwash water is the largest single waste flow in water treatment plants. It is typically managed by directing it to a surge tank and then returning it at a low constant rate to the head of the plant for recycle.

• Brines: produced in desalting processes, in addition to specific contaminants, are very high in dissolved solids content. Brines have been managed by discharge to deep wells or saline surface waters or by lagooning to obtain evaporation.

• Coagulation sludges contain microbial, organic, and inorganic contaminants derived form

the water, the metallic or polymeric coagulants, and any contaminants which the latter may contain.

• Alum sludges have been concentrated by lagooning, dry ing on sand beds, grav ity

thickening, vacuum or pressure filtration, centrifugation, solvent extraction, and freezing.

Alum sludge concentration in centrifuges or pressure filters may produce solids contents as high as 40 percent, permitting or causing the sludge to freeze will separate the water. On thawing, the resulting slurry will settle to about 20 percent solids within 5h and may be further dewatered on sand beds or by mechanical processes. Aliphatic amine solvents: are miscible with water at low temperature (18 0C ), but separate when warmed (550C). Alum may be recovered from coagulation sludges by addition of sulfuric acid. The resulting liquid alum solution can be reused as a coagulant in either water or wastewater treatment plants.

V. MISCELLENEOUS WATER TREATMENT TECHNIQUES Disinfection: is the killing of disease-causing microorganism.

- Chlorination: Chlorine has been the disinfectant most commonly used in the United States and other country . Chlorine will combine with water to form hypochlorous and hydrochloric acids.

- Ozonation: Ozone is an unstable gas that can destroy bacteria and v iruses. It is formed when oxygen molecules collide with oxygen atoms to produce ozone.

- Ultraviolet irradiation: is effective in killing all types of bacteria and v iruses through the probable mechanism of destruction of nucleic acids.

- Algae Control: Algae are microscopic photosynthetic plants which, under certain circumstances, may produce very heavy growths called “blooms” in lakes and reservoirs used for water supply . Both copper sulfate and chlorine have been used to control algae.

- Iron and Manganese Removal: Although iron and manganese are most commonly found in

groundwater, surface waters may also contain significant amounts at times. Iron and manganese contribute to hardness and are removed by water softening. Iron alone in ground waters which contain little or no organic materials can be removed by simple aeration followed by sedimentation and filtration. Both iron and manganese are present or if the water contains organic material such as humic or fulmic acid, aeration is sufficiently rapid only if it is catalyzed by pyrolusite or by accumulation of ox idation products on a porous bed such as a coke.

- Aeration: Aeration is used in water treatment to alter the concentration of dissolved gases, to strip volatile organics, and to reduce tastes and odors.

• Spray nozzle: prov ide a large air-water surface area but exposure time is short. • Cascade: consists of a stairlike assembly over which the water flows in a thin film,

falling one level to the next. • Diffused-air aerators: consists of concrete tanks with depth ranging from 3-5m, width

ranging from 3-10m, and length adequate to prov ide a detention time of 5 to 30 min. Air is applied along one side of the basin through the same sort of diffusers used in sewage treatment.

- Water Softening: If the water is softened by addition of lime, additional benefits include

removal of iron and manganese, coprecipitation of humic and fulv ic acid, and reduction in suspended solids – including bacteria and v iruses. Benefits of softening to domestic users include reduction in soap use, longer life for water heaters, and less incrustation of pipes.

VI. GENERAL CONSIDERATIONS IN SEWERAGE Definition of Terms:

• Sewerage – refers to the collection, treatment, and disposal of liquid waste. • Sewerage works – include all the physical structures required for that collection, treatment

and disposal. • Sewage – is the liquid waste conveyed by a sewer and may include domestic and industrial

discharges as well as storm sewage, infiltration, and inflow. • Domestic sewage – originates in the sanitary conveniences of dwellings, commercial or

industrial facilities, and institutions. • Industrial waste – includes the liquid discharges from industrial processes such as

manufacturing and food processing. • Storm sewage – is flow derived from rainfall events and deliberately introduced into sewers

intended for its conveyance. • Infiltration – is water which enters the sewers from the ground through leaks. • Inflow – is water which enters the sewers from the surface, during rainfall events, through

flaws in the system, or through connections to roof or basement drains. • Sewer – is a pipe or conduit, generally closed, but normally not flowing full, which carries

sewage. • Common sewer – serves all abutting properties. • Sanitary sewer – carries sanitary sewage and is designed to exclude storm sewage,

infiltration, and inflow. • Storm sewer – carries storm sewage and any other wastes which may be discharged into

the streets or onto the surface of the ground. • Combined sewer – carries both domestic and storm sewage. • House sewer – a pipe conveying wastewater from an indiv idual structure to a common sewer

or to other point of disposal. • Lateral sewer – is a common sewer with no tributary flow except from house sewers. • Sub-main sewer – collects flow from one or more laterals as well as house sewers. • Main sewer – collects flow from several sub mains as well as laterals and house sewers. • Force main – pressurized sewer lines which convey sewage from a pumping station to

another main or to a point of treatment or disposal.

• Sewage treatment – process which may be used to favorably modify the characteristics of the wastewater.

• Sewage disposal – refers to the discharge of liquid wastes to the environment.

General Considerations Prov ision of sewerage for an urban areas requires careful design. The sewers must be adequate in size and slope so that they will contain the maximum flow without being sub charged and maintain velocities which will prevent deposition of solids. Liability for Damages Caused By Sewage Deficiencies in design or construction may permit the city to involve the engineer or contractor in any legal difficulties which result. The city , however, as owner of the facilities, may bear the ultimate responsibility if the other parties are unable to pay for the damages. Damages resulting from poor operation or maintenance are always the responsibility of the city . Failure to respond quickly to known deficiencies is normally sufficient to establish legal liability . GROUP 6 – WATER SUPPLY Chapter 10 STORM WATER FLOW

I. Presentation of Data II. Determination of Peak Discharge of Storm Run-off III. Sewer Appurtenances for Storm Drainage IV. Alternative Sewer Systems V. Pipe Networks VI. Components of a Pipe Network

CHAPTER 10 – STORM WATER FLOW Definition of Terms:

- Storm Water: is the water that originates from precipitation evens and snow/ice melt. Storm water can soak into the soil, be held on the surface and evaporate or runoff and end up in nearby streams, rivers or other bodies of water.

- Urban Hydrology: study of the effects of urban conditions on rainfall-runoff relationship.

Functions of the Actual flow in Sewers:

• Statistical frequency of the Design • Distribution of the Storm in Time • Antecedent Condition • Season of the Year • Physical Design of the Collection System

I. PRESENTATION OF RELATIONSHIP BETWEEN INTENSITY, DURATION AND FREQUENCY: The relationship among rainfall intensity , duration and frequency is obtainable from compilation of data to produce both synthetic hyetographs and intensity -duration curves.

• Hyetographs • Intensity Duration Curve

II. DETERMINATION OF PEAK DISCHARGE OF STORM RUN-OFF

• Rational Methods: Simplest method used to determine peak discharge from drainage basin runoff. Q= iA Q= CiA C=0.175t̂ 1/3 C=t/8+t C=0.3t/20+t

Where: Q=peak discharge A=drainage area C=runoff coefficient i=rainfall intensity t=duration of storm

• SCS Technique: originally developed by Soil Conservation Serv ice of the U.S. Dep’t. of Agriculture for use in rural areas; developed from empirical analysis of runoff from small catchments and hills slope plot monitored by USDA

• Hydrograph Technique: developed from empirical analysis of runoff from small catchments and hill slope plot monitored by USDA . (UH) defined as a hydrograph of direct runoff resulting from one unit of effective rainfall which is uniformly distributed over the basin at a uniform rate during the specified period of time.

• Computer Simulation Technique: these models require more or less complete definition of the hydraulic and hydrologic factors which affect the discharge andare capable of producing a great deal of information concerning the response of a drainage system to any selected rainfall pattern. Saint Venant Equation:

- Continuity equation -Momentum equation

III. SEWER APPURTENANCES A. Manhole: A manhole (maintenance hole) is the top opening to an underground utility vault used to house an access point for making connections or performing maintenance on underground and buried public utility and other serv ices.

Types of Manhole: 1. Brick Manhole - Brick manholes tend to be more conical in shape from the manhole rim

to invert and more slender than precast concrete manholes. 2. Precast Concrete Manhole- offers a cost sav ing, time effective solution. The

interlocking joint profile makes the installation quick and effective, and using a sealing material between the sections makes the chamber watertight.

B. Inlets: Inlets are drainage structures utilized to collect surface water through grate or curb openings and convey it to storm drains or direct outlet to culverts. Applicable Settings for Various Inlet Types:

Inlet Type Applicable Setting Advantages Disadvantages

Grate Sumps and continuous grades (should be made bicycle safe)

Perform well over wide range of grades

Can become clogged Lose some capacity with increasing grade

Curb-Opening

Sumps and continuous grades (but not steep grades)

Do not clog easily Bicycle safe

Lose capacity with increasing grade

Combina- tion

Sumps and continuous grades (should be made bicycle safe)

High capacity Do not clog easily

More expensive than grate or curb-opening acting alone

Slotted Locations where sheet flow must be intercepted.

Intercept flow over wide section

Susceptible to clogging

Types of Inlet: 1. Grate Inlets: These inlets include grate inlets consisting of an opening in the gutter covered

by one or more grates, and slotted inlets consisting of a pipe cut along the longitudinal ax is with a grate of spacer bars to form slot openings.

2. Combination Inlets: These inlets usually consists of both a curb-opening inlet and a grate inlet placed in a side by side configuration, but the curb opening may be located in part upstream of the grate.

3. Inverted Siphons: (also called depressed sewers) allow storm water or wastewater sewers to pass under obstructions such as rivers.

C. Sewer Outlets: Most drains have a single large ex it at their point of discharge (often covered by a grating) into a canal, river, lake, reservoir, sea or ocean. IV. ALTERNATIVE SEWER SYSTEMS

1. Vacuum Sewer System: Plastic pipe which is buried deep enough to prevent freezing and a vacuum is maintained.

2. Pressurized Sewer System: pressure sewers differ from conventional grav ity collection systems, because they use pumps instead of grav ity to transport wastewater. A prefabricated pressure sewer unit made out of plastic for outside placement.

V. PIPE NETWORKS Water distribution systems for municipalities Multiple sources and multiple sinks connected with an interconnected network of pipes. Computer solutions:

KYpipes WaterCAD

CyberNET EPANET

Water Distribution System Assumption: Each point in the system can only have one pressure The pressure change from 1 to 2 by path a must equal the pressure change from 1 to 2 by path b

(1) Lhzg

Vpz

g

Vp 2

2

221

2

11

22

(2) a

aa

Lhzg

Vz

g

Vpp 2

2

2

1

2

112

22

***Applicable for path a and b

Pressure change in path a:

Thus,

ba LL hh Or sum of head loss around loop is zero.

Pipe diameters are constant or K.E. is small Model withdrawals as occurring at nodes so V is constant between nodes

1. Find discharge given pressure at A and B - Energy & Swamee-Jain equation - Add flows

2. Find head loss given the total flow

- Assume a discharge Q1’ through pipe 1 - Solve for head loss using the assumed discharge - Using the calculated head loss to find Q2’ - Assume that the actual flow is div ided in the same proportion as the

assumed flow

3. Mass conservation at all nodes 4. The relationship between head loss and discharge must be maintained for each pipe

a. Darcy-Weisbach equation i. Swamee-Jain

Network Analysis Sample Problem: Find the flows in the loop given the inflows and outflows. The pipes are all 25 cm cast iron (e=0.26 mm).

1. Assign a flow to each pipe link Note: Flow into each junction must equal flow out of the

junction

2. Calculate head loss in each pipe

2

25

8Q

gD

fLh f

where f=0.02 for Re>200000

Thus,

mh

mh

mh

mh

mh

i

f

f

f

f

f

i53.31

00.0

39.3

222.0

7.34

4

1

4

3

2

1

3. Compute for k (coefficient)

Sign Convention: +counter clockwise

Thus;

k1,k3=339 k2,k4=169

The head loss around the loop isn’t zero

Need to change the flow around the loop - the clockwise flow is too great (head loss is positive) - reduce the clockwise flow to reduce the head loss

Solution techniques - Hardy Cross loop-balancing optimizes correction - Use a numeric solver (Solver in Excel) to find a change in flow that will give zero

head loss around the loop - Use Network Analysis software (EPANET)

Using Numeric Solver:

1. Set up a spreadsheet as shown below.

2. The numbers in bold(red) were entered, the other cells are calculations initially Q is 0

3. Use “solver” to set the sum of the head loss to 0 by changing Q the column Q0+ Q contains the correct flows

∆Q 0.000

pipe f L D k Q0 Q0+∆Q hf

P1 0.02 200 0.25 339 0.32 0.320 34.69

P2 0.02 100 0.25 169 0.04 0.040 0.27

P3 0.02 200 0.25 339 -0.1 -0.100 -3.39

P4 0.02 100 0.25 169 0 0.000 0.00

31.575Sum Head Loss

*** Better solution is software with a GUI showing the pipe network. VI. COMPONENTS OF A PIPE NETWORK 1. Controls:

Check valve (CV): Valve only allows flow in one direction. The valve automatically closes when flow begins to reverse

Pressure relief valve: Valve will begin to open when pressure in the pipeline exceeds a set pressure (determined by force on the spring). It is used Where high pressure could cause an explosion (boilers, water heaters, …)

Pressure regulating valve (PRV): Valve will begin to open when the pressure downstream is less than the set point pressure (determined by the force of the spring). Similar function to pressure break tank

Pressure sustaining valve (PSV): Valve will begin to open when the pressure upstream is greater than the set point pressure (determined by the force of the spring).

Flow control valve (FCV): Limits the flow rate through the valve to a specified value, in a specified direction. Commonly used to limit the maximum flow to a value that will not adversely affect the prov ider’s system

2. Pumps: need a relationship between flow and head 3. Reservoirs: infinite source, elevation is not affected by demand 4. Tanks: specific geometry , mass conservation applies GROUP 7 & 8 – WATER SUPPLY Chapter 11 WASTEWATER AND WASTEWATER TREATMENT

I. Characteristic of Wastewater II. Sewage Disposal

III. Primary Treatment I. CHARACTERISTICS OF WASTEWATER

Type Of Wastewater Source Gray water Washing waster form kitchen, bathroom, &laundry Black water Water from flush toilet

Yellow water Urine from separated toilets and urinals

Brown water Black water without urine Physical Characteristics of Water

Odor: is produced by gas production due to the decomposition of organic matter or by substances added to the wastewater. Odor is measured by special instruments such as the

Portable H₂S meter which is used for measuring the concentration of hydrogen sulphide. Temperature: Temperature of wastewater is commonly higher than that of water supply .

Depending on the geographic location the mean annual temperature varies in the range of 10 to 21ᵒC with an average of 16ᵒC

Density: Almost the same density of water when the wastewater doesn't include significant amount of industrial waste.

Color: Fresh waste water------- light brownish gray. With time -------------------------dark gray More time-------------------------- black (septic). Sometimes pink due to algae or due to industrial colors.

Types of Solids in a Sewage:

Total Solids (TS): All the matter that remains as residue upon evaporation at 103ᵒC to 105ᵒC.

Settleable Solids: Settleable solids are measured as ml/L, which is an approx imate measure of the sludge that can be removed by primary sedimentation.

Volatile Solids- solids ignitable at 550ᵒC Non Volatile Solids or Ash- residue following ignition

Chemical Characteristics of Water:

Inorganic chemicals 1. Nitrogen- can deplete dissolved oxygen in receiv ing waters, stimulate aquatic

plant growth, exhibit tox icity toward aquatic life, present a public health hazard, and affect the suitability of wastewater for reuse purposes

2. Phosphorus- Its presence causes many water quality problems including increased purification costs, decreased recreational and conservation value of an impoundments, loss of livestock and the possible lethal effect of algal tox ins on drinking water.

3. Toxic inorganic compunds (copper, lead, silver, chromium, arsenic, boron) 4. Heavy metals (Nickels, Mn, Lead, chromium, cadmium, zinc, copper, iron

mercury)

Organic matter- is derived from animals & plants and man activ ities. 1. Proteins 2. Carbohydrates 3. Fats, Oils, and Grease

Measurement of Organic Matter in Wastewater:

1. Biochemical Oxygen Demand (BOD): BOD₅ is the oxygen equivalent of organic matter. It is determined by measuring the dissolved oxygen used by microorganisms during the biochemical ox idation of organic matter in 5 days at 20ᵒC

2. Chemical Oxygen Demand (COD): It is the oxygen equivalent of organic matter. It is determined by measuring the dissolved oxygen used during the chemical ox idation of organic matter in 3hours. The Chemical Oxygen Demand (COD) test is commonly used to indirectly measure the amount of organic compounds in water. Most applications of COD determine the amount of

organic pollutants found in surface water (e.g. lakes and rivers) or wastewater, making COD a useful measure of water quality . It is expressed in milligrams per liter (mg/L) also referred to as ppm (parts per million), which indicates the mass of oxygen consumed per liter of solution.

3. Total organic carbon (TOC) is the amount of carbon bound in an organic compound and is often used as a non-specific indicator of water quality or cleanliness of pharmaceutical manufacturing equipment.

Total Carbon (TC) – all the carbon in the sample, including both inorganic and organic carbon

Total Inorganic Carbon (TIC) – often referred to as inorganic carbon (IC), carbonate, bicarbonate, and dissolved carbon diox ide (CO2).

Total Organic Carbon (TOC) – material derived from decaying vegetation, bacterial growth, and metabolic activ ities of liv ing organisms or chemicals.

Non-Purgeable Organic Carbon (NPOC) – commonly referred to as TOC; organic carbon remaining in an acidified sample after purging the sample with gas.

Purgeable (volatile) Organic Carbon (VOC) – organic carbon that has been removed from a neutral, or acidified sample by purging with an inert gas. These are the same compounds referred to as Volatile Organic Compounds (VOC) and usually determined by Purge and Trap Gas Chromatography.

Dissolved Organic Carbon (DOC) – organic carbon remaining in a sample after filtering the sample, typically using a 0.45 micrometer filter.

Suspended Organic Carbon – also called particulate organic carbon (POC); the carbon in particulate form that is too large to pass through a filter.

Microbiology of Wastewater:

By its nature, domestic wastewater contains quantities of micro organisms. Depending on its

age and the quantity of dilution water, bacterial counts in raw sewage may expected to range from

500,000 to 5,000,000 per ml.

1. Bacteria – are single-celled plants which metabolize soluble food and reproduce by binary fission.

2. Anaerobic Organism - An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It may react negatively or even die if oxygen is present. An anaerobic organism may be unicellular or multicellular

Obligate anaerobes, which are harmed by the presence of oxygen.

Aerotolerant organisms, which cannot use oxygen for growth, but tolerate its presence.

Facultative anaerobes, which can grow without oxygen but use oxygen if it is present.

3. Aerobic or aerobe organism - is an organism that can surv ive and grow in an oxygenated environment.

Obligate aerobes need oxygen to grow.

Facultative aerobes use oxygen if it is available, but also have anaerobic methods of energy production.

Microaerophiles require oxygen for energy production, but are harmed by atmospheric concentrations of oxygen (21% O2).

Aerotolerant anaerobes do not use oxygen but are not harmed by it. Sampling for Microorganisms in Wastewater/Water:

1. Grab Sample: Is simply a portion of the flow removed in a manner which will enhance the probability that it is representative of the flow at instant it is taken. It can be taken from discharge pump, be manually dipped from the flow or automatically dipped.

2. Composite Sample: Is a mixture of grab samples taken over a period of time, with the volume of indiv idual samples usually being proportional to the flow at the time the sample is taken. It can be obtained by manually or automatically

3. Continuous Sample: Represents diversion of a small fraction of the total flow over some period of time. Continuous samplers are most suitable for instrumental measurements which can be performed v irtually , such as temperature, dissolved oxygen, pH, etc.

Typical Sewage Characteristics

PARAMETER WEAK MEDIUM STRONG

Total suspended solids 100 200 350

Volatile suspended solids 75 135 210 BOD 100 200 400

COD 175 300 600 TOC 100 200 400 Ammonia-N 5 10 20

Organic 8 20 40 PO4-P 7 10 20

II. SEWAGE DISPOSAL Kinds of Disposal of Sewage:

1. Reuse 2. Discharge to surface waters 3. By injection or percolation to groundwater 4. By evaporation to the atmosphere

Reducing the Negative Effects of Discharging Sewage in Bodies of Water:

1. Self-Purification: results from a variety of physical, chemical and biological phenomena. 2. Dilution: greatly reduces the impact of all contaminants and is the only mechanism by which

the concentration of some chemical species is naturally reduced. 3. Currents: assist in dispersion of the waste in the receiv ing water, thus reducing the likelihood

of locally high concentrations of pollutants. 4. Sedimentation: results from differences in density between solid pollutants and the water

which carriers them. 5. Bottom Deposits and Non-point-source runoff: prov ide diffuse sources of contaminants

which can cause water quality degradation. 6. Sunlight: acts as disinfectant and stimulates the growth of algae. 7. Temperature: affects the solubility of oxygen in water, the rate of bacterial activ ity , the rate

at which gases are transferred to and from the water. III. PRIMARY WASTEWATER TREATMENT Primary Treatment: is removal of floating and settleable solids through sedimentation Typical materials that are remove during Primary Treatment include:

• Fats, oil and grease ( FOG ) • Sand , Gravel and Rocks ( GRIT ) • Larger settleable Solids including human waste

• Floating materials Sedimentation: is the separation from water, by grav itational settling, of suspended particles that are heavier than water

Objective of Sedimentation:

To Remove coarse dispersed phase

It reduce heavy sediment load before treating water for other purposes.

To settle the sludge Primary Clarifiers: reduce the content of suspended solids and pollutants embedded in those suspended solids. Zones in the Clarifier:

Inlet zone: is a region where the incoming suspension is distributed uniformly over the cross-section of the tank.

Settling zone: the particles settle at the same rate as they would in a quiescent.

Outlet zone: the clarified liquid is collected uniformly over the cross-section of the basin. The solids collect in a sludge zone at the bottom of the tank.

Types of Clarifiers:

A. Rectangular Clarifier: has high tolerance to shock overload ; has a predictable performance; Cost effectiveness due to lower construction cost; Lower maintenance; 35 to 200 ft. ( width ) and 6 to 19 ft. ( depth )

B. Circular Clarifier: 15 to 300 ft. ( diameter ) and 6 to 16 ft. ( depth ) Chemical Coagulation: is the process in which certain chemical agent is mixed with water then colloidal and suspended particles are agglomerated and form insoluble metal hydrox ide known as flocks.

Sedimentation alone is not sufficient o remove all the suspended matter. The process of coagulation is used to remove colloidal particles from water. Colloidal particles which are fine particles of size finer than 0.0001 mm carry electric charges on them. Jar Tests: is a laboratory procedure to determine the optimum pH and the optimum coagulant dose. A jar test simulates the coagulation and flocculation processes