Plant Visit Pba penang(y.suntheren,usm)

INTRODUCTION

Located on a 13 hectare site in Seberang Perai, the Sungai Dua Water Treatment Plant is the most important water treatment plant in the State of Penang. As at 2004, about 80% of the total volume of treated water supplied throughout the State comes from this plant. Phase 1 of the Sungai Dua Treatment Plant was commissioned in 1973, with an initial design capacity of 159 million litres a day (MLD). Following various upgrades and the completion of Phase 2 in 1992, the plant’s maximum design capacity has been increased to 772 (MLD). The plant’s primary source of raw water is the Muda River. However, during dry seasons, the plant also draws water from the Mengkuang Dam, the largest dam in the State. As Penang’s flagship treatment plant, the Sungai Dua Treatment Plant also serves as the control center for PBAPP’s “on-line” supervisory control and data acquisition (SCADA) system [link to ‘Quality Control], which facilitates remote operation.

The Sungai Dua Water Treatment Plant is being further upgraded to meet future water supply needs. Phase 3 of its development involves the construction and commissioning of a new dissolved air flotation (DAF) plant to boost the total design capability to 886 MLD. The DAF plant is operating now with a less capacity but with a better quality of water . As at 31

December 2003, about 80% of the raw water treated by PBAPP for use in the State of Penang is sourced from the Muda River on the mainland. The raw water from Muda River is treated at PBAPP’s main water treatment plant – the Sungai Dua Treatment Plant. The water treatment process in the Sungai Dua Treatment Plant, and in all other PBAPP plants, is similar to the majority of water treatment facilities worldwide, including those in advanced nations. The quality of PBAPP’s treated water complies with the 94 guideline values set by the World Health Organisation (WHO), as well as 120 parameters set by the Ministry of Health, Malaysia (MOH).

Below is the water treatment process involved in the plant :-

Penang State Water Supply Statistics

Total land area of the State of Penang 1,031sq km

Water catchment area 61.4 sq km

Population (2003 estimate) 1.3 million

No. of PBAPP registered water consumers 402,777

Main source of raw water Muda River(80%)

No. of dams 6

Total raw water storage capacity 46,013 million litres

No. of treatment plants 10

Design capacity of treatment plants 1,166 million litres

No. of treated water reservoirs 50

No. of treated water towers 30

Volume of treated water supplied daily 759 million litres

Total daily water consumption 612 million litres

Percentage of non-revenue water (NRW) 20%

Total length of mains and pipelines (100mm in diameter and above) 3,407km

Supply coverage

100% in urban areas

99% in rural areas

Domestic water tariff (1st 35,000 litres) RM0.22 per 1,000 litres

Trade water tariff (1st 500,000 litres) RM0.94 per 1,000 litres

PURPOSE / OBJECTIVE :-

The objective of this visit is to gain practical and hands on knowledge on the water treatment system in a plant.The objective also is to learn the sequence of the treatment process and to create a awareness on water conservation.

ACTIVITY

Firstly, after we entered the plant, there was a presentation on the introduction about the water treatment plant and its history.Then the water treatment process which is conducted in the plant is explained from the start till the end.Then it is followed by a trip around the plant. First of all we visited the water treatment lab, where the monitoring and sampling of water quality process is done. To ensure that the quality of treated water in Penang continues to comply with World Health Organisation (WHO) guidelines and Ministry of Health parameters, officers conduct water quality sampling at 111 sampling points in Seberang Perai and 96 sampling points on Penang Island. The sampling points are at roadside mains and pipelines.The sampling rate of treated water in Penang was about 375 samples per month (4,500 samples per year) which is above the Ministry of Health’s requirement. The WHO’s recommended sampling rate, based on Penang’s population of 1.3 million people, is a minimum of 140 samples a month. Physical parameters such as pH, residual chlorine, turbidity (the measure of murkiness in water) and colour are examined onsite, as are bacteriological samples. All other key parameters are examined in a laboratory within 72 hours after collection.The physical parameters are tested by the lab technician every hour at the plant for 24 hours daily, and the parameters are recorded.

* International guideline values recommended by the World Health Organisation (WHO) 1993 / 1996 / 1998. In general, PBAPP’s treated water complies with WHO guideline values for harmful organisms, chemical substances and radioactive particles.

** National Standard for Drinking Water Quality (revised December 2000) set by the Engineering Services Division, Ministry of Health, Malaysia, based on WHO guideline values.

*** Measured in parts per million (p.p.m.), values should ideally be less than guideline value.

# Singapore water rates are further subject to a water conservation tax of 30% of tariff and a water- borne fee of 30 Singapore cents per 1,000 litres.

Note: Statistics on water quality in other Asian cities are derived from data posted by each city’s respective water supply organisation. (n.a. denotes data which is not available).

Then we move on with our trip to the plant itself at the water treatment area where the raw water is treated till to the user, first we look at the typical or called the conventional water treatment plant.Below are the schematic diagram of the plant :-

The summarised explanation of the process involved at the conventional water treatment plant :-

Intake

The intake screens prevent debris from entering the treatment facility. The screens are located off the bottom of the river to avoid bringing sediments into the treatment plant and below the surface to avoid bringing oils or other floating material into the treatment plant.

Aeration

Aeration process involves bringing air to contact with water to transfer volatile substances from the liquid to the gaseous phase, thus increase the dissolved air in water. It will improve taste and odor and also oxidize iron and manganese.

Coagulation and Flocculation

Chemical coagulants are added to react with the remaining small particles in the water to form particles large enough to settle out. Rapid mixing distributes the coagulant evenly throughout the water. While, flocculation basins gently mix the water with large submerged paddles so smaller particles collide to form large particles called "floc".

Sedimentation

Sedimentation is physical treatment process that utilizes gravity to separated suspended solid from water. Floc settles by gravity to the bottom of a sedimentation basin. Then, clean water spills over to the filters.

Filtration

Filtration removes any remaining particles that carried over after sedimentation. The force of gravity moves the water through filter media usually, sand.

Disinfection

Chlorine adds to prevent bacterial contamination as the treated water flows through the distribution system to customers.

Fluoridation

Addition of fluoride to prevent dental caries and tooth decay

PH Correction

Adjusted pH to be 7.0 at the outlet of contact tank by adding lime.

Then we visited the DAF(dissolved air flocculation) plant. The principle of floatation is based on the transfer of particles to the surface of a liquid through attachment of micro bubbles to the particle surfaces. This principle is opposite to the sedimentation process whereby the unwanted particles or flocs in the latter settle to the bottom of the tank and clarified water is collected at the top to undergo further filtration stage. In the DAF system, size of the micro-bubbles is best maintained at 50 micrometer (microns) in order to increase the contact surface area with the flocs and therefore increase the solid separation efficiency. The particles are then removed as a floating sludge by mechanical skimming units (scrappers), continuously into the Sludge Treatment Plant.

The advantages of the DAF treatment plant is as below :-

Reduced chemical coagulant requirements

In this system, formation of a large settling floc is not required. Small size of flocs would easily attached to the micro-bubbles and float to the surface. With raw water abstracted directly from muda river is at very low turbidity level between <50 NTU, the floc formed is very fluffy. In fact, the coagulant (liquid alum) dosage applied in the plant is slightly lower (within 9 – 14 mg/L) as compared to conventional clarification (18 – 22 mg/L).

Small land area for installation

The required space for installation of DAF system can be minimized as a result of the plant operation at high surface loading rates (higher compared to sedimentation process).The average velocity in DAF stage is in about 10 m/hr as compared to 1 – 1.5 m/hr for the conventional type. Therefore, the shorter hydraulic retention time at the DAF system enables the process plant to be compact and suitable for a limited area.

Higher concentration of sludge solids

The micro-bubbles behave as hydrophobic solids that have more surface area to enhance the agglomeration of flocs in water and theoretically shall increase the total number and concentration of solids, to be discharged into the Sludge Treatment Facility.

Rapid stabilization of the system

Rapid stabilization of clarified water quality upon start-up because of the shorter detention times throughout the process. It takes less than 40 minutes to produce the required level of clarified water upon start-up of the system.

Removal efficiency of small suspended particles

This solid-liquid separating system is more effective in separating light and small suspended solids that can hardly be separated by ordinary air flotation or sedimentation. It was also reported that DAF is a more effective process as compared to a conventional sedimentation for treatment of water containing low-density particles such as algae. In terms of turbidity and iron removal efficiency, DAF is consistently able to remove almost 83% - 89% of the

contaminants. In fact, turbidity and iron in the water is almost completely removed after filtration process.The photo below shows the picture of DAF system in PBA :-

The picture shows the dissolved air which is in white colour is flowed throught the water and the floc is formed at the top of the water surface

The picture above shows the scrapper which is used to scrape the floc from the surface of the water.

The diagram below shows the DAF process :-

Then after the DAF plant we visited the SCADA(Online Supervisory Control and Data Acquisition) room. The SCADA system located in the Sungai Dua Water Treatment Plant facilitates remote operation as well as the following:

• 17 Real-time monitoring of the treatment plant performance

• 18 Real-time monitoring of water quality and distribution process

• 19 Trending of measured parameters (real-time and historical data)

• 20 Archiving historical data

• 21 Generating daily and monthly reports

Photo at the SCADA room

Then as the last visit at the plant we visited the clorine room and the alum mixing room. The picture below shows the alum tank and the chorine room at the plant

Finally our trip end about at 12.30 pm, which was started around 8.45 a.m.

LESSON LEARNT

By this trip we learnt about the process of water treatment and the ways of monitoring it.We also learn the important of water conservation

CONCLUTION

As a conclution, from this trip we learnt about the water treatment process which is mainly for daily use purposes. Where the raw water which is treated is from the river(sg muda) and there are two main treatment process involved in this plant ,which is the typical treatment process or called as the conventional process and also the DAF treatment processs.It is learnt that the DAF water treatment system produces more clear water then the typical treatment process in a sence of lower turbidity ntu count.