Recent Advances in Small-Scale and Household Water Treatment Systems to Prevent Infection Leuis Choi Bikram Brar Fathima Arrafih
Dec 17, 2015
Recent Advances in Small-Scale and Household Water
Treatment Systems
to Prevent Infection
Leuis ChoiBikram Brar
Fathima Arrafih
Where do we get water?
The problemGroundwater often originates as industrial waste
runoffs Contain fecal matter and organisms:
Bacteria, viruses, etc…
Contain toxins and trace elements: Arsenic, cadmium, lead, etc…
Water can house many diseases: Diarrhea Cholera Typhoid fever Hepatitis A The list goes on…
Water Contaminants:Chemical Contaminants Iron/Manganese
– Heavy concentrations have unpleasant taste, result in brownish colour
Nitrites & Nitrates Associated with methaomoglobinameia, leads to
cyanosis
Flouride High levels lead to mottling of teeth and
skeletal flourosis
Arsenic High levels can lead to skin lesions
and higher risk of cancer
Water Contaminants:Biological Contaminants Faecal-borne Pathogens
– Transmitted by water and pass through via faecal-oral route
Parasitic Worms Transmit their eggs to humans via drinking water
(ex. Roundworms, Flatworms, Guinea worms)
Legionella Bacteria Infection happens via inhalation of mist/spray
Causes Legionnaires disease (can lead to pneumonia)
Cyanobacteria Produce cyanotoxins that have various effects
Water Contaminants:Physical Contaminants Particles Suspended Soils Varies seasonally
The problem1.1 billion people lack a safe water supply
Groundwater is main source of supply in many countries
Developing countries are most at risk Many areas lack water treatment plants & facilities
Peri-Urban Areas: Mixtures of land uses Limited Infrastructure
Majority with no access to:
Adequate Water Supply Sanitation Facilities
Peri-Urban Areas: Wastewater Production, Disposal and Re-use
Wastewater disposal problems caused by: Increasing populations Increasing water consumption Proliferation of waterborne sanitation
Peri-Urban Areas: Wastewater Production, Disposal and Re-use
Wastewater Discharged locally onto vacant plots
Creates pondsof foul-smellingstagnant water
Peri-Urban Areas: Wastewater Production, Disposal and Re-use
Wastewater Discharged locally onto vacant plots
Creates pondsof foul-smellingstagnant water
Children/othersmay contactpolluted water
Centralized Wastewater Management: Problems for Peri-Urban Areas
Development requires unaffordable investments
Poor at reaching Peri-Urban areas Not responsive to local needs
Why? Lower population densities Distance from centralized disposal systems
Decentralized Wastewater Management: Wastewater re-use Resource recovery Improved local environmental health
conditions
Advantages Cost effective: Cheaper to construct and
operate Long term Meet public health & water quality goals
Decentralized Wastewater Management: Conventional treatment processes difficult:
High maintinence and operation Require carefull skill and attendance
Use Alternative technologies
Possible Solution:Household Water Treatment Methods
Sedimentation
Filtration
Anaerobic Treatments
Disinfection & Sterilization
SedimentationLet water stand still for a dayThen pour into another container
(leaving sediment behind)
Repeat 2-3 times
SedimentationCoagulants can help speed process
Materials that help sand or clay clump
Natural Coagulants: moringa seeds, prickly pear cactus
Chemical Coagulants: Aluminum Sulphate, polyaluminum chloride, and iron salts
SedimentationPros:
Very simple, very easy, and no cost
Cons:Takes a very long timeDoes not eliminate microscopic contaminants (chlorella, microbes)
FiltrationSlow Sand Filters
Protects the water source Implements both Sedimentation & Filtration Provides clean storage
Pros:Can remove bacteria, algae, and fungiCan be constructed from an oil drumMaterial needed is sand and gravel
Cons:Needs regular maintenanceMay still need to disinfect water after use
FiltrationBio-Sand Filters
Different from slow-sand filter Drain is piped 1-8cm above the sand to create a biofilm
FiltrationBio-Sand Filters
Protects the water sourceImplements both Sedimentation &
FiltrationProvides clean storage
Shown to remove: 90% of faecal coliform 100% of protozoa and helminthes 95-99% of zinc, copper, cadmium, lead 76-91% of arsenic
FiltrationBio-Sand Filters
Can be constructed locally due to use of common materials Sand Gravel Oil drum
or Concrete mould*
*Concrete mould ismore durablebut more expensive
FiltrationBio-Sand Filters
Pros:Provides 30-60L of water per hour
Constructed from local materials
High contaminant removal
Durable
FiltrationBio-Sand Filters
Cons:Not 100% effective in microbial removal
May require post-disinfection
Costs > US$20Additional cost for education and training
Heavy = Limited mobility
Anaerobic Treatment Treatment of faecal sludge
Pros: Requires less land area Produces well stabilized sludge in smaller
quantities Cheap Not dependant on external power source
Anaerobic TreatmentSeptic Tank Settles suspended solids Anaerobic digestion of settled solids
Pros: Can remove 60% of organic load from
sewage
Cons Little pathogen reduction
Waste Stabilization Ponds Anaerobic ponds/ Faculative ponds/ Aerobic
ponds
Pros: Simplicity Long Retention time Economic benefits Resource for irrigationCons: Require large land area
Disinfection & SterilizationChlorination
• Chlorine is an oxidising agent that disinfects water.
• Today, chlorination is used totreat most of drinking water in the world since it is easy, inexpensive and reliable.
Disinfection & SterilizationChlorination
• Chlorination can be achieved by using liquefied chlorine gas, sodium hypochlorite solution or calcium hypochlorite granules and on-site chlorine generators (e.g. WATA).
• Added at doses of one to several drops as a solution per litre of water to treat, or as tablets.
Disinfection & SterilizationChlorination
• When chlorine is added to water, the chemical element dissolves and forms radicals. These kill pathogens such as bacteria and viruses by breaking the chemical bonds in their molecules or by attacking the cells of the microorganisms.
• It is most effective at treating bacteria but may not treat certain types of protozoa.
Disinfection & SterilizationChlorination oPros:• Simple, inexpensive and reliable technique• Effectively kills bacteria and viruses• Provides residual chlorine for some
protection against re-contamination• Widely available in different countries• Easy to use
Disinfection & SterilizationChlorination oCons:• Requires that users purchase chlorine on a
continuous basis and may not affordable by very poor people
• Not so affective in fighting pathogenic parasites like Giardia, Cryptosporidium and Helminth eggs.
• Has a distinct taste - not to everyone’s liking.• Requires clear water to be most effective• Skilled application is necessary since chlorine is
a corrosive substance.
Disinfection & SterilizationSODIS
Uses the sun’s radiation (specifically UV-A rays and heat) to destroy pathogenic micro organisms
Disinfection & SterilizationSODIS – How it is Done?
Check for bright weather
Wash the bottle well the first time you use it.
Collect plastic PET (Poly Ethylene Terephthalate) bottles and fill up the bottles with water.
Check if the screw cap is water tight and clean.
Bottles should be laid out on a suitable heat-reflecting surface – roofing sheets, in a clear spot on the roof or garden. The bottles should be exposed to direct sunlight for at least six hours.
Disinfection & SterilizationSODIS – How to make it more efficient?
Putting black paint on half of the outer surface
Placing the bottles on a reflective surface-aluminium foil or creating a solar collector.
Filling the bottles 75% first and shaking the bottle for 20 seconds
Bottles should be placed horizontally and not upright
Disinfection & SterilizationSODIS
Shown to remove:Bacteria :Escherichia coli, Vibrio cholerae,
Streptococcus faecalis, Pseudomonas aerugenosa, Shigella flexineri, Salmonella typhii, Salmonella enteritidis, Salmonella paratyphiSalmonella species
Viruses : Bacteriophage f2, Rotavirus, encephalomyocarditis virus
Yeast and molds: Aspergillus niger, Aspergillus flavius, Candida, Geotrichum
Disinfection & SterilizationSODIS
Pros:Simple and easily applicable
Low-cost
Sustainable
Laboratory and field tests have shown that SODIS is 99.9% effective against pathogenic
micro-organisms found in water.
Disinfection & SterilizationSODIS
Cons:Care must be taken in the case of
consumption by infants (less than 18 months), very sick children or adults, malnourished children and those suffering from reduced immunity (such as AIDS).
Weather dependency
A large quantity of water cannot be heated up through this process.
Constraints on Replication and Wide Scale Implementation:Lack of Management Expertise: Even after acceptance by policy makers... Lack of capacity to:
Plan Design Implement Operate
Constraints on Replication and Wide Scale Implementation:Economic Constraints: Local government agencies lack resources
to invest
Social Constraints: No real demand for effective wastewater
management Little willingness to pay for services May relate to lack of concern / awareness
of environmental pollution / health implications