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