Introduction:
The World Health Organization said in a report on water sanitation, released to mark World Water Day, that more than one billion people drink unsafe water. Some 3.4 million people, mostly children, die every year from water-related diseases which include malaria, diarrhea and guinea worm. The World Bank estimates that exposure to water pollution and poor sanitation account for one-s
ixth of reported disease cases, and nearly 6,000 premature deaths per year in the Philippines. The cost of treatment and lost income from illness and death due to water pollution is pegged at PHP6.7 billion (US$134 million) per year (Philippine Environment Monitor 2006). Significant discrepancies between rural and urban services contribute to the burdened life in rural areas. Women and girls bear more of the consequences of poor water, sanitation and hygiene, as they are usually the ones who fetch the water and care for the children and other household members who fall sick from water-related diseases. In 2002, the United Nations Committee on Economic, Social and Cultural Rights recognized the right to water. The following criteria have been recognized, in that water must be:
1. Safe and acceptable
3. Accessible
4. Affordable
Through the Biosand Filter Training, Palawan Conservation Corps or PCC aimed to contribute in providing some of the necessary services to enable access to affordable technologies. In providing safer water, communities will have better health and better participation in the sustainable development activities. What is Biosand Water Filter?:
The purpose of constructing the Biosand filter is to enable the user to enjoy good quality water which should lead to better health. The PCC was able to acquire the technology thru a training organized by the A Single Drop for Safe Water (ASDSW) and Palawan NGO Network, Inc. (PNNI) in 2006. The Centre for Affordable Water and Sanitation Technology (CAWST), a Canadian organization, provided the technology reference manual and assisted during the said training in 2006. The Biosand filter is a concrete filter filled with specified amounts of gravel and different sized sand layers. Filters resemble a large concrete box with an estimated weight of 70 kilograms. Water is poured in the top of the filter and comes out through a spout on the filters side after passing four stages of filtration. The filter can make water up to 99% contaminant free when performing at optimum levels. When operating at peak levels, it should filter one liter of water per minute. Benefits of Biosand Water Filter:
• Easy to use and maintain.
• Affordable and lifetime use.
• Microbiological activity of the filter.
• Can provide contaminant free water for schools, rural areas and households.
• Possible income-generating project for the local people’s organization and NGOs. BIOSAND FILTER FACTSHEET
What is it? The BioSand filter works in the same way as traditional slow sand water filters, which have been used for centuries. The difference is that the BioSand filter is smaller, and water does not need to flow through it all the time. The filter can be built anywhere in the world because it is built using materials that are available. It is simply a concrete container, with layers of sand and gravel inside it. The sand and gravel remove dirt, bacteria, viruses and parasites and other impurities from the water. How does it work? Water is poured into the top of the filter whenever it is needed. There is a diffuser plate placed just above the sand bed that absorbs the shock of the falling water so it does not disturb the sand. Traveling slowly through the sand bed, the water then passes through several layers of gravel and collects in a pipe at the bottom of the filter. It is then pushed up through plastic piping that is encased in the concrete, and out of the filter, for the user to collect. How does it remove contaminants? As with all slow sand filters, the removal of pathogens happens in the BioSand filter through a combination of biological and mechanical processes. When water is poured into the top of the filter, the organic material it is carrying is trapped at the surface of the sand, forming a biological layer or 'schmutzdecke'. Over a period of one to three weeks, micro-organisms colonize the schmutzdecke, where they find food (the organic material) and oxygen supplied by the water. Four processes remove pathogens and other contaminants in this filter:
• Predation
• Natural death
• Adsorption
• Mechanical trapping
Predation
The schmutzdecke micro-organisms eat bacteria and other pathogens found in the water. Natural death
Pathogens die because there is not enough food and oxygen to sustain them all. Adsorption
Viruses are adsorbed (become attached) to the sand grains. Once attached, they are metabolized by the cells or are inactivated by antiviral chemicals produced by the organisms in the filter. Certain organic compounds are also adsorbed to the sand and therefore removed from the water. Mechanical trapping
Sediments, cysts and worms are removed from the water by becoming trapped in the spaces between the sand grains. The filter can also remove some inorganic compounds and metals from the water when they are precipitated into solid form. How effective is it? Slow sand filters have been shown to remove almost all the disease-causing organisms found in water. The BioSand filter has proven as effective as traditional slow sand filters, in both laboratory and field tests. The filter has been tested by various government, research, and health institutions, as well as by non-governmental agencies. Overall, these studies have shown that the BioSand filter removes:
• More than 90% of f***l coliform
• 100% of protozoa and helminths
• 50-90% of organic and inorganic toxicants
• up to 67% of iron and manganese
• most suspended sediments
How easy is it to use and maintain? Operation
Operating the filter is very simple: remove the lid, pour a bucket of water into the filter, and immediately collect the treated water in a container. The filter can produce up to 60 litres/hour of filtered water. The following design features of the BioSand filter make it easy to use:
1. The water needs to be filtered only as required.
2. The concrete BioSand filter has no moving parts.
3. The concrete container is small, but extremely stable. Therefore, it can be placed anywhere in the home, in the location most convenient to the user.
4. The plastic piping is encased in concrete and is not easily damaged. Between uses, a layer of water (5 cm deep) is maintained above the sand at all times. It is this design feature that distinguishes the BioSand filter from other slow sand filters and which allows for both small scale construction and for intermittent use. This layer of water is shallow enough that oxygen can diffuse through the whole layer therefore providing the biological layer with enough oxygen to develop. The biological layer typically takes one to two weeks to develop to maturity in a new filter. Removal efficiency and the effectiveness of the filter increase throughout this time. The filter removes more than 90% of bacteria, which means the quantity of bacteria left in the filtered water is often below the infectious dose. However, it is recommended for people with infants or elderly relatives that they use disinfection after filtering the water. Maintenance
Continued use of the filter causes the pore openings between the sand grains to become clogged with debris. As a result, the flow rate of water through the filter decreases. To clean the filter the surface of the sand must be agitated, thereby suspending captured material in the standing layer of water. The dirty water can then simply be removed using a small container. The process can be repeated as many times as necessary to regain the desired flow rate. After cleaning, a re-establishment of the biological layer takes place, quickly returning removal efficiency to its previous level. How much does it cost? Capital
The cost of a concrete filter has varied from US$ 15 to US$ 50 (P700-P2400), depending upon the country in which it is being manufactured and the amount of paid/volunteer labour available. Using concrete to build the container costs less for several reasons:
• Cement is readily available in most developing countries.
• People are familiar with the construction techniques used.
• Household labour or volunteer labour can be utilized in the manufacturing process.
• The concrete container is heavy and durable. It does not need to be replaced as often as a plastic container.
• The plastic piping is located inside the filter. Consequently, it is less prone to damage than a plastic filter, which has piping on its exterior. Operation
As consumables are not required for successful filter operation, the operating costs are negligible. Advantages and Limitations
Advantages
• Removes over 90% bacteria, 100% parasites
• Removes turbidity, some iron, manganese
• Quality of water improves with time
• Costs range from US$15-50.
• High flow rate - 60 litres/hour
• No on-going costs - no replaceable parts
• Durable & robust- lasts forever
• Fabricated from local materials
• Opportunity for local businesses
• Water tastes & looks good
• Easy to maintain
Limitations
• Heavy - difficult to move
• Biological layer takes 1-2 weeks to develop to maturity
• High turbidity (> 100 NTU) will cause filter to clog and require more maintenance
• Requires that the filter be used periodically on a regular basis
• Cannot remove color or dissolved compounds
