...
• The operator needs to be able to observe the backwash process, so the filter media must be visible. This is likely to be impossible with pressure filters.
• The improvement in water quality from filtration is perceived by the community to be small compared to the improvement from the flocculation and sedimentation processes, so the filters need to be less expensive than the flocculation and sedimentation equipment.
• A large tank to hold water for backwashing is not economically feasible.
• The distribution tank is not a viable source of water for backwashing because it is impossible to guarantee that there will be enough water in the distribution tank.
• Many of the communities that will be using our water treatment plants do not have enough water to meet their needs, so the quantity of water that is wasted to clean the filters must be minimized. Stacked filtration and foam filtration may be good options for achieving this.
• If we can't cannot use stored water for backwash, then the maximum flow of water required for backwash must be at most 50% of the design plant flow rate. This will make it possible to run the water treatment plant at a lower than design flow rate and still be able to operate the filters. This requirement means that if we use 7 filters to backwash 1 filter, then we would need to have another set of 8 filters that could potentially be turned off so that plant could function at 50% of design flow capacity. The requirement of being able to backwash at 50% of design flow rate makes the option of using multiple filters to backwash a filter impractical.
• All of the basic principles of AguaClara apply to the filtration research. These include not using electricity, using inexpensive and easily obtainable materials, and training the community members how to build, operate, and maintain the plants.
...