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The purpose of this research subteam is was to develop a sustainable backwash system for granular filtration, which will be incorporated into the AguaClara water treatment process. The backwash system must meet the following requirements:

• When incorporated with the current AguaClara water treatment process, the granular filtration with the clear well backwash system must consistently meet the target effluent goal of 1 NTU or lower.
• Operate without electricity.
• Construction material must be relatively cheap cost-effective and readily available in Honduras.
• Operation costs must be minimal.
• The filtration and backwash system design must be simple in order to facilitate operation and maintenance as much as possible.
• The filtration and backwash system must be open so that easily accessible to the operator so they can easily observe the workings of the system (we assumed this to mean not pressurized).

The clear well design meets these objectives because it is a gravity run system that has water flow from the sedimentation tank through the gravity sand filter and then up into the clear well all by head loss differences. Once the clear well is filled, the water produced is sent to a storage tank to be distributed to the population.

A clear well is simply a large shallow tank that is utilized to clean the filter. When the filter becomes dirty, the flow to the filter is stopped and the clear well water flows back into the filter, elevating the sand particles and washing the dirt out of the filter. Back wash is designed to take about 10 minutes. Once this is completed, flow through the filter is continued and the clear well is filled back up.

Concept of Operation

Basic Operation

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