Granular media filters are at the heart of many water treatment plants and often the final barrier for particle removal. Although water treatment plants may vary in size and complexity, all granular media filters require backwash to recover the filter media after producing a batch of water. Filter Operators typically monitor and trend filter effluent quality and filter capacity. These two items are used by the Operator to determine if a filter is working well or not. To ensure efficient, sustained filter performance a third item should be added. The third item is monitoring and trending the backwash pressure. Unchecked, the backwash pressure across the filter can increase until the filter underdrain system becomes over-pressured and eventually fails. Even with a substantially plugged filter underdrain, the filter effluent quality and filter capacity may remain acceptable. Acceptable, until the filter underdrain fails! While a UFRV decrease or a filter effluent turbidity spike are readily noticeable, gradually increasing backwash pressure is silent.
