Water Treatment > Quality Water Solutions > Operational Issues > Backwash Water

A coagulation program can affect net production in terms of the amount of backwash water and treatment chemicals used, as well as the revenue lost in water that can't be sold. The old rule of thumb was to use less than 5% produced water for backwash or sludge withdrawal. As plants grow more efficient and newer coagulants lengthen filter runs and reduce sludge generation, less water is needed for backwash and sludge purposes.

The use of backwash water is an especially sensitive and costly issue in the West and wherever water is scarce. An evaluation of various coagulants at a large California utility shows how the coagulant effects water production and revenues. Two coagulants had comparable economics for dosages, turbidity, etc., but one had twice the filter run length and half the backwash use. The latter had total savings of more than $300,000/year after factoring in raw water purchased, chemical treatment of backwash, disposal of backwash, power for backwash, labor and lost revenue from backwash waste. The savings almost equaled the cost of the new coagulant.