AWWA WQTC60701

Extended terminal subfluidization wash (ETSW) is an advanced backwash technique developedto reduce the passage of particles thru conventional filters during the ripening period afterbackwash. This technique was investigated on two source waters at the pilot scale under differentcoagulation conditions to represent a wide range of full scale operations based on turbidity andTOC: optimal coagulation (enhanced), sub-optimal coagulation, and sub-optimal coagulationwith a low dose of chlorine at the rapid mix. All filters were monitored for ripening peakturbidity, recovery time (time to a less than 0.1 NTU), and total particle counts. In all coagulationscenarios, the effluent water quality during the ripening period improved with the filters thatutilized the ETSW technique compared to the regular backwash alone. ETSW filters for the first scenariohad ripening peaks less than 0.1 NTU, thus eliminating the recovery time. Suboptimalcoagulation increased the ripening peak turbidities, primarily after the first filter volume ofeffluent had passed. In addition, a sub-optimal coagulation chlorination study with either a lowpre-chlorination dose, or chlorination prior to the filter (with no other preoxidation) yielded anapproximate one log reduction in steady state filter effluent particle counts compared to filterstreating water with no oxidant addition. There was no observable effect on effluent turbidity withor without chlorination under sub-optimal conditions. Includes 11 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/15/2004

Number of Pages:

18

File Size:

1 file , 1.9 MB