Extended terminal subfluidization wash (ETSW) is an advanced backwash technique developed
to reduce the passage of particles thru conventional filters during the ripening period after
backwash. This technique was investigated on two source waters at the pilot scale under different
coagulation conditions to represent a wide range of full scale operations based on turbidity and
TOC: optimal coagulation (enhanced), sub-optimal coagulation, and sub-optimal coagulation
with a low dose of chlorine at the rapid mix. All filters were monitored for ripening peak
turbidity, recovery time (time to a less than 0.1 NTU), and total particle counts. In all coagulation
scenarios, the effluent water quality during the ripening period improved with the filters that
utilized the ETSW technique compared to the regular backwash alone. ETSW filters for the first scenario
had ripening peaks less than 0.1 NTU, thus eliminating the recovery time. Suboptimal
coagulation increased the ripening peak turbidities, primarily after the first filter volume of
effluent had passed. In addition, a sub-optimal coagulation chlorination study with either a low
pre-chlorination dose, or chlorination prior to the filter (with no other preoxidation) yielded an
approximate one log reduction in steady state filter effluent particle counts compared to filters
treating water with no oxidant addition. There was no observable effect on effluent turbidity with
or without chlorination under sub-optimal conditions. Includes 11 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 18 |
| Published : | 11/15/2004 |
