Filter backwashing: When and how
Backwashing filters is a necessary and important part of the filtration process. Many operating problems associated with the filtration process can be traced to delayed or inadequate backwashing. Producing a high-quality and low turbidity filtered water depends on having clean media free of cracks and mudballs. The Interim Enhanced Surface Water Treatment Rule, promulgated on Dec.16, 1998, lowers the required filtered water turbidity from 0.5 to 0.3 ntu and requires monitoring of individual filters. Achieving a filtered water turbidity of 0.1 ntu is also a prudent goal to prepare form compliance with the Long Term 1 (LT1) and LT2 ESWTR. As filtration is pushed toward the lower limits of turbidity measurements, excellent filter operations with the proper backwashing techniques will be required.