Abstract
Abstract:
Practical experience shows that water treatment filters develop problems over time due to the
routine running of the filter, including backwashing. There are difficulties in maintaining
filters in good condition, given the eutrophic state of many South African raw waters, high
water temperatures and the development of difficult-to-remove biofilm as a result. Such
difficulties are often related to deposits accumulated on the filter media and it is, therefore,
expected that the backwash system should be good enough to ensure that the filter is kept
clean in the long run. This paper deals with a fairly simple operational option to significantly
improve backwash efficiency at treatment plants where air and water are used consecutively.
The paper describes methods used and typical results obtained in the testing of the
quantitative benefits of multiple wash cycles. Multiple washing shows great promise for
improving backwash efficiency, with an average of an additional 40% to 50% of the solids
that would have been washed out with a single wash, removed by a second wash.
Furthermore, third and even fourth washes continue to remove additional dirt from the filter.
Multiple washing, therefore, may be a useful tool for the effective rehabilitation of a filter, as
well as for routine operation procedures.