Applying backwash water in order to enhance removal of iron and ammonia from spent filters with fresh filter media

Abstract

In this paper, an enhanced catalytic layer formation for the removal of iron and ammonium without a start up stage - via filtration process was investigated. Tests were made to establish the influence of backwash water on the filter efficiency and the dose of this backwash water to make new filters more efficient. Also its influence on the filtration rate and feed water quality in the fresh filter media and the final water quality was shown. The most common quartz sand-filter media (0.7-2.0 mm coarse-sized sand particles) used at Lithuanian water works were tested in a pilot test-bench constructed for this research in the laboratory in the Water Management Department of Vilnius Gediminas Technical University. In the process tested, fresh backwash water added to the filter media was used as the catalyzing layer and proved to be more efficient in the removal of iron and ammonium from the ground water and in the reduction of the filter media at the start up stage than conventional filter start up procedure. When filtration was carried out at a low filtration rate (3-5 m/h) the results were better compared with those obtained at a higher rate in conventional filtration.