Sloped biofilter for additional wastewater treatment

Abstract

There arc a lot of wastewater treatment systems (for small settlements, stormwater) in Lithuania, where the last stage of treatment are ponds. The paper presents a biofilter which is constructed on the bank of the pond. Rooted macrophites are planted on the bank. As biofilter's bed a layer of washed sand (fraction 0.5-5.0 mm) is used. A height of filtering layer is 0.7-0.8 meters. Under the filter body a drainage system is constructed. On the outlet line some arrangement for level maintenance and flow regulation are equipped. The biofilter is operating under conditions of intermittent flooding and changing direction of filtering. Aveage hydraulic load of the filter is 0.3-0.4 cubic meters/sq. meters per hour. Average effeciveness of the filter is 80% by suspended solids, 66% by oil products and 70% by BDS-5.