Enhanced Primary Treatment in Floating Filters

摘要

Experiments were carried out on the use of a floating filter for primary treatment of municipal wastewater. The floating filter used is based on up-flow filtration through a randomly packed filter-bed consisting of plastic biofilm carriers that are normally used in the Kaldnes moving bed biofilm process. It was demonstrated that, because of the high porosity of the filter bed, head-loss was low, resulting in long filter runs and high sludge accumulation capacities. The SS-removal efficiency experienced was in the range of 75-85percent at a filtration rate in the range of 5-15m/h, making this concept a very interesting one for primary treatment. The key design parameter was found to be the sludge loading rate (kgSS/m~2h). At a typical filter depth of 1 m, a filter run time of 5 hrs was experienced at a surface loading of 2 kgSs/m~2h while doubling the filter run time required cutting the sludge surface loading in half. Pre-coagulation with cationic polymer, possibly in combination with a low metal-coagulant dose, did not significantly improve performance.