Start-up of trickling filters using novel filter medium under low temperature conditions

Abstract

Start-up of three pilot scale trickling filters (3.05 m in height and 0.6 m (1 TF), 0.8 m (2 TF) and 1.0 m (3 TF) in diameter) using the stone-wool substrate medium at low wastewater temperature (2.5–8.5 ºC) was investigated over a period of 123 days. The start-up of the trickling filters was performed without any special inoculation, only by feeding the raw wastewater to the trickling filters. Low temperature did not have an impact on the removal of SS and BOD7: the removal of these substances reached steady state in two weeks of operation, while nitrification was influenced by low temperature. Nitrification was first observed on day 90 of operation, the highest recorded value of nitrification efficiency was only 40.9% and the nitrification performance have not stabilized by day 123 of the experiment. Nevertheless, the further increase in nitrification is expected as the experiment is still continued. Throughout the experimental period the efficiency of SS removal was 96.9±2.4% in 2 TF and 97.5±1.9% in 3 TF with SS loading to the filters up to 1 kg SS/m3 of stone-wool medium/d. BOD7 removal efficiency was 94.3±4.0% in 2 TF and 94.9±3.3% in 3 TF with BOD7 loading to the filters up to 0.8 kg BOD7/m3 of stone-wool medium/d. SS and BOD7 removal efficiencies of 1 TF filter were 96.1±1.9% and 92.6±3.3% respectively until the clogging of the filter on day 90 of operation.