Lipase Activities in Activated Sludge and Scum – Comparison of New and Conventional Techniques

Abstract

AbstractLipase activities in activated sludge and scum were determined by both conventional in vitro methods and in situ measurements using the ELF (enzyme labeled fluorescence)‐technology where enzyme activity can be observed right at the site of activity. Activities were determined in a two‐stage municipal wastewater treatment plant (WWTP) as well as in three one‐stage WWTP's. In the high load first stage (F:M ratio given as mass of BOD5 related to mass of mixed liquor suspendid solids and day: 0.64 kg kg−1 d−1) of the two‐stage municipal WWTP being dominated by nocardioform actinomycetes lipase activity was somewhat higher in activated sludge as compared to scum. In contrast activities in the low load second stage (F:M ratio 0.02…0.05 kg kg−1 d−1) were significantly higher in the scum fraction. High lipase activities were measured in the one‐stage WWTP 2 being dominated by “Microthrix parvicella”. In situ ELF‐technology assigned the lipase activity to “M. parvicella” filaments with high activity in sludge and reduced activity in scum. In WWTP 3 with alternating dominance of actinomycetes and “M. parvicella” in scum both in vitro and in situ measurements revealed lower activities when actinomycetes were dominating. This suggests their lower degradation activity of long‐chain fatty acids (oleate, palmitate). AlCl3 addition in a pilot scale activated sludge treatment plant led to a significant decrease of lipase activity of the dominating “M. parvicella” filaments which could readily be monitored by both techniques after only two days of dosage.