Changes in microbial populations and enzyme activities during nitrogen biodegradation of domestic sewage treatment in the Subsurface Wastewater Infiltration System (SWIS).

During the process of domestic sewage treatment in the Subsurface Wastewater Infiltration System (SWIS), changes in the microbial populations (nitrifying and denitrifying bacteria) and enzyme activities (urease, nitrate reductase and nitrite reductase) involved in the nitrogen removal process were evaluated over a 2-year period. The results showed nitrifying bacteria number declined with depths increasing, while denitrifying bacteria increased, both of which increased nearer the inlet. The depth for nitrate reductase activity from high to low in sequence was 0.3, 0.5, 0.7, 0.9 and 1.1 m. For nitrite reductase, the sequence was 0.5, 0.3, 0.7, 0.9 and 1.1 m. Urease and nitrite reductase activities were in positive correlation with the total nitrogen removal efficiency, with correlation coefficients 0.8662 and 0.9140, respectively and could be alternative to monitor the nitrogen biodegradation process in SWIS. © Springer Science+Business Media, LLC 2011