Nitrogen removal in a shallow maturation pond with sludge accumulated during 10 years of operation in Brazil
V. A. J. Rodrigues1*, E. F. A. Mac Conell1, D. F. C. Dias1, M. V. Sperling1, J. C. de Araújo1 and J. L. Vasel2
1 Department of Sanitary and Environmental Engineering (DESA), Federal University of Minas Gerais, Av. Antonio Carlos 6627, Escola de Engenharia, Belo Horizonte, MG, Brazil. 2 Department of Science and Environmental Management, Unit of Environment and Sanitation; University of Liege, Campus Arlon, Belgium.
(free)
Accumulated sludge in polishing (maturation) ponds reduces the hydraulic retention time (smaller useful volume), what could potentially lead to a decrease in performance. However, settled biomass can assist in other mechanisms that lead to nitrogen removal. This study investigated the influence of sediments present in a shallow polishing pond treating the effluent from an anaerobic reactor on the nitrification and denitrification processes. The nitrification and denitrification rates were determined in sediment cores by applying ammonia pulses. Environmental conditions in the medium were measured and bacteria detected by real time PCR. The pond showed daily cycles of mixing and stratification and most of the bacteria involved in nitrogen removal decreased in concentration from the top surface of the sludge to the bottom of the pond. It was observed that the sediments contributed to nitrogen removal, even with a lower hydraulic retention time in the pond
