Nitrogen removal in a shallow maturation pond with sludge accumulated during 10 years of operation in Brazil

Abstract

Accumulated sludge in polishing (maturation) ponds reduces the hydraulic retention time (smaller useful volume), and this could potentially lead to a decrease in performance. However, settled biomass, present in the sediments, can contribute to nitrogen removal by different mechanisms such as nitrification and denitrification. This study investigated the influence of the bottom sludge present in a shallow maturation pond treating the effluent from an anaerobic reactor on the nitrification and denitrification processes. Nitrification and denitrification rates were determined in sediment cores by applying ammonia pulses. Environmental conditions in the medium were measured and bacteria detected and quantified by real-time polymerase chain reaction (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 upper to the lower part of the sludge layer. The results indicate that denitrifiers, nitrifiers and anammox bacteria coexisted in the sludge, and thus different metabolic pathways were involved in ammonium removal in the system. Therefore, the sediment contributed to nitrogen removal, even with a decrease in the hydraulic retention time in the pond due to the volume occupied by the sludge.

Empirical Characterization of Particle Size Distribution Spatial Dynamics for Helminth Eggs Detection in Waste Stabilization Ponds (WSP)

“…Dry weather bimodal distributions at the top and bottom have modes concentrated around a similar size, with the first peak around 10 microns and the second peak around 67 microns (Figure 3a,c). The similar modes on both top and bottom could be a result of well mixed conditions inside the pond as observed by [22]. In wet weather, the bimodal distribution shifts to the right, with peaks around 15 microns and 100 microns (Figure 3b,d), and the separation of the two peaks is not as clear as the separation for dry weather.…”

“…These locations are found from about mid-pond to the end of the pond, except in areas close to the outlet. The similarity of PSD at the top and bottom indicates a mixing process driven by molecular diffusion due to temperature gradient, with top layers having much higher temperatures than the bottom layers as reported in [22], which take place along the vertical direction. The above-described trends and their locations are almost constant in both wet and dry season, as shown in Figure 4.…”

Nitrogen dynamic in vitro using sludge of a sewage stabilization pond from Patagonia (Argentina)

“…In literature, the nitrification-denitrification and Anammox were described as the processes responsible for part of nitrogen removal in many full-scale wastewater treatment plants, both in conventional (Nourmohammadi et al 2013;Tallec et al 2008) and in natural systems (Saeed and Sun 2012;Rodrigues et al 2017;Foladori et al 2018). However, there are few studies focused to know the kinetics of the processes that occur in anoxic bottom environment in pond systems.…”