Nutrient Content in Sludge Profiles from a Full‐Scale Stabilization Pond in a Temperate Location

Abstract

The inorganic nutrient concentrations in sludge profiles from a full‐scale municipal facultative pond in Puerto Madryn City (Argentina) were measured. Sludge samples were collected with cores during autumn, winter, and summer at three sites: inlet, intermediate, and outlet. In general, the sludge accumulates NH4+ and PO43–, increasing their concentrations with depth. However, NH4+ presented a different behavior at the outlet station during the summer, when the lower concentrations were recorded. This finding reflects a nutrient release, originating in their greater demand from the water column. In the sludge, the NO3– followed the spatial and seasonal pattern recorded in the surface water: detectable concentrations in the warmer months at the outlet. The vertical reduction of NO3– could be an indication of denitrification. The study supported the hypothesis that the sludge can act as a nutrient trap or source, depending on factors such as the temperature, nutrients/oxygen concentration, mixing processes, and location.