Treatment of a slaughterhouse wastewater by anoxic–aerobic biological reactors followed by UV‐C disinfection and microalgae bioremediation

In this study, removal of organic matter and nitrogen from a cattle slaughterhouse wastewater was investigated in a two‐stage anoxic–aerobic biological system, followed by UV‐C disinfection. Ecotoxicity of the raw, biotreated, and disinfected wastewater against the microalgae Scenedesmus sp. was evaluated in short‐term tests, while the potential of the microalgae as a nutrient removal step was addressed in long‐term experiments. Throughout 5 operational phases, the biological system was subjected to gradual reduction of the hydraulic retention time (8–1.5 day), increasing the organic (0.21–1.11 kgCOD·m−3·day−1) and nitrogen (0.05–0.28 kgN·m−3· day−1) loading rates. COD and total ammoniacal nitrogen (TAN) removal ranged within 83%–97% and 83%–99%, respectively. While providing alkalinity source, effluent TAN concentrations were below 5 mg·L‐1. Nitrate was the main nitrification product, while nitrite levels remained low (