A new nutrient removal plant configuration was designed and tested in pilot-scale for the treatment of piggery wastewater. The core of the process is represented by a Hybrid Upflow Anaerobic Filter where both anaerobic digestion and denitrification takes place. The pre-screened piggery wastewater is fed to the mesophilic anaerobic reactor. In the bottom of the sludge bed, anaerobic digestion and sulfate reduction are the prevalent processes. In the upper filter zone, a stream of nitrified clarified effluent is recycled and nitrates are denitrified utilizing the remaining available carbon and sulfides as electron donors. The anaerobic reactor should be slightly overloaded in order to provide VFAs for denitrification. The effluent of the anaerobic reactor is fed to the following P-removal stage, which is composed of a sludge pre-denitrification step, an anaerobic P-release step, an aerobic nitrification tank and a final settler. The pilot-plant treated 5 m3 d−1 of pre-screened piggery wastewater. The anaerobic digester (volume 15 m3) demonstrated it was to couple anaerobic digestion and denitrification. The overall plant removal efficiency was around 96% for COD, 92% for nitrogen and 92% for phosphorus. The anaerobic digester contributed 80% to the overall denitrification capacity.

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