Biological nutrient removal with an internal organic carbon source in piggery wastewater treatment

The feasibility of using an internally available carbon source for biological nitrogen and phosphorus removal was investigated. A new integrated animal wastewater treatment process consisting of two reactors was operated with various sequences for the treatment of high strength piggery manure. The treatment process was operated with real-time control technology, which utilized the oxidation–reduction potential (ORP). In the first operation, the sludge in each reactor was completely separated (sludge separation strategy, SSS), while a portion of the sludge in the first reactor was added into the second reactor in every cycle of the second operational strategy (sludge addition strategy, SAS). None of the operating strategies used a supplemental carbon source to achieve enhanced phosphorus release and denitrification. By achieving successful real-time control, very high removal efficiencies of organic matter, nitrogen and phosphorus were obtained in both operations. These high performances were mainly achieved by means of biological mechanisms, not chemical and physical processes. The real-time control made it possible to utilize an internally available organic material for phosphorus removal and denitrification of produced NOx-N, without any external carbon source. Furthermore, it was found that an optimization of aeration periods could be achieved by using the tested real-time control technology, since the technology stopped the aeration when the targeted oxidation status occurred in treatment system. The HRT obtained in both the SSS and the SAS was proportional to the F/M ratio. Experimental data showed that the sludge addition strategy (SAS) has a practical advantage over the sludge separation strategy (SSS), in that the SAS enhanced the denitrification and resulted in constant and low effluent NOx-N concentrations.