Application of a Series of Continuously Fed Aerated Tank Reactors System for Recycling of Swine Slurry Nutrients

Single tank aeration systems operated in batch mode or sequential batch reactors based on intermittent aeration are generally applied for swine manure treatment in order to reduce nutrient content and odor. This study evaluated the feasibility of aerobic biological treatment conducted in a serial arrangement of continuously fed aerated tank reactors configuration with swine slurry on a pilot-scale. Compared to municipal wastewater treatment swine slurry rich in nutrients and solids requires different treatment standards for the applied methods to be economically and ecologically relevant. This study presents a sequential process scheme, in which biological treatment serves as a means of achieving a pH raise. This makes it possible to separate part of the nitrogen by stripping and enhances slurry precipitating/coagulation characteristics without substantial carbon or nitrogen loss in gaseous form (which is the opposite to that in a conventional active sludge process). The system was run with a hydraulic retention time (HRT) of three to four days (whole system), and a feedback of 0.8±0.2. During treatment, total organic carbon (TOC) reduction varied between 2.4% and 14.6% and the total nitrogen concentration change was less than 3%. Nearly 50% of the total phosphorus was reduced. The results indicated that the odor of liquid manure had decreased efficiently at best to a level at which there was no odor or only very faint odor. Concurrently, manure pH rose to 8.7.