Intermittent aeration of pig slurry – farm scale experiments for carbon and nitrogen removal Available to Purchase

A farm scale treatment plant was studied during a year. Four different aeration cycles were tested in order to optimise the process and to produce an effluent with low carbon and nitrogen concentrations. The treatment plant performance was not significantly affected by a 60% reduction of aeration times, from almost 20 hours per day to 12 hours per day. The high removal rates observed appeared to be related to the low aeration rates achieved through the intermittent operation of the aerator. The operation of the treatment system at very long sludge age resulted in almost complete removal of soluble biodegradable matter and up to 90% removal of soluble COD. The development of simultaneous nitrification/denitrification processes in the aeration tank resulted in very low ammonia levels in the final effluent and a reduction of over 95% in the TKN values. The energy input to the system was estimated to be, in average, 9 kWh/m³ of slurry. Activated sludge quality was monitored through microscopic examination and there was no evidence of an abundant or excessive growth of filaments within the reactor.