Influence of time and oxygenation on the degradation of organic matter, nitrogen and phosphates during the biological treatment of slaughterhouse effluent

The treatment of slaughterhouse effluents still arouses particular interest today because of the complexity of the processes implemented with approximate yields. The objective of this work is to study the influence of time and oxygenation on the biodegradation of organic, nitrogen and phosphate loads in slaughterhouse effluent by biological treatment without the addition of bacterial flora. The effluent sampled in a slaughterhouse in the town of Ngaoundéré (Cameroon) underwent physicochemical characterization. It then underwent biological treatment in two stirred batch reactors, one in anoxia and the other in aeration. During the treatment, the organic, nitrogenous and phosphate pollutants were analysed on samples taken every three (3) days for nine (9) days, then every six (6) days for eighteen (18) days. The results obtained show that the effluent is generally basic in the two reactors during the treatment. The overall reduction rate of all pollutants (organic matter, NH4+, NO3-, NO2-, PO43- and SO42-) monitored, is higher in the reactor operating in anoxia (57 %) than in the one operating in aeration (44 %) at the end of the 27 days of treatment. However, biodegradation is more rapid during the first 9 days of treatment, during which the oxygenation of the medium was a real catalyst for accelerating the biodegradation of certain pollutants such as organic matter, NO2- and PO43-. So, the oxygenation of the environment has favoured the acceleration of the biodegradation of certain pollutants, without necessarily promoting the efficiency of their elimination in the effluent. Also, whether the reactor operating in anoxic or aerobic, there is an effective biodegradation time beyond which microbial activity is no longer effective. [Display omitted] •Biological removal of N and PO43- pollutants are unfolding in a rapid and a slow stage. .•Oxygenation accelerates the biodegradation of nitrogen compounds in the rapid stage.•Oxygenation promotes the production of nitrates during the slow stage of biodegradation.•Oxygenation helps reduce treatment time to the detriment of efficiency.•There is a minimum treatment time beyond which biodegradation is no longer effective.