Anaerobic toxicity mitigation of leachates by mixing with municipal sewage

Abstract

The leachates contain compounds originally present in landfilled waste as well as the ones formed in the waste-degradation processes; when the leachates have a high organic matter content and high BOD5/COD ratio, the biological treatment has a high application potential; however, high levels of nitrogen and other compounds may be inhibitors or toxic for biological process. The anaerobic toxicity evaluation allows to determine the magnitude and inhibition type caused on the microorganisms in charge of the final transformation to methane, and it is determined by comparing the specific-methanogenic activity (SMA) of the control sludge fed only with substrate and the SMA of the sludge fed with the same substrate plus the toxic compound. Due to the increasing interest in leachate cotreatment with municipal sewage (MS), the anaerobic toxicity of pure leachate and leachate mixed with MS was evaluated at lab scale to establish the potential toxic effect of the leachate on the anaerobic digestion. In assays using pure leachate a high reduction of the SMA, occurred identifying two inhibition types: metabolic and physiologic. In assays using leachate mixed with MS (5 and 10%), the inhibition percentage was substantially reduced, achieving no-toxic-substrate conditions. The results suggest the potential application of cotreatment with municipal sewage as an appropriate strategy to leachate management.