Microbes in biological processes for municipal landfill leachate treatment: Community, function and interaction

• Microbial community and function in the LFL treatment bioreactor.
• The interaction of microbes with the reactor's running condition.
• The interaction between microbes in biological processes for LFL treatment.

Landfill leachate (LFL) contains high strength of ammonium and complex organic substances including biodegradable volatile fatty acids (VFAs), refractory aquatic humic substances (AHS) and micro-scale xenobiotic organic chemicals (XOCs), which promotes the diverse microbial community in LFL treatment bioreactors. These microbes cooperate to remove nitrogen, biodegrade organic matters, eliminate the toxicity of XOCs and produce energy. In these diverse microbes, some show dominant in the bioreactor and are prevalent in many kinds of LFL treatment bio-processes, such as Brocadia from the phylum of Planctomycetes, Nitrosomonas sp., the phylum of Proteobacteria, Bacteroidetes and Firmicutes. The bioreactor's operational parameters influence the microbial community, inversely affect the bioreactor's performance. It is practical to accumulate desirable microbes by managing the bioreactor's running condition. High ammonium loading, low DO (<2 mg l−1) and optimal pH value are the practical way to accumulate the desirable AOB and realize the partial nitrification. Nitrite and organic matters inhibit the anaerobic ammonium oxidation bacteria (AnAOB). In anaerobic LFL treatment bioreactors, Methanosaeta and Methanosarcina can outcompete sulfur reducing bacteria and homoacetogens to be the dominant Archaea. Nitrite oxidizing bacteria (NOB), heterotrophic denitrifying bacteria and AnAOB compete nitrite and influenced each other. How to manage NOB, heterotrophic denitrifying bacteria and AnAOB in good cooperation condition is still an issue and need further study.