Landfill leachate typically contains not only a high concentra- tion of organic matter but also salts, ammonium, and metals [10–14]. Sodium, potassium, and ammonium are often detected as major inorganic components in landfill leachate (sodium, up to 10,930 mg L 1; potassium, up to 2243 mg L 1; ammonium, up to 13,000 mg L 1; electrical conductivity (EC), 3–41 mS cm 1) [10–14]. Salt accumulation in landfill bodies can result from repeated leachate recirculation [15], and high salinity and ammonium are known to affect biological processes, including anaerobic digestion [16–19]. However, there are only a few reports on the effect of salinity on waste biodegradation with leachate recirculation [20,21]. To the best of our knowledge, this is the first report on the effect of the accumulation of complex inorganic matter, including salts, ammonium, and metals, on anaerobic waste degradation and microbial communities, as a possible result of leachate recirculation. An evaluation of the impact of salt concentration on microbial activity and community composition should lead to a greater understanding of biogas generation as an end-point reaction.
The purpose of this study was to evaluate the influence of salt accumulation on biogas production and microbial communities with the application of leachate recirculation technology to tropical developing countries in mind.