Landfill leachate treatment by the symbiotic system of bacteria and microalgae: high-efficiency and low-consumption green biological treatment system

Abstract

This study uses domestic sewage to dilute landfill leachate, conserve freshwater resources, and supplement phosphorus. The proportion of landfill leachate is increased, and the microalgae photosynthesis is coupled with the SBR system to process the diluted leachate. A bacterial and algal symbiotic photobioreactor (PBR) was constructed to improve the efficiency of sewage treatment by optimizing parameters (aeration rate, light) for investigating the synergy of microalgae and bacteria, and the effect of treating Landfill leachate. The long-term operational impact of the reactor under two different inoculation conditions was investigated: one group was inoculated only with activated sludge and controlled light to promote the spontaneous growth of microalgae (Rc), and the other group was inoculated with activated sludge and Chlorella (Rs). The highest pollutant removal efficiencies were observed in 4 : 1 (microalgae/sludge) cultures, with COD at 96.5%, NH₄⁺-N at 97.4%, and PO₄³⁻-P at 92.3%. Synergistic growth of bacteria and microalgae was observed, with a total biomass concentration of 2.32 g L⁻¹. Pollutant removal effect was best at an aeration rate of 0.6 L min⁻¹, with removal efficiencies of 72.7% for COD, 78.3% for NH₄⁺-N, and 62.5% for PO₄³⁻-P. A low-aeration method, mechanical aeration and microalgae photosynthesis cooperated to reduce operating costs. When light intensity was 108 µmol m⁻² s⁻¹, pollutant removal efficiencies of COD 82.6%, NH₄⁺-N 84.9% and PO₄³⁻-P 75.9% were achieved. Treatment effect of the Rs system: average volume load of 36.22 mg per L per h COD, 8.53 mg per L per h NH₄⁺-N, 0.44 mg per L per h PO₄³⁻-P. This provides new ideas for achieving high-efficiency, low-consumption green biological treatment of landfill leachate.