Treatment of nanofiltration concentrates of mature landfill leachate by a coupled process of coagulation and internal micro-electrolysis adding hydrogen peroxide

Abstract

In this study, a coupled process of coagulation and aerated internal micro-electrolysis (IME) with the in situ addition of hydrogen peroxide (H₂O₂) was investigated for the treatment of nanofiltration (NF) concentrate from mature landfill leachate. The acceptable operating conditions were determined as follows: initial pH 4, polymeric aluminium chloride dosage of 525 mg-Al₂O₃/L in the coagulation process, H₂O₂ dosage of 0.75 mM and an hydraulic retention time of 2 h in an aerated IME reactor. As a result, the removal efficiencies for chemical oxygen demand (COD), total organic carbon, UV₂₅₄ and colour were 79.2%, 79.6%, 81.8% and 90.8%, respectively. In addition, the ratio of biochemical oxygen demand (BOD₅)/COD in the final effluent increased from 0.03 to 0.31, and that of E₂/E₄ from 12.4 to 38.5, respectively. The results indicate that the combined process is an effective and economical way to remove organic matters and to improve the biodegradability of the NF concentrate. Coagulation process reduces the adverse impact of high-molecular-weight organic matters such as humic acids, on the aerated IME process. A proper addition of H₂O₂ in the aerated IME can promote the corrosion of solid iron (Fe²⁺/Fe³⁺) and cause a likely domino effect in the enhancement of removal efficiencies.

Keywords:

• nanofiltration (NF) concentrate
• mature landfill leachate
• coagulation
• internal micro-electrolysis (IME)
• biodegradability

Acknowledgements

This work was supported by the Foundation of the State Key Laboratory of Pollution Control and Resource Reuse, China (PCRRF13013); the Research Start-up Foundation of Hangzhou Dianzi University (KYS205613030); the Research Foundation of Educational Commission of Zhejiang Province of China (Y201430800); and the National Science Foundation of China (51408171).