Regulation of reactive species for the mitigation of biotoxicity in bio-treated effluent from electrochemically oxidized landfill leachate.
AI summary
75% confidenceElectrochemical oxidation of landfill leachate bio-treated effluent can be improved by regulating hydrogen peroxide to convert reactive species from free available chlorine to singlet oxygen, reducing the production of chlorinated disinfection by-products and eliminating residues.
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Abstract
Landfill leachate bio-treated effluent (LLBE) is characterized by high levels of chloride ions and complex organic pollutants with poor biodegradability. The use of electrochemical oxidation (EO) to the water sample can enhance its biodegradability. However, the generation of chlorinated disinfection by-products (Cl-DBPs) and residual free available chlorine (FAC) can pose risks to subsequent biological treatment processes. This study aims to propose a method based on H 2 O 2 regulation to convert the reactive species in the EO system from a FAC-dominated regime to a 1 O 2 -contributing regime, inhibiting the production of Cl-DBPs and eliminating FAC residues. After treatment by the EO system, the BOD 5 /COD ratio of the water sample increased from 0.15 to 0.49. Under the regulation of H 2 O 2 , the concentration of Cl-DBPs in the effluent of the EO system diminished from 14.02 mg/L to 2.88 mg/L, while the inhibition rate of luminous bacteria reduced from 95.97 % to 19.80 %. Moreover, sludge derived from the effluent of the EO system treated with H 2 O 2 exhibited superior performance and microbial community structure compared to sludge obtained from the original EO system effluent. It is proposed that H 2 O 2 undergoes a series of reactions within the EO system: electron transfer occurs at the electrode surface, generating free radicals such as HO 2 · and O 2 ·- . Free radical chain reactions and the rapid chemical reactions between H 2 O 2 and FAC are the two pathways through which 1 O 2 is produced. It indicated that EO treatment improved the biodegradability and the addition of H 2 O 2 reduced the biological toxicity of the effluent.