Removal of phenolic compounds and phthalic acid esters in two-stage membrane bioreactor treating municipal solid waste landfill leachate

Abstract

Two-stage membrane bioreactor (MBR) was applied to the treatment of leachate from a solid waste disposal site in Thailand. Priority micropollutants in landfill leachate were phenolics 4-methyl-2,6-di-tert-butylphenol (BHT), bisphenol A (BPA) at higher concentrations above 100 µgL-1, PAEs i.e. dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate, di-n-octyl phthalate (DnOP), and di(2-ethylhexyl) phthalate (DEHP). It was found that MBR could remove phenolic compounds and PAEs by 77–96%.The removal efficiency of micropollutants are depends on their log KOW as well as their speciation behaviour. In laboratory scale experiment, the removals of BPA, BHT, and DEHP were 65%, 70%, 72%, respectively at initial concentration of 1,000 µg.L-1. The removal mechanisms can be classified into adsorption, biodegradation, and rejection of micropollutants during membrane filtration. The removals of BPA, BHT, and DEHP were found improve using enriched nitrifying sludge in comparison non-enriched condition. In contrast, DEHP was mainly adsorbed on the sludge surface and subsequently rejection by membrane filtration. The biotoxicity of treated water was reduced during MBR treatment as revealed by acute toxicity and genotoxicity tests.