Anaerobic degradation of nonionic and anionic surfactants in enrichment cultures and fixed-bed reactors

Abstract

Anaerobic biodegradation and inhibitory effects of nonionic and anionic surfactants on methanogenic fermentation were tested in incubation experiments with anoxic sediment samples and sewage sludge. Alkylsulfonates and alkylbenzenesulfonates were not degraded but inhibited meth-anogenesis from sludge constituents at concentrations mehr gleich 10 mg l hoch -1 Sodium dodecylsulfate was at least partly degraded after adaptation at concentrations weniger gleich 100 mg 1 hoch -1 and the sulfate group was reduced to sulfide. The polyethyleneglycol moiety of alkylphenolethoxylates was fermented to methane at concen-trations weniger gleich 500 mg 1 hoch -1 whereas the alkylphenol residue probably remained unchanged. Alkylethoxylates were completely degraded to methane and CO2 at concentrations up to 1.0 g 1 hoch -1. Complete anaerobic degradation of this surfactant type to methane, CO2, and traces of acetate and propionate was demonstrated in a lab scale anaerobic fixed-bed reactor, either with prereduced mineral salts medium or with air-saturated artificial wastewater. This process lends itself as a suited, inexpensive means for treatment of wastewaters containing enhanced loads of nonionic surfactants, e.g. from the surfactant manufacturing or processing industry.