Biodegradability of polyethylene glycol 400 by complex microfloras

In the Clauspol® [Clauspol® process is licensed by Prosernat (http://www.prosernat.com), an IFP subsidiary, and is part of Advasulf™, a complete choice of technologies to reach overall sulphur recovery up to 99.9%.] process from IFP technology, Claus reaction continuation in a solvent phase turns residual acid gas (H2S) into sulphur. Water washing of the unit produces a wastewater loaded of both polyethylene glycol 400 (PEG 400) and sodium sulfate. In order to control efficiency of the biological wastewater treatments and evaluate environmental risks linked to any accidental release, the biodegradability of PEG 400 was studied. In laboratory tests, the PEG-degradation capacities of three distinct types of microfloras, i.e. an activated sludge from an urban wastewater treatment plant, a contaminated-soil microflora and an uncontaminated-soil one, were tested. In liquid cultures with or without Na2SO4, each microflora displayed positive-degradation capacities for PEG. Compared to glucose, hexadecane or pristane as reference compounds, the degradation velocity of PEG was rather low. However, a temperature rise from 20 °C to 30 °C significantly accelerated biodegradation kinetics, multiplying maximal growth rate value by a factor of 15. The biodegradation balance also showed that PEG was totally mineralized without any intermediary metabolite accumulation. From cultures on PEG, Shewanella putrefaciens, Ralstonia basilensis and Leucobacter sp. were isolated and identified by 16s rDNA gene sequencing. These microbial species are known for their huge degradation capacities. This study concludes to an easy biodegradation of PEG contaminating the water issued from the Clauspol® process and limited environmental risks in case of accidental release.