, Volume 354, Issue 1, pp 66-71

Cyclic siloxanes in the biological waste water treatment process – Determination, quantification and possibilities of elimination

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Volatile cyclic organic siloxanes in the biogas of digested sludge can shorten the life time of gas engines producing energy from the biogas. These siloxanes have been determined by gas chromatography on a fused-silca column using flame ionization detection (GC/FID). To extract siloxanes from biogas, spiked biogas or spiked carbon dioxide XAD resins, activated carbon, polyurethane foam and tetradecane have been tested. Adsorption from the gas have been accomplished successfully with XAD resins, activated carbon and tetradecane, but quantitative recoveries from the adsorbens have been achieved only using XAD and ultra sonification. Determinations from waste water, activated or digested sludge could be carried out successfully after stripping the siloxanes from these samples by helium and adsorption on XAD. Elimination from biogas was possible by adsorption or degradation. XAD adsorption eliminated siloxanes quantitatively but the regeneration of the resins was necessary. Aqueous sodium hydroxide solutions at 20 or 60°C have proven as ineffective in degradation whereas concentrated sulfuric acid at a temperature of 60°C eliminated siloxanes quantitatively.

Received: 9 May 1994 / Revised: 11 March 1995 / Accepted: 17 March 1995
This work is part of the master thesis of R. Huppmann
Correspondence to: H. F. Schröder