PARENT SESSION
68 - State of the Art in Analytical Chemistry
8:00 AM to 6:30 PM, Wednesday, 15 May 2002
Exhibition Area

(68-08) Polydimethylsiloxane Concentrations in Sewage Influent and Effluent in the UK.

Webb, Simon^*,1, Christine, Stevens², Powell, David³, ¹ Procter & Gamble, Brussels, Belgium² Dow Corning, Senaffe, Belgium³ Dow Corning, Midland MI, USA

ABSTRACT- Wastewater treatment plants (WWTP) at Stretford (trickling filter) and Crewe (activated sludge) were monitored during June 1997. Composite samples of influent, primary and final effluent (3% v/v formalin), together with grab samples of primary and secondary sludge (8% v/v formalin) were taken for analysis for Polydimethylsiloxane (PDMS) by ICP (SPE filtration and tetrahydrafuran extraction). Samples were also analysed for a suite of physico-chemical determinands. PDMS influent concentrations were in the range 72 - 84 g/l at Stretford WWTP (TF) and 108 - 119 g/l at Crewe WWTP (AS). Spike recovery from the influent samples was 60%. This corresponds to a down-the-drain usage of 30 - 40 mg/capita/day or 580-915 tonnes/annum in the UK. Primary effluent concentrations at Stretford were in the range 62 - 113 g/l. Primary effluent concentrations at Crewe were in the range 41 - 91 g/l. Spike recovery from the primary effluent samples was 50 - 80%. Final effluent concentrations at Stretford ranged from 21 to 30 g/l. Final effluent concentrations at Crewe ranged from 19 to 26 g/l. Spike recovery from the final effluent samples was 80 - 97%. This higher recovery was attributable to a novel filtration and extraction method applied to the final effluent. Concentrations of PDMS in primary sludge were 777 g/g at Stretford and 674 g/g at Crewe. Spike recoveries were in the range 90 - 110%. The PDMS concentration in final sludge cake from Stretford was 515 g/g. The concentration in anaerobically treated sludge from Crewe was 1335 g/g with 90 - 100% spike recovery. The observed overall removal rate for the two UK WWTPs was lower than the >94% reported in North America. Discrepancies in the recovery rates between influent and final effluent samples undoubtedly account for this.

Key words: Polydimethylsiloxane, Sewage, Sludge, Effluent