Removal of linear alkylbenzene sulfonate from a small Yorkshire stream: contribution to GREAT-ER project #7

An in-stream removal experiment has been carried out in Red Beck, a small s tream which receives effluent from Shibden Head Sewage Treatment Works. Thi s trickling filter works serves a purely domestic population of 9408 but is scheduled to be closed, and the flows diverted to another works, as part o f Yorkshire Water's continuing capital investment programme. An anionic det ergent, linear alkylbenzene sulfonate (LAS), boron, and standard water qual ity parameters have been measured at seven sites downstream of the effluent discharge point. Time of travel has been measured by detection of a fluore scent dye added to the effluent sampling chamber, and the increase in flow as the river proceeds through the catchment has been determined from curren t flow measurements, and from boron dilution data. Assuming a first order r emoval mechanism, the overall half-life for LAS removal is just over 2 h (2 h 14 min). Faster removal takes place in the upper portion of the stream, and removal over the last five sampling points is somewhat slower, with a h alf-life of 2 h 40 min. This removal may comprise both primary biodegradati on and the deposition of suspended matter to which the surfactant has been adsorbed. There was no significant difference in the removal half-lives of the individual alkyl chain length homologues. (C) 2000 Elsevier Science B.V . All rights reserved.