UK monitoring study on the removal of linear alkylbenzene sulphonate in trickling filter type sewage treatment plants. Contribution to GREAT-ER project # 2

The results of a linear alkylbenzene sulphonate (LAS) monitoring exercise carried out during August and September, at six different trickling filter sewage treatment plants in the Aire and Calder catchments in the UK are described. The average LAS concentration in flow proportional, composite, crude sewage was 3.25 mg l−1 and ranged from 1.10 to 5.58 mg l−1. Based on consumer usage data and boron measurements these results indicate that up to 60% of the LAS was removed in the sewers prior to reaching the sewage treatment plants. The concentration of LAS in flow proportional, composite final effluents from well-operated plants ranged from 4 to 460 μg l−1, with an average value of 240 μg l−1. Removal through the plants ranged from 70–99% with mean values of 90.7, 93.4, 93.0, 74.6, 97.3 and 92.4% for the six plants. A simple model is described which can be used to accurately predict the diel variation in LAS concentrations in the final effluent when measured influent concentrations, flow and settling tank volumes are known.