Determination of the Removal Efficiency of Linear Alkyl Benzene Sulphonate Acids (LAS) in Fixed Bed Aeration Tank and Conventional Activated Sludge

Linear Alkyl Benzene Sulphonate Acids (LAS) are one of the anionic surfactants that are produced and used in large quantities in different countries and find their way into the natural environment through sewer systems. These compounds may potentially cause environmental hazards in such surface waters as rivers. It is, therefore, necessary to remove as much of these compounds as possible by biological processes in wastewater treatment plants. For this purpose, four parallel biological reactors were constructed that used the conventional activated sludge and aeration tanks with fixed bed on the bench scale in order to evaluate the removal efficiency of LAS. The reactors were operated under conditions similar to domestic wastewater treatment plants. Parameters of interest were measured according to standard methods and ANOVA and T-test were used for the statistical analysis of the data. The results showed that aeration tanks with fixed beds yielded higher values of LAS and COD removal and air consumption compared to the conventional activated sludge system. It was shown that the two systems studied achieved LAS removal efficiencies of 96% and 94% for an influent LAS concentration of 5 mg/L. Further, it was found that the effluents from both systems satisfied water quality standards for discharge into surface waters (<1.5 mg/L) and into ground waters (<.5 mg/L). At LAS concentrations higher than 5 mg/Li, the conventional activated sludge system did not have the required efficiency and its effluent did not meet the environmental discharge standards. In contrast, aeration tanks with fixed bed achieved a removal efficiency of 97% at higher concentrations (15 and 20 mg/L) and were capable of reducing the amount of effluent LAS concentration. Therefore the aeration tank system should be recommended for high LAS concentrations in the influent.