Removal of linear alkylbenzene sulfonate and turbidity from greywater by a hybrid multi-layer slow sand filter microfiltration ultrafiltration system

Abstract

In this study, a new hybrid system using multi-layer slow sand filter (MSSF), micro filter (MF) and ultra filter (UF) was investigated for the chemical oxygen demand (COD), linear alkylbenzene sulfonate (LAS), total suspended solid (TSS) and turbidity removal from the greywater at different organic loading rates (OLRs) (3.15–19.28 gCOD/(L.d) in a laboratory scale over a period of 157 days. The best removal efficiencies for COD, LAS, TSS, and turbidity were 98.22, 99.97, 99.99, and 99.98 percent, respectively using the MSSF-MF-UF hybrid system. The best removal efficiencies of LAS were 86.7, 89.6, and 98.37 percent, respectively in the OLR of 3.15 gCOD/(L.d). The scanning electron microscopy (SEM) images confirmed that biofilm grew appropriately in the media using the MSSF. Moreover, the increase of OLRs in the hybrid system decreased the removal efficiency levels of COD, LAS, TSS, and turbidity. However, the average effluents of LAS, TSS, and turbidity in the hybrid system were 0.04 mg/L, 1.55 mg/L, and 1.04 NTU, respectively for all OLRs, which were lower than the standard measures for reuse of water. In fact, the combination of biological process (MSSF) with membrane process (MF and UF) led to a more effective LAS and suspended solids (SS) removal in the grey water. Therefore, the combination of MSSF-MF-UF can be applied for removal of LAS and SS.