The efficiency of various chemical solutions to clean reverse osmosis membranes processing swine wastewater

Abstract

The increasing use of membrane technology to treat highly charged wastewaters has renewed interest in the development of adequate cleaning strategies. This study investigated the efficiency of various chemicals, including acids, bases, surfactants, chelators, salts, enzymes, and oxidants, to clean two reverse osmosis membranes (BW30 and SW30XLE) filtering one swine wastewater pretreated by aerobic biofiltration and two swine wastewaters pretreated by mechanical solid–liquid separation. Mixes of anionic surfactants and chelators provided optimal cleaning efficiency for all fouled membranes and all effluents. A solution containing 10 mM EDTA (ethylenediamine tetraacetic acid) and 10 mM SDS (sodium dodecyl sulfate) yielded the highest flux recovery after one 20-h fouling cycle with the BW30 membrane and three consecutive fouling–cleaning cycles with the SW30XLE membrane. The EDTA + SDS solution also resulted in the lowest residual protein concentration on membrane surface and the optimal restoration of the initial contact angle of the membranes. Conversely, 75 mM acid citric and 100 mM NaCl solutions were the least efficient to clean the fouled membranes. Most chemical solutions were more efficient to clean the fouling layer generated by the swine wastewater pretreated by aerobic biofiltration than mechanical separation.