Water recovery from cleaning wastewater of traditional Chinese medicine processing via vacuum membrane distillation: Parameters optimization and membrane fouling investigation

Abstract

With the rapid development of traditional Chinese medicine (TCM) industry, the treatment of TCM wastewater has become an important environmental issue. Among them, TCM processing cleaning wastewater is suitable for recovering high-quality water resources from it due to its low chemical oxygen demand (COD). Compared with pressure driven membrane process, Membrane distillation (MD) can yield highly purified distillate under mild operating conditions. Therefore, this work aims to evaluate the effects of feed temperature, feed flow, osmotic side vacuum degree and membrane material on the treatment of cleaning wastewater from TCM processing. Besides, the fouling of membrane in MD process and the efficiency of chemical cleaning on fouling removal were also investigated. The results show that it is feasible to recover high-quality water from traditional Chinese medicine processing cleaning wastewater by VMD. Compared with feed, COD in permeate decreased by 99%. During the 10 h experiment, the flux of both membranes decreased slightly due to the accumulation of fouling layer on the membrane surface. Chemical cleaning, especially alkali as cleaning agent can effectively remove the fouling layer.