Determination of Optimal Conditions for the Purification of Dnipro River Water from Natural Organic Matter by an Integrated Coagulation–Ultrafiltration Process with an Aluminum Coagulant

Abstract

Natural organic matter (NOM) negatively affects water purification quality and leads to the formation of disinfection by-products that exhibit carcinogenic, teratogenic, and mutagenic effects. In addition, biodegradable natural organic matter enhances the growth of microorganisms in the distribution network and causes problems with taste and odor. This necessitates the improvement of existing water treatment methods and the search for more efficient technological solutions, one of which is the use of an integrated coagulation−ultrafiltration process. In this study, the optimal conditions of an integrated coagulation−ultrafiltration process using aluminum sulfate as a coagulant for the purification of Dnipro River water were established. It was shown that, at pH of 6.0–6.5 and a coagulant dose of 2 mg_Al/L, the obtained filtrate quality meets the existing regulatory requirements for drinking water. Water quality was evaluated by turbidity, color, residual aluminum concentration, total organic carbon TOC, UV_254, UV₃₆₄, and SUVA parameters. The mechanism of membrane fouling was determined as a gradual transition from the blocking of pores by multiple particles to intermediate filtration with the further formation of a cake layer on the membrane surface. Membrane regeneration was carried out by direct washing with distilled water, which restored the specific permeate flux by 62.0%, and by reverse washing, which improved the obtained result to 89.4%.