Removal of organics by combined process of coagulation–chlorination–ultrafiltration: optimization of overall operation parameters

Abstract

To gain the run parameters of the combined process of coagulation/in situ chlorination/ultrafiltration (UF) so that the system can remove as much organic contaminants as possible without serious membrane fouling, the impacts of operation conditions in coagulation and pre-chlorination unit were investigated in a pilot-scale test. The characteristics of organics in UF influent were examined by excitation emission matrix spectroscopy to find out fouling behavior of different natural organic matter compositions to UF membrane. Thereafter, the operation parameters of different processing units of the hybrid device were optimized by response surface methodology (RSM). The results showed that the tests with the agitation speed of 40 r min had the lowest membrane fouling rate and the highest COD removal, in addition, inappropriate dosage of sodium hypochlorite in membrane influent might exert negative impacts on membrane by lowering UV rejection, especially during the high algae laden period. The predominant factors of membrane fouling were the existence of tryptophan protein-like substances and the soluble microbial products. Optimum values of the mechanical rotation speed in coagulation unit, chemical dosage in pre-chlorination unit, and membrane flux in UF unit of the integrative process were 41.79 r min, 1.40 mg L, and 82.26 LMH, respectively.

The combined influence of hydrophobicity, charge and molecular weight on natural organic matter removal by ion exchange and coagulation

“…Treatment of surface water to remove natural organic matter (NOM) is important for aesthetic reasons, the reduction of both disinfection byproduct precursors and the associated chlorine demand of the water, as well as minimisation of biofilm formation (Brezinski and Gorczyca, 2019;Fan et al, 2018;Ndiweni et al, 2019). NOM is derived from different sources and is distinguished between that of an allochthonous and autochthonous origin.…”