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⁻¹ had the lowest membrane fouling rate and the highest COD_Mn removal, in addition, inappropriate dosage of sodium hypochlorite in membrane influent might exert negative impacts on membrane by lowering UV₂₅₄ 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, 1.40 mg L⁻¹, and 82.26 LMH, respectively.

KEYWORDS:

• Coagulation
• in situ chlorination
• ultrafiltration
• organics removal
• membrane fouling
• response surface methodology

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Gongduan Fan http://orcid.org/0000-0001-7687-1046

Zhaoyue Su http://orcid.org/0000-0003-1610-2063

Rujing Lin http://orcid.org/0000-0001-6290-2817

Zhuwu Jiang http://orcid.org/0000-0003-0717-1614

Renxing Xu http://orcid.org/0000-0002-5283-6454

Shumin Wang http://orcid.org/0000-0001-8575-372X

Additional information

Funding

This work was supported by the financial support from the National Natural Science Foundation of China (51778146, 51308123, 51409030), China Scholarship Council, China Postdoctoral Science Foundation (2014M561856), Science Foundation of Housing and Urban-Rural Development of Fujian (2014-K-05, 2016-K-42), and Opening Measuring Fund of Large Precious Apparatus of Fuzhou University (2016T041).