Removal efficiency of dissolved organic matter from secondary effluent by coagulation-flocculation processes

Abstract

Wastewater reuse has been widely discussed as an essential strategy to minimize the consumption of drinking water for less noble purposes. During biological wastewater treatment, organic matter is converted into a complex matrix containing a variety of soluble organic compounds. The objective of the present study was to evaluate the removal efficiency of the residual organic load in the final effluent from wastewater treatment plant with a conventional activated sludge process by different coagulants and parameters of coagulation-flocculation process, using dissolved organic carbon (DOC) concentration, molecular weight (MW) size distribution by size exclusion chromatography (SEC) coupled to mass spectrometry (MS), and zeta potential (ZP) analyses. The results showed a DOC removal efficiency up to 45% with iron chloride, and of 38% for aluminum sulfate and 31% for PAC coagulants. ZP was also measured during the procedures and authors conclude that the ZP also does not have a determining role in these removals. SEC and MS assessment was able to detect changes on secondary effluent molecular weight distribution profile after effluent coagulation-flocculation, this technique might be a promising tool to understand the composition of effluent organic matter and be helpful to estimate and optimize the performance of wastewater effluents treatment processes.

Keywords:

• Iron chloride
• PAC
• activated sludge
• secondary effluent
• wastewater reuse
• size exclusion chromatography
• mass spectrometry
• zeta potential

Additional information

Funding

This work was financially supported by the São Paulo Research Foundation - FAPESP (grants No. 2012/04464-9, 2013/07914-8, and 2014/50420-9), the National Council for Scientific and Technological Development - CNPq (grants No. 160424/2011-9, 311048/2016-1, and 439065/2018-6), Coordination for the Improvement of Higher Education Personnel - CAPES (grant No. 23038.001401/2018-92), and the University of São Paulo Foundation - FUSP (Project #1979). Funded by grants from Fundação de Amparo à Pesquisa do Estado de São Paulo (2012/04464-9), and Conselho Nacional de Desenvolvimento Científico e Tecnológico (160424/2011-9).