Understanding and mitigating effects of brine discharge to wastewater on primary sedimentation. Issue 3 (25th June 2021)

• Record Type: Journal Article
• Authors: Adelman, Michael J.; Newman, Rita P.; Seshan, Hari; Zare Afifi, Mehrnaz; Dornfeld, Mitch; Oppenheimer, Joan; Quicho, Joseph
• Is Part Of: AWWA water science. Volume 3:Issue 3(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-06-25
• Subjects: brine discharge -- chemically enhanced primary treatment -- flocculation -- sedimentation; Water -- Analysis -- Periodicals; Water-supply engineering -- Periodicals; Water -- Social aspects -- Periodicals; Water -- Purification -- Periodicals; Water-supply engineering; Water -- Social aspects; Water -- Analysis; Electronic journals; Periodicals; 628.162
• DOI: 10.1002/aws2.1229
• Languages: English
• ISSNs: 2577-8161

Abstract

Abstract: As the implementation of full advanced treatment with reverse osmosis (RO) grows in response to water scarcity, the effects of RO brine disposal to sewersheds on wastewater treatment will become an increasingly important consideration. Unfortunately, there is little existing literature on the actual effects of brine augmentation on wastewater flocculation and settling. In this study, RO brine from a wastewater reuse system was blended into raw wastewater. Jar tests of chemically enhanced primary treatment (CEPT) were conducted with varying brine blends and ferric chloride coagulant doses. Brine augmentation, at volumetric fractions ranging from 2.7% to 54% of the primary influent, was observed to affect CEPT performance, as removal of turbidity and total suspended solids (TSS) decreased in response to increasing brine share. Control jars with 0% brine generally had greater than 80%–90% TSS removal at the baseline coagulant dose of 12.5 mg/L, and this decreased to around 70% at 27% brine and less than 70% at 54% brine. This effect was observed to be roughly proportional to the level of brine addition, and it appears to be driven by changes to the properties of the fluid and primary particles as a result of brine addition. Adding brine both increases the density and viscosity of the fluid through higher total dissolved solids and decreases the density of the primary particles that make up the floc by contributing dissolved organics rejected by RO. CEPT performance was restored to its current baseline of around 80%–90% removal of TSS and turbidity by increasing ferric chloride dose (and thus floc density), with 17 mg/L required at 2.5% brine share and 30 mg/L required at 15% brine share. Overall, there was a roughly linear relationship between influent brine proportion and additional coagulant required to bring CEPT performance back up to brine‐free levels. The impact observed in this study suggests a topic for future research with other sources of brine and other coagulants. Article Impact Statement: By investigating primary settling affected by RO brine, this work addresses a topic of current interest that has not been widely studied.