Abstract
Water reuse is a safe and often the least energy-intensive method of providing water from non-conventional sources in water stressed regions. Although public perception can be a challenge, water reuse is gaining acceptance. Recent advances in membrane technology allow for reclamation of wastewater through the production of high-quality treated water, including potable reuse. This study takes an in-depth evaluation of a combination of membrane-based tertiary processes for its application in reuse of brewery wastewater, and is one of the few studies that evaluates long-term membrane performance at the pilot-scale. Two different advanced tertiary treatment trains were tested with secondary wastewater from a brewery wastewater treatment plant (A) ultrafiltration (UF) and reverse osmosis (RO), and (B) ozonation, coagulation, microfiltration with ceramic membranes (MF) and RO. Three specific criteria were used for membrane comparison: 1) pilot plant optimisation to identify ideal operating conditions, 2) Clean-In-Place (CIP) procedures to restore permeability, and 3) final water quality obtained. Both UF and Micro-Filtration membranes were operated at increasing fluxes, filtration intervals and alternating phases of backwash (BW) and chemically enhanced backwash (CEB) to control fouling. Operation of polymeric UF membranes was optimized at a flux of 25–30 LMH with 15–20 min of filtration time to obtain longer production periods and avoid frequent CIP membrane cleaning procedures. Combination of ozone and coagulation with ceramic MF membranes resulted in high flux values up to 120 LMH with CEB:BW ratios of 1:4 to 1:10. Coagulation doses of 3–6 ppm were required to deal with the high concentrations of polyphenols (coagulation inhibitors) in the feed, but higher concentrations led to increasing fouling resistance of the MF membrane. Varying the ozone concentration stepwise from 0 to 25 mg/L had no noticeable effect on coagulation. The most effective cleaning strategy was found to be a combination of 2000 mg/L NaOCl followed by 5% HCl which enabled to recover permeability up to 400 LMH·bar−1. Both polymeric UF and ceramic MF membranes produced effluents that fulfil the limits of the national regulatory framework for reuse in industrial services (RD 1620/2007). Coupling to the RO units in both tertiary trains led to further water polishing and an improved treated water quality.
Highlights
In the overall growing context of water scarcity and deterioration in water quality, alternative methods to produce water at the lowest costs from non-conventional water sources are being intensively studied (Angelakis and Durham 2008; Hochstrat et al, 2010;2017; Ansari et al, 2017)
This paper provides relevant results from the long-term operation of full-scale innovative membrane-based processes for brewery wastewater recovery
The main focus of this study was to compare the performance of two different membrane processes, UF + Reverse Osmosis (RO) and O3+Coagulation + MF + RO, to treat secondary wastewater from the brewery industry
Summary
In the overall growing context of water scarcity and deterioration in water quality, alternative methods to produce water at the lowest costs from non-conventional water sources are being intensively studied (Angelakis and Durham 2008; Hochstrat et al, 2010;2017; Ansari et al, 2017). The benefits of water reuse are more limited extraction from surface and ground-water sources, reduced impact of treated wastewater discharge into water bodies, and production of highquality treated water for multiple on-site applications. Further economic benefits include lower water intake costs, lower wastewater disposal fees and optimized energy efficiency of water treatment (Pankratz 2004; Vanoppen et al, 2016). The brewery industry is a large consumer of water, and it is estimated that for every 1 L of beer that is brewed, around 5 L of water are used: mostly for the brewing, rinsing, and cooling processes. Breweries generate large amounts of wastewater, characterized by significant levels of organic substances (starch, sugars, ethanol and volatile fatty acids), that require adequate treatment before discharge into the environment. Conventional wastewater treatment in breweries consists of various physico-chemical primary treatment steps followed by secondary biological processes, such as aerobic sequencing batch reactors, up-flow anaerobic sludge blanket reactors or anaerobic membrane bioreactors (Simate et al, 2011; Werkneh et al, 2019)
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