Qualification and quantification of dissolved organic matters in brewery wastewaters and their treated wastewaters

Abstract

Dissolved organic matter (DOM) in wastewater from three breweries in Thailand, namely Sites 1, 2 and 3, was qualified and quantified through DOM surrogates, fluorescent excitation-emission matrix (FEEM), fourier transform infrared (FTIR) spectroscopy, and pyrolysis gas chromatography mass spectrometry (pyrolysis GC/MS), stepwise along the treatment train which typically comprises a series of biological processes, i.e. upflow anaerobic sludge blanket (UASB) followed by activated sludge (AS). To evaluation DOM characteristics in greater detail, DOM in all samples was isolated into six DOM fractions viz. hydrophobic neutral (HPON), hydrophobic base (HPOB), hydrophobic acid (HPOA), hydrophilic base (HPIB), hydrophilic acid (HPIA) and hydrophilic neutral (HPIN) using a series of DAX-8, AG-MP-50, and WA-10 resins prior to further analyses. The results revealed that major organic fractions in brewery wastewater were HPOA and HPIB which were also found to be the main trihalomethane (THM) precursors for all three studied breweries. The major DOM components in brewery wastewater from three sites (both light and lager beers) were groups of tryptophan-like substances and fulvic and humic-like substances. The reduction of DOM was mainly found to occur during the UASB treatment which was attributed to the removal of these two major DOM fractions. This resulted in a direct reduction in trihalomethane formation potential (THMFP). In other words, the reduction in THMFP was mainly due to the disappearance of tryptophan-like substances and partially occurred from decreases of degraded fulvic and humic-like substances of the two main THM precursors. The effectiveness of the UASB and AS treatments on the reductions in DOC, UV254, and THMFP were comparable, i.e. 65, 87, 79 for DOC; 65, 88, 70, for UV254, and 71, 90, and 78% for THMFP were observed for Sites 1, 2 and 3, respectively. However, the existing THMFP of the final effluent from all three breweries was still high when compared to THMFP in the water supply facilities. Among all organic fractions, HPOA, particularly fulvic and humic-like substances, was of particular concern for water reclamation process of treated brewery wastewater, since it was still relatively predominated in residual DOM in the effluents and it was considered likely to be refractory in biological treatments. In addition, FEEM analytical results were consistent with the results from conventional DOM analyses such as DOC and UV254¬ with certain level of confidence, where FEEM was reduced by 55, 86, and 64% for Sites 1, 2 and 3, respectively. Hence, FEEM could be potentially employed as a simple monitoring technique for DOM in brewery wastewater.