Effect of non-feeding period length on the intermittent operation of UASB reactors treating dairy effluents

• Published in: Biotechnology and bioengineering Vol. 96; no. 2; pp. 244 - 249
• Main Authors: Coelho, N.M., Rodrigues, A.A., Arroja, L.M., Capela, I.F.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.02.2007; Wiley; Wiley Subscription Services, Inc
• Subjects: Adsorption; Agricultural wastes; Anaerobic digestion; Anaerobiosis; Biodegradation; Biological and medical sciences; Biomass; Bioreactors; Biotechnology; Dairy industry wastewaters; Dairy products; dairy wastewater; Dairying; Feeding; Fundamental and applied biological sciences. Psychology; intermittent operation; Material balance; Methane - biosynthesis; non-feeding period; Organic loading; Organic matter; Reactors; Time Factors; UASB reactor; Waste Disposal, Fluid - methods; Waste management; Water treatment; Water treatment plants; UASB reactor; dairy wastewater; intermittent operation; non-feeding period; Bioreactor; Upflow anaerobic sludge blanket reactor; Effluent; Waste water
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/bit.21095

Recent environmental concerns have prompted a re‐evaluation of conventional management strategies and refueled the search of innovative waste management practices. In this sense, the anaerobic digestion of both fat and the remaining complex organic matter present in dairy wastewaters is attractive, although the continuous operation of high rate anaerobic processes treating this type of wastewaters causes the failure of the process. This work accesses the influence of non‐feeding period length on the intermittent operation of mesophilic UASB reactors treating dairy wastewater, in order to allow the biological degradation to catch up with adsorption phenomenon. During the experiments, two UASB reactors were subject to three organic loading rates, ranging from 6 to 12 gCOD · L−1 · d−1, with the same daily load applied to both reactors, each one with a different non‐feeding period. Both reactors showed good COD removal efficiencies (87–92%). A material balance for COD in the reactors during the feeding and non‐feeding periods showed the importance of the feedless period, which allowed the biomass to degrade substrate that was accumulated during the feeding period. The reactor with the longest non‐feeding period had a better performance, which resulted in a higher methane production and adsorption capacity for the same organic load applied with a consequent less accumulation of substrate into the biomass. In addition, both reactors had a stable operation for the organic load of 12 gCOD · L−1 · d−1, which is higher than the maximum applicable load reported in literature for continuous systems (3–6 gCOD · L−1 · d−1). Biotechnol. Bioeng. 2007;96: 244–249. © 2006 Wiley Periodicals, Inc.