title: Operating aerobic wastewater treatment at very short sludge ages enables treatment and energy recovery through anaerobic sludge digestion.
abstract: Conventional abattoir wastewater treatment processes for carbon and nutrient removal are typically designed and operated with a long sludge retention time (SRT) of 10-20 days, with a relatively high energy demand and physical footprint. The process also generates a considerable amount of waste activated sludge that is not easily degradable due to the long SRT. In this study, an innovative high-rate sequencing batch reactor (SBR) based wastewater treatment process with short SRT and hydraulic retention time (HRT) is developed and characterised. The high-rate SBR process was shown to be most effective with SRT of 2-3 days and HRT of 0.5-1 day, achieving >80% reduction in chemical oxygen demand (COD) and phosphorus and approximately 55% nitrogen removal. A majority of carbon removal (70-80%) was achieved by biomass assimilation and/or accumulation, rather than oxidation. Anaerobic degradability of the sludge generated in the high-rate SBR process was strongly linked to SRT, with measured degradability extent being 85% (2 days SRT), 73% (3 days), and 63% (4 days), but it was not influenced by digestion temperature. However, the rate of degradation for 3 and 4 days SRT sludge was increased by 45% at thermophilic conditions compared to mesophilic conditions. Overall, the treatment process provides a very compact and energy efficient treatment option for highly degradable wastewaters such as meat and food processing, with a substantial space reduction by using smaller reactors and a considerable net energy output through the reduced aerobic oxidation and concurrent increased methane production potential through the efficient sludge digestion.
authors.affiliation: AWMC, Advanced Water Management Centre, The University of Queensland, St. Lucia, Queensland 4072, Australia.
authors.forename: Huoqing
authors.initials: H
authors.lastname: Ge
authors.forename: Damien J
authors.initials: DJ
authors.lastname: Batstone
authors.forename: Jurg
authors.initials: J
authors.lastname: Keller
mesh_terms: D000003:Abattoirs; D000332:Aerobiosis; D000693:Anaerobiosis; D000818:Animals; D001419:Bacteria / Q000378:metabolism; D061249:Batch Cell Culture Techniques; D001673:Biodegradation, Environmental; D057919:Biological Oxygen Demand Analysis; D019149:Bioreactors; D006868:Hydrolysis; D007700:Kinetics; D008697:Methane / Q000032:analysis; D009566:Nitrates / Q000032:analysis; D009573:Nitrites / Q000032:analysis; D009584:Nitrogen / Q000302:isolation & purification; D010084:Oxidation-Reduction; D010758:Phosphorus / Q000302:isolation & purification; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012722:Sewage / Q000382:microbiology*; D013696:Temperature; D013997:Time Factors; D062065:Wastewater / Q000382:microbiology*; D018508:Water Purification / Q000379:methods*
chemical_list: D008697:Methane; D009566:Nitrates; D009573:Nitrites; D009584:Nitrogen; D010758:Phosphorus; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D062065:Wastewater
keywords: Abattoir wastewater; Activated sludge; Biochemical methane potential; Nutrient removal; Pyrotag sequencing; Sequencing batch reactor