Maximizing energy recovery from wastewater via bioflocculation-enhanced primary treatment: a pilot scale study

• Published in: Environmental technology 2021-06, Vol.42 (14), p.2229-2239
• Main Authors: Dolejš, Petr, Varga, Zdeněk, Luza, Benjamin, Pícha, Aleš, Jeníček, Pavel, Jeison, David, Bartáček, Jan
• Format: Article
• Language: English
• Subjects: Activated sludge process; Advanced primary treatment; Aeration; Anaerobic digestion; bioflocculation; Carbon sequestration; Chemical oxygen demand; Chemical precipitation; Contact stabilization; Denitrification; denitrification potential; Energy harvesting; Energy recovery; Flocculation; Methane; Municipal wastes; Municipal wastewater; Organic carbon; Phosphorus; Primary sludge; Raw sewage; Retention time; Secondary treatment; Separation; Sewage disposal; Sewage sludge; Sewage treatment; Sludge; Sludge digestion; Solid suspensions; Suspended solids; Waste treatment; Wastewater treatment
• ISSN: 0959-3330; 1479-487X
• DOI: 10.1080/09593330.2019.1697377

Anaerobic digestion of municipal sewage sludge is widely used for harvesting energy from wastewater organic content. The more organic carbon we can redirect into the primary sludge, the less energy is needed for aeration in secondary treatment and the more methane is produced in anaerobic digesters. Bioflocculation has been proposed as a promising separation technology to maximize carbon capture in primary sludge. Thus far, only limited data on bioflocculation are available under real conditions, i.e. from pilot-scale reactors treating raw sewage. Moreover, no study has discussed yet the influence of bioflocculation on denitrification potential of sewage. Therefore, we performed bioflocculation of raw sewage in high-rate contact stabilization process in pilot-scale to investigate maximal primary treatment efficiency. During 100 days of operation at sludge retention time of only 2 days, the average removal efficiencies of chemical oxygen demand (COD), suspended solids and total phosphorus were 75%, 87% and 51%, respectively, using no chemicals for precipitation. Up to 76% of incoming COD was captured in primary sludge and 46% for subsequent anaerobic digestion, where energy recovery potential achieved 0.33-0.37 g COD as CH 4 per g COD of influent. This study showed in real conditions that this newly adapted separation process has significant benefits over chemically enhanced primary treatment, enabling sewage treatment process to overcome energy self-sufficiency.