Increasing the energy production in an urban wastewater treatment plant using a high-rate activated sludge: Pilot plant demonstration and energy balance. (20th June 2022)

• Record Type: Journal Article
• Authors: Carrera, Julián; Carbó, Oriol; Doñate, Silvia; Suárez-Ojeda, María Eugenia; Pérez, Julio
• Is Part Of: Journal of cleaner production. Volume 354(2022)
• Publication Date: 2022-06-20
• Subjects: Biomethane potential -- Observed sludge yield coefficient -- COD mass balance -- Partial nitritation -- Autotrophic nitrogen removal; Factory and trade waste -- Management -- Periodicals; Manufactures -- Environmental aspects -- Periodicals; Déchets industriels -- Gestion -- Périodiques; Usines -- Aspect de l'environnement -- Périodiques; 628.5
• DOI: 10.1016/j.jclepro.2022.131734
• Languages: English
• ISSNs: 0959-6526

Abstract

Abstract: The use of high-rate activated sludge (HRAS) reactors for the removal of COD in urban wastewater treatment plants (WWTPs) has been investigated because its potential contribution to energy generating WWTPs. A one-year operation period of a pilot plant treating the effluent of the primary settler of a full-scale WWTP was analyzed. The HRAS pilot plant operated without iron salts addition at temperatures between 12 and 28 °C at an average organic loading rate 2.8 ± 0.5 kg COD m −3 d −1 and with an average inflow COD concentration of 330 ± 86 mg O2 L −1 . The influence of sludge retention time (SRT) on COD recovery and biomethane potential of the produced sludge was investigated and compared to the full scale WWTP performance. The highest observed sludge yield coefficient and biomethane potential of the sludge were achieved at SRT of 0.6 days. The weak point of the HRAS performance at STR of 0.6 days is the high loss of organic matter in the effluent due to the limited efficiency of the solids separation in the secondary settler. At higher SRT (in the range 1.0–2.1 days), the secondary settler efficiency and the COD recovery are higher than those achieved at SRT of 0.6 days but part of the inlet ammonium can be nitrified in the HRAS system at temperatures above 20 °C. A detailed energy balance indicated that two-thirds reduction of aeration requirements and one-third increase of biogas production could be achieved in a plant configuration in which HRAS is coupled to autotrophic biological nitrogen removal (BNR) compared to the heterotrophic BNR configuration, yielding a net energy production of ca. 0.1 kWh m −3 of treated water. Graphical abstract: Image 1 Highlights: A HRAS system worked with influent COD of 350 mg L −1 and OLR of 2.9 kg COD m −3 d −1 . COD removal was 72 ± 7% during 320 days and temperatures between 15 and 25 °C. COD recovery of the HRAS system was 40% higher than that of a CAS system. Biomethane potential of the HRAS system was 43% higher than that of a CAS system.