Anaerobic side-stream reactor for excess sludge reduction: 5-year management of a full-scale plant.
The long-term performances of a full-scale anaerobic side-stream reactor (ASSR) aimed at sludge reduction have been monitored for the first time, in comparison with a conventional activated sludge process (CAS). The plant was integrated with an ASSR treatment of 2293-3293 m(3). Operational parameters in the ASSR were: ORP -250 mV, interchange ratio of 7-10%, hydraulic retention time of 7 d. No worsening of effluent quality was observed in the ASSR configuration and removal efficiency of COD and NH4 was above 95%. A slight increase in the Sludge Volume Index did not cause worsening in effluent solids concentration. The observed sludge yield (Yobs) passed from 0.44 kgTSS/kgCOD in the CAS to 0.35 in the ASSR configuration. The reduction of Yobs by 20% is lower than expected from the literature where sythetic wastewater is used, indicating that sludge reduction efficiency is largely affected by inert mass fed with influent real wastewater. An increase by 45% of the ASSR volume did not promote a further reduction of Yobs, because sludge reduction is affected not solely by endogenous decay but also by other factors such as interchange ratio and aerobiosis/anaerobiosis alternation.
Department of Sanitary and Environmental Engineering, UFSC/CTC/ENS, Campus Universitário, Trindade, Florianópolis, SC 88.040-900, Brazil.
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Velho
Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano, 77, 38123, Trento, Italy. Electronic address: paola.foladori@unitn.it.
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Foladori
Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano, 77, 38123, Trento, Italy.
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Andreottola
Department of Sanitary and Environmental Engineering, UFSC/CTC/ENS, Campus Universitário, Trindade, Florianópolis, SC 88.040-900, Brazil.
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Costa
D000332:Aerobiosis; D000693:Anaerobiosis; D019149:Bioreactors; D012722:Sewage; D018505:Waste Management / Q000379:methods*; D062065:Wastewater
D012722:Sewage; D062065:Wastewater
Activated sludge; Anaerobic side-stream reactor; Excess sludge production; Oxic-settling-anaerobic process; Sludge reduction; Wastewater treatment