Performance evaluation of a UASB - activated sludge system treating municipal wastewater

Abstract

Recent research has indicated the advantages of combining anaerobic and aerobic processes for the treatment of municipal wastewater, especially for warm-climate countries. Although this configuration is seen as an economical alternative, is has not been investigated in sufficient detail on a worldwide basis. This work presents the results of the monitoring of a pilot-scale plant comprising of an UASB reactor followed by an activated sludge system, treating actual municipal wastewater from a large city in Brazil. The plant was intensively monitored and operated for 261 days, divided into five different phases, working with constant and variable inflows. The plant showed good COD removal, with efficiencies ranging from 69% to 84% for the UASB reactor, from 43% to 56% for the activated sludge system only and from 85% to 93% for the overall system. The final effluent suspended solids concentration was very low, with averages ranging from 13 to 18 mg/l in the typical phases of the research. Based on the very good overall performance of the system, it is believed that it is a better alternative for warm-climate countries than the conventional activated sludge system, especially considering the total low hydraulic detention time (4.0 h UASB; 2.8 h aerobic reactor; 1.1 h final clarifier), the savings in energy consumption, the absence of primary sludge and the possibility of thickening and digesting the aerobic excess sludge in the UASB reactor itself.

Treatment of domestic wastewater in an up-flow anaerobic sludge blanket reactor followed by moving bed biofilm reactor

“…COD suspended removal values for the UASB-MBBR were 96, 96 and 94% at a total HRT's of 13.3, 10 and 5.0 h, respectively. Similar removal efficiency of 92% for TSS was achieved using UASB-AS system at a HRT of 9.9 h [31]. In another study, UASB reactor in combination with a submerged aerated biofilter provided 94% for TSS removal [4].…”

“…The total system achieved an overall removal efficiency of 95% of COD. An UASB-activated sludge (AS) system treating domestic wastewater was investigated by Sperling et al [31]. The integrated system achieved a removal efficiency of COD (85-93%) at a total HRT of 7.9 h (4.0 h UASB ?…”

Review of Upflow Anaerobic Sludge Blanket Reactor Technology: Effect of Different Parameters and Developments for Domestic Wastewater Treatment

“…The combined system is energy efficient, less sludge producer, and relatively less complex for domestic wastewater treatment as compared to other options. An added advantage is the biological oxidization of Journal of Chemistry 7 the dissolved methane; however, the overall greenhouse gas reduction will depend on the energy consumption of aerobic step [44,66]. The UASB and posttreatment system can be applied consecutively or in an integrated manner.…”

Aerobic and Anaerobic Sewage Biodegradable Processes: The Gap Analysis

“…Activated sludge process has been the method of interest as it provides various advantages including high efficiency, operational flexibility, and nutrient removal. Application of UASB reactor with AS system is able to produce less sludge and consume less energy than conventional AS system [32]. Up to 60% sludge reduction and 40% energy consumption have been shown through the use of UASB-AS system on low strength domestic wastewater (340 mg/L BOD 5 ) [20].…”