Sludge Minimization Coupled with Biological Nitrogen and Phosphorus Removal - A Step towards Sustainable AS Process Operation
Abstract:Excess biomass generated during municipal wastewater treatment using activated sludge processes is one of the main drawbacks of this treatment process. In this study, two sequencing batch reactors (SBRs) were operated and monitored to evaluate, (i) the long term sustainability of sludge reduction and nutrient removal and (ii) fate of carbon in the lab scale reactors as well as in full scale plants run under similar sludge reduction modes. One of the lab scale reactors (called control SBR) was run in standard operational mode at 10-day SRT while the other reactor (called modified SBR) was run in sludge minimizing mode at nearly 100-day SRT to induce the anaerobiosis of the returned biomass in a sidestream reactor. Furthermore, to compare the overall biomass yields in both reactors, the wasted biomass from the conventional reactor was taken to a conventional anaerobic digester. Overall, both reactors achieved more than 85 % removal of phosphorus to exhibit successful EBPR performance, and showed complete ammonia nitrogen removal. The modified SBR generated 60 % less biomass than the control SBR. This research in particular highlights the suitability of the sludge minimizing activated processes for nutrient removal. Carbon mass balance and partitioning experiments based on 13C substrate reveal that both modified SBR and the associated sides-stream reactor demonstrated better mineralization in terms of CO2 production. Furthermore, for the modified SBR, less 13C partitioned into biomass and more 13C went into head space in the form of CO2, thus providing a putative explanation for why modified SBR enabled low biomass yield.
Document Type: Research Article
Publication date: January 1, 2012
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