Comparison of an anaerobic feed and split anaerobic–aerobic feed on granular sludge development, performance and ecology

Abstract

The retrofitting of existing wastewater sequencing batch reactors (SBRs) to select for rapid-settling aerobic granular sludge (AGS) over floc-based conventional activated sludge (CAS), could be a viable option to decrease reactor cycle time and increase hydraulic capacity. Successful CAS-to-AGS conversion has previously been shown to be highly dependent on having a dedicated anaerobic feed, which presents additional engineering challenges when retrofitting SBRs. In this study we compared the performance of a split anaerobic-aerobic (An-Aer) feed with that of a traditional dedicated anaerobic feed regarding AGS formation and stability, nitrogen removal performance and microbial ecology. Using pilot trials, we showed that AGS could be established and maintained when using a split An-Aer feed at low organic loading rates analogous to that of a parallel full-scale conventional SBR. Additionally, we showed that AGS start-up time and nitrogen removal performance were comparable under a split An-Aer feed and dedicated anaerobic feed. Microbial ecology characterisations based on whole-of-community 16S rRNA profiles and targeted analysis of functional genes specific for nitrifying and denitrifying microorganisms, showed that the two different feed strategies had only subtle impacts on both the overall community composition and functional ecology. A much greater divergence in microbial ecology was seen when comparing AGS with CAS. Data presented here will be of value to those planning to retrofit existing CAS-based SBRs to operate with AGS and demonstrates the viability of using a more cost-effective split An-Aer feed configuration over a dedicated anaerobic feed.

Phosphorus Removal from Aerobic Granular Sludge: Proliferation of Polyphosphate-Accumulating Organisms (PAOs) under Different Feeding Strategies

“…Pulse feeding followed by anaerobic mixing allows for the formation of stable granules due to the stable growth rate, which allows for a suitable balance between the growth of heterotrophic and autotrophic microorganisms [22]. Nevertheless, while one study found the split anaerobic-aerobic feeding strategy suitable for aerobic granule formation and stable granules at low organic loading rate [23], another study reported the contrary [24].…”

Anaerobic biodegradation and dewaterability of aerobic granular sludge

“…A rising number of full‐scale sequencing batch reactors (SBRs) are operated using the commercial Nereda process, which is reported to be more cost‐efficient compared to the conventional wastewater treatment technology with an overall lower energy consumption . Although numerous studies have focused on the process stability and treatment performance of AGS cultivated under laboratory‐scale as well as under full‐scale conditions, information about the impacts on advanced sludge stabilization is limited.…”

Rheology and Microbiology of Sludge from a Thermophilic Aerobic Membrane Reactor

“…Almost all the biological processes have been explored in terms of biomass composition (bacteria, protozoa, metazoan, and fungi) and activity: conventional activated sludge, attached biomass, membrane reactors, and treating either municipal [27][28][29][30][31][32][33][34] or industrial wastewater [35][36][37][38][39]. Likewise, identification and quantification of microorganisms operating under different conditions (aerobic, anoxic, and anaerobic) have been reported [25,[40][41][42][43][44][45][46].…”