Pilot-scale investigation of sludge reduction in aerobic digestion system with endospore-forming bacteria

- A pilot-scale sludge treatment process was developed and investigated.
- Membrane-based aerobic digestion system could accumulate the sludge.
- 90% of sludge reduction was achieved in sludge treatment process.
- Bacillus species was dominant and influenced on the sludge reduction.
- Endospore-forming bacteria-based process could be suitable for sludge reduction.

A pilot-scale investigation of membrane-based aerobic digestion system dominated by endospore-forming bacteria was evaluated as one of the potential sludge treatment processes (STP). Most of the organic matter in the sludge was removed (90.1%) by the particular bacteria in the STP, which consisted of mixed liquor suspended solid (MLSS) contact reactor (MCR), MLSS oxidation reactor (MOR), and membrane bioreactor (MBR). The sludge was accumulated in the MBR without wasting, and then the effluent in STP was fed into the first step in water resource recovery facility (WRRF). According to the analysis of microbial communities in all reactors, various Bacillus species were present in the STP, mainly due to their intrinsic resistance to the extreme conditions. As the surviving Bacillus species might consume degraded microorganisms for their growth, these endospore-forming bacteria-based STP could be suitable for the sludge reduction when they operated for a long time.

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