Repeated Batch-Fed Bioevaporation of Food Waste Using Biofilm-Developed Sponge

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ABSTRACTBy aerobically cultivating the fragmented sponge in synthetic wastewater containing activated sludge obtained from a wastewater treatment plant (WWTP), biofilm was developed on its surface, and this biofilm-containing sponge was used as a bulking agent and microbial carrier for food waste (FW) bioevaporation. The water of the FW was evaporated by metabolic heat released from the aerobic microbial degradation of the volatile solids (VS) contained in FW. Repeated running of FW bioevaporation for 10 cycles was successful in that 85–96% of the H2O added as FW was removed by consuming 56–71% of the FW VS during the second to tenth cycles. For the first cycle, it was found by microbial community analysis using a pyrosequencing technique that heat production was less than subsequent cycles (second to tenth cycles) because thermophilic microorganisms were not fully developed yet. From the second to tenth cycles, thermophilic bacteria, mostly belonging to the genus Bacillus, accounted for 43–83% of the total population, whereas less than 1% was identified as Bacillus among microorganisms contained in the FW, fresh biofilm, and the feed (mixture of FW and biofilm-developed sponge). B. thermolactics, B. coagulans, and Pseudoxanthomonas taiwanensis were the major species in the second to tenth cycles of the bioevaporation process. It was also found that the accumulated VS was further degraded by adding water into the bioevaporation reactor. From these results, it was concluded that repeated bioevaporation was possible by using biofilm-developed sponge.