Calcium phosphate granules formation: Key to high rate of mesophilic UASB treatment of toilet wastewater

Toilet wasiewaler, a rich source of organic mailer and nutrients, can be treated anaerobically to recover energy and resources al mesophilic conditions (35 degrees C) using an upflow anaerobic sludge blanket (UASB) digester. However, low organic loading rates (OLR) have often been reporlecl, which may be allribulecl to the flocs biomass applied in previous studies. In the present study, CaP granules were developed in the UASB reactor during the reactor operation of 250 days, which accounted for 89.2% of the UASB sludge, and had high VSS (25.9 +/- 0.3 g/L) and high methanogenesis rates (0.34 +/- 0.04 g CH4-COD/(gVSS.d)). An OLR of 16.0 g/(L.d) and a hydraulic retention time (HRT) of 025 days, were achieved, with a total chemical oxygen demand (COD) removal rate of 75.6 +/- 6.0%, and a methane production rate 01 84 +/- 0.9 g CH4-CODAL. d). The efficiency of the hydrolysis of Ofganic substrates ranged from 32.6 2.8% to 43.4 1.4%. Microbial community analysis revealed that syntrophic bacteria Vittrophtis, together with diverse H-2-utilizing methanogens, proliferated; and eventually resulted in a hydrogenotrophic dominant pathway in the UASB reactor. The performance, mechanism of CaP granule formation, and the application of the process were discussed in detail. The present paper provided insight of high rale biomethane production from anaerobic toilet wastewater treatment. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

In this study, CaP granules were developed in the UASB reactor during 250 days of operation, leading to high VSS and methane production rates. Microbial community analysis revealed the proliferation of syntrophic bacteria Vittrophtis and diverse H-2-utilizing methanogens, resulting in a hydrogenotrophic dominant pathway in the UASB reactor.