Quick Startup of EGSB Reactor Seeded with Anaerobic Digestion Sludge for the Treatment of Actual Domestic Sewage under Ambient Temperature

Abstract

To obtain the rapid startup of EGSB reactor seeded with anaerobic digestion sludge for the treatment of actual domestic wastewater under ambient temperature, two startup methods i.e. A and B were tried out at 25℃. For method A, reactor A (RA) was fed with brewery wastewater to incubate granular sludge and then treated domestic sewage, for method B, reactor B (RB) was fed with sanitary waste directly to bring up granular sludge. In RA, superficial flow rate of 2.9m.h-1 was employed to offer a suitable hydraulic condition. Primary HRT and OLR were set at 4h and 2.5-5.1kgCOD·m-3·d-1, respectively to select the predominant groups, and then by stepwise shortening HRT and increasing OLR, granulation completed within 46 days namely granules with diameter more than 0.45mm accounted for 86%. During this stage, more than 90% COD was removed even at OLR of 19.1 kgCOD·m-3·d-1. Then fed with domestic wastewater, about 80% COD removal was obtained after 15 days which meant a successful startup. For RB, superficial flow rate was set at 2.7m·h-1, and HRT of 1.2h-1.5h was used to increase the OLR of low strength domestic wastewater (149-615mg•l-1) to stimulate the microbial activity. Granulation was accomplished within 60 days, although granules with diameter larger than 0.45mm only took up 57%. At this time, COD removal was above 60% regardless influent fluctuate, which meant the successful startup. Compared with the inoculum, the specific methanogenic activity of RA and RB were increased from the original 0.22gCODCH4•gVSS-1•d-1 to 0.75 gCODCH4•gVSS-1•d-1 and 0.58 gCODCH4•gVSS-1•d-1, respectively. The experimental result showed that both methods could start up successfully within two months. Nevertheless, granulation could be accelerated and higher activity of granular sludge could be obtained through method A so as to treat domestic sewage efficiently and stably in a short stage.