The Effect Of Inert Carrier And Polymer On Granulation Treating Low-strength Wastewater At Room Temperature

Effect of inert carrier and flocculants on granulation in lab-scale UASB reactors treating low-strength wastewater(COD350～500mg/L) at room temperature (25℃)was examined. A reactor was operated with adding cationic quaternary ammonium polymer. The other reactor was operated with adding powdered activated carbon and cationic quaternary ammonium polymer. The third reactor was operated with adding powdered activated carbon and polyaluminium chloride. This study assessed the influence of cationic polymer and inert carrier on granule formation and start-up in UASB.The major conclusions are as follows:(1) Inert carrier and flocculants was more effective additive for enhancing sludge granulation. Forming speed of granular sludge was same in the two added inert carrier and flocculants reactors; After 60 days, the two reactors had a large number of small granular sludge, and also appeared a few larger size particles; After operating 120 days, they formed mature granular sludge, and the size of sludge particle > 0.5mm particles accounted for 60% of total sludge. The reactor which only added cationic quaternary ammonium polymer formed mature granular sludge with running after 196 days, and the size of sludge particle > 0.5mm particles accounted for 54.0⁶4.3% of total sludge; The size of sludge particle > 0.5mm particles only accounted for 34.7⁴8.3% of total sludge in the reactor which operated with no addition after 196 days. There was the shortest time formed mature granular sludge in reactors which added powdered activated carbon and flocculants.(2) In terms of characteristics of granular sludge: the granular sludge which added powdered activated carbon and flocculants reactors has better settling performance and specific methanogenic activity (SMA) than the reactor which has no addition.â‘ While the end of reactor operation, the value of VSS/SS was 0.76⁰.77 in reactors with adding powdered activated carbon and flocculants. The value of VSS/SS was 0.76 in adding flocculants reactor. In no additive reactor,the value of VSS/SS was 0.74, the value of VSS/SS in several reactors has little difference. This showed that it had little influence on the growth of anaerobic micro-organisms and had not toxic effect on anaerobic micro-organisms that added inert carrier and flocculants.â‘¡Compared to other reactors, the granular sludge which added powdered activated carbon and flocculants reactors had better settling performance, and the value of SVI of the granular sludge was in 29.0 30.5mL/gSS.â‘¢I n adding powdered activated carbon and flocculants reactors, the value of specific methanogenic activity (SMA) in each sampling place has between 1.20 2.14gCH₄-COD/gVSS·d and 1.09².25gCH₄-COD/gVSS·d. In only adding flocculants reactor, the value of SMA in each sampling place was in 1.27¹.55gCH₄-COD/gVSS·d. Compared to no additive reactor, the reactors which added powdered activated carbon and flocculants had higher SMA. This showed that it could improve specific methanogenic activity that added powdered activated carbon and flocculants.(3) Reactors which added powdered activated carbon and flocculants round superior to the no additive reactor in the system stability and performance. In adding powdered activated carbon and flocculants reactors, the value of effluent's VFA were about 25mg/L, the value of alkalinity was 510mg/L and 500mg/L separately. COD removal efficiency was stable at 85% in each reactor at later stage. This showed that UASB reactor could achieve higher COD removal rate treating low-strength wastewater at room temperature.