Abstract:
This research aims to study effect of carbon source on microbial sludge granulation in UASB system for treatment of sulfate and nitrate containing wastewater using 3 identical UASB reactors. The research was divided into 2 experiments; the first experiment used synthetic wastewater by varying carbon source in reactor no.1, 2 and 3 such as sucrose, tapioca flour and waste rice-flour, respectively. COD concentration started from 600 and increased to 1,200, 1,800 and 2,400 mg/L, respectively. Nitrate and sulfate concentration was kept constant at 60 and 90 mg/L, as a result COD:SO42- ratios become 6.7:1, 13.3:1, 20.0:1 and 26.7:1, respectively. The second experiment aims to study effect of sulfate loading rate in reactor no.1, 2 and 3 to be 1.08, 1.62 and 2.16 g/L/day, respectively. The selected carbon source was waste rice-flour and kept constant nitrate 60 mg/L for every reactor. At steady state condition, The result obtained in the first experiment showed that reactor no.1, 2 and 3 had percentages for COD removal were 94.06, 92.06 and 92.30%, respectively; for nitrate were 97.80, 97.83 and 97.31% , respectively ; for sulfate were 62.75, 62.14 and 62.22 % ,respectively. It could summarize that three carbon source could remove COD, nitrate and sulfate at similar efficiency. Also, COD:SO42- ratios 20.0:1 presented the highest removal efficiency moved toward the second experiment and used waste rice-flour as carbon source. The result showed that reactor no.1, 2 and 3 had percentages for COD removal were 97.08, 97.95 and 98.95 % , respectively ; for nitrate were 95.03, 94.94 and 95.40 %, respectively ; for sulfate were 74.64, 85.53 and 85.67 % , respectively. Therefore, waste rice flour that obtained from the waste product can be used as an alternative carbon source for sludge granulation in UASB system and the system could accept higher sulfate loading rate 2.16 g/L/day. Moreover, from Scanning Electron Microscope (SEM) observation of the sludge granule and % electron flow assessment, it was found that inside the granule consisted of various shape of bacteria and the predominant microorganisms were Sulfate Reducing Bacteria (SRB).