Performance evaluation of continuous and fed batch sequential moving bed reactors for removals of phenol thiocyanate and ammonia-nitrogen from wastewater
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Date
2012
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Abstract
(SMA) was achieved up to feed SCN- 200 mg/L in R1/B1. Increased HRT enhanced the pollutant removal efficiencies. Phenol and COD removal in R1 was significantly inhibited at feed phenol, SCN- and NH4 +-N concentration 1500, 200, and 500 mg/L or above whereas inhibition in B1 was observed at phenol, thiocyanate and pyridine concentrations of 2000, 400 and 50 mg/L, respectively. Increased fill time negatively affected phenol/COD removal; however, instant fill was strongly unfavorable and gradual short fill facilitated performance of B1. Increased cycle time enhanced pollutant removal efficiency in B1 by increasing reactor HRT. In both R1 and B1 Lactobacillus sp. and Streptococcus sp. were common. Influent to R2/B2 constituted by effluent from R1/B1 and recycle from R3/B3 (recycle ratio 1) with additional nitrate. Simultaneous phenol, thiocyanate, COD and nitrate removals were achieved. NH4 +-N concentration increased along with sulfate due to thiocyanate degradation. SCN- concentration of 54-400 mg/L in influent caused no significant inhibitory effect on phenol, thiocyanate and COD removal in R2/B2; however higher phenol concentration (above 468 mg/L in R2 and 511 mg/L in B2) showed negative effect on SCN- removal. Contribution of R2 and B2 in SCN- removal was significantly high compared to R3 and B3. In FMBR system B1 highly contributed in total phenol and COD removal, whereas in CMBR system both R2 and R3 were significantly responsible for phenol and COD removals. It was observed that nitrate- nitrogen was essential for SCN- removal. COD:N removal ratio was 3-7 in R2 and 2.2-6 in B2. R2 showed presence of Streptococcus sp., Neisseria sp., Corynebacterium sp. and Citrobacter sp.. Similar to thiocyanate removal, B2 showed higher pyridine removal compared to B1 and B3. Pyridine caused no inhibitory affect in B2 in terms of phenol/COD removal though at high concentration (127 mg/L) it affected SCN- removal. Increased cycle time enhanced pollutant removal whereas change in fill time showed insignificant affect on performance of B2 and the optimum fill time was 3-5 hour. Pseudomonas sp., Enterobacter sp., E. coli and Citrobacter sp. were observed in B2..
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Supervisor: S. Chakroborty
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ENVIRONMENT