| Abstract | Two lab scale anaerobic filters (AFs) were operated to investigate the potential of
AFs for the treatment of chlorophenolic wastewater. With AF1, a substrate loading rate of
150 mg/l/day (2-MCP) was possible and with AF2, 20 mg/I/day (2,4,6-TCP) was completely
dechlorinated, but major intermediate degradation product, 4-MCP was virtually persistent.
About 91 % of total influent TCP organic carbon was converted to 4-MCP. And AF2,
community did not have species that could degrade 4-MCP. TCP follow pathways i. e, TCP->
2,4-DCP--> 4-MCP and 2,4-DCP --> 2-MCP -->phenol. Very less concentration of 2-
MCP could be detected in the reactor effluent. The TOC reduction was about 98 % , with
mass balance 82 % , and 18 % of the carbon was being utilized for biomass production.
In both AFs effluent pH increased (6.8 to 7.9),due to consumption of hydrogen ions,
while _reduction of sulfate to H2S and Hs·. SEM study of reactor sludge, fed with 2-MCP
showed the dominancy of Methanothrix and Desulfovibrio spp.
Concentration of maximum influent possible chloride ions and actual effluent
concentration were same, which confirmed that the chlorophenols reduction was due to the
biodegradation mechanism, through reductive dechlorination but not due to volatilization,
or some abiotic mechanism.
Addition of molybdate (20 mM), a specific inhibitor of Sulfate Reducing Bacteria
(SRB) completely inhibited the dechlorination of 2-MCP and ring cleavage of phenol did not
occur also. But degradation of 2-MCP also completely stopped in the MPBs inhibited
enrichment with the addition of 0.5 mM chloroform. So it can be inferred that 2-MCP
degradation was not only due to SRBs, but due to syntrophic association with MPBs.
Relative disappearance of monochlorophenols isomers, in the TCP acclimated
community, was in this order: ortho > meta >para, demonstrated that rate of dechlorination
of different monochlorophenol isomers was related to position of chlorine substituent on the
benzene ring. Presence of glucose as cosubstrate stimulated, dechlorination of chlorophenols. |