The feasibility of treating of chemical synthesis-based pharmaceutical wastewater containing rich
organic sulfur compounds and sulfate using an upflow anaerobic sludge blanket (UASB) was investigated.
The initial COD/SO4
2 ratio of 8 in the wastewater varied from 5 to 1.5 after adding sulfate. Of interest that
under the condition of COD/SO4
2 at 8 and 5, despite the simultaneous generation of sulfide and hydrogen
sulfide, the sulfate concentration in the effluent was higher than in the influent. This is due to the sulfur
release in the form of sulfate during the degradation of these organic sulfur compounds in this reactor.
Conversely, at COD/SO4
2 of 1.5, influent sulfate was higher than effluent sulfate due to reduction of more
sulfates in the reactor. At COD/SO4
2 of 8, for practical application, the optimum OLR was found to be 8 kg
COD/m3
/d, where a nearly 70% COD reduction occurred with biogas containing 63% methane. In this
stage, the distribution of the archaea and bacterial community varied greatly with altered OLR
(accompanied with prolonged operation time). Some species, such as Lysinibacillus sphaericus, Clostridium
cellulovorans were expected to be partly responsible for S release from some organic sulfur compounds in
the reactor. By increasing the sulfate loading at a COD/SO4
2 ratio up to 1.5 resulted in a light inhibition of
methanogenesis due to the high sulfide concentration (1212 SO4
2 – S mg/L) with no obvious suppression
of sulfidogenesis.
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