Influence of a supplemental carbon source on anaerobic dechlorination of pentachlorophenol in granular sludge

Abstract

Anaerobic dechlorination of pentachlorophenol (PCP) was studied in two upflow anaerobic sludge blanket reactors. One reactor received glucose (0.9 g liter-') as an additional carbon source; the other one served as a control. The concentration of PCP in the medium was 4.5 and 3.0 mg liter-' in the experimental and control reactors, respectively. The reactors were inoculated with granular sludge previously grown on sugarcontaining wastewater. After 10 months of continuous operation, the removal of PCP was 99% in the glucose-amended reactor, whereas the removal in the control reactor varied between 32 and 77%. Furthermore, 94% of the PCP was completely dechlorinated in the glucose reactor compared with a maximum of 20% in the control reactor. In the same period, the amount of biomass in the glucose reactor had increased by approximately 150% compared with that in the control reactor, where no growth of the sludge bed occurred. Batch culture activity tests showed that the addition of glucose had a stimulatory effect on the dechlorination rate of PCP per gram of volatile solids. This indicated that the better performance of the glucose-amended reactor was due to a higher concentration of biomass and a direct stimulatory effect of glucose on the dechlorination rate. The pattern of dechlorination of PCP showed that an initial para cleavage was followed by two ortho cleavages.

Toxicity and biodegradation of chlorophenols in anaerobic propionate enrichment culture

“…2,3,5-TCP was dechlorinated at the arrho position to produce 3,5-DCP ( Figure 6B); this was consistent with earlier observations (Dronamraju, 1994, andHendriksen et al, 1992). However, the two m-dechlorination intermediates, 2,5-DCP and 2,3- sequentially to produce 2,4-DCP and 4-CP ( Figure 78); this was consistent with the reductive dechlorination pathway observed by Kohring er at.…”

“…(1993) reported that reductive dechlorination could take place at any position, that is, ortho, meta, or para. Hendriksen et at. (1992) found the significant intermediates of pentachlorophenol (PCP) degradation were 2,3,5,6-TCP; 2,3,5-TCP; 3,5-DCP; and 3-CP.…”

Microbial breakdown of halogenated aromatic pesticides and related compounds

“…5). Initial para-dechlorination of pentachlorophenol has also been observed [87,90,91], and in several cases pentachlorophenol is incompletely dechlorinated, with accumulation of tetra-, tri-and dichlorophenols [72,73,77,90]. This accumulation of lesser chlorinated phenols has lead to speculation that the higher chlorinated phenols tend to be more readily dehalogenated [4].…”

“…The rates of dechlorination and growth of the anaerobic population can be enhanced by auxiliary carbon sources ( [91,92]; H~iggblom et al, submitted). A methanogenic mixed culture which degraded 2-chlorophenol via phenol completely to methane and CO 2 was recently enriched from sewage sludge [93].…”

Physiological meaning and potential for application of reductive dechlorination by anaerobic bacteria

“…Because of the low dechlorination rates, the latter treatment will become more feasible, when large quantities of the desired biomass can be retained in the reactor. The use of sugar-grown granular UASB sludge, containing high concentrations of acetogenic and methanogenic bacteria, has been successful in the dechlorination of pentachlorophenol [58]. 3(13…”