Abstract
Using Ca-alginate immobilized cells of Acinetobacter sp. strain W-17, the effects of ammonium-N and nitrate-N on the biodegradation of phenol were investigated.Degradation experiments in three different culture media; minimal salts medium (MSM), simulated (SW) and modified simulated wastewater (MSW) were performed. With the freely suspended cells (cell dry weight 0.2 g/l), complete phenol (500 mg/l) degradation was achieved after incubation for 120 h. Using the immobilized cells, the time was reduced to 24 h in MSM medium, and 15 h in the MSW. The results also indicate thatstrain W-17 can tolerate to high concentrations of NH4+-N (63 mg/l) and NO3--N (1000 mg/l) without a significant loss in the phenol biodegradation rate. Moreover, the presence of 500 mg/l phenol in the MSW had no considerable effect on the removal of both ammonium-N and nitrate-N. Repeated use of immobilized cells revealed that they could be used as much as five times without loss of activity. Our findings could be extended to enhance biotreatment of phenol contamination in a variety of biological treatment processes. Key words: Phenol, biodegradation, immobilization, Acinetobacter, Ca-alginate, ammonium, nitrate.
Highlights
Phenols are distributed either as natural or artificial mono-aromatic compounds in various environmental sites
Phenol biodegradation experiments using strain W-17 showed that with the freely suspended cells about 30% of the phenol was degraded within 72h of incubation
The time needed for complete degradation of the total amount of phenol was reduced to 24 h by
Summary
Phenols are distributed either as natural or artificial mono-aromatic compounds in various environmental sites. As major pollutants, their existence in industrial wastewater treatment plants, such as oil refineries, petrochemical plants, coking plants, and phenol resin industry plants, has been well established (Watanabe et al, 1996). The toxicity of phenolic compounds often results in the reduction of wastewater biotreatment even at relatively low concentrations (Hinteregger et al, 1992). Phenol toxicity studies have shown that bacteria can adapt to low phenol concentrations, but increasing phenol concentrations appear to decrease the overall phenol biodegradation (Dean-Ross, 1989). In municipal wastewater treatment plants, the microorganisms selected for certain phenol bioremediation application have to be adapted for the high concentrations of ammonium, nitrite and nitrate. It is possible that biodegradation rate of phenol can be significantly affected by the presence of a high load of nitrogen pollutants
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