Biological Treatment of Phenol in the Presence of 4-Chlorophenol by Mixed Microbial Cultures via Cometabolism

摘要

-Aromatic hydrocarbons like phenol and 4-chlorophenol (4-CP) are known as highly toxic, carcinogenic, hazardous, and therefore wastewaters containing these pollutants have to be treated. Microorganisms with bioremediation ability can be used very effectively in the treatment of wastewaters polluted with these recalcitrant chemicals. This work is focused on considering the capability of mixed microbial cultures for the treatment of wastewaters contaminated with phenol and 4-CP. For this purpose, nine different samples were taken from Emet Boron Work (BW) of Eti Mine General Directorate, petroleum-contaminated soil, Tatlar Wastewater Treatment Plant, drug mill wastewater (DW1, DW2, DW3), Stenkim Construction Chemicals, Kipas Paper Factory and Kipas Textile Factory. These samples were used as sources of different mixed microbial cultures. To prepare different mixed microbial cultures, an enrichment procedure was used consisting of a periodic subculturing of the samples into the mineral salt medium with 1% molasses (v/v) (MSM) at pH 7. Obtained mixed microbial cultures were tested in media with pure solutions of phenol and 4-CP or their binary mixtures. The effect of different pH levels (6; 7 and 8) and initial phenol concentrations in the presence of 4-CP (nearly 5.0 mg/L) and the absence of it on pollutant removal by nine mixed microbial cultures were determined. Of these, the most efficient culture was BW mixed culture with anoptimal pH of 8, although it could not degrade pure 4-CP. We succeeded to mineralize the pollutants 100% of 164.4 mg/L phenol and 5.3 mg/L 4-CP. Under the same media conditions, the maximum specific phenol and 4-CP values (q_m) for BW mixed culture were 94.1 and 3.0 mg/g, respectively. Molasses were also used as supplementary material to support the growth of the microorganisms as an additional carbon and energy source, which might enhance cometabolic 4-CP degradation in the presence of phenol.