peptones and 2-4-dichlorophenol

  The removal of 2,4-dichlorophenol (2,4-DCP) by a pure culture of Bacillus endophyticus strain immobilized on ceramic balls was studied in a packed bed biofilm reactor (PBBR). The biodegradation of 2,4-DCP was studied in fed-batch and continuous mode and the effect of different parameters such as hydraulic retention time (HRT), biogenetic substrate concentration, and loading rate on the removal of 2,4-DCP were evaluated. Field emission scanning electron microscope (FESEM) results established the biofilm formation on the ceramic beads. The maximum volumetric removal rate found to be 127.2 mg/L·d at loading rate of 172.8 mg/L·d with 73.6% degradation (12.5 hours of HRT, 90 mg/L of 2,4-DCP, 0.2 g/L of peptone). The bioreactor showed more than 98% removal of 2,4-DCP at loading rate of 115.2 mg/L·d at 12.5 hours of HRT and 0.2 g/L of peptone. Effect of peptone showed that lower peptone concentration increases the removal efficiency; however, some peptone is necessary to maintain the 2,4-DCP removal efficiency.

Topics: Bacteria; Bacterial Physiological Phenomena; Biodegradation, Environmental; Biofilms; Bioreactors; Chlorophenols; Microscopy, Electron, Scanning; Peptones; Time Factors; Waste Disposal, Fluid; Water Pollutants, Chemical

Effect of a biogenic substrate (peptone) concentration on the performance of sequencing batch reactor (SBR) treating 220 mg/l 4-chlorophenol (4-CP) and 110 mg/l 2,4-dichlorophenol (2,4-DCP) mixtures was investigated. In this context, peptone concentration was gradually decreased from 300 mg/l to null in which chlorophenols were fed to the reactor as sole carbon and energy sources. By this way, the effect of peptone concentration on observed yield coefficient (Y), biomass concentration, chlorophenols and COD removal performances were investigated. Decreasing peptone concentration accompanied with lower biomass concentration led to increase in peak chlorophenol and COD concentrations within the reactor during each SBR cycle. This, in turn, caused noteworthy declines in the removal rates as chlorophenol degradations followed Haldane substrate inhibition model. Also, increased peak chlorophenol concentrations led to the accumulation of 5-chloro-2-hydroxymuconic semialdehyde (CHMS), which is -meta cleavage product of 4-CP. Despite the decreased removal rates, complete chlorophenols and CHMS degradation, in addition to high COD removal efficiencies (>90%), were observed for all studied conditions, even chlorophenols were added as sole carbon and energy sources. Another significant point is that 2,4-DCP at slightly elevated concentrations (>20 mg/l) within the reactor caused a strong competitive inhibition on 4-CP degradation. In SBR, feeding the influent to the reactor within a certain period (i.e. filling period) provided dilution of coming wastewater, which decreased the chlorophenols concentrations to which microorganisms were exposed. Therefore, use of SBR may help to avoid both self and competitive inhibitions in the treatment of 4-CP and 2,4-DCP mixture especially in the presence high biogenic substrate concentrations. In addition, isolation and identification studies have indicated that Pseudomonas sp. and Pseudomonas stutzeri were dominant species in the acclimated mixed culture.

Topics: Biodegradation, Environmental; Bioreactors; Chlorophenols; Kinetics; Osmolar Concentration; Peptones; Water Pollutants, Chemical; Water Pollution, Chemical