peptones and 4-chlorophenol

4-Chlorophenol (4-CP) is a persistent organic pollutant commonly found in petrochemical effluents. It causes toxic, carcinogenic and mutagenic effects on human beings and aquatic lives. Therefore, an environmentally benign and cost-effective approach is needed against such pollutants. In this direction, the chlorophenol degrading bacterial consortium consisting of Bacillus flexus GS1 IIT (BHU) and Bacillus cereus GS2 IIT (BHU) was isolated from a refinery site. A composite biocarrier namely polypropylene-polyurethane foam (PP-PUF) was developed for bacterial cells immobilization purpose. A lab-scale moving bed biofilm reactor (MBBR) packed with Bacillus sp. immobilized PP-PUF biocarrier was employed to analyse the effect of peptone on biodegradation of 4-CP. The statistical tool, i.e. response surface methodology (RSM), was used to optimize the process variables (4-CP concentration, peptone concentration and hydraulic retention time). The higher values of peptone concentration and hydraulic retention time were found to be favourable for maximum removal of 4-CP. At the optimized process conditions, the maximum removals of 4-CP and chemical oxygen demand (COD) were obtained to be 91.07 and 75.29%, respectively. In addition, three kinetic models, i.e. second-order, Monod and modified Stover-Kincannon models, were employed to investigate the behaviour of MBBR during 4-CP biodegradation. The high regression coefficients obtained by the second-order and modified Stover-Kincannon models showed better accuracy for estimating substrate degradation kinetics. The phytotoxicity study supported that the Vigna radiata seeds germinated in treated wastewater showed higher growth (i.e. radicle and plumule) than the untreated wastewater.

Topics: Biofilms; Bioreactors; Chlorophenols; Humans; Kinetics; Peptones; Waste Disposal, Fluid; Wastewater

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

Two sequencing batch reactors (SBRs) instantaneously fed with 200 mg/l 4-chlorophenol (4-CP) were operated at different feed peptone concentrations to investigate the effect of biogenic substrate (peptone) concentrations on reactor performance, yield coefficient (Y) and 4-CP degradation kinetics. One of the reactors was operated at 10 days of sludge retention time (SRT) and the other was operated at 20 days of SRT. High chemical oxygen demand (COD) removal efficiencies (90-95%) and complete 4-CP removals (detection limit was 0.05 mg/l) were observed even in the absence of peptone. Accumulation of 5-chloro-2-hydroxymuconic semialdehyde (CHMS), meta cleavage product of 4-CP, was observed, which was completely removed at the end of the reactor cycle. It was concluded that decreasing peptone concentrations did not affect 4-CP degradation profiles and Haldane equation can be satisfactorily used to predict time course variation of 4-CP concentrations. It was assumed that specialists (competent biomass) are only responsible for 4-CP degradation and its concentration was constant although peptone concentration in the feed was varied, as competent biomass grows on 4-CP only. Model developed using this assumption well tracked the experimental data. The kinetic coefficients obtained for the reactor operated at 10 days of SRT were also valid for the reactor operated at 20 days of SRT although higher degradation rates were observed due to higher steady state biomass concentrations.

Topics: Bacteria; Biodegradation, Environmental; Biomass; Bioreactors; Chlorophenols; Chromatography, High Pressure Liquid; Dose-Response Relationship, Drug; Glass; Kinetics; Peptones; Sewage; Time Factors; Waste Disposal, Fluid; Water Purification

Unacclimated and acclimated activated sludges were examined for their ability to degrade 4-CP (4-chlorophenol) in the presence and absence of a readily growing substrate using aerobic batch reactors. The effects of 4-CP on the micro (specific growth rate), COD removal efficiency, Y (yield coefficient), and q (specific substrate utilization rate) were investigated. It was observed that the toxicity of 4-CP on the culture decreased remarkably after acclimation. For example, the IC(50) value on the basis of micro was found to increase from 130 to 218 mg/L with the acclimation of the culture. Although an increase in 4-CP concentration up to 300 mg/L has no adverse effect on the COD removal efficiency of the acclimated culture, a considerable decrease was observed in the case of an unacclimated culture. Although 4-CP removal was not observed with an unacclimated culture, almost complete removal was achieved with the acclimated culture, up to 300 mg/L. The Haldane kinetic model adequately predicted the biodegradation of 4-CP and the kinetic constants obtained were q(m)=41.17 mg/(gMLVSSh), K(s)=1.104 mg/L, and K(i)=194.4 mg/L. The degradation of 4-CP led to formation of 5-chloro-2-hydroxymuconic semialdehyde, which was further metabolized, indicating complete degradation of 4-CP via a meta-cleavage pathway.

Topics: Adaptation, Physiological; Bacteria, Aerobic; Biodegradation, Environmental; Bioreactors; Chlorophenols; Colony Count, Microbial; Kinetics; Models, Biological; Peptones; Sewage; Waste Disposal, Fluid