The Biodegradation of 4-Chlorophenol in a Moving Bed Biofilm Reactor Using Response Surface Methodology: Effect of Biogenic Substrate and Kinetic Evaluation.

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.

Construction of integrated system for the treatment of Acid orange 7 dye from wastewater: Optimization and growth kinetic study.

In this work, an effort has been made to develop an integrated system (ozonation followed by biodegradation) for the treatment of Acid orange 7 (AO 7) dye. The process parameters such as pH (3.0-11) and ozone dosage (5-25 mg/L) were optimized and obtained as 3.0 and 25 mg/L, respectively to treat the AO 7 by ozonation. Similarly, the process parameters, namely pH (5.0-9.0) and temperature (25-45 °C) were optimized and found to be 7.0 and 35 °C, respectively by biological treatment. Bacillus sp. was found to be the most effective bacteria to remove the AO 7. An integrated system obtained an overall 98.7% removal of AO 7 under optimum conditions. Andrews-Haldane model was best to predict the experimental data and the bio-kinetic constants; µmax: 0.1875 day-1; Ks: 49.53 mg/L; Ki: 133.32 mg/L were obtained. The developed integrated system can be a promising option for the treatment of azo dye containing-wastewaters.

Application of Arjuna (Terminalia arjuna) seed biochar in hybrid treatment system for the bioremediation of Congo red dye.

In the present study, a hybrid treatment system (biological and ozonation) was developed and used in the decolorization of Congo red (CR) dye. The biological treatment was performed in packed bed bioreactor (PBBR) containing Arjuna (Terminalia Arjuna) seeds biochar immobilized with Providencia stuartii, whereas ozonation was carried out in an ozone reactor. The process variables such as temperature, process time, and inoculum size were optimized and found to be 30 °C, 2 48 h, and 3 × 105 CFU/mL, respectively with 92.0 ± 5.0% of dye decolorization. Furthermore, biologically treated effluent was subject to ozone treatment for the decolorization of the remaining CR dye. The hybrid approach reveals almost complete decolorization of Congo red (CR) dye. The kinetic study of microbial growth was examined by Monod model. In addition, the cost analysis estimation for the removal of CR dye was done, and removal per liter was found to be economic.