Isolation and characterization of organic matter-degrading bacteria from coking wastewater treatment plant

Optimisation of PAHs biodegradation by Klebsiella pneumonia and Pseudomonas aeruginosa through response surface methodology

Response Surface Methodology (RSM) with Box-Behnken Design (BBD) is used to optimise the Phenanthrene (PHE) degradation process by Klebsiella pneumoniae (K bacteria) and Pseudomonas aeruginosa (P bacteria). Wherein substrate concentration, temperature, and pH at three levels are used as independent variables, and degradation rate of PHE as dependent variables (response). The statistical analysis, via ANOVA, shows coefficient of determination R2 as 0.9848 with significant P value 0.0001 fitting in second-order quadratic regression model for PAHs removal by Klebsiella pneumonia, and R2 as 0.9847 with significant P value 0.0001 by P bacteria. According to the model analysis, temperature (P < 0.0006) is the most influential factor for PHE degradation efficiency by K bacteria, while pH (P < 0.0001) is the most influential factor for PHE degradation by P bacteria. The predicted optimum parameters for K bacteria, namely, temperature, substrate concentration, and pH are found to be 34.00℃, 50.80 mg/L, and 7.50, respectively, and those for P bacteria are 33.30℃, 52.70 mg/L, and 7.20, respectively. At these optimum conditions, the observed PHE removal rates by two bacteria are found to be 83.36% ± 2.1% and 81.23% ± 1.6% in validation experiments, respectively. Thus RSM can optimise the biodegradation conditions of both bacteria for PHE.

Constructed microalgal-bacterial symbiotic (MBS) system: Classification, performance, partnerships and perspectives

The microalgal-bacterial symbiotic (MBS) system shows great advantages in the synchronous implementation of wastewater treatment and nutrient recovery. To enhance the understanding of different MBS systems, this review summarizes reported MBS systems and proposes three patterns according to the living state of microalgae and bacteria. They are free microalgal-bacterial (FMB) system, attached microalgal-bacterial (AMB) system and bioflocculated microalgal-bacterial (BMB) system. Compared with the other two patterns, BMB system shows the advantages of microalgal biomass harvesting and application. To further understand the microalgal-bacterial partnerships in the bioflocculation of BMB system, this review discusses bioflocs characteristics, extracellular polymeric substances (EPS) properties and production, and the effect of microalgae/bacteria ratio and microalgal strains on the formation of bioflocculation. Microalgal biomass production and application are important for BMB system development in the future. Food processing wastewater characterized by high biodegradability and low toxicity should be conducive for microalgal cultivation. In addition, exogenous addition of functional bacteria for nutrient removal and bioflocculation formation would be a crucial research direction to facilitate the large-scale application of BMB system.

Combination of Coagulation and Ozone Catalytic Oxidation for Pretreating Coking Wastewater

In this study, coagulation, ozone (O₃) catalytic oxidation, and their combined process were used to pretreat actual coking wastewater. The effects on the removal of chemical oxygen demand (COD) and phenol in coking wastewater were investigated. Results showed that the optimum reaction conditions were an O₃ mass flow rate of 4.1 mg min⁻¹, a reaction temperature of 35 °C, a catalyst dosage ratio of 5:1, and a O₃ dosage of 500 mg·L⁻¹. The phenol removal ratio was 36.8% for the coagulation and sedimentation of coking wastewater under optimal conditions of 25 °C of reaction temperature, 7.5 reaction pH, 150 reaction gradient (G) value, and 500 mg·L⁻¹ coagulant dosage. The removal ratios of COD and phenol reached 24.06% and 2.18%, respectively. After the O₃-catalyzed oxidation treatment, the phenols, polycyclic aromatic hydrocarbons, and heterocyclic compounds were degraded to varying degrees. Coagulation and O₃ catalytic oxidation contributed to the removal of phenol and COD. The optimum reaction conditions for the combined process were as follows: O₃ dosage of 500 mg·L⁻¹, O₃ mass flow of 4.1 mg·min⁻¹, catalyst dosage ratio of 5:1, and reaction temperature of 35 °C. The removal ratios of phenol and COD reached 47.3% and 30.7%, respectively.