Phycoremediation of pollutants from secondary treated coke-oven wastewater using poultry litter as nutrient source: a cost-effective polishing technique

Harmless treatment of cyanide tailings by functional bacteria: Degradation of cyanide and the secondary pollutant ammonia nitrogen

The eco-friendly treatment of cyanide tailings (CT) using microorganisms is a cost-effective and promising technology. However, this process often generates the secondary pollutants, such as ammonia nitrogen (NH4+-N), which can adversely impacts the surrounding environment. The accumulation of NH4+-N is also toxic to cyanide-degrading microorganisms, presenting a significant challenge in achieving simultaneous cyanide degradation and NH₄⁺-N mitigation. In this study, a group of functional bacteria CG305-1 with the ability to degrade cyanide and perform nitrification and denitrification was successfully enriched for the first time and used to treat CT by in situ microbial drenching technology. Results demonstrated that the total cyanide (CNT) concentration in the leaching solution decreased from 49.96 ± 1.51 mg/L to 0.19 ± 1.11 mg/L. NH₄⁺-N was degraded to 0.25 ± 0.18 mg/L, and nitrate nitrogen (NO3--N) was reduced to 0.41 ± 0.20 mg/L. Furthermore, CNT in the CT leachate was reduced to 0.94 ± 0.11 mg/L, meeting the storage standard for CT leachate (CNT < 5 mg/L). The potential synergistic microbial degradation mechanisms were elucidated through Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Metagenomic sequencing. This study provides significant insights into green and sustainable methods for the harmless treatment of CT.

Use microalgae to treat coke wastewater for producing biofuel: Influence of phenol on photosynthetic properties and intracellular components of microalgae

Using microalgae to treat coking wastewater has important application prospects and environmental significance. Previous studies have suggested that phycoremediation of pollutants from coking wastewater is feasible and can potentially enhance biodiesel production. This work investigates the effects of phenol in coking wastewater on C. pyrenoidosa and S. obliquus growth, photosynthesis activity, and intracellular components. The results indicated that when the phenol concentration was lower than 300 mg L-1, both microalgae maintained good photosynthetic and physiological activity, with a maximum quantum yield potential ranging from 0.6 to 0.7. At the phenol concentration of 300 mg L-1, the biomass of C. pyrenoidosa was 2.4 times that of the control group. For S. obliquus, at the phenol concentration of 150 mg L-1, the biomass was approximately 0.85 g L-1, which increased by 68% than that of the control group (0.58 g L-1). The lipid content in both microalgae increased with the phenol concentrations, with the maximum content exceeding 40%. The optimal phenol concentrations for C. pyrenoidosa and S. obliquus growth were determined to be 246.18 and 152.73 mg L-1, respectively, based on a developed kinetic model. This work contributes to further elucidating the effects of phenol on microalgae growth, photosynthesis, and intracellular components, and suggests that using microalgae to treat phenol-containing coking wastewater for producing biofuel is not only environmentally friendly but also holds significant energy promise.

Tertiary treatment of coke-oven wastewater using suspended and immobilized whole live cells of constructed bacterial-microalgal consortium: modeling and optimization using ANN-GA hybrid methodology

Coke-oven wastewater (CW), containing an array of toxic pollutants above permissible limits even after conventional primary and secondary treatment, needs a tertiary (polishing) step to meet the statutory limit. In the present study, a suitable bacterial-microalgal consortium (Culture C) was constructed using bacterial (Culture B: Bacillus sp. NITD 19) and microalgal (Culture A: a consortium of Chlorella sp. and Synechococcus sp.) cultures at different ratios (v/v) and the potential of these cultures for tertiary treatment of CW was assessed. Culture C4 (Culture B:Culture A = 1:4) with inoculum size: 10% (v/v) was selected for the treatment of wastewater since the maximum growth (3.08 ± 0.57 g/L) and maximum chlorophyll content (4.05 ± 0.66 mg/L) were achieved for such culture in PLE-enriched BG-11 medium. During treatment of real secondary treated coke-oven effluent using Culture C4 in a closed photobioreactor, the removal of phenol (80.32 ± 2.76%), ammonium ions (47.85 ± 1.83%), fluoride (65.0 ± 4.12%), and nitrate (39.45 ± 3.42%) was observed after 24 h. In a packed bed bioreactor containing immobilized C4 culture, the maximum removal was obtained at the lowest flow rate (20 mL/h) and highest column bed height (20 cm). Artificial intelligence-based techniques were used for modeling and optimization of the process.