Recent escalating concerns surrounding textile wastewater pollution and the urgent need for sustainable treatment solutions to mitigate its environmental impact. This study investigates the multifaceted effects of Spirulina platensis (SP) cultivation in textile wastewater from two different sources (TWW1 and TWW2), focusing on growth kinetics, Chemical Oxygen Demand (COD), and nutrient removal percentage, and seed germination enhancement. Results showed that SP exhibited comparable growth performance in TWW1 and TWW2 to the control, indicating its potential for sustainable wastewater treatment. Moreover, maximum COD removal percentages were achieved, reaching 62.59 ± 1.88 % for TWW1 and 46.68 ± 1.40 % for TWW2 on day 5. The COD removal process aligns best with the first-order kinetic model. Nutrient removal rates showed decreasing trends over time, with maximum phosphate removal percentages of 36.42 ± 0.73 % for TWW1 and 62.18 ± 1.24 % for TWW2, and maximum ammonia removal percentages of 59.34 ± 1.18 % for TWW1 and 69.31 ± 1.39 % for TWW2. FTIR analysis confirmed pollutant removal-induced changes in algal biomass functional groups. Seed germination studies indicated enhanced shoot and root development of vigna radiatas using treated TWW1 and TWW2 compared to the control, suggesting potential applications for irrigation. An increase in the lipid & carbohydrate content post-treatment was observed and it would be suitable for biofuel production. This comprehensive assessment demonstrates the synergistic benefits of phycoremediation in simultaneously removing pollutants, promoting plant growth, and enhancing wastewater treatment efficiency, underscoring its potential for sustainable water management practices.

Supercritical water gasification technology provides a favorable technology to achieve pollution elimination and resource utilization of phenolic wastewater. In this study, the reaction mechanism of phenolic wastewater supercritical water gasification was investigated using a combination of experimental and computational methods. Five reaction channels were identified to elucidate the underlying pathway of phenol decomposition. Importantly, the rate-determining step was found to be the dearomatization reaction. By integrating computational and experimental analyses, it was found that phenol decomposition via the path with the lowest energy barrier generates cyclopentadiene, featuring a dearomatization barrier of 70.97 kcal/mol. Additionally, supercritical water plays a catalytic role in the dearomatization process by facilitating proton transfer. Based on the obtained reaction pathway, alkali salts (Na2CO3 and K2CO3) are employed as a catalyst to diminish the energy barrier of the rate-determining step to 40.00 kcal/mol and 37.14 kcal/mol. Alkali salts catalysis significantly improved carbon conversion and pollutant removal from phenolic wastewater, increasing CGE from 58.44% to 93.55% and COD removal efficiency from 94.11% to 99.79%. Overall, this study provides a comprehensive understanding of the decomposition mechanism of phenolic wastewater in supercritical water.

A continuous stirred tank bioreactor (CSTB) with cell recycling combined with ceramic membrane technology and inoculated with Rhodococcus opacus PD630 was employed to treat petroleum refinery wastewater for simultaneous chemical oxygen demand (COD) removal and lipid production from the retentate obtained during wastewater treatment. In the present study, the COD removal efficiency (CODRE) (%) and lipid concentration (g/L) were predicted using two artificial intelligence models, i.e., an artificial neural network (ANN) and a neuro-fuzzy neural network (NF-NN) with a network topology of 6-25-2 being the best for NF-NN. The results revealed the superiority of NF-NN over ANN in terms of determination coefficient (R2), root mean square error (RMSE), and mean absolute percentage error (MAPE). Three learning algorithms were tested with NF-NN; among them, the Bayesian regularization backpropagation (BR-BP) outperformed others. The sensitivity analysis revealed that, if solid retention time and biomass concentrations were maintained between 35 and 75 h and 3.0 g/L and 3.5 g/L, respectively, high CODRE (93%) and lipid concentration (2.8 g/L) could be obtained consistently.

OBJECTIVE: A microbial fuel cell (MFC) has been conceived and constructed for the treatment of the sheep manure wastes and their conversion into clean sustainable renewable energy. The aim of the present investigation was to examine the performance of this bioelectrochemical device, in breaking down the organic matter (pollutant removal) and simultaneously producing electricity. Furthermore, the objective was to enhance the low electric energy by using an adequate amplification system.
RESULTS: So, the chemical oxygen demand (COD) removal was increased by 58.7% with the MFC running for 10 days. However, this technology faces practical barriers as it produces low electrical energy. A power management system was therefore elaborated in this respect. It included the MFC, operational amplifier (OA), solar photovoltaic panel and a boost DC/DC converter. The low voltage output obtained was thus increased substantially using the OA prior to its polarization by the solar photovoltaic module. The amplified voltage was sufficiently enough and in consequence, utilized to feed a light emitting diode. The low output voltage 0.5 V was simply harvested, successfully boosted up to approximately 2 V (i.e. 4 times higher) and finally harnessed as a power supply.
CONCLUSIONS: The MFCs association shows the positive stacking effect successfully, when the cells were connected in parallel. This novel application is very interesting to utilize the natural bioenergy contained in wastes to supply small electronic devices.

The performance of an innovative decentralized multistage constructed wetland (DMCW) treating institutional wastewater is studied covering three seasons. The DMCW system with Canna lily efficiently removed organics contaminants like COD and BOD, and nutrients from the wastewater, showing its dependency on meteorological factors. Overall the performance is maximum in summer and least in monsoon, with a COD removal of 85.6% in summer followed by 82.5% in winter and 61.2% in monsoon. Removal of TSS (67.7-85.5%), PO43--P (52.1-64.4%), NH4+-N (56.6-71.6%), NO3--N (47.3-63.4%) and NO2--N (62-75.4%) were achieved along with heavy metals like Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, Hg and Pb. Removal of pathogens like Vibrio is >98%, E. coli 95%, Pseudomonas 99%, and Aeromonas 63% was observed. Mass removal rate of COD was maximum in summer (97.3 g/m2/d) followed by winter (78.7 g/m2/d) and monsoon (43.5 g/m2/d). Majority of organics removal during the treatment was highlighted through Gas Chromatography-Mass Spectrometry (GCMS) and Fourier Transform Infrared Spectroscopy (FTIR) confirmed wastewater to be complex. The Canna lily accumulated various elements and oxides during the treatment with no stress on its health. The treated water quality is within the permissible limits and stands suitable for irrigational purposes. Better plant health and increased microbial diversity in the garden proves the suitability of treated water for irrigational activities. The results were validated using statistical tools like Mann-Whitney U test and principal component analysis.

In this research, treatment of a pharmaceutical wastewater (PhW) obtained from a factory by electro-Fenton (EF) and photoelectro-Fenton (PEF) processes was investigated. The effects of several parameters involving pH, current density, H2 O2 /Fe2+ molar ratio, volume ratio of H2 O2 /PhW, UVA light, and time were studied. The experiments were designed by Design Expert software, and response surface methodology (RSM) was applied to determine the optimum conditions for the highest COD removal. According to the analysis of variance (ANOVA), time was the most significant parameter on the process response (COD removal) followed by current density. The optimal conditions for 86.85% of COD removal through the EF process were at pH of 2.96, current density of 42.90 mA/cm2 , H2 O2 /Fe2+ molar ratio of 3.78, volume ratio of H2 O2 /PhW of 1.37 ml/L, and reaction time of 58.49 min, while the optimal conditions for 93.00% of COD removal through PEF process were at pH of 2.91, current density of 43.71 mA/cm2 , H2 O2 /Fe2+ molar ratio of 4.29, volume ratio of H2 O2 /PhW of 1.67 ml/L, UVA light of 6 W, and reaction time of 54.24 min. It was concluded that UVA light can increase the COD removal through PEF process around 7% more than that of the EF process at optimum conditions. PRACTITIONER POINTS: Treatment of a pharmaceutical wastewater by EF and PEF processes was investigated. Effects of several parameters were entirely studied on both the processes. RSM was applied to determine optimum conditions for the highest COD removal for both the processes. UVA light increased COD removal through PEF process (around 7%) at the optimum conditions.

Electrocatalytic treatment of real textile wastewater was investigated in continuous electrochemical reactor using dimensionally stable Ti/RuO2 anode. Effects of various parameters such as: elapsed time, current, pH, retention time on the COD removal, color removal and specific energy consumed were evaluated. Central Composite Design under RSM was used for experimental design, data analysis, optimization, interaction analysis between the various electrochemical parameters and steady state time analysis. GC-MS and UV spectrophotometric analysis of the untreated and treated wastewater were conducted to identify the oxidized and transformed/degraded compounds during the oxidation process, and a suitable degradation mechanism was proposed. Treated wastewater may contain toxic chlorinated compounds due to mediated oxidation by various hydrolyzed chlorine species. Therefore, disposability of treated wastewater was assessed by conducting toxicity bioassay test. The optimal set of operating parameters were found to be elapsed time = 124 min, current = 1.37 A, pH = 5.54 and retention time = 157.6 min to simultaneously achieve COD removal, color removal and specific energy consumed as 86.22%, 94.74% and 0.012 kW h, respectively. GC-MS analysis showed presence of chlorinated compounds in the treated wastewater. The toxicity bioassay test resulted acute toxicity with 100% mortality rate within one minute and one hour exposure with untreated and treated textile wastewater, respectively.