Journal of Water Chemistry and Technology最新文献

Selenium (Se) is an important nutritional element which exists at very low concentrations, easily accumulates via the food chain and creates adverse effects such as a deprived reproduction rate and diminutive growth in human and aquatic organisms. So, it has become a severe concern around the world. We explore electrocoagulation using Al and Fe electrodes and activated sludge process (ASP) in batch process and also in an integrated process to remove Se. The optimized parameters of the current density in the batch process were: 6.7 and 5.7 mA/cm² for Al and Fe, respectively. The mass transfer coefficient has been estimated through numerical modelling for batch and integrated processes using the equations K = ({text{0}}{text{.0146}}C_{{{text{Se}}}}^{{{text{0}}{text{.3651}}}}{{I}^{{{text{0}}{text{.8916}}}}}) and K = ({text{295}}{text{.387}}C_{{{text{Se}}}}^{{{text{6}}{text{.607}}}}{{I}^{{{text{3}}{text{.587}}}}}); the energy consumption and metal dissolution were 138240 and 384 MWh/m³, 60 and 3.58 g, respectively. The response surface methodology (RSM) was implemented in Box−Benken design to assess the parametric optimization, and the validation of experimental data was done using ANOVA and regression analysis. The obtained p-values and model F-values were 0.000 and 63.09 for Al and 0.000 and 79.98 for Fe, which indicated the significance of the model. The chemical oxygen demand (COD) reduction values estimated along with Se reduction in real effluent treatment were above 90 and 60% in electrolytic and 80% in an integrated ASP with very high-cost efficiency. The results assure that this proposed hybrid work will provide a higher reduction, improved energy and cost efficiency for the effluent with indeterminate influent Se and COD concentration. The proposed model also helps to make predictions of removal efficiency without requiring an extensive time and cost burden.

This paper discusses the results and observations of experiments that were performed to investigate the presence and implication of total petroleum hydrocarbons (TPH) in oil produced water (OPW) samples from an oil depot. An analytical method based on gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) was developed for the determination of TPH. The effect of the extracting organic solvent was studied, and n-hexane was found to be the best extraction solvent as it resulted in 96.28% extraction efficiency. The TPH were determined in both influent and effluent samples. Various TPH fractions were identified including n-alkanes, branched alkanes, alkenes, etc. The TPH determination was investigated on a seasonal basis and the winter period (June-August) registered many compounds especially from the influent compartments than they were found in autumn. This suggests that the physical treatment employed by the oil depot does remove the TPH to a certain degree which is above the limit thresholds set by the regulatory authorities which is not satisfactory and thus the effluents need to be subjected to secondary treatment. The TPH analysis and identification results presented are mainly qualitative except for 1-chloro-octadecane, the surrogate standard. The TPH compounds were identified based on similarity indices to the databases.

The oxidative degradation of an antibiotic, Ofloxacin (OFX), has been investigated using the electro-Fenton (EF) process with a constant current between 100 and 500 mA and a carbon-felt cathode. The kinetics of oxidative degradation and the efficiency of mineralization were examined about the applied current and catalyst (Fe²⁺) concentration. The absolute rate constant for the oxidation of OFX by hydroxyl radical was determined using the competition kinetic approach as 3.04 ± 0.19 × 10⁹ M^–1s^–1. For efficient degradation of OFX at the relevant operating conditions, the ideal current value is 400 mA at a concentration of the catalyst (Fe²⁺) at 0.10 mM. After 6 h of electrolysis, in the present study, it is demonstrated that several cathodes, including carbon felt (CF), carbon-graphite (CG) and stainless steel (SS), had an impact on the electrochemical oxidation of the organic contaminant, OFX. A high level of mineralization (>97%) was attained. The development of F⁻, ({text{NH}}_{{text{4}}}^{{text{ + }}}) and ({text{NO}}_{{text{3}}}^{ - }) ions was also monitored and their evolution during their release into the medium was discussed. Several intermediate products were identified using LC-MS/MS (liquid chromatography-mass spectrometry) and HPLC (High-performance liquid chromatography) analyses. Based on the identity of these products, a feasible route for the mineralization process is proposed. Finally, biodegradability was studied and the results indicated the following ratio of biological oxygen demand within 5 days to chemical oxygen demand BOD₅/COD through OFX mineralization by EF treatment for the possibility of evaluating the combination of electro-Fenton and biological treatment.

Quantum chemical analysis using the density functional theory (DFT) was used to characterize the adsorption mechanism of metronidazole on the surface of polypyrrole (PPy). Researchers have established the electrophilic character of metronidazole and the nucleophilicity of PPy, as well as the electrophilic and nucleophilic zones responsible for non-covalent interaction in the processes of physical sorption of metronidazole on PPy as part of the decontamination of water using a drug. The adsorption mechanism of metronidazole on PPy is mainly governed by physical interactions (water bonds) between the adsorbate and adsorbent, and also the energy and structure results indicate that physically the process is sorption. These structural and energetic procedures match well with experimental results. The changes in thermochemical enthalpy and entropy showed the non-negotiable and exothermic phenomenon of physical adsorption. Thus, PPy can be considered an environmentally friendly and effective adsorbent material for the removal of metronidazole and, possibly, other pharmaceutical pollutants from pharmaceutical and municipal wastewater.

Despite being a water-rich state in South Asia, more than 70% of Afghan communities currently lack access to safe and reliable drinking water. This deficiency is largely attributed to the presence of contaminants, e.g., arsenic, fluoride, nitrates, sulfate, boron, etc., in groundwater aquifers. This study aims to trace the concentration of arsenic in groundwater aquifers in major cities in Afghanistan. The findings suggest that among the tested water samples in Ghazni, Kabul and Logar—the last two provinces are characterized parts of Kabul River Basin—Herat and Bamyan provinces, 70, 7, 2, and 23% of the examined water samples, respectively, exceed the permissible arsenic limit set by the World Health Organization (10 μg/L) and the National Drinking Water Quality Standard of Afghanistan (NDWQSA) (50 μg/L). The elevated concentration of arsenic in these aquifers results from excessive agricultural pumping and industrial and urban waste discharge. Additionally, inadequate sanitation and hygiene practices coupled with the absence of waste disposal network systems contribute significantly to the heightened level of arsenic in these provinces. It is concluded that unless the government adopts sustainable strategies to reduce the elevated arsenic concentration in groundwater aquifers, environmental and human health crises will continue to escalate.

With the rapid growth of industrialization/urbanization, the discharge of industrial effluent into the environment is increasing day by day. Conventional technologies for wastewater treatment possess difficulties in meeting all the requirements of wastewater discharge standards, and therefore, the exploration and establishment of new procedures to treat wastewater is a need of hour. Advanced oxidation processes (AOPs) possess an ability of strong oxidation, complete destruction and mineralisation, and no secondary pollutants. It has been proved in the literature that the addition of the catalyst in AOPs can largely enhance the treatment efficiency. The current study mainly emphasizes the practical applications of AOPS towards textile wastewater treatment. The study includes the pros and cons of individual AOPs, fixed photocatalysis, the dual process of photocatalysis and photo-Fenton coupled photocatalysis/photo-Fenton and biological treatment process. This article summarizes the useful theoretical foundation of the scientists and discusses the key areas that need more investigation in the fields of AOPs for industrial wastewater treatment.

Waste rocks obtained from mining operations are typically stockpiled due to the lack of their economic value. This practice resulted in significant land occupation and potential for secondary pollution risks due to the lack of probability of leaching. The present study explores the possible utilization of waste rocks as a novel adsorbent for treating F⁻ enriched groundwater. Shale, a coal mine waste was chemically modified by ferrous chloride in a 3 : 1 ratio. Optimization of the adsorption process was done by performing batch adsorption. Surface morphological characterization of the adsorbent was performed by scanning electron microscopy (SEM), energy-dispersive X-ray (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectrophotometer (FTIR). The best results were obtained when 100 mg/L was used to defluoridate contaminated water for 60 min at neutral pH. The efficiency of management was 32% removal at 10 ppm fluoride contamination. Post-treatment adsorbent can be utilized in brick formation to rule out any possibility of secondary/tertiary contamination.

Spirulina is extensively studied among cyanobacteria. It has been used as a source of protein since ancient times. The present investigation addressed the cultivation of Spirulina in kitchen wastewater with the aim of water remediation. Water quality parameters were evaluated by analysing physicochemical parameters both before and after the growth of Spirulina. The microscopic inspection revealed the presence of Spirulina exhibiting spiral and helical shapes. Water quality parameters, including total suspended solids, total dissolved solids, chlorides, sulfates, phosphate, total hardness, and total alkalinity, were found to be high in the wastewater before the cultivation of Spirulina. In addition, it had very acidic conditions with a pH range of 4.5 to 6.0. The cultivation of Spirulina resulted in favourable changes in various chemical parameters. Specifically, the total suspended solids, total dissolved solids, chlorides, sulfates, phosphate, total hardness, and total alkalinity decreased while the sodium level increased. Further, it increased the pH level to the neutral range. According to the findings of this study, it can be inferred that cultivating Spirulina in wastewater positively altered the physicochemical characteristics of the wastewater and resulted in an increased yield of Spirulina.

This study aims to evaluate the performance of a bioreactor at an upflow packed bed with synthetic wastewater containing phenol under continuous operation. The used microorganism was formed by a mixed culture isolated from a wastewater treatment plant. The mean residence time (t_m = 3.92 h) in the bioreactor was obtained experimentally by following the tracer NaCl 0.5 M concentration in a continuous effluent stream. For the first time, we calculated the superficial velocities of liquid (u_L) and gas (u_G) in a three-phase medium (air-water-sand) in the absence of biomass; these velocities vary from 5.40 × 10^–3 to 5.84 × 10^–3 and from 0.36 × 10^–3 to 3.67 × 10^–3 m/s, respectively. Afterwards, the effects of airflow (AF = 10, 20, and 30 L/h), liquid flow rates (LF = 3, 5, and 9 mL/min), and initial phenol concentration (C₀ = 100, 200, 300, 500, and 700 mg/L) on the biodegradation rate of phenol were studied. The results indicate that the rate of continuous biodegradation increases with the initial phenol concentration and decreases both with the AF and LF rates. The biofilm concentration uniformly increases with increasing the height of the sand bed. The process in the continuous model also contributed to a high elimination efficiency of 100%.