Journal of Water Chemistry and Technology最新文献

Chromium is an element present in the Earth’s crust that acts as an impurity in food, water, soil and air and causes benign effects on the human body. Among the various oxidation states, the hexavalent form has higher toxicity, higher solubility in water, and higher mobility in soil. The maximum recommended permissible limit of Cr in drinking water is 0.01 mg/L by the United States Environmental Protection Agency (USEPA), whereas 0.05 mg/L by the Bureau of Indian Standards (BIS) and World Health Organization (WHO). Several physical and chemical methods have been developed for the removal of chromium from contaminated water. In most techniques, there is a higher chance of re-contamination after the disposal of generated sludge. In this study, Bacillus firmus has been exploited for in-situ bioremediation of hexavalent chromium (Cr⁶⁺) from wastewater under batch mode. The effects of operating conditions such as pH, initial concentration, centrifugation rate (rpm), external carbon, and nitrogen sources were investigated. The maximum Cr⁶⁺ conversion of 99.9% was obtained at 0.5 and 1 mg/L initial concentration, pH 7, 30°C, and 120 rpm. Dextrose was found to be the potential C source for enhancing microbial growth and efficient conversion at higher Cr⁶⁺ concentrations. Furthermore, living and dead biomass revealed a comparatively high biosorption of 18.3% at 100 mg/L Cr⁶⁺ concentration.

In this paper, scientifically substantiated recommendations on the technological processing and utilization of wastewater sludges for the production of energy resources are formulated. The analysis of earlier studies shows that sludges contain mineral, organic, and bacterial origin contaminants of different composition in the form of solutions, colloids, and floating and suspended compounds. It is demonstrated that the removal of sludges is one of the most urgent environmental problems associated with the propagation of bacteria, which have a negative effect on the environment, people, animals, and plants. The most attractive alternative to sludge utilization is the production of energy syngas from it. The objective of studies is to develop an innovative technology for the production of energy syngas from wastewater sludges. Some characteristics of initial materials and equipment used for investigations are given. A syngas production process flowchart based on a patented setup with two screw retorts from a catalytically active material is proposed to optimize the temperature regimes of outer sludge heating from 200 to 850°C. The setup provides the production of multicomponent energy syngas at atmospheric pressure without air access with a conversion of 90% and a calorific value of 3300–3600 kcal/m³ to be superior to the known technologies of gasification at the same temperatures and pressure. The developed technology for the production of energy syngas from wastewater sludges results in syngas of increased calorific value due to gas generator elements providing rational temperature regimes for the chemical destruction reactions of sludges with an increased humidity. The combination of fuel gas and steam generation processes results in a high degree of sludge gasification with the formation of syngas with an increased calorific value due to acceleration of chemical reactions.

Low strength wastewaters (LSW) are those that have a chemical oxygen demand COD < 1000 mg/L. Nitrogen and phosphorus are the major nutrients present in LSW in addition to the organic carbon. The present study was undertaken to develop an optimal combined treatment system for removing nitrogen from LSW at high hydraulic loading rates as there are hardly any reports on the same. The biological removal of carbon in LSW has been studied in detail earlier using the anaerobic hybrid reactor (HR) and activated sludge process (ASP). The biological nitrogen removal was studied through the conventional route of nitrification process. The effect of different operational parameters was studied to optimize the nitrification in rotating biological contactor (RBC) and aerobic HR. RBC showed better nitrification rate over aerobic HR.

The overwhelming majority of commercial nonionic surfactants (NIS) represent a mixture of many chemically related compounds, a number of which and some metabolites are resistant to biochemical assimilation and pose a serious threat to living organisms. The degree and efficiency of their removal from water can be increased by combining destructive adsorption methods in water treatment systems, in which the preliminary partial chemical oxidation of resistant compounds leads to the formation of products capable of efficient adsorption and microbial assimilation in an activated carbon (AC) bed at subsequent purification stages. For resistant organic impurities, the degree of their transformation at the previous stage of chemical oxidation is an important technological parameter, which essentially influences the combined water treatment efficiency. Using the “conditional component” method, the effect of the degree of primary NIS (Triton X-100, OP-10) destruction by ozone itself or ozone in combination with UV radiation on the adsorption energy of newly formed mixtures of their decomposition products on activated carbon was studied under isothermal adsorption conditions. The decrease in the equilibrium adsorption values ​​of the reaction mixtures and the change in the molar Gibbs free energy of the adsorption system were estimated with the decomposition of the aromatic ring of NIS in the range of 30–88%. A rational regime without long-term treatment and high specific ozone consumption was proposed for the preliminary oxidation of the studied NIS to increase the bioassimilated organic carbon fraction without absorption system capacity losses.

The research results on a new technology for preparing water for hot water supply by chloro-anionization are presented. According to this technology, water for treatment is passed through a high-base anionite in chlorine form and regenerated by a NaCl solution. In the treated water, the concentrations of Cl⁻ and OH⁻ ions are reduced while maintaining the amount of water hardness cations necessary for the healthy development of the human body. The mathematical experimental design was used to obtain expressions which determine the working exchange capacity of A200EMBCl anionites. The results include the successful implementation of this technology at a system of 6 m³/h performance in Baku. The World Health Organization (WHO) does not set strict requirements for total water hardness levels. However, based on research conducted in various countries over the past 50 years, WHO recommends keeping both the maximum (≤7 g-eq/m³) and minimum hardness levels within the range of 2–4 g-eq/m³. This is because consuming softened or desalinated water can lead to serious health issues. WHO also states that even in developed countries, the intake of hardness cations, including those found in food, is not sufficient to support normal human development. For the first time, the technology developed in this study was implemented at the Azerbaijan Diplomatic Academy (Baku, Azerbaijan Republic) in a drinking water treatment system with a capacity of 6 m³/h. In this system, water is passed through a 400 mm diameter filter loaded with A200EMBCl anionite, with a layer height of 1 m, and equipped with an automatic control valve of Clack WS1 type. The average alkalinity of the treated fresh water, with its initial value of 4.4 g-eq/m³, was decreased to be within the range of 1.8–2.2 g-eq/m³. The working exchange capacity of anionite absorption for ({text{HCO}}_{3}^{ - }) ions, with a specific consumption of NaCl for regeneration between 45–55 kg/m³, falls within the range of 300–370 g-eq/m³, which conforms well with the data from laboratory research. According to operational data, the formation of scale in hot water heaters has been prevented. There were even observations of pipe cleaning from the existing scale.

The rapid advancement of medical science has increased the availability and use of pharmaceutical products. Consequently, pharmaceutical compounds contaminate natural water bodies, raising concerns in global environmental policy. This study examines various types and pathways of aquatic pollution, highlighting the health and ecological risks associated with wastewater discharge into surface waters. When excessive concentrations of contaminants enter rivers, they can alter biodegradation dynamics, reduce aquatic biodiversity, and consequently impair the natural self-purification capacity of water bodies. The study also underscores the importance of monitoring wastewater treatment efficiency through bioindication and biotesting methods. Contemporary scientific research focuses not only on the toxicity of pharmaceuticals but also on their transformation and degradation processes, which remain largely unexplored in terms of their characterization, presence, fate, and effects in natural environments. These findings demonstrate that the environmental risks associated with pharmaceutical compounds and their metabolites should not be overlooked.

This work presents a novel analytical method for detecting lead ions (Pb(II)) based on backward light scattering (BLS). The BLS intensity was significantly enhanced by the formation of ion-association complexes between ciprofloxacin (CIP), Congo Red (CR), and Pb(II) through electrostatic attraction and hydrophobic interaction in a Britton−Robinson (BR) buffer solution at pH 4.56. The maximum BLS peak was observed at 399 nm. The BLS intensity showed a linear relationship with Pb(II) concentrations ranging from 0.5 to 60.0 μM, with a limit of detection (LOD) of 50 nM. Studies on the BLS spectrum, absorption characteristics, and reaction mechanism were conducted, and optimal reaction conditions as well as the impact of interfering substances were investigated. This method was successfully applied to the determination of Pb(II) in environmental water samples, achieving recoveries between 91 and 104%, with a relative standard deviation (RSD) ≤ 4.7%. The proposed BLS method offers rapid analysis, high sensitivity, environmental friendliness, and good stability, providing a theoretical basis for real-time, online monitoring of lead ions using BLS technology.

In the process of wastewater treatment from electroplating industries, solid residues containing compounds of Fe, Cu, Ni, Zn, and other metals are generated. To determine the optimal leaching conditions for metals and identify the limiting stage of the process, an experimental study of the leaching kinetics was conducted, focusing on key technological parameters—temperature and the concentration of reacting substances. The kinetic parameters of the reaction were investigated using electroplating sludge containing up to 50% Fe compounds, 9.6% Cu compounds, ~1% Zn compounds, 0.5% Ni compounds, and less than 0.1% Cr, Pb, Cd, Mg, and Ca compounds. Sulfuric acid (H₂SO₄) with concentrations ranging from 0.15 to 0.75 M was used as the leaching reagent, in significant excess relative to the metal content. The process was carried out at a pH of the equilibrium solution that limits the dissolution of iron compounds and allows only the dissolution of nonferrous metal compounds. The concentration of copper in the leaching solution reached 17.8–18.1 g/dm³.

Radionuclides contaminated water is a serious issue for human beings and ecological systems. In particular, they cause various types of cancers and mutagenic affects. Removal of radionuclides from contaminated water is a challenging task, since efficient and cost-effective materials are required for extraction of radionuclides from water. Under this objective, modified zeolite beads (MZBs) were prepared and characterized. The beads were evaluated for extracting of cesium (Cs) and strontium (Sr) from contaminated water using column method. Breakthrough capacity (BC), total capacity (TC) and column efficiency (CE) obtained for Cs were 0.167, 0.279 g/g and 59.75% respectively. BC, TC and CE for obtained for Sr were 0.153, 0.239 g/g and 64.4% respectively. Based on these results, MZBs column can be used as radionuclides removal cartridge in water purifiers.

A comprehensive spatiotemporal qualitative investigation and assessment of groundwater resources of Manipur Valley were carried out to evaluate their suitability for irrigational uses and geospatially identify the vulnerable groundwater zones. In this regard, 140 grided representative samples during pre-monsoon and post-monsoon were collected from the region along with their in-situ parameters. The groundwater suitability for irrigational uses was evaluated based on significant water quality parameters and indices. The study highlights that except for a few parameters and indices for selected parts of the region, most of the samples were found under suitable categories. Few samples with elevated electrical conductivity values and higher sodium concentrations signify the possibility of alkalinity and salinity hazards for prolonged uses of groundwater for irrigation. The study witnessed the presence of saline aquifer in the region where samples exhibit higher salinity (>1000 ppm) and can potentially cause salinity hazards for prolonged uses of groundwater for irrigation. The hydrogeochemical classification reveals the dominance of the ({text{HCO}}_{3}^{ - })-Ca²⁺ type of water followed by mixed-type water due to rock weathering dominance during both seasons. Thus, the study highlights the comprehensive spatiotemporal scenario of groundwater quality for irrigational uses in the region through spatial mapping to identify the vulnerable groundwater zones for sustainable agricultural soil management.