Journal of Water Chemistry and Technology

The species composition of bacterial community of the drinking tap water and water samples taken at different purification stages of the water conditioning plant at an enterprise producing special drinks has been analyzed. This study involves the analysis of 16S rRNA gene sequences and the use of molecular biology methods based on the phylogenetic analysis. The following bacterial species were identified: Bacillus nanhaiensis, Brevibacterium frigoritolerans, and Lysinibacillus fusiformis. All the studied strains belong to phylum Firmicutes, class Bacilli representing Gram-positive microorganisms that are not pathogenic to human. The presence of the bacteria investigated in different habitats such as the drinking chlorinated water, in the presence of stress factors (arid climate, high or low temperatures, depleted soil, and the occurrence of disinfectants) indicates their ability to easily adapt to new living conditions expanding their habitat.

A simple, sensitive and rapid gas chromatography-mass spectrometry (GC-MS) method is proposed for the analysis of some environmentally important highly toxic phenols in water. The concentration level of phenol was determined in water at the sampling stations of Savar, Dhaka Export Processing Zone (DEPZ) and Bank Colony of the Bangsai River, Bangladesh. Water samples were collected from different depth of the sampling stations. The phenolic compounds were extracted with dichloromethane, which was further preconcentrated by evaporation. Different concentrations of toxic phenol were obtained in the river water at the various sampling stations. The concentration of highly toxic phenol was found in the range of 0.01–0.998 μg L−1. This method could permit the analysis of water for phenol as well as phenolic derivatives with detection limit as low as 100 ng L−1.

A promising technology offering significant environmental benefits compared to classical nitrification/denitrification processes appears to be the partial nitrification/Anammox that can be carried out in a one single reactor. In this paper the results of start-up of the CANON process in two lab-scale Sequencing Batch Reactors with continuous and batch flow, at low temperature (20 ± 2°C) were presented. The results indicate that the CANON process in its initial phase is characterised by high instability. It was showed that the system needs the intensive control of basic technological parameters and that the temperature of 20 ± 2°C is insufficient for the fast start-up of the CANON process. During first four months of the research, the stable CANON process was not achieved. Further analysis on this pilot-scale system showed that Anammox appeared after about 5.5 months. Results also showed that dissolved organic and free ammonia is the key factor to start-up CANON process.

The papers devoted to the purification of aquatic environments from industrial contaminants with the use of ZnO based nanosized photocatalysts in the period of 2018–2020 are analyzed. The data published in these papers have made it possible to determine the dye (V) destruction rate used further as a photocatalytic activity criterion. As shown by the comparative analysis of the photocatalytic activity of the studies structures, the highest rates of water purification from industrial azodye contaminants are demonstrated by hybrid ZnO/Au structures. At a destruction rate of V = 10%/min, the ZnO/Au structures are much better than all the other considered types of catalysts due to their morphology, low recombination rate of photogenerated electron-hole pairs, and nanoparticles with an absorption spectrum close to the solar spectrum. The review of literature data shows that the greatest attention of researchers in the considered time period is focused on the problem of the purification of water sources from industrial contaminants and, first of all, azodyes. Essential attention is also paid to the technological approaches applied by the authors to increase the photocatalytic activity of ZnO based nanostructures.

The article has investigated the efficiency of biofiltration of solutions 2,4-dinitrophenol and 2-nitriphenol through activated carbon of the grade KAU—usual and modified by iron oxide. It has been shown that both sorbents are characterized by a high selective adsorption for substances being investigated. The impact of modification of carbon by iron oxides when removing nitrophenols is manifested in an increase of active life of biofilter operation and activization of the biofilm development.

Investigations dealing with the treatment of aqueous systems by physical methods show that ultrasound is an effective reagentless and highly ecological method of water purification of organic pollutants and microorganisms. Its use is particularly effective in combined methods of treatment: ultrasound + ultraviolet irradiation; ultrasound + ultraviolet + ozonization; ultrasound + hydrogen peroxide; ultrasound + Fenton’s reagent, etc. In many cases the combined techniques make it possible to achieve better purification results due to a synergistic effect. The most promising techniques involve the application of high frequency ultrasound (200–500 kHz), simultaneous ultrasound treatment with two frequencies, and the use of hydrodynamic cavitators.

The study illustrates the use of polyelectrolyte multilayer (PEM) membranes prepared with weak/strong polyelectrolyte combination of poly(ethyleneimine)/chondroitin sulfate A (PEI/CS) for the removal of metolachlor (MTR) from water samples. The proposed PEM membranes were characterized by chemical, physical, thermal, and morphological properties. The removal of MTR herbicide by PEI/CS multilayer deposited on a microfiltration polyamide membrane was found to be efficient with a retention rate of about 96.46% for 8 bilayers sat an excellent permeate flux of 6.27 m3/m2 day. The photodegradation of metolachlor which got trapped in PEMs in the presence of riboflavin (Rb) sensitizer was investigated at various concentrations. A comparative study on photo-elimination of MTR without the presence of Rb was also done. The degradation time was greatly shortened from more than 1 h for direct photolysis to 5–15 min depending on the initial concentration of the sensitizer. The degradation of metolachlor in the presence of Rb as well as direct photolysis was also experimentally studied.

A method has been developed for the utilization of salts of heavy metals generated due to chemical regeneration of complexes of concentrates after the baromembrane treatment of polluted waters. This method implies the immobilization in glass-ceramic matrices. The optimal composition of matrices was determined and their physico-mechanical properties were investigated. The matrices featuring good performance characteristics and good decorative effect were also obtained. On the basis of investigations performed a production process was developed and proposed for manufacturing the glass-ceramic materials used in construction and paint-and-varnish industries.

Today, the treatment of dye wastewater discharged by various industries, such as textiles, has attracted the attention of many researchers due to the non-biodegradability nature of dye contaminants. Methylene blue is one of numerous dyes existing in this wastewater that causes a variety of human health problems. Because of the low efficiency of biological treatment processes in the removal of this range of contaminants, physicochemical technologies such as adsorption and advanced oxidation processes have been studied as efficient alternatives. Among them, advanced oxidation processes can provide almost complete removal of these contaminants with the least requirement to manage final products. In these processes, the objective is the production of reactive radicals (such as $$^{\centerdot }{\kern 1pt} {\text{OH}}$$ and $${\text{SO}}_{4}^{{\centerdot - }}$$ ) which are suitable for rapid and non-selective reactions with organic contaminants. So, in this study, decolorization and mineralization of methylene blue in aqueous solutions were investigated by the persulfate/Fe2+ process. For this purpose, the effect of different parameters such as pH, per-oxydisulfate/Fe2+ ratio, peroxydisulfate concentration, and initial methylene blue concentration were evaluated. In addition, predominant radicals and mineralization of methylene blue were studied. Finally, the contribution of each sub-process and degradation of methylene blue in real wastewater were investigated. In the first step of this study, the effect of initial pH on methylene blue removal by persulfate/Fe2+ process, it was observed that with increasing pH from 3 to 9, the removal efficiency of 50 mg/L of methylene blue was decreased from 84.4 to 69.7%. In the second step, obtained results showed that with increasing peroxydisulfate/Fe2+ ratio from 2 to 16, methylene blue removal efficiency was decreased to 18%. The supplementary experiments for determination of predominant radicals using tert-butanol and methanol revealed that sulfate radical was predominant in the applied process. Although complete decolorization of methylene blue was attained at 20 min, when the time lasted to 40 min, 96% mineralization of methylene blue was observed by peroxydisulfate/Fe2+ process. Finally, the studied process showed efficient removal of methylene blue dye from aqueous solution and real wastewater containing a high concentration of methylene blue.