Effective denitrification of water using photocatalytic reaction of active TiO2 particles doped with different oxides and metals has been the subject of numerous studies. For a particular research area, the potential of silica bond and its silicate based matrices with titanium dioxide and improving the photocatalytic performance using more economic methods is still challenging, and research in this field is attractive and ongoing. In this study, the effect of cement matrix and its complex bonds with industrial grade TiO2 particles was evaluated on the rate of water denitrification in a fixed bed circulating flow photoreactor. For this purpose, silica fume was substituted for cement in constant percent of 10 as a rich source of amorphous silica. Industrial grade TiO2 was added to the mix as5, 10 and 15 percent weight of cementitious materials (CM). Nano TiO2 was considered as a supplementary photocatalytic material with a constant 1% weight of CM in two mix designs. The results implied that the addition of 5% TiO2 increased the rate of nitrate concentration reduction by up to 10 times. Also, the specimen including 10% TiO2 increased denitrification rate by 107% compared to the previous content, which had much less impact. Also, the addition of nanoTiO2 increased denitrification rate up 113%.

In Mirzapur (U.P.), a power-starved district, the UASB (Upflow Anaerobic Sludge Blanket) technique was adopted. Almost all of the available technologies do not treat heavy metals, so, is the case with the UASB also. The present study is to assess how much heavy metal can get accumulated in plant tissues in different species. The result of the present study was that the concentration of Pb(1106.31)>Zn(221.45)>Cd(49.26)>Hg(23.37) mg/Kg in the sludge while the concentration of Zn(93.35)>Pb(52.00)>Hg(16.93)>Cd(1.53) mg/Kg in the soil. When the sludge was mixed with the soil the trend got changed and the trend was Pb(596.36)>Zn(219.86)>Cd(24.70)>Hg(22.63) mg/Kg. Three different species that were chosen for the study were Basella Alba (Spinach), Solanum Lycopersicum (Tomato) & Brassica Juncea (Mustard). The trend of accumulation of studied heavy metals in the Brassica Juncea (Mustard) was Zn(85.33)>Pb(25.88)>Hg(11.23)>Cd(0.99) mg/Kg. In Solanum lycopersicum (Tomato) the trend was Pb(231.11)>Zn(108.72)>Hg(12.43)>Cd(9.41) mg/Kg  and in Basella alba (Spinach) was Zn(103.81)>Pb(83.90)>Hg(10.78)>Cd(4.18) mg/Kg. Overall the study reveals that the accumulation of heavy metals takes place in plants grown in soil mixed with sewage sludge. The reduction in the concentration of Pb, Cd, Hg and Zn in sludge mixed with soil after the harvesting of plant in case of Solanum lycopersicum were 39.38%, 47.93%, 6.18% and 49.89% respectively; while in case of Basella alba these were 25.23%, 57.53%, 71.58% and 49.16% respectively; and in case of Brassica Juncea these reduction were 25.86%, 60.80%, 70.96% and 49.04% respectively.

In this research, a response surface methodology (RSM) was used to investigate the effects of independent parameters (pH, contact time, temperature, adsorbent dosage, and initial concentration of pollutant), their simultaneous interactions, and quadratic effects on crystal violet adsorption onto two starch based materials in the form of batch experiments. The characterizing results indicated that there is no significant difference between the potato starch and synthesized starch phosphate, as phosphorylation has not changed the crystalline structure of starch inside the granules. The maximum removal efficiency of crystal violet ions was obtained 99 % at the optimum adsorption conditions of initial concentration 213.54 mg/L, adsorbent dosage 0.25 g, contact time 14.99 min, temperature 15 °C, and initial pH of solution 9. RSM outputs showed that the maximum adsorption of crystal violet ions by could be achieved by raising pH and adsorbent dosage, and decreasing the initial crystal violet concentration. While temperature and contact time are not effective parameters in crystal violet removal from aqueous solutions using synthesized starch phosphate. Generally, the RSM model is suitable to optimize the experiments for dye elimination by adsorption, where the modified starch phosphate would be an effective adsorbent for treating crystal violet solution.

The present study investigates an NF process for removal of copper and hexavalent chromium, studying the effect of pH (5, 7, 9) as well as contaminants' concentration (50, 500, 5000 µg/L) at a constant pressure of 8 bar; with the recovery rate, regulated at 75±2%. To determine the main factors, affecting the system performance, and evaluate the interaction effects among the factors, the experiment is designed via RSM Method. The chrome shows a higher rejection, compared with Copper, all over the range of investigated factors. As Copper concentration grows, Cu removal efficiency drops while, the Cr (VI) removal efficiency ascends. Also by increasing chrome concentration, the Cu removal efficiency decreases, while Cr (VI) removal efficiency increases. Results show that with an increase in pH, the Cu removal drops and Cr removal is increased. The pH is the main parameter, influencing the removal rate. It has been found that the maximum removal efficiency is up to 99% and 73% for Cr (VI) and Cu, respectively. There is an adequate agreement between real data and that obtained from the models (R2 was found to be 0.9889 and 0.9664, for Cu and Cr (VI) rejection, respectively).

Sludge/TiO2 composite was synthesized from drinking water treatment sludge, as a waste material and TiO2 , by a sol- gel method. Various sludge adsorbent / TiO2 ratios (1:1, 1:2 and 2:1 w/w) were prepared, and characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray Fluorescence (XRF), and BET. The prepared composites were applied successfully for photodegradation of methylene blue (MB) dye from a solution. The photocatalytic degradation of MB dye was investigated using UV irradiation, or UV/H2O2. Initial dye concentration, solution pH, composite dosage, and UV irradiation time were applied to study the optimum conditions for MB degradation. The results revealed the highest MB dye degradation with composite (2:1). It was found that the maximum MB degradation efficiency was at pH=7, 4 h irradiation time, 0.125 g composite dose, and 50 ppm initial dye concentration. MB removal efficiency was 95.7% using UV irradiation, and 99.8% of that using UV/ H2O2. The rate of MB dye degradation followed the first order kinetics. Results from this study offer the best conditions for recycling drinking water treatment sludge, and use it for wastewater treatment.

The term bioremediation describes biological machinery of recycling wastes to make them harmless and useful to some extent. Bioremediation is the most proficient tool to manage the polluted environment and recover contaminated river water.  Bioremediation is very much involved in the degradation, eradication, restriction, or reclamation varied chemical and physical hazardous substances from the nearby with the action of all-inclusive microorganisms. The fundamental principle of bioremediation is disintegrating and transmuting pollutants such as hydrocarbons, oil, heavy metal, pesticides and so on. Different microbes like aerobic, anaerobic, fungi and algae are incorporated in bioremediation process. At present, several methods and approaches like bio stimulation, bio augmentation, and monitoring natural recovery are common and functional in different sites around the world for treating contaminated river water. However, all bioremediation procedures it has its own pros and cons due to its own unambiguous application. Above all, utilization of bioremediation paving a minimal inconsiderably contaminated, healthy as well as safe and sound future.

Use of per- and polyfluoroalkyl substance (PFAS)-containing aqueous film-forming foams (AFFF) at firefighting training sites (FFTS) has been linked to PFAS contamination of drinking water. This study investigated PFAS transport and distribution in an urban groundwater aquifer used for drinking water production that has been affected by PFAS-containing AFFF. Soil, sediment, surface water and drinking water were sampled. In soil (n = 12) at a FFTS with high perfluorooctane sulfonate (PFOS) content (87% of ∑PFAS), the ∑PFAS concentration (n = 26) ranged from below detection limit to 560 ng g⁻¹ dry weight. In groundwater (n = 28), the ∑PFAS concentration near a military airbase FFTS reached 1000 ng L⁻¹. Principal component analysis (PCA) identified the military FFTS as the main source of PFAS contamination in drinking water wellfields >10 km down-gradient. Groundwater samples taken close to the military FFTS site showed no ∑PFAS concentration change between 2013 and 2021, while a location further down-gradient showed a transitory 99.6% decrease. Correlation analysis on PFAS composition profile indicated that this decrease was likely caused by dilution from an adjacent conflating aquifer. ∑PFAS concentration reached 15 ng L⁻¹ (PFOS 47% and PFHxS 41% of ∑PFAS) in surface river water (n = 6) and ranged between 1 ng L⁻¹ and 8 ng L⁻¹ (PFHxS 73% and PFBS 17% of ∑PFAS) in drinking water (n = 4). Drinking water had lower PFAS concentrations than the wellfields due to PFAS removal at the water treatment plant. This demonstrates the importance of monitoring PFAS concentrations throughout a groundwater aquifer, to better understand variations in transport from contamination sources and resulting impacts on PFAS concentrations in drinking water extraction areas.

Surface water is one of the primary sources of irrigation water for produce production; therefore, its contamination by foodborne pathogens, such as Salmonella, may substantially impact public health. In this study, we determined the presence of Salmonella in surface water and characterized the relationship between Salmonella detection and environmental and anthropogenic factors. From April 2019 to February 2020, 120 samples from 30 sites were collected monthly in four watersheds located in two different central Chile agricultural regions (N = 1080). Water samples from rivers, canals, streams, and ponds linked to each watershed were obtained. Surface water (10 L) was filtrated in situ, and samples were analyzed for the presence of Salmonella. Salmonella was detected every month in all watersheds, with a mean detection percentage of 28% (0%–90%) across sampling sites, regardless of the season. Overall, similar detection percentages were observed for both regions: 29.1% for Metropolitan and 27.0% for Maule. Salmonella was most often detected in summer (39.8% of all summer samples tested positive) and least often in winter (14.4% of winter samples). Random forest analysis showed that season, water source, and month, followed by latitude and river, were the most influential factors associated with Salmonella detection. The influences of water pH and temperature (categorized as environmental factors) and factors associated with human activity (categorized as anthropogenic factors) registered at the sampling site were weakly or not associated with Salmonella detection. In conclusion, Salmonella was detected in surface water potentially used for irrigation, and its presence was linked to season and water source factors. Interventions are necessary to prevent contamination of produce, such as water treatment before irrigation.

The removal of excessive ammonium from water is vital for preventing eutrophication of surface water and ensuring drinking water safety. Several studies have explored the use of biochar for removing ammonium from water. However, the efficacy of pristine biochar is generally weak, and various biochar modification approaches have been proposed to enhance adsorption capacity. In this study, biochar obtained from giant reed stalks (300, 500, 700 °C) was modified by sulfonation, and the ammonium adsorption capabilities of both giant reed biochars (RBCs) and sulfonated reed biochars (SRBCs) were assessed. The ammonium adsorption rates of SRBCs were much faster than RBCs, with equilibrium times of ∼2 h and ∼8 h for SRBCs and RBCs, respectively. The Langmuir maximum adsorption capacities of SRBCs were 4.20–5.19 mg N/g for SRBCs, significantly greater than RBCs (1.09–1.92 mg N/g). Physical-chemical characterization methods confirmed the increased levels of carboxylic and sulfonic groups on sulfonated biochar. The reaction of ammonium with these O-containing functional groups was the primary mechanism for the enhancement of ammonium adsorption by SRBCs. To conclude, sulfonation significantly improved the adsorption performance of biochar, suggesting its potential application for ammonium mitigation in water.

The bacteria toxicity of nanoscale zero-valent iron (nZVI) can be changed during its application in water treatment but the toxicity mechanism is still not well understood, particularly under anaerobic conditions. Here, the toxicity of nZVI and its aging products towards Escherichia coli (E. coli) and the mechanisms of extracellular and intracellular reactive oxygen species (ROS) damage were deeply probed in the presence and absence of oxygen in ultrapure water. Under aerobic conditions, the ROS damage primarily caused by the generation of extracellular free •OH can be a major contributor to the toxicity of nZVI to E. coli. By contrast, in anaerobic nZVI treatment system, the intracellular •OH can be quenched by benzoic acid which is a cell permeable quencher and the electron spin resonance (ESR) signals of 5,5-dimethy-1-pyrroline (DMPO)- •OH were evidently observed in system with the addition of F⁻ which could desorb the surface •OH into solution. It indicated that the intracellular •OH adsorbed on the particle surface can also play an indispensable role in inactivating cells under anaerobic conditions. Moreover, nZVI can steeply decline the membrane potential, causing severe membrane disruption and therefore resulting in the stronger toxicity in anaerobic conditions. Furthermore, the chemical composition transformation of nZVI and generation of benign iron corrosion products (e.g., Fe₃O₄, γ-Fe₂O₃, γ-FeOOH) are mainly responsible for the reduced toxicity with the increasing aging time. These results provide insights into the extracellular and intracellular ROS damage occurred in aerobic and anaerobic nZVI treatment systems, offering more perspective to the risk assessment of nZVI application.