The energy-free purification of trace thallium(I)-contaminated potable water using a high-selective filter paper with multi-layered Prussian blue decoration

Thallium is a highly toxic metal,and trace amount of thallium(I)(Tl+)in potable water could cause a severe water crisis,which arouses the exploitation of highly-effective technology for purification of Tl+contaminated water.This report proposes the multi-layered Prussian blue(PB)-decorated composite membranes(PBx@PDA/PEI-FP)based on the aminated filter papers for Tl+uptake.Extensively characterization by Fourier transform infrared spectrometer-attenuated total reflectance,scanning electron microscope,thermogravimetric analysis,X-ray photoelectron spectroscopy and X-ray diffraction were performed to confirm the in situ growth of cubic PB crystals on filter paper membrane surfaces via the aminated layers,and the successful fabrication of multi-layered PB overcoats via the increasing of aminated layers.The effect of PB layers on Tl+removal by PBx@PDA/PEI-FP from simulated drinking water was evaluated as well as the influence of different experimental conditions.A trade-off between PB decoration layer number and PB distribution sizes is existed in Tl+uptake by PBx@PDA/PEI-FP.The double-layered PB2@PDA/PEI-FP membrane showed the maximum sorption capacity,but its Tl+uptake performance was weakened by the acid,coexisting ions(K+and Na+)and powerful operation pressure,during filtrating a large volume of low-concentrated Tl+-containing water.However,the negative effect of coexisting ions on the Tl+uptake could be effectively eliminated in weak alkaline water,and the Tl+removal was increased up to 100%without any pressure driving for PB2@PDA/PEI-FP membrane.Most importantly,PB2@PDA/PEI-FP displayed the high-efficiency and high-selectivity in purifying the Tl+-spiked Pearl River water,in which the residual Tl+in filtrate was less than 2μg·L^(–1) to meet the drinking water standard of United States Environmental Protection Agency.This work provides a feasible avenue to safeguard the drinking water in remote and underdeveloped area via the energy-free operation.

Salinity exchange between seawater/brackish water and domestic wastewater through electrodialysis for potable water

Two-thirds of the world’s population has limited access to potable water.As we continue to use up our freshwater resources,new and improved techniques for potable water production are warranted.Here,we present a general concept called“salinity exchange”that transfers salts from seawater or brackish water to treated wastewater until their salinity values approximately switch,thus producing wastewater with an increased salinity for discharge and desalinated seawater as the potable water source.We have demonstrated this process using electrodialysis.Salinity exchange has been successfully achieved between influents of different salinities under various operating conditions.Laboratory-scale salinity exchange electrodialysis(SEE)systems can produce high-quality desalinated water at~1 mL/min with an energy consumption less than 1 kWh/m3.SEE has also been operated using real water,and the challenges of its implementation at a larger scale are evaluated.

The effect of coupling coagulation and flocculation with membrane filtration in water treatment:A review

Water supply and sanitation demands are foreseen to face enormous challenges over the coming decades to meet the fast growing needs in a global perspective. Significant growth in the industry is predicted and membrane separation technologies have been identified as one of the possible solutions to meet future demands. Application and implementation of membrane technology is expected both in production of potable water as well as in treatment of wastewater. In potable water production membranes are substituting conventional separation technologies due to the superior performance, potential for less chemical use and sludge production, as well as the potential to fulfill hygienic barrier requirements. Membrane bio-reactor （MBR） technology is probably the membrane process which has had most success and has the best prospects for the future in wastewater treatment. Trends and developments indicate that this technology is becoming accepted and is rapidly becoming the best available technology for many wastewater treatment applications. A major drawback of MBR systems is membrane fouling. Studies have shown that fouling mitigation in MBR systems can potentially be done by coupling coagulation and flocculation to the process.

Comparative Analysis of Chemical, Physical and Biological Contaminants in Drinking Water in Various Developed Countries around the World

Sustaining a reliable and contaminant-free drinking water is becoming an increasing challenge worldwide due to human activity, industrial waste, and agricultural overuse. Surface water is the main source of drinking water around the world. However, groundwater is also becoming increasingly popular, due to its clarity and minimal need for processing to reduce turbidity. Over the years, the demand and growth in the agricultural industry has also been the means of groundwater contamination. Due to the health burden that raw water can pose, water must be processed and purified prior to consumption. Raw water quality can be compromised by physical, chemical (heavy metals and disinfection by-products), and biological contaminants. Biological contaminants can significantly impact immunocompromised populations, while chemical contaminants can impact the growth and development of young children. Although obtaining a steady and high-quality water flow to the general population is an increasing challenge, developed countries have utilized state-of-the-art technologies and techniques to provide contaminant-free water to their citizens. This research aims to provide information about the regulatory parameters, characteristics, and sources of safe drinking water in the world as a model for future use in the developing world. In this, secondary data was used to compare and contrast drinking water quality among countries in the European Union, the United States, Canada, the United Kingdom, Singapore, New Zealand, Australia, Qatar, and the United Arab Emirates. The data indicates that Ireland and the United Kingdom have relatively lower amounts of contaminants in their drinking water. Upon completing this research, it is recommended that countries desiring clean drinking water systems should initiate and invest in programs that control and protect treatment plants, water distribution systems, water sources, and catchments.

Physico-Chemical Characterization of Sludge from the Goudel Drinking Water Production Plant in Niamey (Niger)

Population growth and increasing needs make our current societies a considerable source of environmental threats. Going towards sustainable cities where harmony exists between economic, socio-cultural and environmental issues is a necessity that is essential if we want to bequeath a livable world to future generations. Cities produce huge quantities of domestic and industrial waste, the management of which is becoming a growing problem for city managers. Located on the banks of the Niger River, the city of Niamey, capital of the Republic of Niger, is supplied with drinking water from this river. Significant quantities of sludge are produced by the plant following the treatment of this water. This study focuses on the physico-chemical characterization of this sludge which is now directly discharged into the Niger River. A total of 12 samples of pasty sludge taken from the pre-settling ponds were analyzed. The samples were previously dried, crushed, sieved and packaged. Physical (pH, EC and particle size), chemical (Ca, Mg, Na, K, CEC, AE, P, C, MO and N) and metallic trace elements (Pb, Ni, Cu, Zn, Cd, Mn) parameters and Al) were analyzed in the laboratory. The results show that the sludge is weakly acidic (pH between 4.16 and 5.71), conductive (<0.35 mS/cm) and rich in fine elements (12.1% to 77.71% clay). The nutrient content is low in nitrogen (<0.25%), phosphorus (<2.5 ppm), potassium (between 1 to 188 Mèq/100g) and organic matter (less than 2.88%). The concentrations of ETM comply with the values admissible in residual materials (French decree of 08/01/1998). This sludge can be recovered, especially in agriculture.

Evaluation of the Physico-Chemical Quality and Potability of Groundwater Consumption in Department of Collines at Benin

The purpose of this study is to assess the physical and chemical quality of borehole water intended for consumption in the collines department in Benin. At the end of a sampling campaign, twenty-one (21) drinking water points were sampled. Different physico-chemical parameters were measured using standard analysis methods. The results of the analysis of the samples, showed that the groundwater of the department of the hills is characterized by a neutral pH and an average electrical conductivity in accordance with the WHO and Benin standard relating to the potability of groundwater. With this pH neutrality which would be linked to the nature of geological formations made up of crystalline rocks, the water in the hills is moderately hard with hardness values of 208 mg/L on average for magnesium ions of 22.54 mg/L on average and calcium ions of the order of 46.03 mg/L on average at the scale of the various localities and an alkalinity is of 43.81 mg/L on average. The values between 0 and 163.91 mg/L are low in the South-East and very high, even exceeding the standard accepted by WHO in the West and North-East of the study area. This nitrate pollution and the fairly high levels of organic matter in total nitrogen observed in the groundwater of the hills could also have an impact on the vulnerability of the water table. And this pollution with nitrates associated with electrical conductivity and chloride levels modifies and degrades from one drinking water point to another the potability of underground water in the hills.

Role of water chemistry on estrone removal by nanofiltration with the presence of hydrophobic acids

Hydrophobic acid organic matter （HpoA） extracted from treated effluent has been known to improve the rejection of steroid hormone estrone by reverse osmosis （RO） and nanofiltration （NF） membranes. In this study, the effects of solution chemistry （solution pH and ionic strength） on the estrone rejection by NF membrane with the presence of HpoA were systematically investigated. Crossflow nanofiltration experiments show that the presence of HpoA significantly improved estrone rejection at all pH and ionic strength levels investigated. It is consistently shown that the ＂enhancement effect＂ of HpoA on estrone rejection at neutral and alkaline pH is attributed to the binding of estrone by HpoA macromolecules via hydrogen bonding between phenolic functional groups in feed solutions, which leads to an increase in molecular weight and appearance of negative charge. The membrane exhibited the best performance in terms ofestrone rejection at pH 10.4 （compared to pH 4 and pH 7） as a result of strengthening the electrostatic repulsion between estrone and membrane with the presence of HpoA. At neutral pH level, the ability of HpoA macromolecules to promote estrone rejection became stronger with increasing ionic strength due to their more extended conformation, which created more chances for the association between estrone and HpoA. The important conclusion of this study is that increasing solution pH and salinity can greatly intensify the ＂enhancement effect＂ of HpoA. These results can be important for NF application in direct/indirect potable water reuse.