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World Water Crisis and Climate Change
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Reverse osmosis is one of several pressure-driven membrane processes for water purification, which also include nanofiltration, ultrafiltration, and microfiltration. Reverse osmosis is a very useful and well-developed technique for the purification and desalination of water and is one of the major processes for purifying saltwater for domestic use and for renovating wastewater to recycling standards. As illustrated in Figure 7.7, it consists of forcing pure water through a semipermeable membrane that allows the passage of water but not of other material. This process, which is not simply sieve separation or ultrafiltration, depends on the preferential sorption of water on the surface of a porous cellulose acetate or polyamide membrane. Pure water from the sorbed layer is forced through pores in the membrane under pressure. If the thickness of the sorbed water layer is d, the pore diameter for optimum separation should be 2d. The optimum pore diameter depends on the thickness of the sorbed pure water layer and may be several times the diameters of the solute and solvent molecules.
Nano-Based Wastewater Treatment Technology
Published in M. H. Fulekar, Bhawana Pathak, Environmental Nanotechnology, 2017
Water purification is the process done to provide the palatable water because the water rapidly absorbs both natural and artificial substances, which makes it to be unsuitable for drinking (Kulkarni et al., 2000). Water treatment must produce the water that is Edible, which means no unpleasant taste should be presentNot containing pathogens or chemicals harmful to the consumers.Clear—it must be free from solids and turbidityColourless and odourless and aesthetic to drinkReasonably soft to allow wash clothes, dishes, themselves, without use of excessive quantities of soap or detergentsNon- corrosive to protect pipe work and prevent discharge of metals from tanks or pipesLow in organic content because the high organic content results in unwanted biological growth in pipes and storage tanks that often affects quality, these merits can be achieved by a variety of methods of water purification
Water Treatment
Published in Frank R. Spellman, The Drinking Water Handbook, 2017
Filtration treatment unit processes most commonly used in water purification systems include slow or rapid sand filtration, diatomaceous earth filtration, and package filtration systems. Slow and rapid filter systems refer to the rate of flow per unit of surface area. Filters are also classified by the type of granular material used in them. Sand, anthracite coal, coal–sand, multilayered, mixed bed, and diatomaceous earth are examples of different filtering media. Filtration systems may also be classified by the direction the water flows through the medium: downflow, upflow, fine-to-coarse, coarse-to-fine. Finally, filters are commonly distinguished by whether they are gravity or pressure filters. Gravity filters rely only on the force of gravity to move the water down through the grains and typically use upflow for washing (backwashing) the filter media to remove the collected foreign material. Gravity filters are free surface filters commonly used for municipal applications. Pressure filters are completely enclosed in a shell so most of the water pressure in the lines leading to the filter is not lost and can be used to push the water through the filter.
Adsorption of Rhodamine B from an aqueous solution by acrylic-acid-modified walnut shells: characterization, kinetics, and thermodynamics
Published in Environmental Technology, 2023
Xianzhe Guo, Zhuozhuang Liu, Zhiming Tong, Nan Jiang, Wu Chen
The walnut shell (WNS) is a common agricultural by-product in China and inexpensive source of raw materials. However, WNSs have not been reasonably utilized for a long time [35]. Modifying WNSs to adsorb pollutants in wastewater not only allows the use of WNSs as high-quality resources but also reduces air pollution caused by the direct incineration of WNS. For pollutants with large molecular sizes, such as dyes, WNS is generally prepared into activated carbon for water purification [36]. The preparation process of activated carbon is more complicated and requires a lot of energy. In contrast, direct chemical modification of WNS has the characteristics of simple process and rapid response [5]. However, no study has been done on the utilization of removal RB by acrylic acid modified WNS. In addition, the characterization of adsorption process and parameters has not been deeply studied. Considering the potential applicability of this technology in environmental industry, it is necessary to systematically study the adsorption of RB by MWNS.
Estimation of Hydroxyl Radical Exposure in a three-stage Countercurrent Ozone Contactor – Reduction in Musty Odor Compounds and Formation of Bromate
Published in Ozone: Science & Engineering, 2023
Kyohei Uchigami, Hideyasu Nakamura, Kazuo Ogura, Tadao Mizuno
The current water purification process consists of flocculation/sedimentation, ozonation, GAC process, flocculation/sedimentation, rapid sand filtration, and chlorine disinfection in sequence at both the Inagawa and Amagasaki DWTPs. The Inagawa DWTP adopts a three-stage countercurrent ozone contactor. The side view of the contactor is shown in Figure 2, and its specifications for System II are described in Table 1. An equivalent ozone dose was injected into each three-dissolution chamber through diffusers. The residual ozone concentration was monitored regularly by a dissolved ozone monitor at sampling port IV located immediately before the water flows into the GAC adsorption tank. The GAC adsorption tank is an upward stream type tank. These tanks are troublesome for system operation and maintenance because biofilms are generated at the bottom of the flow rectifier. To prevent the biofilms from being generated, a concentration of residual ozone was originally monitored and maintained at sampling port IV. Currently, the residual ozone concentration at sampling port IV has been utilized as an indicator to prevent the biofilms from being generated at the bottom of the flow rectifier as well as to determine the ozone dose to ensure an appropriate balance between substrates oxidation and by-products formation in water. In the span of five years, from 2013 to 2017, the residual ozone concentration at sampling port IV has been controlled in the range of 0.14–0.32 mg/L, and the consequent ozone dose has ranged from 0.47 to 2.86 mg/L.
Different regulatory approaches to enhanced water protection in selected European jurisdictions
Published in Water International, 2023
Nicole Grmelová, Anu Lähteenmäki-Uutela, Petr Štěpánek
Slovenia is a European country that has abundant water resources and a population of 2 million. Water distribution became the subject of public debate after private companies had gained legal rights over managing a large part of Slovenian water resources, and some Slovenian water companies had been taken over by global companies. A large Dutch brewery company took over two local breweries and obtained water allowances for a local water supply in Laško, causing a 30% increase in drinking water costs for the city’s inhabitants. Another company acquired a concession for a water purification plant leading to a deteriorated water quality. These facts triggered the civil society to join forces with the Members of the Slovenian Parliament (Eman & Meško, 2020). Citizens started to worry about their access to drinking water and wanted to strengthen the public control of water. The unprecedented mobilization of citizens and their interplay with politicians has been examined in literature (Loen & Gloppen, 2021).