No abstract

Drinking water prepared using the most effective and popular reverse osmosis method is absolutely safe but for the most part does not meet the requirements for physiologically complete water. The latter must meet, in addition to the basic requirements, the following requirements: salt content, at least 100, and not more than 1000 mg/dm3; total hardness; in the range of 1–7.0 mmol/dm3. Now, to fulfill these requirements, the stage after desalting employs various methods of domineralization of reverse osmosis water, each of which has certain disadvantages. This paper considers the task of obtaining safe physiologically complete water immediately after the stage of membrane desalting by using modified reverse osmosis membrane elements with the predefined selectivity. The study object was the process of obtaining reverse osmosis membrane elements with the predefined selectivity by modifying them with sodium hypochlorite solution for use in the process of obtaining physiologically complete drinking water. The required level of selectivity of modified elements was calculated to obtain safe physiologically complete water from starting water, depending on its salt content. Thus, for the starting water with a salt content of 200–300 mg/dm3, the specified selectivity of the membrane element should be no more than 60 % at a temperature of 25 °C. Rational conditions for conducting the modification process for obtaining a membrane element with such exact selectivity have been established. The nature of the influence of changes in water temperature on the selectivity of the modified element was studied. A prototype of the modified element was tested in a vending machine for pouring water, which purified tap water in the city of Kyiv, with a salt content of 230 mg/dm3 at a temperature of 8–12 °C. The test results showed the possibility of one-stage obtaining safe physiologically complete water by reverse osmosis using a modified membrane element with the predefined selectivity of 50 %.

More than 70 percent of our planet is covered with water. And yet water is a scarce resource, and it is our future. According to the World Wildlife Fund, 1.1 billion people do not have access to it, and 2.7 billion experience a shortage of drinking water at least once a year. By 2025, two-thirds of the world's population may face water shortages. The shortage of drinking water and the search for renewable resources are of the most important problems in the modern world, the solution of which is directed to considerable intellectual and financial resources. Reverse osmosis is one of the most common technologies for obtaining high-quality drinking water. Technological solutions constantly improve the process of reverse osmosis and reverse osmosis spiral wound membrane elements used, science and business go hand in hand. But the price of this progress is the annual generation of a large amount of waste generated from used reverse osmosis roll membrane elements, which are usually sent to the landfill, while there are no technological solutions for their disposal. This work provides information on the available amount of such waste in the world and the dynamics of its growth in order to assess the scale of environmental damage that occurs as a result. The work collected information about the market of reverse osmosis spiral wound membrane elements in the world, and directions of their use. The structure, composition of components and technical characteristics of reverse osmosis spiral wound membrane elements are considered in detail, which makes it possible to evaluate the ways and possibilities of their utilization. The problems of surface contamination due to various types of fouling are considered. The main attention in the work is given to the reasons that cause the formation of waste. Based on the collected data, the scale of annual waste generation, which is formed due to spent reverse osmosis roll membrane elements, was analyzed. The possibility of reusing reverse osmosis spiral wound membrane elements and the main methods of their safe disposal are also considered. Summarizing the work carried out, recommendations were made on ways to solve the problem.

In the present paper, the information on the influence of various factors on the carbon block cartridges production technology and their potential impact on the properties of the finished product is presented. The possibilities of increasing the sorption-filtering efficiency of carbon block cartridges are presented. The technical and exploitation characteristics are influenced by the size of the mixture components granules, the physicochemical properties of active carbon and binder polymers, their ratio in the mixture, and the addition of bactericidal additives into the composition. The study of this topic is relevant, as evidenced by the analysis of the increasing number of publications on this matter over the past ten years. However, the production technology of carbon block cartridges is the know-how of manufacturing companies. This information is confirmed by the analysis of the technical characteristics of sixty carbon block cartridges from nine world manufacturers, whose products are WQA certified according to the NSF/ANSI 42 standard. The recommendations given by a number of authors on the size of activated carbon granules in the range from 40 to 120 mesh and polyethylene particles from 80 to 160 mesh with a flow rate of 1.4-3 g/10 min, can be taken as "reference points" in the development of extrusion mixtures with different components ratio. The following factors play an important role in obtaining effective cartridges: the quality of pre-extrusion mixing of the composition, its resistance to delamination during the “transition” from the mixer to the extruder loading zone, extrusion temperature regimes by zones, product cooling temperature, backpressure on the billet leaving the extruder. The information given in this article will be useful when producing new carbon block cartridges, improving the parameters of existing technologies, as well as in the research development of cartridges with new properties.

Conventional methods for water disinfection, especially chlorination, have a lot of disadvantages and should be perfected or substituted with safer and more efficient methods. One of the possible solutions to this problem is the application of sorbents with high disinfection efficacy. In this study, the opportunity of producing sorbents with biocidal properties based on non-oxidizing biocides and anion exchange resins (AERs) was investigated. A wide range of different type of AERs were tested for the ability to sorb biocides (dibromonitrilopropionamide (DBNPA) and polyhexamethyleneguanidine (PHMG)) and to exert disinfection activity. Most suitable AERs for production of biocidal sorbents were outlined.