Historically, as far back as the 19th century, Dr. John Snow, Louis Pasteur and Robert Koch contributed significantly to the systematization of knowledge about the quality of potable water thanks to a significant contribution to fundamental research: cholera, the influence of microscopic organisms on the aquatic environment and the development of a separate branch of science – bacteriology. Towards the end of the nineteenth century, potable-water quality problems began to focus on contaminants by pathogenic microbial organisms.
Since that time, in most countries of our planet, the processes of state regulation of drinking water quality have begun with relevant directives, sanitary norms and other specialized documents. For example, the American Health Service back in 1914 established the first federal standards for drinking water. By the sixties of the 20th century, standards included standards for twenty-eight pollutants and guidelines for water supply systems.
Chlorination and ozonation for water purification
At first glance, solving the problem of water purification from pathogenic microorganisms is not a very difficult matter. After all, disinfectants such as chlorine and ozone are highly active chemicals that are very effective in the inactivation of pathogens. However, in the mid-seventies of the last century in Rotterdam, a group of chemists led by Dr. J. Rook concluded that, after chlorination of water from surface water sources, an increase in the content of hazardous compounds, trihalomethanes, was observed. In recent years, Dutch and South Korean scientists have shown that not only chlorine, but also ozone reacts with natural organic substances, forming dangerous disinfection by-products.
Water purification using coagulants and flocculants
Taking into account the results of recent studies, the first steps of the water treatment process strategy can be formulated – this is either replacing a highly effective disinfectant, which is not a very good idea, or removing (coagulating, flocculating, followed by filtering) the organic precursor that is the source of the formation of hazardous substances.
Hence, coagulation is a process by which suspended, colloidal and dissolved substances are destabilized by the addition of a specialized chemical (coagulant). Traditional coagulants, such as ferric chloride, ferric sulfate and aluminum sulfate, etc., quickly hydrolyze when dispersed in water, forming insoluble precipitates and compress the double electric layer of suspended particles. Precipitation is adsorbed on the surface of polluting particles in water, neutralizing their charge, which subsequently allows them to connect with each other. Flocculation is a process in which particles are destabilized to form heavy agglomerates with a higher deposition rate.
Modern methods of water purification
Nowadays, Ukraine runs the government standarts 2.2.4-171-10, according to the provisions of which there is regulation of indicators of the quality of drinking water to ensure the population. High indicators of drinking water quality are achieved by a set of actions, including: coagulation, flocculation, filtration and disinfection. ALC “POLOGY CHEMICAL PLANT “COAGULANT” produces a wide range of reagents for the preparation of drinking water for both municipal and industrial enterprises.
