Methods for cleaning up this group are based on the chemical interaction of certain substances (reagents) with contaminants, resulting in a second or decomposed into harmless components, or move to a different state (for example, to form insoluble compounds that fall into the precipitate is separated). Although not a huge variety of potential contaminants and chemical reactions in which these contaminants may enter, emit a number of purification methods, fundamentally different according to the type of chemical interaction:
Neutralization is, as the name implies, the implementation of the neutralization process in which there is an alignment of acid-base balance through the interaction of acids and alkalis with the subsequent formation of the corresponding salts and water. The neutralization is carried out either by mixing of treated water with acid and alkaline medium, and by adding reagents in the water environment creating a specific reaction (acid or alkaline). To neutralize the acidic effluent typically use ammonia water (NH4OH), sodium and potassium hydroxides (NaOH and KOH), soda ash (Na2CO3), lime milk (Ca (OH) 2), etc. In the case of alkaline waste solutions using various acids and acid gases containing oxides such as the CO2, SO2, NO2, etc. As the acid gases are routinely used flue gases that are passed through the cleaned water is carried out simultaneously with the process of purification of gases and solids from themselves.
Oxidation and recovering is also used to purify water from various pollutants, although in practice the ratio of their use is strongly biased toward oxidants. Despite the fact that the neutralization reaction proceed as parallel processes of oxidation and reduction, the method is characterized by a much more powerful oxidizing and reducing agents, as a target contaminants will not react with the substances used in the cleaning method of neutralization. With their help conduct neutralization of various toxic substances, and as substances derived from hard water by other means. The reaction of oxidation of toxic pollutants achieve translated into less toxic or non-toxic form. Also, through the use of strong oxidants achieved the death of microorganisms, occurs due to the oxidation of cellular structures. The chlorine-containing oxidants mainly used: chlorine gas (CL2) and various chlorine compounds such as chlorine dioxide (CLO2), hypochlorides potassium, sodium and calcium (KCLO; NaCLO; Ca (CLO) 2). Besides using hydrogen peroxide (H2O2), potassium permanganate (KMnO4), ozone (O3), air oxygen (O2), potassium dichromate (K2Cr2O7), etc.
Chlorination, that is, compounds of chlorine treatment of water, the process is well established and widely used in water treatment. Handling also chlorine has prolonged antibacterial effect, which is especially important for the water supply in a worn-out pipelines where secondary water contamination can occur. Additionally, chlorinating reagents are relatively inexpensive and accessible. At the same time, this method has several disadvantages, which induce to look for alternatives. In some cases, side-compounds formed after chlorination may be less toxic, besides chlorine itself is poisonous, thus requiring carefully observe the conditions of the chlorination dosing.
At the moment, all the more widespread treatment of water with ozone (ozone treatment), because the effectiveness of this method surpasses chlorination, ozone does not form hazardous compounds and eventually breaks down into harmless diatomic oxygen (the O2), so that an overdose of ozone does not result in undesirable and dangerous consequences. The wide dissemination of Ozonation only impede technical and economic complexity of its production in sufficient quantities, and the explosiveness of ozone, which requires compliance with stringent safety regulations on wastewater treatment plants.
This water disinfection method, which uses an iodine compound. As iodine bactericide used for a long time and is commonly used in medicine. The problem is the low solubility of iodine in water, and for this reason it is typically used compounds. Iodination is often used for water disinfection in sports pools. There are a number of funds (the so-called iodine tablets) used for personal disinfection of water on the road. According to the research the most effective method of disinfecting a small volume of water in field conditions.