Comparative characteristics of some water disinfectants

Name and description of disinfectant	Advantages	Disadvantages
Basic disinfectants
Chlorine Applied in gaseous form, requires safety measures to be strictly observed.	effective oxidizer and disinfectant; effective against unpleasant odours and flavours; provides aftereffect; prevents growth of algae and biofilms; destroys organic compounds (phenols); oxides iron and manganese; destroys hydrogen sulphide, cyanide, ammonia and other nitrogen compounds.	strict requirements towards transportation and storage; potential health risks in case of escape; formation disinfection by-products – trihalometans; forms bromates and bromorganic disinfeciton by-products over bromides.
Sodium hypochlorite Applied in liquid form (product concentration of solutions - 10 -12%), on-site electrochemical generation is possible.	effective against majority of pathogens; relatively safe when stored and applied; on-site generation does not require transportation and storage of dangerous chemicals.	not effective against cysts (Giardia, Cryptosporidium); not active when long stored; potential danger of gaseous chlorine isolation during storage; forms disinfection by-products including trihalometans (bromoforms and bromates over bromides); on-site generation requires immediate usage or (to ensure storage) special measures are required for initial water and salt cleaning from heavy metals ions; during storage of NaClO solutions with active chlorine concentration over 450 mg/l and pH over 9 chlorates are accumulated.
Chlorine dioxide On-site generation only. At present considered to by the most effective disinfectant among chlorinated reagents for water with high pH values treatment.	operates at lower doses; does not form chloramine; does not make for trihalometans formation; destroys phenols – source of unpleasant flavor and odour; effective oxidizer and disinfectant against all kinds of microorganisms including cyst (Giardia, Cryptosporidium) and viruses; does not form bromates and bromorganic disinfection by-products over bromides; furthers removal of iron and manganese from water by way of their quick oxidation and oxides precipitation.	on-site generation is obligatory; requires transportation and storage of highly inflammable initial matters; forms chlorates and chlorites; In combination with certain materials leads to specific flavor and odour.
Chloramine Formed as a result of ammonia and active chlorine compounds interaction , applied as a disinfectant of durable action.	provides steady and durable aftereffect; provides for removal of unpleasant flavor and odour; reduces level of formation of trihalometans and other chlororganic disinfection by-products;	weak disinfectant and oxidizer in comparison with chlorine; not effective against viruses and cyst (Giardia, Cryptosporidium); high dosing and durable contact time are required for disinfection; represents a danger to people using dialyzers as is capable of penetrating through dialyzer’s membrane and affect erythrocytes; forms nitrogen-containing by-products.
Alternative disinfectants
Ozone Applied during several decades in a number of European countries for disinfection, color removal, odor removal and flavor improvement.	strong disinfectant and oxidizer; very effective against viruses; mostly effective against Giardia, Cryptosporidium, as well as any other pathogenic microflora; provides for turbidity removal from water; removes unpleasant flavors and odors; does not form chlorinated trihalometans.	forms by-products, including: aldehydes, ketones, organic acids, bromic trihalometans (including bromoform), bromates (over bromides), peroxides, bromacetic acid; requires application of biologically active filters for removal of the formed by-products; does not provide for residual disinfecting benefit; requires high initial inputs for the equipment; requires considerable inputs for personnel training and servicing o equipment; when reacting with complex organic compounds, озон , ozone decomposes them into fragments which become nutrient medium for microorganisms in water distribution systems.
Ultraviolet The process lies in irradiation of water by ultraviolet capable of destroying different kinds of microorganisms.	does not require transportation and storage of chemicals; does not form by-products; effective against cyst (Giardia, Cryptosporidium).	no residual benefit; requires high inputs for equipment and technical servicing; requires high operational (power) inputs; disinfecting activity depends on water turbidity, water hardness (formation of sediment on the lamp’s surface), deposition of organic impurities on the lamp’s surface, as well as power circuit variation having impact on wave-length change; no possibility of on-line control of water disinfection effectiveness.
AQUACHLORs oxidants solution Electrochemical synthesis from sodium chloride solution of wet gaseous mixed oxidants – chlorine, chlorine dioxide, ozone, hydroperoxide compounds.	operates at lower doses;   does not make for formation of trihalometans; destroys phenols – source of unpleasant odor and flavor; effective oxidizer and disinfectant for all kinds of microorganisms including cyst (Giardia, Cryptosporidium) and viruses; does not form bromates and bromorganic disinfection by-products over bromides; provides for iron and manganese removal from water by way of their quick oxidation and deposition of oxides; provides for removal of turbidity from water; removes unpleasant odors and flavor; does not require transportation and storage of dangerous chemicals.	requires availability of power; pressure water line; requires little consumption of hydrochloric acid for de-scaling of electrodes when low quality salt is used ( with high content of calcium, magnesium and iron ions), or requires system of chemical softening of the initial sodium chloride solution (for example by sodium bicarbonate).