REDUCTION OR DESTRUCTION OF HARMFUL SUB-PRODUCTS THAT ARE PRODUCED DURING THE DISINFECTION PROCESS OF DRINKING WATER
The disinfection sub-products are produced by the compounds of disinfection and organic substances in the water.
As a result of researches, it was determined that such sub-products can lead to some health problems and act as the stimulator in some cancer types.
It is known that all cancer types are the diseases which develop slowly within the body and led by some various varying accumulations in the body. The most dangerous sub-products formed in drinking water;
• Chlorite (CIO2) accumalations formed during the disinfection process of water with (CIO2) ;
• Bromat (BrO3) accumalations formed during the disinfection process of water with Ozone (O3) ;
• Trihalometan (THM) accumalations formed during the disinfection process of water with Gas Chlorine (Cl2) ;
• Haloacetic acid (HAA5) accumalations formed during the disinfection process of water with Gas Chlorine (Cl2);
• Heavy metal accumulations (Cu+Ag) formed during the disinfection process of water with ion.
As it is seen, even if using amounts are kept under control, the mentioned disinfectants represent potential risks.
The sub-products as stated above are formed 20-50% less in disinfection process carried out with on-site produced Hypoklorozon (Chlorine and oxygen based disinfectant).
Concentrate-Commercial Sodium Hypochlorite pH 13,0 - 13,5:
Combining chlorine and caustic under favorable conditions, Sodium Hypochlorite is obtained containing 12-15% chlorine. It contains 8-10 gr/lt NaOH. (means containing caustic 50 times more than on-site produced hypochlorite). It loses chlorine rapidly and sodium chlorate is formed. PH value is around 13,0-13,5. Due to high value of pH, it features slow and delayed disinfection effect.
[Hypochlorite 15% loses chlorine 28% in dark environment under 27 °C during 28 days so measures as 108.1 g/lt.. ]*
* Resource: Water and Wastewater applications. Leonard W. Casson. James W. Bess,Jr.
EFFICIENCY TABLE DEPENDING ON pH VALUE
Using the water, salt and electricity, Sodium Hypochlorite [pH8.5 ] can be produced in amount of 8 gpl as standard by means of modern Electrolyzers including Titanium anode and cathode in any place where it is necessary. The Titanium anodes are coated with precious metal-oxide catalysts so the production achieved on based of constant efficiency. For using, the products are stored. The produced hypochlorite is more efficient and quicker at 10 times than concentrated hypochlorite due to low value of pH 8.5. It is cost effective and does not content any harmful chlorine compounds. The harmful and carcinogenic by-products that can be produced during the gas chlorine and water disinfection process do not form. It is fast and efficient due to law value of pH 8.5.
Hypochlorite and oxygen based oxidizers can be produced by using water, salt, and electricity in any place where is necessary. It is faster and more efficient than the concentrated and on-site produced hypochlorite. This product is cost effective and does not contain harmful chlorine compounds. It has less harmful and carcinogenic sub-products forming in scope of gas chlorine and water disinfection. The good results can be acquired with low dosing and low residual chlorine. Due to the oxidizers, it is fast and efficient. It contains Hypochlorite [OCl], acid [HOCI], Ozone [O3], Chlorine dioxide [CIO2]. [Sodium Hypochlorite 80% and oxidizers 20%].
Hypochlorous acid can be produced with an FTM or lon exchanger Membrane technology by using water, salt, and electricity in any place where is necessary. With low pH, high ORP value, the product is faster and more efficient than the concentrated and on-site produced hypochlorite. The most important feature is that it does not lead to the formation of harmful chlorine compounds produced in chlorine gas-water reaction. It contains the acid by 90% and hypochlorite by 10%. It does not contain chlorine gas and it is the most effective in range of 5,5-6,5 pH.
Hypochlorous acid Equilibrium Diagram
Thanks to the recent development of analytic devices, the gas chlorine compounds with the aquatic organics can be measured (1976) so it has proved that such compounds are they are carcinogenic and toxic thus particularly THM and DOM compounds can lead to the bladder and Colorectal cancer and harmful effects on kidneys, nervous system, liver, eyes, reproductive systems. the use of chlorine gas has been still ongoing today due to its cheap, easy carriage and non-instant harmful effects. Since the mixing possibility of domestic and industrial polluted waters into the water lines even the clean water networks, the use of chlorine unfortunately becomes necessary however it increases the chlorine and harmful compounds as well. In the developed countries, some measures are taken to keep such harmful effects of such organic compounds at low levels thus tries to reduce the harmful effects accordingly.
*Resource: Dr. Mehmet Çakmakçı Dr. Bestamin Özkaya
Yıldız Technical University Environmental Engineering Department January 2011
Chlorine dioxide is found in gas form; it is not stored or cannot be compressed. Despite the total amount of killed microorganisms are more than chlorine, it is not quick as much as Hypochlorous acid. It is obtained through HCI reaction with Sodium Chlorite. Therefore, it leaves the balance of Chlorite (ClO2) in the water. The experiments have shown that it causes to reduce the volume of liver and brain. The max allowable amount present in water is 0,2-0,5 mg/lt*. The raw material inputs in production and the cost are important issues. Generally, dosing and mixing unit are given as free of charge while raw material is being sold.
*Resource: 2005 Richardson. Who,Italia,England.
Ozone is a strong oxidizer used in disinfection process of water and wastewater.
It does not produce harmful and carcinogenic sub-products that are formed as a result of Chloride-water combination. It is ideally used for even smell and tasteful effects. It is used instead of gas chlorine to prevent carcinogenic sub-products (THM-HAA5) during the pre-chlorination process when the chlorine gas is used intensively. However ozone becomes in reaction with bromide thus it leads to bromate sub-products causing the risk of cancer. High level of bromate in drinking and usage waters becomes the reason for kidney and nervous system disorders. WHO, (2005) identified maximum concentration of bromate as 10pg/L.
This limit was also made enforceable in Turkey by publishing through the Gazette in the same year( February 2005).
Ozone is not be classified as the primary disinfectant since it is unstable, features to escape from the environment rapidly, becomes insufficient in oxidizing and not possibly measurable by the end user in practically..So using ozone does not eliminate the use of chlorine. The investment and operating costs are important. The customer should know what expect from ozone and also be sure that ozone fulfills the requirements technically and ergonomically. Ozone is a corrosive, dangerous and toxic gas thus the experts should take the necessary measures for this.
Although it is the oldest known method, it is seen that the use of ion becomes wider especially in swimming pools. Using ion in drinking water creates serious risk of danger.
Due to its heavy metal ions left in the environment, it constitutes serious risks for human health. It is seen as a primary system that should not be used since the heavy metal ions are difficultly controllable in water and disinfection process is rather slow.