Issues Investigation- Part B- Angus Dally
Do the benefits of the chlorination of drinking water outweigh the risks?
Introduction
Public water in Australia and abroad, is chlorinated for disinfection. While effective at disinfection, disinfection by-products (DBP’s) pose many long term health risks. This begs the question: Do the benefits of the chlorination of drinking water outweigh the risks? There some alternatives to chlorination, such as ozonation and nano-filtration, and adopting even a slightly better way to disinfect water will have huge benefits, because of the sheer number of people using the current method.
Chemical Background
Chlorine acts to disinfect water by reacting with water to produce hypochlorous acid.
Cl2(g)+H2O(l)HCl(aq)+HOCl(aq)
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Sodium Hypochlorite is sometimes used instead, because of the health and safety risks associated with handling chlorine gas. (Dnr.gov, 2015)
NaOCl(l)+ H2O(l)Na(s)++HOCl¬(aq)+OH(aq)-
HOClH++OCl-
HOCl and OCl- are referred to as free available chlorine, and are the primary disinfection agents.
Before any of these reactions occur, and by extension, before any disinfection occurs, the chlorine demand must be met. Chlorine demand is the chlorine that is consumed in reactions before the primary, intended reactions. There are three main categories of chlorine demand:
1. Instantaneous
Instantaneous chlorine demand is the reactions with iron (Fe2+) and manganese (Mn2+) to form insoluble oxides.
2. Intermediate
Intermediate chlorine demand is the reactions of chlorine with ammonia to form chloramines. These chloramines provide limited disinfection, but not as much as hypochlorous acid and hypochlorite
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Diseases such as cholera, typhoid fever, dysentery and gastroenteritis, which were once extremely prevalent, have been virtually eradicated in countries like Australia and the US due to the use of chlorine in the disinfection process. Infant mortality rates have also been heavily decreased. The use of chlorinated water is considered one of the key factors in the massive increase in life expectancy, from around 45 years in the early 1900’s to almost 80 years today. (Waterandhealth.org, 2015). Chlorine is widely considered to be the best disinfection option, and in a survey of American public health officials 92% agreed that chlorine is crucial to eliminating waterborne diseases, and 87% believed that chlorination is the safest way to assure quality drinking water. (Waterandhealth.org, 2015)Over 98% of US water supplies are disinfected using chlorine, with the remainder primarily being from rural properties which source their water from a well or river. (Waterandhealth.org, 2015)
Chlorine is a very cheap method of disinfection. As of 2003, the cost of chlorinating water was 0.03 cents/litre. (Cdc.gov, 2015)Alternatives to chlorination, such as ozonation and nano-filtration, cost far more to implement and maintain. According to figure 1, the operating costs for a large treatment plant using chlorine are approximately $117,000 each year, while the cost when using ozone is about $2,000,000,
CL-, as the ions of H+ and OH- react to form H2O. These spectator ions
In the mining field, hydrochloric acid can be used to clean ore and concentrates (a concentrate is the desirable metal along with undesired substances such as dirt, sand, or minerals). You want to do this because there are salts in the concentrates that make it impossible to recover the gold with mercury. When you use hydrochloric acid it reacts with these salts to make new salts that are soluble in water. The new salts, having been dissolved in water, can then just be poured out. You are then able to do whatever is was that those salts wouldn't allow you to do in the first place. Now, you can get hydrochloric acid at a hardware store, and it may be called “muriatic acid”. You should dilute this about 1 to 6 with water before using it.
Despite the significant benefits of pool chlorines in their capacity to kill hazardous bacteria, it is evident that some of the side effects can be disadvantageous. The general smell of chlorine can be overwhelmingly unpleasant, and the agent can irritate the skin and eyes. It is also has the capability to bleach some fabrics, potentially damaging clothing. Most significantly, excessive air pockets of chlorine gas that surround pools can be hazardous for peoples’ health and possibly even be carcinogenic. For these reasons, some industries have started to investigate new alternative methods to chlorine for sterilising pools. According to Smith and Monteath et al. (2006, pp. 1 - 37), ‘some of these are good alternatives, but they do not achieve the cleanliness, oxidation levels or low price that chlorine provides’.
Koeman, M., Van der Ven, A., Hak, E. (2006). Oral Decontamination with Chlorhexidine Reduces the Incidence of Ventilator-associated Pneumonia. American Journal of Respiratory and Critical Care Medicine, 173, 1348-1355.
Bleaches are used as household chemicals to whiten clothes, remove stains and to be used as disinfectants, often by oxidation (Mittal, 2007). Numerous types of bleach contain strong bactericidal properties, and are used for disinfecting and sterilizing, thus why chlorine-based bleaches are popularly used in swimming pool sanitation to control bacteria, viruses and algae and in any institution where sterile conditions are needed (Reader's Digest). Chlorine is the basis for commonly used bleaches; for example, the solution of sodium hypochlorite. The concentration of chlorine-based bleaches are often expressed as percent active chlorine, where one gram of a 100 percent active chlorine bleach has the same bleaching power as one gram of chlorine. These bleaches can react with other common household chemicals like vinegar or ammonia to produce toxic gases (Bleach, 2014).
It’s no mystery that having clean water is a fundamental element to living in a prosperous society and one of the few things essential for human survival. Water not only sustains our health, but is required in making everything from electronics to clothes. Clean water may seem as ordinary as putting on your shoes, but it’s a daily party of our life that’s being threatened.
Measures to expand and improve public delivery systems of drinking water, contributing to a reduction in morbidity and mortality associated with enteric diseases, because these diseases are associated directly or indirectly with providing substandard water or poor provision water. Currently, 1,400 million people lack access to safe drinking water and nearly 4,000 billion lack adequate sanitation. According to estimates by the World Health Organization (WHO), 80% of diseases are transmitted through contaminated water.
Clean water is needed for good human and animal health, but as DoSomething.org states, over 1 billion people worldwide don’t have a means of getting clean drinking water, an...
The basic set of reactions that involve this process are: Cl + O3 -->ClO + O2 and ClO + O -->Cl + O2 The net result: O3 + O -->2O2 Chlorine is initially removed in the first equation by the reaction with ozone to form chlorine monoxide. Then it is regenerated through the reaction with monatomic oxygen in the second equation. The net result of the two reactions is the depletion of ozone and atomic oxygen.6 Chlorofluorocarbons (CFCs), halons, and methyl bromide are a few of the ozone depletion substances (ODS) that break down ozone under intense ultraviolet light.
The forth step in water treatment is a disinfection. During this stage, disinfectants will be added to kill or inactivate microorganisms that can cause disease in humans. The research on the water sample shows presence of protozoa that cause diseases such as Entamoeba histolytica, Giardia lamblia and Naegleria fowleri (Nemerow, Agardy, Sullivan, & Salvato, 2009). Some protozoa and viruses, which may present in water supplies are extremely harmful. There are two kinds of disinfection which is primary disinfection and secondary disinfection. Primary disinfection functioning in killing or inactivation of microorganism in the desired level while secondary disinfection maintains a disinfectant effectiveness that prevent from the microorganisms grow again. Disinfection treatment methods include chlorination, ozone and ultraviolet light. Chlorination is the most common method of disinfection used to treat water for municipal and individual supplies. It is because chlorination method is easy to conduct and cheapest compare to other method. In municipal supply systems, chlorine is used basically in three forms which are chlorine gas, sodium hypochlorite solution and solid calcium hypochlorite (Cheremisinoff, 1995). Chlorine is very effective for removing almost all microbial pathogens and is appropriate as both a primary and secondary disinfectant. Unfortunately, this method will produce water in which the chlorine can be smelt and tasted by users which most of them find it unpleasant. Binnie and Kimber (2009) stated that the problem can be overcome by dechlorination process after sufficient time for disinfection process. The water will be added with sulfur dioxide or sodium sulfate which reduces the chlorine to chloride (Binnie & Kimber, ...
Approximately 844 million people (one tenth of the population) in the world do not have access to clean and 2.3 billion do not have access to a decent toilet. This poor sanitation and contaminated water quality is the cause of death for over 289 000 children under the age of 5 every year.
Having clean water to drink means that water must have microbial, chemical and physical characteristics that meet WHO guidelines or national standards on drinking water quality. Around 780 million people in the world don’t have access to clean drinking water (Millions Lack Safe Water). More than 3.4 million people die each year from water, sanitation, and hygiene-related causes. Nearly all deaths, 99 percent, occur in developing countries. Around the world, diseases in unclean water kill about 1,400 children every day (Clean Drinking Water). There are many organizations that raise money in order to help develop ways or create ways for people to obtain clean drinking water. However, many people are unaware that this is even a problem in other countries because we take clean water for granted.
People from many developing countries are suffering from the scarcity of clean water, while the rest of the country simply take for granted. Habitants of rural poor communities such as Sub-Saharan Africa, are living in a water stressed environment. Residents of these communities have to walk miles at time just to gather water from streams and ponds, even though the water source may contain water-borne disease that can make them very sick. In the rural places that don’t have access to safe clean water, it is very difficult to prevent the spread of viruses. The consumption of contaminated water can be dangerous for health reasons and several people have passed away from these water-borne diseases. Some of these diseases include Cholera, Typhoid, Dysentery, Giardiasis, and Malaria. These unfortunate diseases are currently the cause of numerous deaths, especially in small children. The availability of clean water can prevent many problems in low income communities. The available resources for clean water are very rare, so these water sources need to pass through a process of water sanitation in order to just be sustainable to drink, “The world’s surface is made up of approximately 80% water, which is an indestructible substance. Of this water approximately 97% is salt water, 2% frozen in glaciers, and only 1% is available for drinking water supply using traditional treatment methods” (Thornton). Therefore, properly treated or disinfected
...rtied by bacteria and viruses not chemicals. To compliment this the UV oxidation would be used in more developed countries to destroy chemicals within the water allowing water to be cleaned worldwide ultimately in the end possibly ending the lack of water supply for the world.
In the end, water sanitization owners acquainted society by initiating carbon filters. Such filters have an extensive surface territory, a surface that can pull in and hold certain chemicals. The presently flow information on this methodology of decontamination permits mortgage holders and entrepreneurs to appreciate clean, unadulterated, extraordinary tasting