Chemistry of Wastewater and Treatment - Coursework Example

Water treatment Name Course Date Contents Executive summary 3 Introduction 3 Manganese 4 Occurrence of manganese in water 4 Risks caused by manganese 5 Removal of manganese 5 Oxidation 5 Filtration 6 Arsenic 7 Effects of arsenic 7 Arsenic removal 7 Nitrates 8 Effects of nitrates 8 Nitrate removal 8 References 9 Appendix 9 Executive summary Water is vital for hygiene, health plus the output of the community. Safe and clean water is important for our daily life. The process of treating water may differ a little at various places depending on the expertise of the plant plus the water it requires to treat; nevertheless the fundamental techniques are basically the same. It is not a requirement for the drinking water to be completely pure to be considered safe. Since water is a high quality solvent, it is impossible to get pure water which is free of other elements. The major requirement is to provide safe drinking water to the community in every stages of their life inclusive of kids who are older than six months and the elderly people in the society (WHO, 2014). The water should be free of concentrations of harmful chemicals or any disease causing microorganisms. The water should be pleasing aesthetically in terms of taste, odor and appearance. People of all stages of their life risk contaminating waterborne diseases. The risky groups are the young kids and the infants, the elderly and those people living in conditions which are unhygienic (WHO, 2014). Introduction The process of water treatment can be illustrated as the procedures applied to make water extra suitable for the desired purpose of use. These comprise of drinking water, medical, industrial use plus other applications. The main aim of the process of treating water is the removal of contaminants that exist in water, or decrease the levels of contamination to acceptable levels. One of the methods is the returning of used water into the natural environment devoid of unfavorable impact on the ecology (WHO, 2014). The major processes used to treat water meant for drinking involve separation of solids through the use of physical methods like filtration and settling. Chemical methods like coagulation and disinfection. Biological methods like activated sludge, slow sand filters and aerated lagoons are also used in water treatment. This paper will discuss the different methods used to removal and control manganese, arsenic and nitrate compounds from drinking water and the chemicals that can be used to remove these compounds (NHMRC& NRMMC, 2011). The paper will also discuss why the compounds occur in water and the health risks that these compounds cause Manganese Occurrence of manganese in water Manganese is a compound which occurs naturally in most of the ground water and surface water in additional to soils which erode in to these waters, Therefore e making manganese common in water. Human activities are also to blame for the manganese occurrence in water in various areas. Areas with high traffic density have high concentration of manganese. Manganese occurs I divalent, tetravalent and heptavalent states i.e. Mn(II), Mn(IV) and Mn(VII) respectively. The divalent compounds are soluble in water, tetravalent are insoluble and heptavalent is soluble (WHO, 2014). Rivers and streams that are not contaminated have low manganese concentrations with a range between 0.001 mg/L - 0.6 mg /L. Polluted Rivers, ground water and deep lakes and reservoirs which are under anoxic environment have high manganese concentrations (NHMRC& NRMMC, 2011). Risks caused by manganese Manganese is an important element which is necessary for the growth and development of birds and mammals. Its deficiency has an effect on the brains, reproduction and brains of various species of animals. Excess manganese hinders dietary iron absorption which may result to anemia due to iron deficiency. High intake of the compound may also cause hypertension in people above 40 years of age (WHO, 2014). Clothes washed with water contaminated with manganese become stained with a brown color. The taste and flavor of drinks like coffee and tea is affected by manganese. There is formation of particles which are brownish – black in color which provides a metallic flavor to food or water (NHMRC& NRMMC, 2011). Removal of manganese Most treatment system utilizes the process of filtration and oxidation. Through the process of oxidation, the oxidant is oxidizes manganese chemically to form a particle. This kills the manganese bacteria in addition to any other present disease causing bacteria. The filtration process afterwards removes the manganese particles (NHMRC& NRMMC, 2011). Oxidation Manganese need to be oxidized into insoluble particles before they can be filtered. Oxidation is the transfer of electrons from the manganese to the oxidizing agent. Manganese Mn2+ is oxidized to Mn4+ which turns to the insoluble MnO2. The major oxidants that are used to treat water include chlorine, ozone, potassium permanganate and chlorine dioxide. Chlorination is mostly applied for the oxidation of the divalent manganese. But, due to formation of trihalomethanes in colored water the process is a problem. Potassium permanganate is the efficient method of manganese removal in drinking water. The stoichiometric equation for the oxidation of manganese by manganese ion by potassium permanganate is represented below. 3Mn2+ + 2KMnO4 + 2H2O 5MnO2 + 4H+ + 2K+ Filtration After oxidation the manganese requires a detention time of 10-30 min before filtration. There are numerous filtration methods for the removal of manganese. This includes electromedia, ceramic, iron-man sand and manganese greensand. Figure 1: chlorination and filtration for removal of manganese in water. Arsenic Arsenic is a compound which occurs naturally but can be found in drinking water by means of minerals and ores dissolution. Water flowing through rocks which are rick in arsenic is bound to have the compound. Atmospheric deposition and industrial effluent are also contributing factors increasing the concentration of arsenic to water. In organic arsenic occurs in various forms in the environment but in drinking water it occurs as; As(III) trivalent arsenite or As(V) pentavalent arsenate (NHMRC& NRMMC, 2011). Effects of arsenic After a long-term exposure to arsenic through drinking water, chronic arsenic poisoning occurs. The exposure also causes cancer of lungs, skin, kidney, urinary bladder plus other changes in the skin like pigmentation and hyperkeratosis. All these are observed when the concentration of arsenic in drinking water is below 0.05 mg/L. arsenic also causes peripheral vascular diseases. Deaths may also occur as a result of cancer caused by consuming contaminated water (WHO, 2014). Arsenic removal The process of conventional coagulation can be used to remove arsenic from drinking water. Before treatment, it is advisable to change arsenic from the trivalent form to pentavalent by oxidation through the use of potassium permanganate or chlorine. Softening of hard water using lime is also an effective way but this is dependent on the valence state and the pH. The machines manufacture for the removal of arsenic can perform up to0.01 mg/L (10 µg/L) or a lesser amount therefore making it difficult to remove the concentration to below 10 μg/L in most of the cases (NHMRC& NRMMC, 2011). Nitrates Nitrate plus the nitrite ions are nitrogen oxides that occur naturally and form part of the nitrogen cycle. Increase in farming practices plus the effluent sewage disposal to the rivers contribute to the high quantities of nitrates in drinking water especially the ground water (NHMRC& NRMMC, 2011). Effects of nitrates Nitrate becomes toxic when it is reduced to nitrite. Nitrite in humans is involved in the oxidation of hemoglobin to methahemoglobin. Methahaemoglobin is not capable of transporting oxygen to the tissues leading to a condition known as methaemoglobinaemia. Young children are vulnerable to methaemoglobin as compared to older kids and adults. Pregnant women and individuals who have a scarcity of glucose-6-phosphate dehydrogenase are also vulnerable of deficiency of methaemoglobin reductase (WHO, 2014). Nitrate removal Traditional water treatment methods are not successful for removal of nitrate. The procedures of decreasing Nitrate are lavish to work with and include the utilization of anion exchange resins (NHMRC& NRMMC, 2011). References NHMRC, NRMMC (2011) Australian Drinking Water Guidelines Paper 6 National Water Quality Management Strategy. National Health and Medical Research Council, National Resource Management Ministerial Council, Commonwealth of Australia, Canberra WHO (World Health Organization) (2004). Guidelines for Drinking-water Quality. First addendum to 3rd edition. Volume 1. Recommendations. WHO. Appendix Figure 1: chlorination and filtration for removal of manganese in water. Read More