Water Decontamination Methods Advantages and Disadvantages

Water Decontamination Methods Advantages and Disadvantages synopsisAbstractIn Malaysia, for the past galore(postnominal) years, intoxication piddle pr all(prenominal)ing was only limited to body of peeing dis vitiateion by using chlorine further it had been concluded that its use in potable weewee administration interposition ass be harmful to human come upness.(Subedi, et al., 2012) Fol baseborning the schooling in drinkable water interference, conventional methods in three different technologies argon open to gather in more purified water. They be biologic, physico chemic substance and advanced oxidation make for (AOPs) technologies. Each of the technologies has different roles in purifying water and they can be combined to treat tipsiness water as well. In this assignment, the lists of methods of severally technology argon say and both(prenominal) of the main subprogrames argon discussed, including the advantages and disadvantages of distri neverthel essively of them. For biological technology, easy smooth filtration and perchlo post addresses atomic number 18 discussed in 3a.For physicochemical technology, curdling do is discussed in details in 3b. Lastly, the advanced oxidation process, AOPs, take on both photochemical and non-photochemical oxidation. The fenton system and photocatalytic processes which are categorized in photochemical oxidation are discussed in 3c.IntroductionSafe beverage water that drop by the wayside of contaminants is essential to human health and development issue at national, regional and local directs. Its accessibility is humans rights and a cistron of effective policy for health protection. (who et al) thitherfore, there are many drinking water regulations and acts set by specialized agency such(prenominal)(prenominal) as WHO to have standard on safe drinking water to springiness awareness to public and thus limit the levels of contaminants. The national primary drinking water regulations and number of regulated contaminants shown in Figure 2.1 and Figure 2.2 in appendix 2.According to the regulations and standards, the characteristics of safe drinking water are contaminants free, natural minerals rich, saltlike pH, taste good and odorless. Firstly, microbiological and chemical contaminants in drinking water whitethorn cause acute or chronic health cause or undesirable aesthetic properties when present at excessive concentrations. Microbiological contaminants refer to pathogenic microorganisms such as bacteria, viruses and protozoan parasites. Chemical contaminants refer to toxicity, in perfect and perfect chemicals. The other contaminants are pesticides, herbicides and radioactive materials (radionuclide). Besides that, pH of water should be retained from 6.5 to 8.5. This is because alkaline water is able to neutralize stored acids and help in eliminating toxins. Because of these, various casefuls of technologies of drinking water treatments are introduced to minimize the deleterious effects of polluted drinking water on human health. Details of contaminants by National Secondary Drinking Water Standards and details of contaminants and potential health effects by National Primary Drinking Water Standards as shown in Figure 2.3 and Figure 2.4 respectively in appendix 2. In the following, three different technologies which are biological, physicochemical and advanced oxidation process (AOPs) are introduced to treat drinking water to a safety level so that human health is check overd. The goal of all of the developed water treatment technologies is to remove turbidity as well as chemical and pathogenic contaminants from drinking water descent in the most affordable and expedient manner possible.3.Content 3a.Biological TechnologyWater apply for drinking and kinsfolk use, even water from a ground water supply, should be tempered originally it is employ to ensure it is safe and aesthetically pleasing. One forward-looking method of wat er treatment is biological water treatment. Biological drinking water treatment is one technology that has the potential to further many of these objectives. This technology is based on the ability of microorganisms specifically non-pathogenic bacteria to expeditiously catalyze the biochemical oxidation or reduction of drinking water contaminants and produce biologically stable water. (Snoeyink, 1984) .Biological drinking water treatment is a good deal use in combination with other chemical and chemical processes including ozonation and filtration. There are some oddballs of biological drinking water treatment such as slow mother wit filtration, rapid biological filtration, ozone-enhanced biological filtration and mealy activated carbon biological adsorption.Firstly, the slow sand filtration is a type of centralized or semi-centralized water purification system. A well-designed and properly maintained slow sand filter (SSF) effectively removes turbidity and pathogenic organism s by various biological, physical and chemical processes in a single treatment step. According to (Patrick J. Evans, 2010), slow sand filtration involves very low filtration runs (e.g. 0.04 to 0.10 gpm/ft2) through with(predicate) sand media without pre-oxidation or pre-disinfection (Awwa, 2005). During initial operation of slow sand filtration, a point of biological matter will be produced on the outdoors of filter media by the separation of organic matter and other solids. This layer is called as schumutzdecke which acts as the predominant filtering mechanism. It supports the biological matter that works as the primary biofiltration process to remove BDOC, pathogenic microorganisms, and deviateiculates (Page, 2006).To maintenance the slow sand filtration process, periodic scraping and removal of the top layer of sand are needed. Besides that, there is another more precise term to convert slow sand filtration which is called biological filtration (SBF) since the biologically active schmutzdecke is an integral part of this process. Besides that, the advantages of slow sand filters is very effective in upward(a) the microbiological and physicochemical qualities of water and it is very easy to operate and maintain. The disadvantages of slow sand filters are vulnerability to clogging when the incoming water is of high turbidity. When dealing with such waters, pre-treatment, such as sedimentation or roughing pre-filtration is required.Next, biological perchlorate or nitrate process. Perchlorate and nitrate have the ability of being an aerophilically biodegraded to chloride and nitrogen gas. (Patrick J. Evans, 2010) stated the process involves addition of an electron donor such as acetic acid plus nutrients to water to promote biochemical reduction of biological perchlorate or nitrate process. Moreover, perchlorate and nitrate act as the terminal electron acceptors for respiration by these bacteria. As a result, BPNP vary from the predate biological drinki ng water treatment processes that are aerobic and employ aerobic bacteria that use oxygen as a terminal electron acceptor for respiration. BPNP can be employed in diverse arrangement including jammed beds, fluidized beds, and membrane systems. BPNP is followed by an aeration process to promote aerobic biodegradation of assimilable organic (AOC) and biodegradable dissolved organic carbon (BDOC) in combination with a filtration process for turbidity removal.3b.Physicochemical TechnologyPhysicochemical drinking water treatment is frequently utilise in the area of drinking water treatment. This proficiency is applied to remove the heavy metals, oils and suspended matters. This physiochemical drinking water treatment proficiency is used to treat drinking water in target to become process water. According to (Spellman, 2009)the steps that are under this technique are coagulation, flocculation, sedimentation, filtration, disinfection and arsenic removal from drinking water. The coagula tion process that occurs in this drinking water treatment technique will be discussed in details in this assignment.The definition of coagulation is the destabilization of colloidal particles.(L.Droste, 1997)The particles are coated with a chemically abidey layer that enables them to stick with each other, forming a large molecule and mollify in a improvident period of cadence. The ability of an agent to agglomerate the tiny particles found in water is directly related to its charge. The other factor that will prompt the ability is the size of synthetic polymers.The most leafy vegetable materials that are used to coagulate the water are alum (aluminum sulfate) and iron salts. (L.Droste, 1997) stated that the polyvalent characteristic of these coagulants effectively attracts them to supercharged colloidal particles and their high insolubility helps to ensure their removal from the water to a high degree.When coagulant such as alum is being added into the water, a chemical reac tion that produces positively charged will occur. This reaction will indirectly reduce the electrical charges of the particles and therefore form a sticky substance which also known as floc. In this reaction, turbidity, color and microorganisms can be removed(p) easily. The formation of floc is the primary step of coagulation process. For perfect efficiency, intimate, rapid mixing of the water must be done and coagulant must be present. after(prenominal) mixing, the water should be stirred slowly so that the particles can stick to each other forming a large molecule.According to (Spellman, 2009) , the factors that will bear on the coagulation process are pH, turbidity, temperature, alkalinity and he use of polymers. The degree to which these factors impact coagulation process relies on the type of coagulant use. The condition of tippy water, optimum pH to coagulate the water and other factors must be taken into account forward making decision on which chemical to be used.Acc ording to(E.Manathan, 2009), the main advantage of using this technique is dismantle cost compared to biological treatment. It requires less worker force and able to settle the issues regarding toxic materials effectively. On the other hand, it has its disadvantage too, which is require careful hustler control and use up huge amount of vitality.3c.Advanced Oxidation work out (AOPs)Advanced oxidation process (AOP) is an oxidation process which affects water treatment by generating a sufficient quantity of hydroxyl radicals.(Goi, 2005) Hydroxyl radicals ( OH), are non-selective reactive species, helps to oxidize pollutants into mineral end-products, yielding CO2 and inorganic ions.This process can treat those organic pollutants with high chemical stability and low biodegradability which cannot be treated by conventional techniques. Basically, refractory compounds cannot be removed businesslikely by conventional biological processes, but AOPs will do and help to improve the overal l compound removal efficiency in water treatment.Refers to Figure3.1 in appendix 2, in biological systems, AOPs are used as pre- and post-treatment. The pre-treatment improve wastewater biological treatability by common microorganism whereas post-treatment is targeted on the contaminants removal which not completely done during the biological treatment. (Cesaro, et al., 2013) ingrained contaminants such as halogenated hydrocarbons (trichloroethane, trichloroethylene), pentachlorophenol (PCP), detergents, pesticides, etc can be destroying by this process easily. Besides, the inorganic contaminants (cyanide, nitrite, and sulfide) can be oxidized by this process.Non-photochemical and photochemical methods are used to generating the OH radicals. These two methods are as shown as table belowFenton systemIn Fenton system, hydrogen bleach (H2O2) acts as an oxidation agent. When hydrogen peroxide presents in excess, Fe (II) oxidizes to Fe (III) within few seconds or proceedings and hydr oxyl radicals will be generated. The reactions are as shown as belowFe2+ + H2O2 Fe3+ + OH +.OHThe catalyst used in this process is iron salts which generate ferric ion, Fe2+as the Fentons reagent. Besides, ozone (UV- swinging) and transition metal salts are used.Mostly, ironsalts are used as transition metal salts. (Munter, 2001)Under the UV-radiation, the feltons reagent undergoes oxidation processes that utilize energizing of H2O2, has high efficiency to treat the hazardous organic pollutants that present in water. (Albert, 2010)Fenton reagent uses in wastewater treatment to convert the contaminants to harmless compound such as carbon dioxide and inorganic salts. This Fentons oxidation is the most efficient method in removing effluent toxidity and color compare to coagulation-flocculation process. It helps to decrease the rate of chemical oxygen demand (COD), aromatic compounds, and total polyphenols in the wastewater. However, Fenton process also can be combined with coagulatio n to reduce flocs remission time, amount of COD, and enhanced color removal.Photo-Fenton-type oxidation is a process when Fe3+ ions added to H2O2/UV process, resulted Fe (OH)2+ complex in pH3 condition.Fe3+ + H2O Fe (OH)2+ + H+Fe (OH)2+ Fe3+ + OHWhen Fe (OH)2+ will further decompose into .OH and Fe2+ ions with the presence of UV light.Fe(OH)2+hv Fe2+ + .OHThis type of reaction very relies on UV barb to start up the .OH generation. Besides, this UV irradiation can mineralize organic pollutants completely. Efficiency of Fenton/Fenton-like reagents with UV irradiation can be increased by efficient use of light quanta and photo-reduction of ferric ion.(Munter, 2001)Photocatalytic oxidationPhotocatalytic oxidation is an alternative AOP method which introduced high muscularity (photons of ultraviolet light,UV) into the treatment system. Besides that, it is a potentially green chemistry drinking water treatment process. Throughout the whole process, no reagents are added and only rela tively harmless catalyst TiO2 and sunlight (source of UV) is needed. Solid te dioxide, TiO2 is used as the photocatalyst leading to chain reaction for the production of HO. free radicals. (E.Manathan, 2009)When the issue of TiO2 is irradiated with ultraviolet radiation, holes (h) are generated at sites where excited electrons (e) are producedTiO2 +hv TiO2 (h + e)The surface holes may take electrons from dissolved hydroxyl ion to produce reactive hydroxyl radicals on the TiO2 surfaceTiO2 (h) + OH OH.Refers to theFigure 3.2 in appendix 2, solar disinfection (SODIS) and solar photocatalytic disinfection (SPCDIS) are appropriate technologies for water disinfection of Cryptosporidium oocysts at household level. Cryptosporidium species are protozoan parasites that infect humans and causes diarrheal disease by the food-borne or waterborne routes. Cryptosporidium is assailable to survive in the environment for long periods and even treated water is not guarantee to be safe from these i nfective parasites. and so, SODIS and SPCDIS are introduced to muster out these microorganisms to reduce the risk of infection.SODIS and SPCDIS are both using the same method to reduce the oocyst viability. Both of them involve storing contaminated drinking water in transparent containers that are placed in direct sunlight before purpose.The disinfection effect of sunlight only occurs at temperatures exceeding 45 . Therefore during cloudy conditions, this process may take a longer time to ensure the safety of the drinking water.Photocatalytic disinfection, SPCDIS uses the non-toxic photocatalyst, TiO2 to enhance and accelerate the inactivation rate of the parasites. For SPCDIS, the photocatalyst particles would have to be removed after solar exposure and before consumption. ascribable to this additional step, the probability of compliance within communities in developing countries is low and lead to the inefficiency of the treatment.In order to overcome this problem, this photo catalyst,TiO2 has been isolated onto some form of coated flexible insert, which would reside permanently within the SODIS reactor. Due to the effectiveness of the cheap, flexible insert coated with the non-toxic photocatalyst TiO2, the photocatalytic oxidation is recommended since it enhances the diminution of the oocyst viability by as much as 50%.4.ConclusionsThe three technologies in treating contaminated drinking water used different methods to purify water. Each of them has advantages and disadvantages. They have faced respective challenges in cost of added research and development. Some of the common challenges are techniques for effective removal of emerging contaminants, synthetic chemicals and pesticides, as well as problems in dealing with spills of chemicals in navigable rivers and lastly the development of sustainable treatment. The challenge involving technological development is the needs of economic, appropriate, relevant and sustainable developing technology. (Ray Jain, 2011) In fact, three of the technologies can be combined to strike the greatest efficiency in water treatment process. For biological technology, the slow sand filtrationand perchlorate processes are discussed. The biological treatment is environmental friendly but the limitation of the processes are low effectiveness when the turbidity of water source is high. For physicochemical technique, the method discussed is coagulation, one of the challenges it meets is large amount of energy consumption whereas its future prospect could be get use of solar energy which is environment friendly. For AOPs, fentonand photocatalytic process are discussed. Both of the processes still need a further research about the fundamental concepts and reaction mechanism. It is because there are still much remain to be done in terms of maximizing its efficiency, by enhancing the performance-related properties of oxide materials.5.References/abstract 1 /intro 2,3 *4+WHO *5+natural regulations *biologi cal /physico 6,7,8 carson /aops9,10,11,12 /13,14,15,16,17,18 (6) /conclu191