Water Chemistry lies upon various minerals, halogens (in

Water Chemistry lies upon various minerals, halogens (in form of compounds) and organic species that are present in water. The minerals in water include a lengthy list of heavy metals such as Mercury, Copper, Arsenic etc. The halogens in water includes another list of nitrogen compounds and oxygen concentrations. Last but not the least the organic chemistry involved in water includes any bacteria or infection such as E Coli, fecal etc. The study of each is required to ensure the standard of water.The minerals included some of the very dangerous heavy metals (like Arsenic, Chromium and Mercury etc..), their little quantity can be fatal for humans and other living organisms. And even if the little quantities of metals are not directly fatal they cause DNA mutation and bioaccumulations in the food chain. The DNA mutation causes lethal diseases such as Cancer. Certain ions in the bloodstream can lead to neurological disorders in humans. The polluted water when reaches to the green producers of ecological food chains damages them and their consumers. They may be found in trace amounts but can lead to bioaccumulation and biomagnification in the ecological food chain.Arsenic, mercury, lead, chromium and cadmium etc. are harmful for health. Among these, arsenic and lead have been prominently visible in groundwater in Pakistan. WHO has recently in its report has stated Pakistan as in Arsenic Threat levels.WWF (World Wild Federation) and EPA (Environmental Protection Agency) have worked out the Maximum allowable ranges of many minerals and contaminants in an irrigation water. The analysis of the water parameters and then designing of an appropriate system required wide study of various research papers and books. However, the study has concluded that a few variables cannot be solved without experiments. The water science still needs a lot of efforts of researchers to contribute in many calculations and relations of various components.Water is divided into various categories based on their needs and thus purification. International Water Association such as EPA, FAO have agreed in dividing water into the following categories: Class AA: Public Water Supply Class I, Class A: Public Water Supply Class II, Class B: Recreational Waters, Class C: Waters for aquatic Life and Class D: Irrigation WaterClass AA is defined as water for drinking that does not require any treatment since it was not in contact with any contaminant ever. Class A is defined as water for drinking only after it has gone through some treatment. Class B is defined as water for external use such as swimming. Class C is defined as water for fish and aquatic lives, this can also be used as industrial process water. Class D is defined as water for irrigation and cooling purpose. The primary focus of this project is on Class D water however through additional measures the water will be brought to Class A.These water classes have different allowed values for RSC, SAR, pH, DO etc. In fact, these chemical properties divided the water into distinctive characteristics.ObjectiveThe objective of the proposed water treatment plant is to bring down the levels of harmful component so that groundwater can act as Class D water. The design and manufacturing of a water treatment plant has been scaled down to its table-top sized prototype that is user friendly. The laboratory assessment of the feed water is present in Table 3 (see Appendix). There are a few secondary aims attached with the project such as feasibility of proposed system in large scale plants and low operating costs.ScopeThe project has wide applications in agriculture, horticulture and cooling of machineries since water is the basic need!Chapter 2: Literature ReviewIn a report of 2007 by WWF (World Wild Funds), we found that the groundwater is polluted by the seepage of drain water into the ground causing unusual diseases. The team of WWF studied this in detail during their project ‘Hudiara Drain’ in their ‘Fresh Water and Toxics Programme’. The team proposed water quality standard chart and presented WHO/EPA standard chart in their report. The report explains a total of 29 basic parameters’ limit which includes minerals and a few water chemical properties such as pH. Fortunately, Pakistan have been among countries which have showed their concern regarding the issue. There are three major components that have been mentioned by the WWF in their report as the genuine those are Total Dissolved Solids (TDS), Sodium Absorption Rate (SAR) Residual Sodium Carbonate (RSC) and Boron.Although the WWF report was helpful enough to give an initial boost and an idea to how to continue with the project. The articles and reports by EPA and WHO were also studied to verify the parameter ranges. The reports state the maximum allowable range, in irrigation water, as stated in the Table 1 of Appendix.Different water sources have different contaminants with different quantities. Any water that must be treated first needs its contaminant identification, then its quantification, since allowable traces/quantities can be allowed and do not need treatment whereas large quantities need treatment. A few contaminants can be grouped as they can be treated via a single treatment technique. Even though there has been little participation of researchers, the practices from the past have been recognized as golden practices. The book, by Keraita et. al 1, named ‘On-farm treatment options for wastewater, greywater and fecal sludge with Special Reference to African’, published in 2011, works over the already existing ideas of field water treatment in subcontinent and African states. It talked about filtration, sedimentation, flocculation and aeration as the main ideas for water treatment. It also introduces readers to on-farm practices such as sedimentation followed by ultra violet treatment, weir filtration and pathogen removal through adsorption.The work of Keraita et. al 1 (i.e. compilation existing practices) and the work of Mark et.al 2 (i.e. detailed processes with numerical assessments) lead us to build an idea of our processes in cascade. It was evident that aeration and filtration were important for any treatment plant.Filtration is considered as primary treatment of water. In filtration one must simply stop the solid particles from flowing with the water. The problem that arises during filtration is ‘Cogging’. In cogging larger solid particle block the small openings of the filter causing block of fluid flow. To counter this a sieve or a filter of a rough mesh is placed first, to stop larger solid particles followed with a better mesh to stop small particle followed by a fine mesh to stop very small solid particles. These solid particles are stop for these reasons: they can disturb the flow, damage the structure of the treatment plant (such as accumulating in pipes), damage the pumps, they are unwanted by the consumer of the plant. Several innovations have been brought to reduce the cogging and increase the lifetime of a filter such as excavating the filtered particles and dropping them into another tank so there is less chance of cogging. The water from filters goes into another treatment phase.Many practices of filtration have been adopted in the history. The conventional methodologies are far better since they not only provide solid particle filtration but also provides removal of microbes. See Table 2 from Keraita et al 1 , it summarises all conventional ways of filtration.Aeration is said to be the secondary treatment of water, unlike filtration it is a chemical/biological treatment. The term aeration refers to the introduction of air into the water. The aeration is required to fill the deficiency of oxygen in water due to consumption of many Biological and colonial elements. There are many ways, such as Air Stripping, in which efficiency of aeration is increased as Jame et. al 3says in his work, the ‘Aeration: Principles and Practices, “Typically, these are used to improve dissolved oxygen concentrations to desired levels in natural water where the demand of oxygen is greater than can be supplied by natural reaeration.”Aeration depends upon the oxygen transfer rate. Although aeration is an uncomplicated process but to achieve optimum efficiency of the system one needs to study the concept and design calculations. ‘Aeration: Principles and Practice, Volume 11’ by James et. al 3 states that aeration depends upon interfacial area of air to water, oxygen transfer rate. The book has a comprehensive calculations and graph representing various relations such as relation of air diffuser to oxygen transfer efficiency. The calculations require the knowledge of the term Volumetric-mass transfer coefficient (Kla).The Volumetric-mass transfer coefficient refers to mass transfer that takes place at the free surface exposed to atmospheric pressure and oxygen content. This is an important parameter such that Pisut et. al 4 in his papers writes, ‘A better forecast of the kLa value would help the optimization of the installations in term of both cost and effectiveness’. The coefficient is related to chemical diffusing property and the interfacial area which can be improved via mechanical ways such as turbines and rotors etc. The coefficient cannot have derived via simple diffusion theory and needs relevant experiment to deduce the relation and value.The search of right way to determine kLa took a bit long since behavior of kLa changes with respect to different setups of aeration. For example, aeration with spinning water tanks has a different kLa relation to its parameters whereas aeration with rotating turbine has a different kLa behavior. A research paper, by Wolf et. al 5, ‘Correlation between mass transfer coefficient kLa and relevant operating parameters in cylindrical disposable shaken bioreactors on a bench-to-pilot scale’ was a helpful in building of concept. The research paper can be a reliable source to provide the values of kLa however the research paper was restricted for shaken bioreactors and not any other form.The kLa values used in this project have originated from the research paper by Pisut et. al 4, ‘Theoretical prediction of volumetric mass transfer coefficient (kLa) for Designing an Aeration Tank’. Since this article was based on as simple aerator as used in this project, the determination of KLa from designed variables of aeration became easy. The article by Pisut, gave us the concept that how is kLa dependent upon interfacial area, bubble rising velocity, bubble diameter and its frequency. The article purely provides the experimental data and the resultant equations to conclude a theoretical figure of kLa.KLa was not the only missing value there were two more things that affects the aeration, that is how much suspended particles are present in the water and how much clean is water in terms of biological species in water. The two factors are numerical assessed using alpha and beta with beta having the value 0.95, this is provided in the lectures of Assist. Prof. Bilge Alpaslan Kocamemi from Marmara University of Istanbul. The value of alpha is dependent upon the MLSS (Mixed Liquor Suspended Solids). MLSS is determined through laboratory tests.According to Aeration: Principles and Practices by James Mueller et.al 3 aeration is followed by Sludge settling tank. Sludge Settling Tank has another story. Mechanically it does not require much definition though the time the water needs to stay in this tank is the actual riddle. To solve this riddle, one must possess the knowledge of Sludge settling tanks. The thesis by LI et. al 6 ‘Modelling and optimizing aeration system of activated sludge process to reduce energy consumption’, guides the estimated hydraulic retention time with respect to Standard Oxygen Transfer. A proper study of elements in sludge processing makes it understandable that the process requires hardware i.e. the sludge tank after treatment of aeration. Since we need to know the settling time of the water, that has no direct prediction method, we need to test our system.7Coagulation is a most imperative physiochemical operation utilized as a part of water treatment. This is a procedure used to cause the destabilization, little particle into bigger. Water contaminants, for example, particles (overwhelming metals) and colloids (organics and inorganics) are essentially held in arrangement by electrical charges.The Electrocoagulation procedure depends on substantial logical standards including reactions of water contaminants to solid electric fields and electrically actuated oxidation and decrease responses. This procedure can take out more than 99 % of some substantial metal cations in the water. It is additionally ready to encourage charged colloids and evacuate significant measures of different particles, colloids, and emulsions.Compound coagulation has been utilized for a considerable length of time to disrupt suspensions and to impact precipitation of dissolvable metals, and in addition otherinorganic species from fluid streams, consequently letting their evacuation through sedimentation or filtration. Benefield et. al 7The report by MRWA shows 8 that a slight mixing, flocculation after coagulation, expands the molecule estimate from microscopic microflow to noticeable deferred particles.Through slow mixing the crashes of micro flocs particles contact with each other and form larger flocs. The floc measure keeps on working through extra impacts and communication with inorganic polymers framed by the coagulant or with natural polymers included. High sub-atomic weight polymers, called coagulant helps, might be added among this progression to enable scaffold, to tie, and fortify the floc, include weight, and increment settling rate. After, the floc formation the water is then ready for further procedure. Through slow mixing the micro flocs particles contact with each other and form bigger flocs. 8 (from report by MRWA)Sedimentation is an uncomplicated process used to reduce settable solid under the effect of gravitational attraction. The more settling time in a higher suspension of solids and pathogens result. It is also cost effective. Referenced from Gregory et. al 9pH is the last thing that needs to be corrected. A very low pH can make water acidic and therefore harmful for the plants. The more the pH is nearer the neutral value, the better it is. During almost all the processes in a water treatment plant, either pH has gone down or has increased. In aeration the pH has lowered down since oxidation of water has made it more acidic. A pH settler is always present in a plant. The pH can be controlled using CO2 and oxygen. These two regents, unlike other reagents, do not give new element contamination to water.


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