SEJ446- Engineering Project BFinal Report

Project Title: Modelling the performance of a sand filter that is used to treat a polluted pond

Submitted in fulfilment of the requirements for SEJ446 Engineering Project B,School of Engineering and Technology, Deakin University

Student Name: Busiku SilengaStudent ID: 210037589

Supervisor Name: Associate Professor Jega JegatheesanPlagiarism Declaration

This thesis is an account of research and experimentation work undertaken between March 2014 and October 2014 at the School of Engineering and Technology, Deakin University, Australia. I hereby certify that the attached work submitted for assessment is entirely my own except for where material is quoted or paraphrased in the text; the owner of the material is then acknowledged. I also certify that the material presented in this thesis is, to the best of my knowledge, original and has not been submitted in whole or in part in any other unit or for a degree in any other university.

Abstract

Sand filters have proven effective in achieving high removal efficiencies for sediments, biochemical oxygen demand and fecal coliform bacteria; however their total metal removal is moderate and nutrient removal is often low. Very few studies have prospectively examined how the performance of a sand filter can be modelled, in order for it to be used to clean a polluted pond. The objective of this thesis is to outline, firstly a literature review of current methods of modelling and enhancing the performance of a sand filter, followed by an outline of the methodologies and experimental processes that were used in our project to model the performance of a sand filter, which is to be used to clean a polluted pond. The primary outcome of the project is the design of an optimum model process that is to be used to treat a polluted pond, based on the initial parameters (conductivity, pH, temperature and turbidity) of the polluted pond water samples collected around the Deakin University Waurn Ponds campus. The thesis includes an evaluation of different coagulants (Ferric chloride, poly aluminium chloride, alum) and different coagulant doses using jar test experiments, and also includes a selection of the best coagulant and its optimum dose. The performance of two sand filters with different filter media configuration/sizes (River sand, sizes 6 and 6.5) is compared, and comparisons between conventional and direct filtration are made in order to determine which process is the most effective. The design of a backwash system and the point at which it is necessary is also addressed. As an alternative, a 0.2 micron ceramic membrane is used to process the filter permeate in order to evaluate how much the water quality can be improved. Evaluation of the water quality before and after treatment using chlorine decay studies is performed and modelled using AQUASIM software. In summary a recommendation of the most effective process, which includes the best coagulant and selection of its optimum dose, the best filter size and its most effective process (Direct or indirect filtration) and a suitable backwash volume, is made. Started in March the project is expected to be completed in October.

Acknowledgement

My sincere gratitude goes to my supervisor; Associate Professor Jega Jegatheesan for offering me the opportunity to undertake this project. I am grateful for his continued guidance, encouragement and professional assistance throughout the duration of my project. His input has added immeasurable value to the completion of my project. I would also like to express my utmost gratitude for the technical assistance of staff in the Civil Engineering laboratory, especially Mrs. Leanne Farago, who all contributed immensely to my experimental work in their various capacities. I would also like to thank all the staff of the Civil Engineering department whose input has made this project a success. Also, I owe so much to my family, whose financial support, moral support, encouragement and belief in me, has helped see me this project through to completion. Last but not least I would like to thank all my friends who have all, in some shape or form contributed to the success of this project.

ContentsPlagiarism DeclarationIIAbstractIIIAcknowledgementIVI-NomenclatureVIIII-List of FiguresVIIIIII-List of TablesIXIV-Project InformationXIV.I-Key ObjectivesXIV.II-Project BenefitsXIIV.II.I-Economic benefitsXIIV.II.II-Environmental benefitsXIIIV.II.III-Health benefitsXIIIV.II.IV-Technological benefitsXIIIIV.III-Project DeliverableXIIIChapter 1.Introduction11.1Introduction1Chapter 2.Literature Review32.1 Introduction32.2 Water Quality32.3 Sand Filtration Technology42.3.1 Inflow regulation:52.3.2 Pretreatment:52.3.3 Filter bed and filter media:52.3.4 Mechanism of filtration:52.3.4 Filter hydraulics:62.3.5 Backwashing:82.4 Sand Filtration Processes92.4.1 Direct Filtration92.4.1 Conventional Filtration92.5 Limitations of Sand Filtration Technology102.5.1 Limitations102.5.2 Maintenance102.6 Enhancement of Sand Filtration Technology102.6.1 Pretreatment102.6.2 Additional methods of enhancing sand filter performance122.7 Chlorine Decay and AQUASIM Software13Chapter 3.Methodology163.1Methodology173.2 Raw Water173.3 Coagulation Tests (Refer to section 2.6.1- Pretreatment; for technical aspect of Jar testing)183.3.1 Apparatus183.3.2 Method183.4 Sand filter (Refer to section 2.3- Enhancement of sand filter for more technical aspect)193.4.1 Apparatus193.4.2 Before use:193.4.3 Operation:193.4.3 Backwashing:203.5 Chlorine decay experiments - (Refer to section 2.7- for more technical aspect of chlorine decay)203.5.1 Chlorine demand studies:203.5.2 Chlorine decay studies:213.7 AQUASIM Software (Refer to section 2.6- for more technical aspect of chlorine decay and AQUASIM software)22Chapter 4.Results and Discussion23Chapter 5.Recommendations24Chapter 6.Conclusions25Rfrencs26

I-Nomenclature

NOM..Natural Organic matterBOD ....Biochemical Oxygen Demand TN.Total NitrogenTSS. Total Suspended SolidsTOC....Total Organic CarbonTP...Total PhosphorusNTU...Nephelometric Turbidity UnitTCU.True Color UnitWQ.Water QualityCl2............................................................................................................Free chlorineFRA... Fast reducing agentsFRNFast reducing Nitrogenous CompoundsSRA... Slow reducing agentsSRNSlow reducing Nitrogenous CompoundsCCCombined chlorine

II-List of Figures

III-List of Tables

IV-Project InformationThe primary outcome of the project is the design of an optimum model process that will enhance the performance of a sand filter that is to be used to treat a polluted pond, based on the initial parameters (conductivity, pH, temperature and turbidity) of the polluted pond water samples collected around the Deakin University Waurn Ponds campus.IV.I-Key Objectives The overall aim of this project is to model the performance of a sand filter that is to be used to clean a polluted pond, using research and experimental techniques. AQUASIM software will be used to evaluate the water quality before and after treatment using chlorine decay studies. The project will include the following; Evaluation of different coagulants Determination of required water treatment process based on the initial parameters of the polluted water samples Comparison of different filter media sizes and selection of the most effective Design of a backwash system Comparison of different treatment processes (pretreatment, direct and indirect filtration) in order to evaluate which is the most effective and establish a relationship between experimental and predicted data. Use AQUASIM software to evaluate the water quality before and after treatment using chlorine decay studies. Reduction in chlorine demand will help to evaluate the performance of treatment in removing organic compounds and others that consume chlorine. Chlorine decay results to be modelled using AQUASIM software.IV.II-Project BenefitsThe use of any resource usually generates a waste. The immense impact of water pollution on peoples daily life has increased the importance of conducting research that will enable assessment of environmental damage in economic terms. Water (Pond) pollution control and treatment is an important topic in Environmental Engineering. Gaining an understanding of water (pond) pollution control and how the performance of a sand filter can be modeled in order to clean polluted ponds would have huge financial, environmental and health benefits. Principles addressed in this project, although done on a relatively small scale can be applied to pollution control/treatment in larger water bodies.IV.II.I-Economic benefits Water pollution relates to industrialization, civilization and living standards which are all directly related to the economic level of people. Water pollution usually causes loss in society, economy, natural environment and many other areas. The more serious the harm by polluted water is, the more the economic loss is. For example in Florida, $10.5 billion is spent annually on water pollution control and treatment, however clean freshwater and marine ecosystems attract $67 billion in tourism and recreational spending [USEPA, 2002]. Many industries require the use of fresh water, some are entirely based on it and as more water becomes polluted the price of purify this water begins to grow as do the costs involved in those industries. Treatment methods such as sand filters and chemical additives help to prevent pollution of nearby water bodies. These are very simple techniques that are easy to implement, although they cost money to maintain, it is much cheaper preventing pollution than cleaning up water that has already significantly occurred. This project will help us explore ways in which we can make treatment methods like sand filters more cost performance and environmentally effective.Table .1 shows how sites with higher water quality are more economically viable. Table 1: Mean per trip benefits per person IV.II.II-Environmental benefits The effects of water pollution on the environment are far reaching. Water pollution has been extensively documented as a contributor to health problems in marine ecosystems, wildlife health and well-being. For example it is possible for the pollutants to raise the temperature of the water enough to force fish out in search of cooler water, this in itself can create an ecological dead zone. Pollutants can also significantly increase the rate of algal blooms. These blooms create massive fish dye-offs as the oxygen levels in the water gets depleted [Jared Skye, 2014]. If the right treatment methods are implemented such cases can be avoided, this project will help explore more environmental, performance and cost effective ways of doing that by modelling the performance of sand filter.

The following formula and figure demonstrate how pollution affects aquatic ecosystems. Increase in pollutants => Increase in temperature (68-89oF) => Increase in algae blooms = Decrease in oxygen levels (>5mg/L, aquatic life under stress) => Death of marine life.

Figure 1: Contrast between polluted and healthy aquatic ecosystems.IV.II.III-Health benefits One of the greatest dangers to human health is water pollution. Water pollution can pose health dangers to humans who come into contact with it, either directly or indirectly. Risks include contaminated drinking water, high mercury level risks and other health effects of toxic runoff. Developing cost effective ways to treat water would result in huge health benefits especially in developing countries, where people spend more money on treatment of sicknesses resulting from polluted waters instead of treating the polluted water which would result in solid financial and health benefits. This project will help us gain an elementary theoretical and practical understanding of how water treatment methods, specifically sand filters can be designed and enhanced in order to achieve high water quality in areas affected by pollution.The table below shows some diseases that are directly related to water pollution;

Table 2: Common diseases transmitted through drinking contaminated drinking water.IV.II.IV-Technological benefits This project will help us to expand and improve on the already existing water treatment methods specifically, sand filter technology. Our design will explore ways in which to make treatment of polluted water using sand filters more effective, in terms of maintenance cost, purchase cost, accessibility, ease of use and performance.IV.III-Project DeliverableThe findings of this project will be presented in a formal verbal presentation and a formal written report. It is expected that the project will provide valuable information and a clear understanding of pollution in ponds (types of pollutants and their effects and how they behave in water bodies) and how sand filters can be enhanced in order to make the treatment more effective. It is also expected that a clearer understanding on backwash systems and how they can be designed will be gained. Also the project will provide an understanding of different coagulants and their effectiveness in treating polluted water. Overall the project will produce the optimum polluted pond treatment process design that will be used to treat the provided, polluted water samples and is both cost and environmentally effective. This design will then be evaluated by AQUASIM software in order to observe the water quality before and after treatment using chlorine decay studies.

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Chapter 1.Introduction

1.1 IntroductionSlow sand filtration is the earliest technology to water treatment. It was initially developed by John Gibb in Scotland in 1804 to obtain pure water. After linking outbreak of diseases such as cholera and typhoid to waterborne contamination, slow sand filters became a legal requirement for all potable water extracted from the River Thames in 1852 [Huisman and Wood, 1974]. The introduction of chlorination and chemical coagulation techniques in water treatment followed by the development of rapid sand filters led to a decline in the use of slow sand filters [Bowles et al., 1983]. The city of Austin, Texas first pioneered the use of sand filters in the early 1980s [Richard A Claytor, 1996] Filtration has since become one of the most important elements in traditional water treatment systems. A large number of ponds are unfenced and multipurpose; consequently making most pond water moderately or seriously polluted and thus cannot be considered for use without treatment. Ponds are preferred because of their proximity to the point of use, lower turbidity and reliability. These sources may be developed using a sand filter. Sand filters because of their simplicity, efficiency and economy are appropriate means of water treatment [Nigel Graham and Robin Collins, 1996]. The sand filter technology relies on a straining, settling and adsorption to purify water [Huisman and Wood, 1974].Since filters are not generally designed to remove dissolved compounds, which can constitute roughly half of certain pollutants, and enhancement of the sand filter can greatly enhance the removal of these compounds. When source water quality is beyond the range recommended for Sand filters used alone, pretreatment can extend the capability of this process. Higher turbidity, color, natural organic matter (NOM) and synthetic organic chemicals can be removed when pretreatment or post treatment processes are added [Gary S Logsdon, 2008]. Water is the most essential material for human survival, after air [Ahuja, 1986]. The uses we make of water in lakes, rivers, ponds and streams is greatly influenced by the water quality found in them. Water quality is the summation of all physical, chemical, biological and aesthetic characteristics of water that influence its beneficial use [Claude E. Boyd, 1998].The introduction of pollutants from human activities, is the primary cause of water pollution. Water pollutants are categorized as, point source and nonpoint sources. Point sources discharge pollutants at single specific locations through pipelines or sewers into the surface water (factories, sewage treatment plants). Nonpoint sources are sources that cannot be traced to a single site of discharge (agricultural runoff), [Shubinski and Tierney, 1973]. The total waste load in a water body is represented by the sum of all point and nonpoint sources. The large number of water pollutants is broadly classified under the categories of: Organic pollutants, Inorganic pollutants, sediments, radioactive materials and thermal pollutants [Ruth F Weiner, 2003].Water pollution is any chemical, physical or biological change in the dynamic equilibrium in an aquatic ecosystem that disturbs the normal functioning and properties of pure water. Water pollution is caused by domestic sewage (84%) and industrial sewage (16%), though the latter has less load on water bodies, it contains matter which is more hazardous [Anil K., 2009]. The symptoms of water pollution of any water body include bad taste of drinking water, offensive smells from water bodies, unchecked growth of aquatic weeds (Eutrophication). Water pollution has been extensively documented as a contributor to health problems in marine ecosystems, as well as human health and well-being.

Chapter 2.Literature Review

2.1 Introduction Pond treatment technology is used in tens of thousands of applications serving many millions of people across the globe because it is efficient and effective. While pond treatment technology offers relative simplicity in its application, it incorporates a host of complex and diverse mechanisms that work to treat and cleanse polluted waters before their return to our environment .While performance and cost are obviously key bottom line requirements, the importance of selecting a technology that is appropriate to the needs and constraints of the local situation where it is installed is essential to achieving long term reliability and success [Andy Shilton, 2005]. The following literature review will take a look at how the performance of a sand filter can be modeled in order for it to be used to clean a polluted pond. Part one of the literature review will give an overview of water quality. The second section will give an overview of sand filters. The section that follows will look at the limitations of sand filters. The fourth section will look at different ways in which the performance of a sand filter can be enhanced using different methods including pre and post treatment techniques. Chlorine decay and how it relates to water quality and the AQUASIM software will be addressed in the fifth section. The final section will conclude the literature review.2.2 Water Quality Water quality refers to the chemical, physical and biological characteristics of water [Diersing Nancy, 2009].It is a measure of the condition of water relative to the requirements of one or more biotic species and/or to any human need or purpose [A.E. Winter-Nelson, 1997].The common standards (guidelines) used to assess water quality relate to health of ecosystems, safety of human contact and drinking water. A water quality guideline is a numerical concentration limit or narrative statements recommended to support and maintain a designated water use [Australian and New Zealand Guidelines for Fresh and Marine Water Quality, 2000].Water quality parameters can be divided into those that have direct toxic effects on organisms and animals (insecticides, herbicides, heavy metals ad temperature) and those that indirectly affect ecosystems causing a problem for a specified environmental value( nutrients, turbidity and enrichment with organic matter).Appendix A shows water quality guidelines for different water uses. Table 3 below, shows considerations concerning risk levels in surface water sources;

Table 3: Considerations concerning the risk levels in surface water sources (Joseph Cotruvo, 1998) 2.3 Sand Filtration Technology Filtration is one of the most important elements in traditional water treatment systems. Sand filters are intended primarily for water quality enhancement. The effectiveness of filtration systems is determined by their ability to remove microorganisms, turbidity and color (Color is imparted to water supplies by organic material and can be removed by coagulation) [US EPA, 1999]. Sand filters have proven effective in removing several common pollutants from polluted water. Sand filters generally control storm water quality (storm water runoff is a major contributor of pollutants in water bodies), providing very limited flow rate control. Sand filters take up very little space and can be used on highly developed sites and sites with steep slopes. Sand filters are able to achieve high removal efficiencies for sediment, biochemical oxygen demand, and fecal coliform bacteria. Total metal removal however, is moderate and nutrient removal is often low [EPA, 1999]. The separation of solids from a suspension in a liquid of a porous medium or which retains the solids and allows the liquid to pass through is termed filtration. Sand filters operate in a similar manner to bioretention systems, with the exception that water passes through a filter media (typically sand) that has no vegetation growing on the surface. Sand filters do not incorporate vegetation because the filter media does not retain sufficient moisture to support plant growth [WSUD, 2003].Prior to entering a sand filter, flows must be subjected to pre-treatment to remove litter, debris and coarse sediments. Following pre-treatment flows are spread over the sand filtration media and water percolates downwards and is intercepted by perforated pipe located at the base of the sand media. A sand filter system typically consists of three chambers: and inlet chamber that allows sedimentation and removal of gross pollutants, a sand filter chamber and a high flow bypass chamber. The shape of a sand filter can be varied to suit constraints and maintenance access, provided each of the chambers is adequately sized [Richard A Claytor, 1996].In all filters the primary design/operating parameters are quality and head loss through the filter and appurtenances [EPA, 1999].2.3.1 Inflow regulation:The inflow regulator is used to divert runoff from a pipe, open channels or impervious surface into the filtering system. The inflow regulator is designed to divert the desired water quality volume into the filter. [Richard A Claytor, 1996]2.3.2 Pretreatment:The second key component of any filtration system is pretreatment. It is needed in every design to trap coarse sediments before they reach the filter bed. Without pretreatment, the filter will quickly clog, and lose its pollutant removal capability. Sediments deposited in the pretreatment chamber must be periodically removed to maintain the system. [Richard A Claytor, 1996]2.3.3 Filter bed and filter media:Each filtering system utilizes some kind of media such as sand, gravel, peat, grass, soil or compost to filter out pollutants entrained in water. The selection of the right media is important, as each has different hydraulic, pollutant removal and clogging characteristics. The filter medium should be mechanically strong, resistant to the corrosive action of the fluid and offer as little resistance as possible. The filter media is incorporated into the filter bed. The three key properties of the bed are its surface area, depth and profile. The required surface area for a filter is usually based as a percentage of impervious area treated and the media itself. The depth of most filtering systems ranges from 18 inches to four feet. [Richard A Claytor, 1996]

- darcys equation

Where;Q; Flow through pipe; k=permeability rate of filter media; i= hydraulic gradient; A=Area of flow; V=face velocity2.3.4 Mechanism of filtration: Filtration systems are affected by physical characteristics such as size of the filter medium, filtration rate, fluid temperature, size and density of suspended solids. As the particles reach the surface of the filter media, an attachment mechanism is required to retain it. This occurs due to electrostatic interactions and chemical bridging or adsorption. Four processes have been found to be part of the filtration process- straining, adsorption, biological action and absorption.2.3.4 Filter hydraulics:Headloss is usually what determines time to backwashing. As filtration proceeds, an increasing amount of pressure, called head loss across the filter, is required to force the water through the filter. The loss of pressure (head loss) through a clean stratified-sand filter with uniform porosity and laminar flow is given by;

Table 4: typical pollutant removal efficiency [Galli 1990] Figure 3: Sand filtration system

Table 5: Estimated pollutant removal capability of different filtration systems.2.3.5 Backwashing: Backwashing is used to remove solids that accumulate in the filter media and is generally performed by backwashing clean water in the opposite direction of flow. Proper backwashing is a very important step in the operation of a filter. If the filter is not backwashed completely, it will eventually develop operational problems. If the filter is to operate efficiently, it must be cleaned before the next filter run. The filter should be backwashed when the following conditions have been met: The head loss is so high that the filter no longer produces water at the desired rate Floc starts to break through the filter and the turbidity in the filter effluent increases.Backwashing of filters is the single most important operation in the maintenance of the sand filter. If the filter is not backwashed effectively, problems may occur that may be impossible to correct without totally replacing the filter media. The following problems could be caused by improper backwashing procedures: Mudballs: These are formed by the filter media cementing together with the floc that the filter is supposed to remove. Problems such as filter cracking and separation of the media from the filter walls may result because of mud-ball formation. Filter bed shrinkage: filter bed shrinkage or compaction can result from ineffective backwashing. Filter media in a dirty filter are surrounded by a soft layer which cause it to compact. This causes filter bed cracking and separation of the filter media from the walls of the filter, resulting in excessive turbidity in the effluent Media Loss: Media loss is normal in any filter, but if a large amount of media is being lost, the method of the washing should be inspected and corrected.

2.4 Sand Filtration Processes2.4.1 Direct FiltrationDirect filtration involves the addition of coagulant, rapid mix, flocculation and filtration. The major difference relative to conventional treatment is the absence of a separation process, such as sedimentation or flotation, between coagulant addition and filtration [EPA, 2014].Direct filtration is designed to filter water with an average turbidity of less than 25 NTU. Direct filtration has the advantage of having lower chemical costs due to the lower coagulant dosages used, lower capital costs as the sedimentation (and sometimes flocculation) tank is not needed and lower operation and maintenance costs as sedimentation(and sometimes flocculation) tank need not to be powered or maintained. Direct filtration also has disadvantages which include; not being able to handle water supplies that are high in turbidity and/or colour and less detention time for controlling seasonal taste and odour problems.COAGULATIONFLOCCULATIONFILTER

INFLUENTEFFLUENTCOAGULANT FILTER-AID (OPTIONAL) CHEMICALS CHEMICALS

2.4.1 Conventional FiltrationConventional filtration provides effective treatment for just about any range of raw-water turbidity. Its success is due partially to the clarification that precedes filtration and follows coagulation and flocculation. Clarification (or flocculation/sedimentation) includes any solid/liquid separation process following coagulation, where accumulated solids are removed. Clarification, if operated properly, should remove most of the suspended material.

COAGULANT CHEMICALS FLOC-AID CHEMICALS (OPTIONAL) FILTER-AID CHEMICALS (OPTIONAL)SEDIMENTATIONNFILTERFLOCCULATIONCOAGULANT

INFLUENT EFFLUENT

2.5 Limitations of Sand Filtration Technology2.5.1 Limitations Sand filters usually require adequate pre-treatment (coagulation, flocculation) and post treatment(chlorine) Both construction and operation are cost-intensive Not effective in removing bacteria, viruses, fluoride, arsenic, salts and organic matter. Usually requires power-operated pumps, regular backwashing /cleaning and flow control of the filter outlet. Sand filters have no vegetation to break up the filter surface; therefore maintenance is critical to ensuring continued performance, particularly in preserving the hydraulic conductivity of the filtration media (McGarry and Eddie 2011).2.5.2 Maintenance Regular maintenance involves removing the surface layer of fine sediments that can tend to clog the filtration media. In order to significantly increase ease of maintenance for a sand filter, direct physical access to the whole surface of the sand filter chamber will be required to remove fine sediments from the surface layer of the filter media as they accumulate forming a crust. Also the sedimentation chamber needs to be drained for maintenance purposes. Having freely drained material significantly reduces the removal and disposal maintenance costs. Also provision should be made for flushing of any sediment build up that occurs in the pipes. [McGarry and Eddie 2011].2.6 Enhancement of Sand Filtration Technology2.6.1 Pretreatment The performance of sand filtration technology is greatly impacted by the processes that precede it. Chemical feed, rapid mix, flocculation and sedimentation may need upgrading to improve overall system performance or accommodate system expansions. The three basic aspects of chemical feed systems are chemical type, dosage management and the method of chemical application [US EPA, 1999]. Coagulation: Coagulation is used to remove turbidity, organic and inorganic matter, colour, taste and odour producing substances. Chemicals that assist in the removal of suspended solids are added to the untreated water. Coagulants, rapidly add electrochemical charges that attract the small particles in water to clump together as a floc. The initial charge neutralization process allows the formed floc to agglomerate but remain suspended. Coagulation is usually a high energy, rapid mix unit process. Detention time of the coagulation is about 2-3 seconds. The factors that affect coagulation are (i)kind of coagulant, (ii) Quantity of coagulant,(iii) pH value of water, (iv) Temperatureetc. [McGarry and Eddie 2011]. Coagulant pH Range Dosage mg/L

Ferric sulphate (FeSO47H2O) 5.5-11 8.5-51

Ferric Sulphate (Fe2(SO4)3 5.5-11 8.5-51

Ferric Chloride (FeCl3) 5.5-11 8.5-51

Sodium Aluminate (Na2Al2O4) 5.5-8 3.4-34

Aluminium Sulphate(Alum)- Al2 (SO4)3, 18H2 5.5-8 5-85

Table 6: Common coagulants and dosage for best floc formation Flocculation: In this process the precipitates combine into larger particles Flocs. The large amorphous aluminium and iron (III) hydroxides adsorb and enmesh particles in suspension. By slower mixing, turbulence causes the flocculated water to from larger floc particles and increase in mass. These flocs are then easier to remove via the subsequent processes of sedimentation and filtration. Large paddles as mixing devices enhance the formation of the floc. Detention time of flocculation ranges from 10-30 minutes [McGarry and Eddie 2011]. In the treatment of water and wastewater the degree of mixing is measured by the velocity gradient, G. The velocity gradient is best thought of as the amount of shear taking place.

Where;

G= Velocity gradient, p=power input, =Volume of water in mixing tank, =Dynamic viscosity.Note: Enough mixing must be provided to bring the floc into contact and to keep the floc from settling in the flocculation basin. Too much mixing will shear the floc particles so that the floc is small and finely dispersed. Therefore, the velocity gradient must be controlled within a relatively narrow range. Sedimentation: flocculated water is applied to large volume tanks where the flow speed slows down (the flow is almost devoid of turbulence) and the dense floc settles to the bottom. The settled floc is then removed after it resides at this point to remove all settleable particles from coagulation and is then treated as waste product., i.e detention time is inversely proportional to the incoming flow rate- as the flow rate increases, the detention time decreases [McGarry and Eddie 2011] 2.6.2 Additional methods of enhancing sand filter performance In addition to pretreatment, other methods of enhancing sand filter performance can be utilized. Research on enhancing sand filters and designing them to remove dissolved phosphorus as well is currently being researched [Erickson et al.2012]. Research on other enhancements to remove dissolved metals is also under way [Andrew J Erickson, 2013]. Improving filtration systems can increase plant capacity and improve effluent quality. This is usually achieved by; Changing the configuration of the filter media, for example changing the filter media to dual or mixed media or replacing the top layer of sand with anthracite coal. Filtration aid application is also another way in which filtration systems can be improved. These aids prevent premature turbidity breakthroughs by controlling floc penetration into the filter. Addition of polymers to the backwash water can reduce the initial turbidity peaks during filter ripening following backwash and extend filter operation before breakthrough occurs [US EPA, 1999]. Although filters are not generally designed to remove dissolved compounds, dissolved phosphorus removal can be significantly enhanced if the sand is amended with iron, calcium, aluminum or magnesium [Arias te al.2001]. Another modification that may improve sand filter design and performance that is being tested is the addition of a peat layer in the filtration chamber. The addition of peat to the sand filter may increase microbial growth within the sand filter and improve metals and nutrient removal rates [Arias te al.2001].

Table 7: Comparative properties of different filtering media (Galli, 1990)2.7 Chlorine Decay and AQUASIM Software The program AQUASIM was developed for the identification and simulation of AQUATIC systems in nature, in technical plants and in the laboratory. It lets the user define a model using a set of predefined compartments and links and arbitrary transformation processes and perform simulations, sensitivity analyses and parameter estimations with this model [Sven E. Jorgensen, 1996]. AQUASIM software will be used to evaluate the water quality of our project before and after treatment using chlorine decay studies. Reduction in chlorine demand will help to evaluate the performance of treatment in removing organic compounds and others that consume chlorine [Jega Jegatheesan, 2014]. When chlorine is added to water, a mixture of hypochorous acid (HOCl) and hydrochloric acid (HCl) is formed [Gary S Logsdon,2008];

Water supplies are disinfected primarily to inactivate micro-organisms that are harmful to human health. Chlorine is possibly the most popular disinfectant because of its low cost and efficacy [D.Boccelli, 2003]. Chlorine as a non-selective oxidant reacts with both organic and inorganic chemical species in water. Chlorine decays after it reacts with compounds in water. Due to a complex set of reactions and an initial fast reaction, followed by a slower reaction; it is often difficult to describe chlorine decay. Chlorine decay behavior also varies significantly depending on the quality of water, types of treatment processes etc. Temperature has also been shown to have a significant effect on chlorine decay characteristics, and any change in this parameter should be considered [J.C. Powell, 2000].The general chlorine decay model includes the following reactions between chlorine and other constituents in water (Bell-Ajy et al., 2000).

In this study, the experimental chlorine decay data are used to estimate values of chlorine demand. The total amount of total chlorine demand which is the sum of chlorine demand for fast and slow reacting agents can be used as an indication of the disinfection by product [DBP] precursors concentration in the water.

Combined chlorine= Combined chlorine is total chloramines. They are generated when free chlorine reacts with contaminants in water. Free chlorine= Amount of chlorine available to kill microorganisms in water.The graphs below show the AQUASIM software output of 6mg/L and 10mg/L inputs as shown in the tables below.Time(min)00.010.0830.1660.250.330.4160.511.5234517

6 mg/L(Free chlorine)61.231.291.290940.90.890.80.670.560.550.390.340.340.07

6 mg/L(Total chlorine)61.31.251.171.111.071.020.970.870.790.720.640.550.460.22

Table 8: 6mg/L dosage of chlorine (free and total) with time

Figure 4: AQUASIM software output for 6mg/L chlorine dosage.Time00.010.0830.1660.250.330.4160.511.5234517

10 mg/L(Free chlorine)106.466665.85.75.254.84.243.60.63

10 mg/L(Total chlorine)106.76.76.66.46.36.36.35.85.5.44.94.64.64.4

Table 9: 10mg/L dosage of chlorine (free and total) with time

Figure 5: AQUASIM software output for 10mg/L chlorine dosage.

Chapter 3.Methodology

This chapter describes the materials and methods used in this project. A strategies chart has been constructed and is shown below.

Figure 6: Methodology strategies chart.3.1 Methodology This project includes both theoretical study and practical experiments. The theoretical study mainly discusses the theories behind water pollution, its effects and information on different types of pollutants and how they affect water quality. An extensive literature review of methods that can used to model the performance of a sand filtration system that is to be used to clean a polluted pond are addressed. This part of the project is covered by using academic and scientific resources such as, academic journals and papers from academic databases, as well as scientific data sheets.The practical part of the assignment will be done in the Civil Engineering laboratory at Deakin University Waurn Ponds Campus. It will basically be implementing the theories and designs discussed in the theoretical part. Several experiments were carried out in order to establish the optimum method that can be used to model the performance of a polluted pond, this included determining the best coagulant and establishing its optimum dose, recommending sand filter size and a recommendation of backwash volume. Chlorine decay studies were also performed and water quality was modelled using AQUASIM software.

3.2 Raw Water All experiments were carried out with raw water collected from ponds 3 and 6, located at the Deakin university Waurn ponds Campus. Their initial parameters were measured (pH, Turbidity, conductivity, etc).

Figure 7: Deakin University Waurn Ponds Campus map with ponds labelled.3.3 Coagulation Tests (Refer to section 2.6.1- Pretreatment; for technical aspect of Jar testing)Jar testing was used to perform the coagulation experiments and evaluate the different coagulants (Alum, Ferric chloride and poly aluminium chloride) and coagulant doses, to see which is more effective in terms of cost and performance. The Jar Testing method and apparatus is outlined below [Adapted from Water Training Centre notes].Jar testing is a bench scale experiment used by drinking water treatment plants. The test simulates a water treatment plants coagulation, flocculation and sedimentation units using a range of chemical doses. It is performed to determine the optimum dose of coagulant to be added during the water treatment process to obtain flocs with good settling characteristics [Leanne Farago, 2014]3.3.1 Apparatus

Jar tester-stirrer with 4 to 6 paddles and variable speed 2 liter square beakers 2 liter measuring cylinder Water samples Syringes Bottles containing 5% W/V ploy aluminium chloride, 1% W/V alum and 1% ferric chloride. Turbidimeter pH meter Conductivity meter Filtration apparatus3.3.2 Method

Ensure raw water sample is well mixed and then measure turbidity, pH, conductivity and Transfer 2 liters of raw water sample to each beaker using a graduated cylinder Lower the stirrers into the beakers, start stirring at 200 rpm With a syringe, add the relevant dose of coagulant to each beaker. The coagulant should be added as close as possible to the hub of the stirrer and added with a 2-3 second dosing time Continue stirring at max rpm for 1 minute Reduce the speed to 30rpm and continue stirring for 20 minutes, then turn off the paddles and lift out of water Allow 20 minutes settling time, during this time observe the rate of settling in each container. After settling for 20 minutes measure the turbidity, pH and conductivity of each sample.

Figure 7: Jar testing (Deakin University 2014)3.4 Sand filter (Refer to section 2.3- Enhancement of sand filter for more technical aspect)Sand filtration experiments were performed on two sand filters with different sand filter media sizes (river sand sizes 6 and 6.5). Two filtration processes were performed, which included conventional and direct filtration (refer to section 2.4 for sand filtration processes) in order to establish which one was the most effective. Initial parameters of raw water (turbidity, pH, conductivity) were measured. Turbidity was also then consecutively measured at 5 minute intervals, pH wand conductivity was measured at 30 minute intervals and head loss was measured at 5 minute intervals. Flow rate was also measured at 30 minute intervals. The filtration method and apparatus is outlined below.3.4.1 Apparatus

2 Sand filters with different sand filter media sizes measuring cylinder Water samples Bottles containing 1% ferric chloride. Turbidimeter pH meter Conductivity meter Stopwatch3.4.2 Before use:

Measure raw water initial parameters (turbidity, pH, conductivity) Coagulate raw water (direct filtration) and allow to settle (conventional filtration) Check all manometers are at the same height Check all manometers have been connected to column via click on connections Make sure valve at base of column is turned off Check that feed pump outlets are inserted into tops of columns and overflow outlets are running back into the feed tank3.4.3 Operation:

Fill feed tank with desired sample Start pump and allow columns to fill Make sure there are no air bubbles within manometers, if there are push water back through manometers using squeeze water bottle to add water to manometers Make sure columns are not overflowing at the top Open valve at base of column and adjust to desired flow rate. Use a measuring cylinder and stopwatch to calculate flow rate Mark starting height of water in manometers and mark at set intervals throughout the experiment. These markings will be used to calculate the head loss of the filter columns. Record height changes throughout the experiment. Finally measure parameters of filter permeate.3.4.3 Backwashing:

Backwash columns to remove contaminants Disconnect all manometers before backwashing Connect garden hose to outlet at base of columns Ensure overflow pipe is running to drain Slowly run water through hose and allow to flow until sand is swirling within column. Do not apply too much water pressure as this will cause sand to overflow from column. Continue washing until water in the top of the column is clear. Take note of backwash volume.

3.5 Chlorine decay experiments - (Refer to section 2.7- for more technical aspect of chlorine decay) AQUASIM software will be the primary means we will use to evaluate water quality before and after treatment using chlorine decay studies. Before being able to measure the chlorine decay of a sample you first need to know the demand. The chlorine demand and decay experimental method and apparatus is outlined below.3.5.1 Chlorine demand studies: Take 10 x 100 ml glass bottles, rinse well with demineralized water and wrap in aluminium foil so that no light can enter the bottle (light will cause the chlorine demand to change faster) Fill each bottle with 100ml of sample Add from the 100mg/l Cl2 stock the following volumes of solution; 1,2,3,4,5,6,7,8,9,10 (ml) Wait 5 minutes between each addition (this time will become important when measuring total chlorine) Note time chlorine is added. Shake all bottles well and leave to sit for 60 minutes After 60 minutes measure all samples for total and free chlorine using the free and total chlorine meters. Plot results in excel spreadsheet. The lowest point ids the breakpoint, this is the required chlorine dose for this sample. Repeat again after 120 minutes.3.5.2 Chlorine decay studies: Calculate the amount of chlorine stock solution to be added to the two litre sample volumes to give the desired chlorine dose rate (mg/L).

You will need to use a 2lt water sample as we will be taking out a lot of samples over the course of the test and we want to keep a representative sample volume, 1 litre is too small, 2 lt is manageable.

For example: (Final concentration / initial concentration) * final volume= (2/100)*2000= 40ml stock solution to be added to 2L sample

Stock solution: 100mg/LFinal volume: 2000ml (2L)Final concentration: 2mg/L

So in this case we would add 40 ml to a two litre sample (giving us a dose of 2mg/l Cl) and 80 ml to a 2lt sample giving us a 4mg/l dose.

The 4mg/l needs to use the HR mode on the chlorine meter. Make sure you follow the method for HR chlorine. (1 pillow, 1cm cell)

The 2mg/l needs to use the LR mode on the chlorine meter. Make sure you follow the method for LR chlorine. (1 pillow, round cell)

Use brown glass bottles to prevent growth of algae and rapid breakdown of chlorine due to interaction with light Add 2L of sample to be chlorinated to bottle. Add required chlorine dose and shake well. Start stop watch (this gives a total experiment time) and note time of day. Samples need to be taken immediately after chlorine is added for a time =0 result You will need 3 x 10ml samples - zero, free and total chlorine. Dont mix up the cells you use for these as it can result in false high results due to contamination. Sample every 5 mins for the first half hour. This can get a bit tricky given the 3 minute wait for the total chlorine. Make sure you note the time the pillow is added. This will give you an accurate representation of time. After 30 minutes sample at 15 minute intervals until 2 hours since chlorine addition has taken place. After 2 hours has elapsed, sample at hourly intervals. Sample only until chlorine results reach 0.2mg/l

3.7 AQUASIM Software (Refer to section 2.6- for more technical aspect of chlorine decay and AQUASIM software) AQUASIM software will be used to evaluate the water quality before and after treatment using chlorine decay studies. Reduction in chlorine demand will help to evaluate the performance of treatment in removing organic compounds and others that consume chlorine.

Chapter 4.Results and Discussion

Chapter 5.Recommendations

Chapter 6.Conclusions

Rfrencs

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