Water Treatment and Purification PDF

WATER SUPPLY PLANNING AND DEVT WATER TREATMENT AND PURIFICATION To make water safe and accessible for human use Water Treatment and Purification WHY TREAT WATER? Safe drinking water is essential for health, hygiene, and wellbeing. Water treatment is critical in preventing waterborne...

WATER SUPPLY PLANNING AND DEVT WATER TREATMENT AND PURIFICATION To make water safe and accessible for human use Water Treatment and Purification WHY TREAT WATER? Safe drinking water is essential for health, hygiene, and wellbeing. Water treatment is critical in preventing waterborne diseases such as cholera, dysentery, and typhoid, which are caused by drinking contaminated water. Water is treated not only for human consumption but also for industrial uses, agriculture, and environmental protection. Water Treatment and Purification What is the differences between pollution and contamination? Pollution ○ Pollution can take the form of microbial, chemical, or energy (including noise and radiation) in various media. ○ Pollution fits into the concept of the “epidemiological triad”: agent (pollutant), environment (medium), and host (exposed person). Contamination ○ It indicates the presence of an impurity ○ It is maybe natural and is not due to human activity. Water Treatment and Purification QUESTION What is the presence of a substance where it should not be or at concentrations above background? Water Treatment and Purification QUESTION What is the presence of a substance where it should not be or at concentrations above background? Contamination Water Treatment and Purification QUESTION It is due to the influence or activities of people Water Treatment and Purification QUESTION It is due to the influence or activities of people Pollution Water Treatment and Purification QUESTION It always creates harmful effects Water Treatment and Purification QUESTION It always creates harmful effects Pollutants Water Treatment and Purification QUESTION It does not always creates harmful effects Water Treatment and Purification QUESTION It does not always creates harmful effects Contamination Water Treatment and Purification All pollutants are contaminants, but not all contaminants are pollutants Water Treatment and Purification WATER TREATMENT The process of improving the quality of water to make it suitable for a specific end-use such as drinking, industrial water supply, irrigation, river flow maintenance, or safe discharge into the environment. WATER PURIFICATION A subset of water treatment that focuses on removing contaminants from water to produce drinking water that is safe for human consumption. The process typically involves removing harmful substances such as bacteria, viruses, dissolved solids, chemicals, and other impurities. Contaminants Water Treatment and Purification CATEGORIES OF CONTAMINANTS Physical Contaminants ○ Sediments, debris, and particulates Chemical Contaminants ○ Heavy metals, nitrates, pesticides Biological Contaminants ○ Bacteria, viruses, protozoa Radiological Contaminants ○ Radon, uranium These parameters include a range of characteristics that make water appealing and useful to consumers, and that ensure the water presents no harm or disruption to the environment or to humans within a wide range of possible water uses. Water Treatment and Purification PHYSICAL CONTAMINANTS Physical contaminants are substances that affect the physical properties of water, such as its appearance, smell, and taste. These are generally visible or can be filtered out using physical methods. Effects: Physical contaminants can cause water to appear cloudy or murky (high turbidity), make it unpleasant to drink, and clog treatment systems. Though not always harmful, their presence can indicate potential contamination by other harmful substances. Water Treatment and Purification CHEMICAL CONTAMINANTS Chemical contaminants include substances that can dissolve or mix with water and alter its chemical composition. These can come from natural sources or human activities Effects: ○ Heavy metals can cause severe health issues, such as nervous system damage, kidney failure, and developmental disorders. ○ Nitrates are particularly harmful to infants, leading to a condition known as "blue baby syndrome" (methemoglobinemia), which affects the ability of blood to carry oxygen. ○ Pesticides can be toxic to humans and wildlife, causing long-term health problems like cancer and hormonal disruption. Water Treatment and Purification CHEMICAL CONTAMINANTS Water Treatment and Purification BIOLOGICAL CONTAMINANTS Biological contaminants, also known as pathogens, include microorganisms that can cause diseases when present in water. These contaminants are a major public health concern Effects: ○ Waterborne pathogens can lead to serious diseases such as cholera, dysentery, hepatitis, and other gastrointestinal illnesses, especially in areas with poor sanitation. ○ Biological contaminants are a leading cause of death in many developing countries, particularly affecting children. Water Treatment and Purification BIOLOGICAL CONTAMINANTS Water Treatment and Purification RADIOLOGICAL CONTAMINANTS Radiological contaminants are radioactive substances that can be present in water due to natural processes or human activities such as mining, nuclear energy production, and medical waste disposal. Effects: ○ Long-term exposure to radiological contaminants can increase the risk of cancer, particularly lung cancer from radon exposure. ○ Ingesting or drinking water contaminated with radioactive substances can lead to damage to organs and tissues, causing serious long-term health problems. Basic Water Quality Parameters and its Importance Water Treatment and Purification pH pH is a measure of the hydrogen ion concentration in a solution, indicating how acidic or basic (alkaline) the water is. It is measured on a scale ranging from 0 to 14, where: A pH of 7 is neutral (pure water). A pH below 7 indicates acidity (more hydrogen ions). A pH above 7 indicates alkalinity (fewer hydrogen ions, more hydroxide ions). Water Treatment and Purification Importance of pH 1. Chemical Reactions and Solubility: a. Water Chemistry: The pH of water affects the solubility of minerals and metals. For example, at lower pH levels (acidic conditions), metals like lead, copper, and iron dissolve more easily into water, which can lead to contamination. b. Chemical Additives: Chemicals used for treatment, such as chlorine for disinfection or coagulants like aluminum sulfate (alum) for coagulation, work best within specific pH ranges. If the pH is too high or too low, these processes may be less effective. Water Treatment and Purification Importance of pH 2. Corrosion Control: Acidic Water (Low pH): Water with a low pH (below 7) is more corrosive, meaning it can corrode pipes, metal fixtures, and water infrastructure. This can lead to the leaching of harmful metals like lead and copper into drinking water. Alkaline Water (High pH): While less corrosive than acidic water, highly alkaline water can cause scaling in pipes, which reduces flow and efficiency in water distribution systems Water Treatment and Purification Importance of pH 3. Biological Impact: Microorganisms: The pH of water can influence the survival of bacteria, viruses, and other pathogens. Disinfectants like chlorine are more effective at neutralizing harmful microorganisms in slightly acidic to neutral water (pH 6.5 to 7.5). Beyond this range, disinfection efficiency decreases. Aquatic Life: The pH of water also affects aquatic ecosystems. Most aquatic organisms thrive in a pH range of 6.5 to 8.5. Extremes in pH can be harmful to fish and other aquatic life. Water Treatment and Purification pH Adjustment in Water Treatment 1. pH Adjustment Chemicals: To raise pH (reduce acidity): Lime (calcium hydroxide), soda ash (sodium carbonate), or sodium hydroxide can be added to water to increase pH and reduce corrosiveness. To lower pH (reduce alkalinity): Sulfuric acid or carbon dioxide can be added to water to lower pH when it is too alkaline. 2. Target pH range: For drinking water, the ideal pH range is typically between 6.5 and 8.5, which is considered safe and minimizes corrosion or scaling in pipes. Water Treatment and Purification CONDUCTIVITY Conductivity is a measure of water’s ability to conduct an electric current, which is directly related to the concentration of dissolved ions in the water. It is measured in units of microsiemens per centimeter (µS/cm) or millisiemens per meter (mS/m). Higher conductivity means more dissolved ions (charged particles), typically indicating the presence of salts, metals, or other dissolved solids. Lower conductivity suggests purer water with fewer dissolved ions. Water Treatment and Purification INDICATOR OF WATER QUALITY Natural Water Sources: Conductivity can help indicate the purity of water in lakes, rivers, or groundwater. Freshwater usually has lower conductivity (50 to 1500 µS/cm), whereas seawater has high conductivity (about 50,000 µS/cm) due to high salt content. Contaminants: Higher-than-normal conductivity levels in freshwater can indicate contamination from sources like: ○ Industrial discharges (heavy metals, chemicals) ○ Agricultural runoff (fertilizers, pesticides) ○ Sewer overflows (chlorides, nitrates, phosphates) Water Treatment and Purification INDICATOR OF WATER QUALITY Total Dissolved Solids (TDS): Conductivity is closely related to TDS, which includes salts, minerals, and other ionic compounds dissolved in the water. Higher TDS (and therefore higher conductivity) can make water taste salty or metallic and may lead to scaling in pipes and equipment. TDS levels are regulated in drinking water standards, with typical acceptable limits around 500 mg/L for safe drinking water. Water Treatment and Purification SALINITY Salinity refers to the concentration of dissolved salts in water, primarily consisting of sodium chloride (NaCl), but also including other salts like magnesium, calcium, and potassium. Freshwater: Less than 0.5 ppt Brackish Water: Between 0.5 and 30 ppt Seawater: Around 35 ppt (or 35,000 mg/L) Hypersaline Water: Greater than 40 ppt, such as in salt lakes Water Treatment and Purification Importance of Salinity in Water Treatment Drinking Water: Water with high salinity is not suitable for human consumption because it can lead to dehydration, increase the risk of kidney problems, and affect blood pressure. The World Health Organization (WHO) recommends that the salinity of drinking water should not exceed 500 mg/L of total dissolved salts (TDS) for palatability. Agriculture: In irrigation, water with high salinity can lead to soil degradation and reduced crop yields, as excessive salt concentrations inhibit plant growth by disrupting water absorption. Industrial Use: Many industrial processes, such as cooling systems and boilers, require low-salinity water to avoid scaling, corrosion, and inefficiency in equipment. Water Treatment and Purification DISSOLVED OXYGEN Dissolved oxygen (DO) refers to the amount of oxygen that is present in water. Oxygen enters water through direct diffusion from the atmosphere, aeration (such as the movement of water over rocks or in waterfalls), and as a byproduct of photosynthesis by aquatic plants. Measured in milligrams per liter (mg/L) or as a percentage of saturation. DO levels are critical for maintaining aquatic life and determining water quality. Water Treatment and Purification DISSOLVED OXYGEN Role in Water Quality and Aquatic Life Aquatic Ecosystems: DO is essential for the survival of fish, invertebrates, and other aquatic organisms. Different species require different DO levels to thrive: Fish like trout and salmon need high DO levels (around 6-7 mg/L). Other species, such as carp, can survive in waters with lower DO concentrations. Low DO levels can result in hypoxia, a condition where oxygen levels are too low to support aquatic life, leading to dead zones where organisms cannot survive. Hypoxic conditions can occur naturally or due to human activities, such as nutrient pollution from agriculture (which causes algal blooms and subsequent oxygen depletion). Water Treatment and Purification DISSOLVED OXYGEN Role in Water Quality and Aquatic Life Temperature Influence: The solubility of oxygen in water decreases as water temperature rises. Colder water can hold more dissolved oxygen than warmer water. This makes DO levels in summer months critical for maintaining healthy ecosystems. Water Treatment and Purification DO Levels in Drinking Water Treatment Taste and Odor: High levels of dissolved oxygen in drinking water can improve its taste by making it fresher, while low DO levels may cause a flat taste. However, too much DO can also lead to corrosion in water pipes. Oxidation of Contaminants: DO plays a role in the oxidation of certain contaminants in water, such as iron and manganese. In the presence of DO, these metals can be converted to their insoluble forms, which are then removed by filtration. Prevention of Anaerobic Conditions: In the treatment of drinking water, maintaining adequate DO levels helps prevent anaerobic conditions, which can lead to the formation of harmful gases like hydrogen sulfide, resulting in a rotten egg odor and potential water quality issues. Water Treatment and Purification TURBIDITY Turbidity is a measure of the cloudiness or haziness of water caused by suspended solids, such as silt, clay, organic matter, plankton, and other microscopic organisms. It quantifies how much the particles in water scatter light rather than allowing it to pass through. Measured in Nephelometric Turbidity Units (NTU) or Formazin Nephelometric Units (FNU) using a device called a turbidimeter. Higher turbidity indicates murkier water, while low turbidity indicates clearer water. Water Treatment and Purification TEMPERATURE In the context of water treatment and aquatic systems, temperature refers to the degree of warmth or coldness of water. It is measured in degrees Celsius (°C) or Fahrenheit (°F). Dissolved Oxygen (DO): As water temperature increases, its capacity to hold dissolved oxygen decreases. Warmer water can lead to lower DO levels, which are vital for the survival of aquatic life and the effectiveness of aerobic biological treatment processes. Solubility of Gases: Gases such as oxygen and carbon dioxide become less soluble in warmer water. This can lead to oxygen depletion and an increase in carbon dioxide levels, affecting both aquatic ecosystems and water treatment. Water Treatment and Purification Effects of Temperature on Drinking Water Taste and Odor: Water temperature can affect the taste and odor of drinking water. Warmer water is more likely to produce undesirable tastes and odors, especially if organic matter is present, as microbial activity increases. Water Pipe Corrosion: Higher temperatures can accelerate the corrosion of pipes and plumbing systems, especially when combined with certain chemical conditions. This can lead to increased levels of metals, such as iron, copper, or lead, in drinking water. Water Treatment and Purification BIOCHEMICAL OXYGEN DEMAND Biochemical Oxygen Demand (BOD) refers to the amount of dissolved oxygen (DO) required by aerobic microorganisms to break down organic matter in water over a specific period, typically 5 days at 20°C. It is a key indicator of organic pollution in water. A high BOD value indicates a large amount of organic matter in the water, which requires more oxygen for decomposition, often resulting in lower oxygen levels available for other aquatic organisms Water Treatment and Purification Importance of BOD in Water Treatment BOD is a critical parameter for assessing the level of organic pollution in both natural water bodies and wastewater. It reflects how much oxygen is being consumed by microorganisms as they break down organic pollutants, such as: Sewage and wastewater Agricultural runoff Industrial discharges (e.g., from food processing or paper mills) Decaying plant matter High BOD levels indicate that there is a high concentration of organic materials, which can lead to oxygen depletion in water bodies. This can create hypoxic or anoxic conditions, negatively impacting aquatic life Water Treatment and Purification Relationship Between BOD and Aquatic Life Oxygen Depletion: When BOD is high, a large amount of oxygen is consumed by bacteria and other microorganisms to break down the organic material. This reduces the amount of dissolved oxygen available for aquatic organisms, such as fish and invertebrates. Low dissolved oxygen can cause fish kills and the collapse of aquatic ecosystems. Algal Blooms: Excess nutrients, particularly from sewage and agricultural runoff, can stimulate algal blooms. As these algae die and decompose, the process consumes large amounts of oxygen, further increasing BOD levels and reducing oxygen availability for other organisms. Water Treatment and Purification SOLIDS Solids in water refer to the various suspended, dissolved, or settled particles that can be found in natural water bodies, wastewater, and treated water. Solids come from organic and inorganic materials and play a critical role in determining water quality. Water Treatment and Purification Types of Solids Total Solids represent the sum of all organic and inorganic matter, both suspended and dissolved, in the water. It is the combination of both Total Suspended Solids (TSS) and Total Dissolved Solids (TDS). The level of total solids is an important measure of water pollution and treatment efficiency. Suspended Solids (SS): These are particles that do not dissolve in water but remain suspended in the liquid. Suspended solids can be organic or inorganic, including: ○ Silt and clay particles from erosion or runoff. ○ Organic matter, such as decaying plant material or algae. ○ Industrial waste and sewage particles. Water Treatment and Purification Types of Solids Dissolved Solids (DS): These are minerals, salts, and organic compounds that have dissolved into the water. Dissolved solids are typically small enough to pass through filters and remain in the water even after initial treatment steps. ○ Common dissolved solids include calcium, magnesium, sodium, chlorides, sulfates, and bicarbonates. ○ Dissolved solids are measured as Total Dissolved Solids (TDS), which provides a gauge of water's mineral content. Water Treatment and Purification Key Processes for Solids Removal in Water Treatment Sedimentation Coagulation Flocculation Filtration Reverse Osmosis Disinfection Water Treatment and Purification ALKALINITY Alkalinity refers to the water’s capacity to neutralize acids, primarily due to the presence of bicarbonates (HCO₃⁻), carbonates (CO₃²⁻), and, to a lesser extent, hydroxides (OH⁻). It is measured in terms of milligrams of calcium carbonate (CaCO₃) per liter (mg/L). Alkalinity is a crucial parameter in water chemistry because it indicates the ability of water to maintain a stable pH level. Water Treatment and Purification Sources of Alkalinity Geological Sources: The dissolution of rocks like limestone (calcium carbonate) and dolomite (calcium magnesium carbonate) releases carbonate and bicarbonate ions into the water. Atmospheric Carbon Dioxide (CO₂): CO₂ dissolves in rainwater, forming weak carbonic acid (H₂CO₃), which reacts with minerals in soils and rocks to increase alkalinity. Industrial and Agricultural Activities: Certain industrial effluents and agricultural runoff, particularly from areas with lime or fertilizer application, can increase alkalinity in water. Water Treatment and Purification Importance of Alkalinity in Water Treatment Prevents pH Fluctuations: In natural water bodies, alkalinity helps maintain a stable pH, which is essential for aquatic life. ○ For instance, sudden acid inputs (such as acid rain) can lower pH levels, but water with high alkalinity can neutralize this acidity, preventing harmful drops in pH. Reduces Corrosion: Water with sufficient alkalinity (but not excessively high) is less corrosive to pipes and water infrastructure. Low alkalinity water is often more acidic and corrosive During the coagulation process in water treatment, alkalinity is important for maintaining the optimal pH range. Chemicals like alum (aluminum sulfate) are commonly used as coagulants and work best within a specific pH range, often around 6.5 to 7.5 Water Treatment and Purification Effects of High and Low Alkalinity Acidic and Corrosive Water: When alkalinity is too low, the water’s pH becomes unstable, making it prone to becoming acidic In water treatment, excessively high alkalinity can reduce the effectiveness of disinfectants like chlorine. High alkalinity can contribute to scaling, particularly in hot water systems Water Treatment and Purification WATER HARDNESS Water hardness refers to the concentration of dissolved minerals, primarily calcium (Ca²⁺) and magnesium (Mg²⁺) ions, in water. These minerals are the main contributors to what is called total hardness. Hardness is measured in milligrams of calcium carbonate (CaCO₃) per liter (mg/L), or sometimes in grains per gallon (gpg). Hard water is water with high levels of calcium and magnesium, while soft water has low concentrations of these minerals. Water Treatment and Purification Types of Hardness Temporary Hardness ○ caused by the presence of bicarbonates of calcium and magnesium (Ca(HCO₃)₂ and Mg(HCO₃)₂). This type of hardness can be easily removed by boiling the water, as the heat causes the bicarbonates to decompose into carbonates, which precipitate out as solid minerals (such as calcium carbonate, CaCO₃). ○ Groundwater passing through regions rich in limestone or chalk. Permanent Hardness ○ due to the presence of sulfates or chlorides of calcium and magnesium (CaSO₄, MgSO₄, CaCl₂, MgCl₂). This hardness cannot be removed by boiling and requires chemical treatment methods to reduce. ○ Water sources that have percolated through rock formations containing gypsum (calcium sulfate) or areas with heavy mineral deposits. Water Treatment and Purification Types of Hardness Total hardness ○ Sum of both temporary and permanent hardness, representing the total concentration of calcium and magnesium ions in the water. ○ This is the most commonly measured value when assessing water hardness. Water Treatment and Purification Hardness in Water Treatment Ion Exchange Method Life Softening Reverse Osmosis Water Treatment and Purification COLIFORMS Coliforms are a broad group of bacteria that are commonly found in the environment, including soil, vegetation, and the intestines of warm-blooded animals. They are used as indicator organisms in water testing because their presence suggests that water may be contaminated with more harmful pathogens such as bacteria, viruses, and protozoa. Coliforms themselves are generally not harmful, but their presence indicates that water may have been contaminated by sewage or animal waste, potentially introducing dangerous microorganisms like E. coli, Salmonella, or Cryptosporidium into the water supply. Water Treatment and Purification Types of Coliforms Total Coliforms ○ Total coliforms include all coliform bacteria present in the environment. They are widespread and can be found in soil, water, and plants. While total coliforms are not usually harmful, they are used as a general indicator of water quality Fecal Coliforms ○ A subset of total coliforms, are more specific to the intestines of warm- blooded animals, including humans. Their presence in water is a stronger indicator of fecal contamination from sources like sewage, animal waste, or runoff from agricultural areas. Water Treatment and Purification Types of Coliforms Total Coliforms ○ Total coliforms include all coliform bacteria present in the environment. They are widespread and can be found in soil, water, and plants. While total coliforms are not usually harmful, they are used as a general indicator of water quality Fecal Coliforms ○ A subset of total coliforms, are more specific to the intestines of warm- blooded animals, including humans. Their presence in water is a stronger indicator of fecal contamination from sources like sewage, animal waste, or runoff from agricultural areas. Water Treatment and Purification Types of Coliforms E. coli (Escherichia coli) ○ A species of fecal coliform that lives in the intestines of humans and animals. Most strains of E. coli are harmless, but some, such as E. coli O157, can cause serious illness. ○ The detection of E. coli in water is a clear indicator of recent fecal contamination and suggests that pathogens harmful to human health may be present. Water Treatment and Purification Health Implications of Coliforms in Water Bacteria: Such as Salmonella, Shigella, and pathogenic E. coli strains, which can cause gastrointestinal illness. Viruses: Including hepatitis A, rotavirus, and norovirus, which are spread through fecal contamination of water. Protozoa: Like Giardia and Cryptosporidium, which can cause severe intestinal infections. Symptoms of waterborne illnesses caused by these pathogens include: Diarrhea Nausea and vomiting Cramps Fever Water Treatment and Purification Treatment Methods for Removing Coliforms Coloration Ultraviolet Disinfection Ozone Filtration Boiling Stages of Water Treatment and Advanced Water Treatment Techniques Water Treatment and Purification Water Treatment and Purification COAGULATION AND FLOCCULATION The process of decreasing the stability of the colloids in water is called coagulation. Coagulation results from adding salts of iron, aluminum, or cationic polymer to the water. It is a physical process of slowly mixing the coagulated water to increase the probability of particle collision. Water Treatment and Purification Most Common Coagulants Aluminum Sulfate Sodium Aluminate Ferric Sulfate Ferrous Sulfate Ferric Chloride Polyaluminum Chloride Cationic Polymers Coagulants tend to be positively charged. Due to their positive charge, they are attracted to the negative particles in the water Water Treatment and Purification Purpose of Coagulation The purpose of most coagulant chemicals is to neutralize the negative charges on the turbidity particles to prevent those particles from repelling each other. The amount of coagulant which should be added to the water will depend on the zeta potential, a measurement of the magnitude of electrical charge surrounding the colloidal particles. If the zeta potential is large, then more coagulants will be needed. Positively charged coagulants attract to negatively charged particles due to electricity. Water Treatment and Purification COAGULATION Water Treatment and Purification FLOCCULATION This process forms the floc. Floc is a snowflake-looking material that is made up of the colloidal particles, microorganisms, and precipitate. Water Treatment and Purification COAGULATION AND FLOCCULATION The purpose of these processes is to: Remove turbidity (cloudiness in water caused by suspended particles) Improve the efficiency of filtration and sedimentation Reduce microbial contaminants, pathogens, and other harmful particles Improve aesthetic qualities of drinking water, such as clarity and color Water Treatment and Purification ADSORPTION It is an adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. Adsorption of a substance involves its accumulation onto the surface of a solid called the adsorbent. In water and used water purification, adsorption is applied for the removal of dissolved impurities. Water Treatment and Purification Adsorbents An adsorbent is a solid substance used to remove contaminants from liquid or gas that can harm the environment. ○ Activated Carbon ○ Activated Alumina ○ Molecular Sieves (Zeolite) ○ Silica Gel Water Treatment and Purification Water Treatment and Purification SETTLING Sedimentation a process of settling that allows the flocculated or coagulated particles to settle by gravity in a sedimentation tank. Water Treatment and Purification FILTRATION A physical process of separating suspended and colloidal particles from water by passing the water through a filter media. Water Treatment and Purification FILTRATION: Media Filtration A filter media can consist of silica sand, greensand, anthracite coal, activated carbon, and many other types of media. These media can be used as single media filter or mixed to provide improved filtration characteristics. Water Treatment and Purification FILTRATION: Membrane Filtration Membrane filtration offers high filtration efficiency due to the smaller pore sizes of the membranes. They can effectively remove a wide range of particles, including suspended solids, colloids, microorganisms like bacteria and viruses, and various dissolved substances. Membrane filters also provide precise and reliable separation, ensuring high- quality filtrate. Water Treatment and Purification FILTRATION: Membrane Filtration Water Treatment and Purification FILTRATION: Membrane Filtration Membrane Catridge Filtration ○ Bag or cartridge filters capable off removing giardia and cryptosporidium Microfiltration ○ Membrane filters capable of removing pathogenic organisms larger than 0.1 micrometers in size. Ultrafiltration ○ Membrane filters capable of removing pathogenic organisms larger than 0.005 micrometers in size. Water Treatment and Purification FILTRATION: Membrane Filtration Nanofiltration ○ Membrane filters capable of removing pathogenic organisms and dissolved organic contaminants larger than 0.001 micrometers in size. Reverse Osmosis ○ Membrane filters capable of removing pathogenic organisms, dissolved organic, and salts contaminants larger than 0.0001 micrometers in size. Water Treatment and Purification FILTRATION: Reverse Osmosis With 90% removal rate Osmosis Water flows from the side that has the lowest concentration to the side that has the highest concentration. Reverse Osmosis Water flows from side that has the highest concentration to the side with the lowest concentration by applied pressure. Water Treatment and Purification FILTRATION: Reverse Osmosis Water Treatment and Purification DISINFECTION Water is clear after the filtration process but still contaminated by microorganisms which must be killed by using disinfectant. Water Treatment and Purification DISINFECTION: Types Physical disinfection - boiling water and irradiation with ultraviolet light. Chemical disinfection - adding chlorine , bromine, iodine, and ozone to water. Water Treatment and Purification DISINFECTION: Boiling (Physical) It kills vegetative bacterial cells, but spores, virus, and some protozoa may survive long periods of boiling. A effective method for small batches of water during water emergencies. Boiling is prohibitively expensive for large quantities of water. Water Treatment and Purification DISINFECTION: UV Radiation (Physical) UV radiation is an effective and relatively safe disinfection method, but is relatively expensive and not widely used. UV light disrupts DNA of microbial cells, preventing reproduction. Specific wavelengths, intensities, distances, fowrates, and retention time are required. Water Treatment and Purification DISINFECTION: Chemical Chemicals added to water for disinfection include chlorine, bromine, and iodine. Bromine is not recommended for drinking water disinfection, but may be used for pool water. Iodine is sometimes used for drinking water disinfection, but causes a bad aftertaste. Water Treatment and Purification DISINFECTION: Chlorination (Chemical) Chlorination is employed primarily for microbial disinfection. Chlorine is widely used because it is: ○ Readily available ○ Cheap. ○ Easy to apply (it is highly water soluble). ○ Harmless residual in solution which protects the distribution system. ○ Very toxic to most microorganisms. Water Treatment and Purification DISINFECTION: Chlorination (Chemical) Chlorination is employed primarily for microbial disinfection. Disadvantages It is a suffocating and irritant gas that requires careful handling. It gives taste and odour problems. Chlorine can react with naturally occurring organic compounds found in the water supply to produce compounds known as disinfection byproducts (DBPs). The most common DBPs are trihalomethanes (THMs) which is carcinogenic. Water Treatment and Purification DISINFECTION: Types of Chlorine Residual (Chemical) The residual chlorine test determines the amount of residual chlorine in water that has completed testing and is ready for release into the distribution and delivery systems. Residual chlorine is an important measure to prevent microbial contamination. 1. Free chlorine - kills microogranisms more effectively 2. Combined chlorine - formed when free chlorine reacts with other chemicals in water 3. Total chlorine - the sum of free and combined chlorine Water Treatment and Purification DISINFECTION: Ozonation (Chemical) Ozone (O3) is an effective, relatively harmless disinfection method, but is expensive (and therefore less popular than chlorine). Ozone is a strong oxidant, that produces hydroxyl free radicals that react with organic and inorganic molecules in water to kill microbes. Water Treatment and Purification SOFTENING To remove hardness (Ca and Mg) in water. Water Treatment and Purification SOFTENING: Lime-Soda Ash Method Lime (Ca(OH)2) is used to remove chemicals that cause carbonate hardness. Soda ash (Na2CO3) is used to remove chemicals that cause non-carbonate hardness. When lime and soda ash are added, hardness-causing minerals form nearly insoluble precipitates. Water Treatment and Purification SOFTENING: Chemistry of Soda Lime Process As slacked lime is added to a water, it will react with any carbon dioxide present: The lime will react with carbonate hardness: Water Treatment and Purification SOFTENING: Chemistry of Soda Lime Process The product magnesium carbonate is soluble. To remove it, more lime is added. Also, magnesium non-carbonate hardness, such as magnesium sufate is removed. Water Treatment and Purification SOFTENING: Chemistry of Soda Lime Process Lime addition removes only magnesium hardness and calcium carbonate hardness. In eq. 5, magnesium is precipitated, however an equivalent amount of calcium is added. Now, the water contains the original calcium non-carbonate hardness and the calcium non-carbonate hardness produced in eq. 5. Soda ash is added to remove calcium non-carbonate hardness: Water Treatment and Purification SOFTENING: Chemistry of Soda Lime Process To precipitate CaCO3, it requires a pH of 9.5. And to precipitate Mg(OH2), it requires a pH of about 10.8. After softening, the water will have a high pH and contain the excess lime and the magnesium hydroxide and the calcium carbonate that did not precipitate. Recarbonization is used to stabilize the water which also reduces pH from 10.8 to 9.5 Further recarbonization, will bring the pH to about 8.5 and stabilize the calcium carbonate. Alternative Purification Methods Water Treatment and Purification BOILING Boiling water is one of the simplest and most effective methods to purify water. It involves heating water to its boiling point (100°C or 212°F) for a specific period to kill harmful microorganisms, including bacteria, viruses, and protozoa. How It Works: Boiling water kills most disease-causing microorganisms by denaturing their proteins and disrupting their cellular processes. Boiling for at least 1 minute (or 3 minutes at higher altitudes where water boils at a lower temperature) ensures the destruction of bacteria, viruses, and protozoan cysts such as Giardia and Cryptosporidium Water Treatment and Purification SOLAR DISINFECTION (SODIS) Solar disinfection (SODIS) uses sunlight to inactivate pathogens in water, making it a simple, low-cost method suitable for small-scale water treatment. How It Works: Water is placed in transparent plastic or glass bottles and exposed to direct sunlight for a minimum of 6 hours on sunny days (or 48 hours on cloudy days). The UV-A radiation from the sun and heat generated within the water help to kill or inactivate microorganisms such as bacteria, viruses, and protozoa. Water Treatment and Purification BIOSAND FILTERS A household-scale, slow-sand filtration system that uses a layer of sand to remove contaminants through a combination of biological, chemical, and physical processes. How It Works: The filter consists of layers of fine sand, gravel, and biological organisms that form a biological layer (biofilm) on the top layer of sand. As water flows slowly through the filter, microorganisms in the biofilm break down pathogens, while the sand physically traps particles, turbidity, and contaminants. The process removes bacteria, viruses, protozoa, and physical contaminants. Water Treatment and Purification CERAMIC FILTERS Ceramic filters are porous filtration devices made from natural materials, designed to remove bacteria, protozoa, and particulate matter from water through physical filtration. How It Works: Water is poured through the ceramic filter, which has tiny pores that physically block pathogens and particulates from passing through. Pathogens larger than the pore size (usually 0.1 to 0.5 microns) are trapped on the surface of the filter. Some ceramic filters are impregnated with silver or other antimicrobial agents to further inhibit bacterial growth. INTRODUCTION ‘ THANK YOU ‘