Water Treatment PDF

EXECUTIVE SHORT-TERM COURSES IN ENVIRONMENTAL STANDARDS TRACK B: PROFICIENCY CERTIFICATE IN ENVIRONMENTAL STANDARDS MODULE 2 DAY 12 SESSION 2 WATER TREATMENT Facilitated By: John Gushit...

EXECUTIVE SHORT-TERM COURSES IN ENVIRONMENTAL STANDARDS TRACK B: PROFICIENCY CERTIFICATE IN ENVIRONMENTAL STANDARDS MODULE 2 DAY 12 SESSION 2 WATER TREATMENT Facilitated By: John Gushit, PhD, MRSC, CEvn University of Jos, Nigeria [email protected] Dr. Maged Hamed, Ph.D, P.E. Regional Safeguard Coordinator And Co-TTL of SPESSE 24th July 2024 The Environment Global Practice of the West and Central Africa - SAWE4 March 2022 Course Content The Water Content and Percent of Fresh Water Major Water Properties Water in the Human Body Water Purification Requirements Turbidity Coagulations Flocculation Copyright © All rights reserved. Filtering No part of this publication may be reproduced, distributed, Disinfection or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical Water Sludge methods, without the prior written permission of the National Universities Commission of Nigeria and the World Bank, except in the case of brief quotations embodied in critical reviews and certain other noncommercial uses permitted by copyright law. For permission requests, write to the Executive Secretary, National Universities Commission, Abuja-Nigeria, Attention: Coordinator, Special Projects, and to the World Bank, Attention: Dr. Maged Hamed, Lead Environmental Specialist.  Percent of Fresh Water Most of the world's freshwater ≈2.4 million cubic miles (10 million km3) is contained in underground aquifers. The rest comes from: o Rainfall (after accounting for evaporation): 28,500 cubic miles (119,000 km3) o Man-made reservoirs: 1,200 cubic miles (5,000 km3) o Lakes: 21,830 cubic miles (91,000 km3) o Rivers: 509 cubic miles (2,120 km3) o But freshwater isn't evenly distributed throughout the world. More than half of the world's water supply is contained in just nine countries: the United States, Canada, Colombia, Brazil, the Democratic Republic of Congo, Russia, India, China and Indonesia https://science.howstuffworks.com/reverse-osmosis.htm World Business Council for Sustainable Development  Major Water Properties o Cohesion & Adhesion: Refers to the fact that water sticks o Density Anomaly: Unlike most substances, water to itself very easily. Adhesion means that water also sticks reaches its maximum density at 4 degrees Celsius very well to other substances. before becoming less dense as it freezes into ice. These properties are essential for capillary action, the This anomaly is crucial for aquatic life because movement of water against gravity in plants, and the ice floats on water, insulating the liquid below surface tension that allows certain insects to walk on and allowing organisms to survive in sub-zero water. temperatures. o Universal Solvent: Water is often referred to as the o High Specific Heat Capacity: Water has a high specific "universal solvent" because it has the ability to dissolve a heat capacity, meaning it can absorb and retain a wide range of substances. significant amount of heat energy without a large change in temperature. This property is crucial for various biological and chemical This property helps regulate Earth's processes, as it allows for the transport of nutrients and the temperature and allows organisms to maintain formation of solutions in living organisms. relatively stable internal temperatures. o High Heat of Vaporization: Water has a high heat of vaporization, which means it requires a substantial amount of heat energy to change from a liquid to a gas. This property is important for processes like sweating in animals and transpiration in plants, both of which contribute to cooling mechanisms. https://science.howstuffworks.com/environmental/earth/geophysics/h2o.ht Major Water Properties Water in the Human Body o Our bodies are about 60 percent water [source: Mayo Clinic]. Water regulates our body temperature, moves nutrients through our cells, keeps our mucous membranes moist and flushes waste from our bodies. o Our brains are 70 percent water and our blood is more than 80 percent water. o Most people sweat out about two cups of water per day (0.5 liters). Each day, we also lose a little more than a cup of water (237 ml) when we exhale it, and we eliminate about six cups (1.4 l) of it. o We also lose electrolytes -- minerals like sodium and potassium that regulate the body's fluids. https://science.howstuffworks.com/reverse-osmosis.htm Water Treatment Process Requirements o The water treatment process needed to deliver safe and wholesome water to customers includes; o Coagulation, flocculation, sedimentation, filtration, and disinfection o They make up the conventional surface water treatment plant. o These water treatment processes ensure that the water consumers receive is safe to drink and aesthetically pleasing. https://wateroperatorhq.com/water-treatment-process/  Water Systems Process Requirements o Water systems that operate a surface water treatment plant must meet the Surface Water Treatment Rule (SWTR). o The goal of the SWTR is to reduce illnesses related to pathogens in drinking water. o These pathogens include coliform, Giardia, and Cryptosporidium. o Meeting the SWTR requires a multi- barrier approach to treatment. o This means that the treatment plant must both remove and inactivate pathogens. ▪ The disinfection water treatment process inactivates them ▪ The water treatment process of coagulation, flocculation, sedimentation, and filtration remove the pathogens. o The small particles in water may consist of silt and clay, color bodies, precipitated iron or manganese oxides, and even bacteria and algae. https://wateroperatorhq.com/water-treatment-process/  Turbidit oy The small particles in water may consist of silt and clay, color bodies, precipitated iron or manganese oxides, and even bacteria and algae. o Together, these particles make the water appear cloudy. This cloudiness is known as turbidity. Visual turbidity is unpleasant to consumers. o Visual turbidity is also an indicator to operators and regulators that the water may still contain pathogens. o The SWTR therefore requires that turbidity be removed to very low levels. The process to remove that turbidity begins with coagulation https://wateroperatorhq.com/water-treatment-process/  Coagulation o Aluminum and iron salts have been used in the coagulation process since the beginning. These salts are still the most commonly used coagulants today. o Common coagulants used today include aluminum sulphate (alum), ferric sulphate, ferric chloride, and sodium aluminate. o Synthetic organic polymers were introduced in the 1960s. Depending on your system’s water quality, it may be necessary to employ a combination of two or more coagulants. o Aluminum and ferric coagulants put a large number of positive ions in the water. These ions begin to form flocs, which then attract the negatively charged particles in the water. o As the particles collide in the mixing area, they begin to stick together and form larger and larger flocs. o Temperature, pH, alkalinity, and the amount of turbidity in the water control the reactions of aluminum and ferric salts in the water. o The optimal pH range for coagulation is 6 to 7 when using alum, and 5.5 to 6.5 when using iron. https://wateroperatorhq.com/water-treatment-process/ Flocculation o Following the coagulant chemical addition and the rapid mix processes, the raw water will continue on to a flocculation basin. o The goal of the flocculation treatment process is to increase the size of the flocs in order to increase their ability to settle out. Inside the flocculation basin are typically large, very slow-moving paddle mixers that promote the interaction of particles. In order to enhance floc formation and increase the strength of the floc structure, some systems may add a flocculant to the water. Larger flocs will be able to settle out of the water more quickly further down the water treatment process chain https://wateroperatorhq.com/water-treatment-process/ Coagulation and Flocculation o Employed to transform colloidal solids into suspended solids o Typical coagulant added are: o Alum (AL2SO4), Ferrix ( Fe2SO4) o Flocks crated with Aluminum hydroxide https://images.search.yahoo.com/yhs/search?p=what+is+the+difference+between+coagulation+and+floccula t  Sedimentation or Clarifiers o The water continues on to the sedimentation basin, or clarifier, after the flocs have been formed. o The goal of this stage of the treatment process is to reduce the amount of solids in the water before the water is filtered in the next treatment step. o The large flocs will settle out of suspension via gravity. o Clarifiers can remove a very large percentage of the suspended materials in water. o In some plants, clarifiers remove as much as 90% of the suspended solids load. o Particles that do not settle will be removed by filtration in the next treatment step. o The particles that settle out are known as sludge and must be regularly removed from the clarification tank. o Clarifiers will normally be equipped with rakes to capture the sludge. Some plants may try to dewater the sludge to collect some of the raw water. o This captured water will be plumbed back to the head of the treatment plant in order to go through the whole treatment process again. https://wateroperatorhq.com/water-treatment-process/ Filtration o Filters are typically classified based on the type of media used. There are single-media, dual-media, and multi-media filters. o Single media filters are typically just sand and are not common in modern treatment plants (expected to remove particles from 25-50 microns in size). o Dual- media filters are the most common types of filters. Anthracite coal and sand are the typical filter materials in dual-media filters (expected to remove particles down to 10-25 microns). o Anthracite coal, sand, and garnet sand are the typical components in a multi-media filter. o Backwashing the filters is used to dislodge and remove particles trapped within the filter bed, to reduce head loss across the filter, and to keep the filter media clean. o The goal of the backwashing process is to remove the captured particulates without removing the filter media. o The flow of water is reversed through the filter during the backwash. o The reversed flow of water expands the media and washes the captured particulates off of the media. https://wateroperatorhq.com/water-treatment-process/  Disinfection o The SWTR requires both the filtration and disinfection of surface water sources. o The water must be disinfected now that it has been filtered. o The primary function of disinfection is to reduce the number of pathogens in the water. o Water can be thought to have a natural chlorine “demand”. This means that when you add chlorine to the water, things other than the pathogens you are targeting will react with and consume some of the chlorine. o This includes both inorganic material https://wateroperatorhq.com/water-treatment-process/ (iron, manganese, ammonia, etc.) and Disinfection Methods UV Radiation Excess Lime o UV radiation is another disinfection method that Lime when added to water increases its pH value and makes it extremely alkaline. This extreme alkalinity effectively destroys pathogenic bacteria and viruses disrupts growth and survival of bacteria in the treated by disrupting the biological processes and water. reproduction. o This disinfection method is preferred by most people Treatment with Ozone (O3) as it is relatively simple, produces no known toxic Ozone easily breaks down into normal oxygen, residuals, and requires short contact times. liberating nascent oxygen in the process. This nascent o This method is however not suitable for purifying oxygen is a very strong oxidizing agent that helps in water that has high levels of turbidity, color, eliminating harmful bacteria from the water. suspended solids or soluble organic matter Chlorination NB: Chlorine acts as an excellent disinfectant in the solid, o Ozonation and UV have their own set of unique liquid as well as the gaseous form. Chlorine when used challenges that must be taken into account to as a disinfectant penetrates the cell walls of bacteria operate effectively. and disrupts the enzymes which are imperative for the metabolic processes of living organisms. o The SWTR requires that systems maintain a *Liquid sodium hypochlorite, gaseous chlorine, or solid detectable residual in the distribution system. calcium hypochlorite. o Neither of these alternative disinfectants provide a *Chlorine is a strong oxidant. It is used to both disinfect residual.http://www.thewatertreatmentplants.com/disinfection.htm Flow Chart: Disinfection Water Treatment Potable Water Treatment Sludge o Potable water treatment plants also generate sludge, though this material poses minimal potential issues relative to sewage treatment plant sludge. o There are two main types of sludges produced: ▪ Flocculation sludge, which represents the precipitate from the addition of aluminum sulfate or other flocculating agent to turbid water (e.g., containing fine mineral particles in the form of clays and silts); and ▪ Filtration sludge, which represents the fines accumulating on sand filters in potable treatment plants. While these sludges do not typically represent a direct public health or environmental risk, they should be disposed of properly in a landfill. If dumped into a river or other water body, the silts can re-suspend and cause turbidity, potentially impact aquatic ecosystems and/or downstream users of the water. DISCUSSION: What is/are the advantage (s) of gaseous chlorine over solid chlorine in water treatment? Thank you for your Patience and Attention Any Questions?