Environmental Engineering I−61350

An-Najah National University College of Engineering Environmental Engineering I−61350 Chapter 8 Introduction To Treatment Systems and Processes Dr. Sameer Shadeed Dr. Sameer Shadeed

Why Treat Water and Wastewater? • Reasons for treating: • Protect public health • Protect surface water quality • Meet legal requirements Dr. Sameer Shadeed

Introduction to Water Treatment • Water treatment in a typical water treatment plant is shown in the figure • Based on the characteristics of the raw water, this treatment process may vary considerably from place to place • As water is pumped from the source (a well, spring, river, or lake) it is screened to remove debris • Then, at the water plant, various characteristics of the raw water are tested Dr. Sameer Shadeed

Introduction to Water Treatment • The water may be pre-chlorinated to kill microorganisms, control odors and taste, and aid in coagulation and settling • The water may also be aerated, which removes carbon dioxide (CO2) and raises pH, oxidizes iron (Fe) and manganese (Mn), removes hydrogen sulfide (H2S), and removes organic contaminants • Potassium permanganate (KMnO4) may be added to the water in the collection tray of the aerator in order to remove iron and manganese from the water • Ozone may be added to the water to treat iron and manganese, remove algae, neutralize hydrogen sulfide (H2S), and aid in flocculation • Many of these are dependent upon the plant and the amount of water being distributed daily Dr. Sameer Shadeed

Introduction to Water Treatment • In most cases, the water then enters a flash mix chamber. Here, various chemicals are added and are mixed into the water • Coagulants cause fine particles to clump together into larger particles • Alkali are added to adjust the pH as well as to oxidize iron and manganese. Hexametaphosphate may be added to prevent corrosion of pipes • After flowing out of the flash mix chamber, the water goes through a chamber which causes coagulation and flocculation to occur • Here, the fine particles of contaminants gather together into large clumps called floc • When the water flows into the sedimentation basin, some of the floc settles out of the water and is removed Dr. Sameer Shadeed

Introduction to Water Treatment • Next, the water is passed through filters which remove particles too small to settle out in the sedimentation basin • Finally, chlorine is added to the water. The water may also be fluoridated to reduce tooth decay in the consumers • The water is left in the clear well for a period of time to allow the chlorine to kill bacteria in the water and to oxidize hydrogen sulfide • The water is now treated and ready to be distributed Dr. Sameer Shadeed

Water Filters • There are a number of methods of water filtration, each with varying degrees of effectiveness, and varying costs • The general purpose of filtering water is to improve the water's hygiene and aesthetic qualities • Some of the available water filters are Activated Carbon (AC) Water Filters, Ultraviolet (UV) Water Filters, Water Distillation (Water Distillers), Sand Filters and Reverse Osmosis • These types are described in the following slides Dr. Sameer Shadeed

Water Filters • Activated Carbon (AC) Water Filters are an established technology that work through absorption of the problematic compounds, primarily to remove taste and odor but systems will also remove some harmful contaminants. AC is a highly porous material with a very large surface area. Chemical pollutants are attracted to and held by the AC's surface. These water filters are best suited for the removal of organic compounds • Ultraviolet (UV) Water Filters are able to kill the majority of bacteria and viruses in the water which passes through them. However, they won't remove chemical pollutants from the water Dr. Sameer Shadeed

Water Filters • Water Distillation (Water Distillers) involves heating the water to boiling point and condensing the steam. Pollutants with a boiling point near that of water are hard to remove, but generally the distilled water is of a very high quality. The major drawback to this method is that it requires a large amount of energy. Some people will also complain that the distilled water tastes flat • Sand Based Water Filters have been used for over 100 years to treat wastewater. They are generally used on a larger scale to treat a water supply for a whole community, and will be custom made. Most units require a constant flow of water to work correctly • Reverse Osmosis: In water filter terms, reverse osmosis (or hyper-filtration) is the process of filtering water under pressure through a semi-permeable membrane, allowing water to pass through but rejecting other particles such as bacteria, toxins, salts, and anything bigger than around 150 Daltons Dr. Sameer Shadeed

Introduction to Wastewater Treatment • Wastewater (sewage) treatment is considered as a water use because it is so interconnected with the other uses of water • Much of the water used by homes, industries, and businesses must be treated before it is released back to the environment • Nature has an amazing ability to cope with small amounts of water wastes and pollutions, but it would be inundated if we didn't treat the billions of gallons of wastewater and sewage produced every day before releasing it back to the environment • Treatment plants reduce pollutants in wastewater to a level nature can handle Dr. Sameer Shadeed

Introduction to Wastewater Treatment (What Is Wastewater?) • Wastewater is used water which includes substances such as human waste, food scraps, oils, soaps and chemicals • In homes, this includes water from sinks, showers, bathtubs, toilets, washing machines and dishwashers • Businesses and industries also contribute their share of used water that must be cleaned • Wastewater also includes storm runoff. Although some people assume that the rain that runs down the street during a storm is fairly clean, it isn't. Harmful substances that wash off roads, parking lots, and rooftops can harm our rivers and lakes Dr. Sameer Shadeed

Introduction to Wastewater Treatment (Why Treat Wastewater?) • The major aim of wastewater treatment is to remove as much of the suspended solids as possible before the remaining water, called effluent, is discharged back to the environment • As solid material decays, it uses up oxygen, which is needed by the plants and animals living in the water • There are a lot of good reasons why keeping our water clean is an important priority: • Fisheries • Wildlife Habitats • Recreation and Quality of Life • Health Concerns Dr. Sameer Shadeed

Introduction to Wastewater Treatment (Why Treat Wastewater?) • Fisheries:Clean water is critical to plants and animals that live in water. This is important to the fishing industry, sport fishing enthusiasts, and future generations • Wildlife Habitats:Our rivers and ocean waters teem with life that depends on shoreline, beaches and marshes. They are critical habitats for hundreds of species of fish and other aquatic life. Migratory water birds use the areas for resting and feeding • Recreation and Quality of Life: Water is a great playground for us all. The scenic and recreational values of our waters are reasons many people choose to live where they do. Visitors are drawn to water activities such as swimming, fishing, boating and picnicking • Health Concerns: If it is not properly cleaned, water can carry disease. Since we live, work and play so close to water, harmful bacteria have to be removed to make water safe Dr. Sameer Shadeed

Introduction to Wastewater Treatment (In the Treatment Plant) • In the treatment plant there are many steps involved in treating wastewater • In the figure is a quick overview of the possible steps involved • The general principle in wastewater treatment is to remove pollutants from the water by getting them either to settle or to float, and then removing this material • Some pollutants are easily removable. Others must be converted to a settleable form before they can be removed Dr. Sameer Shadeed

Introduction to Wastewater Treatment (In the Treatment Plant) • Treatment facilities are designed in stages. Each stage either removes particles from the wastewater or changes dissolved and suspended material to a form that can be removed • A modern wastewater treatment plant may include the following stages: • Influent • Primary treatment • Secondary treatment • Tertiary treatment • Disinfection and effluent discharge Dr. Sameer Shadeed

Introduction to Wastewater Treatment (In the Treatment Plant) • Influent: Is the raw material that has been collected and conveyed to the plant for treatment. It includes all the water and debris that entered the collection system • Primary Treatment: To prevent damage to pumps and clogging of pipes, raw wastewater passes through mechanically raked bar screens to remove large debris, such as rags, plastics, sticks, and cans. Smaller inorganic material, such as sand and gravel, is removed by a grit removal system. The lighter organic solids remain suspended in the water and flow into large tanks, called primary clarifiers. Here, the heavier organic solids settle by gravity. These settled solids, called primary sludge, are removed along with floating scum and grease and pumped to anaerobic digesters for further treatment. Primary treatment removes about 60 percent of suspended solids from wastewater Dr. Sameer Shadeed

Introduction to Wastewater Treatment (In the Treatment Plant) • Secondary Treatment: The primary effluent is then transferred to the biological or secondary stage. Here, the wastewater is mixed with a controlled population of bacteria and an sufficient supply of oxygen. The microorganisms digest the fine suspended and soluble organic materials, thereby removing them from the wastewater. The effluent is then transferred to secondary clarifiers, where the biological solids are settled by gravity. As with the primary clarifier, these solids are pumped to anaerobic digesters, and the clear secondary effluent may flow directly to the receiving environment or to a disinfection facility prior to release. Secondary treatment removes more than 90 percent of suspended solids. There are several variations of secondary treatment, including: • Activated sludge, trickling filtration, rotating biological contactors (RBC), lagoons and ponds Dr. Sameer Shadeed

Introduction to Wastewater Treatment (In the Treatment Plant) • Tertiary Treatment: Tertiary, or advanced, wastewater treatment is the term applied to additional treatment that is needed to remove suspended and dissolved substances remaining after conventional secondary treatment. This may be accomplished using a variety of physical, chemical, or biological treatment processes to remove the targeted pollutants. Advanced treatment may be used to remove such things as color, metals, organic chemicals, and nutrients such as phosphorus and nitrogen • Disinfection: Before the final effluent is released into the receiving waters, it may be disinfected to reduce the disease-causing microorganisms that remain in it. The most common processes use chlorine gas or a chlorine-based disinfectant such as sodium hypochlorite. To avoid excess chlorine escaping to the environment, the effluent may be dechlorinated prior to discharge. Other disinfection options include untraviolet light and ozone Dr. Sameer Shadeed

Al-Beireh WWTP Dr. Sameer Shadeed

Disinfection • This is the water that came out of the end of the chlorine contact tank. Very clear! This water is approved for recreation, meaning you could swim in it Dr. Sameer Shadeed

Introduction to Wastewater Treatment (Close Up) • That was a quick overview of the wastewater treatment process and what happens to sewage as it goes through the plant step by step • You will get into greater details in later course (Environmental Engineering III) so that you will understand each step of the process, why it is done and how to make sure each step is being done efficiently Dr. Sameer Shadeed

Environmental Engineering I−61350