Water Pollution Module 3 PDF

Module 3 ◼ Water pollution Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 1  The Importance of Water ◼ All living things need water ◼ Composes majority of the body of organisms ◼ Habitat for many organis...

Module 3 ◼ Water pollution Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 1  The Importance of Water ◼ All living things need water ◼ Composes majority of the body of organisms ◼ Habitat for many organisms ◼ Helps regulate climate ◼ Shapes earth’s surface ◼ Dilutes & degrades wastes Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 2  Use of water ◼ Uses of Freshwater Water resources are used in various fields such as agricultural, industrial, domestic, recreational, and environmental activities. Most of the uses require fresh water. ◼ However, around 97 percent of the water on the earth is saltwater and only three percent is freshwater. About two-thirds of the available freshwater is frozen in glaciers and polar ice caps. The remaining freshwater is found underground and a negligible portion of it is present on the ground or in the air.The following are detailed views on how water is used in different sectors. Water footprint Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 3  Agricultural Use ◼ Agriculture accounts for about 69 per cent of all water consumption especially in agricultural economies like India. Agriculture thereby becomes the largest consumer of the Earth’s available freshwater. By 2050, the global water demand for agriculture is estimated to increase by an additional 19% due to irrigation needs. Increasing irrigation needs are likely to put immense pressure on water storage. It is still not concluded whether further expansion of irrigation and additional water withdrawals from rivers and groundwater is possible in the future. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 4  Industrial Use ◼ Water is the lifesaver of the industry. It is used for various purposes such as a raw material coolant, a solvent, a transport agent, and as a source of energy. Manufacturing industries are considered to have a considerable share of the total industrial water consumption. Besides, paper and allied products, chemicals, and primary metals are major industrial users of water. Worldwide, the industry consumes around 19 percent of total water consumption. In industrialized countries, the industries use more than half of the water available for human use. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 5  Domestic Use ◼ Itincludes usages like drinking, cleaning, personal hygiene, garden care, cooking, washing of clothes, dishes, vehicles, etc. Since the end of World War II, there has been a trend of people migrating out of the country to the ever-expanding cities. This trend has an important role in our water resources.The government and communities are in a need to provide large water-supply systems to deliver water to new growing populations and industries. Comparing all water consumption in the world, domestic uses about 12 percent of the total water consumed. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 6  Use for Hydropower ◼ Electricity generated from water is called hydropower. Hydropower is one of the highly renewable sources of electricity in the world. It accounts for around 16 percent of the total electricity generated globally. There are numerous opportunities for hydropower development around the world.At present, the leading hydropower generating countries are China, the US, Brazil, Canada, India, and Russia. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 7  Use for Navigation and Recreation ◼ Navigable waterways are defined as watercourses that can be used to transport interstate or foreign commerce. Moving of agricultural and commercial goods on the water is done on a large scale around various parts of the world. Water is also used for recreational purposes like boating, swimming, and sporting activities. These usages affect the quality of water and pollute it. The highest priority should be given to public health and drinking water quality while permitting such activities in reservoirs, lakes, and rivers. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 8  Water on Earth ◼ About 97% Earth’s water is salty–less than 1% of the planet’s water is available fresh H2O ◼ Fresh water is distributed unevenly ◼ 2025: 1/3 human population will live in areas lacking fresh water Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 9  Types of water resources ◼ Marine water or saline water ◼ Surface water ◼ Groundwater Fresh water Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 10  Water, water, everywhere? (NOT) Comparison of population sizes and shares of the world’s freshwater among the continents. (Only 7 countries account for 60% of global water availability) Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 11  Water Wars Many countries in the Middle East, which has one of the world’s highest population growth rates, face water shortages. Desalinization Rainwater Tanushree Bhattacharya. CEE101 harvesting 2/16/2024 module 3, BIT Mesra 12 The Hydrologic Cycle Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 13  Surface Water ◼ Streams, rivers, lakes, ponds, reservoirs, wetlands ◼ Runoff replenishes surface water ◼ Watershed (A watershed is an area of land that drains or “sheds” A watershed is an area of land that drains water into a specific all the streams and rainfall to a common outlet such as the outflow of a reservoir, waterbody. mouth of a bay, or any point along a stream Tanushree Bhattacharya. channel. CEE101 2/16/2024 module 3, BIT Mesra 14  Groundwater ◼ Supply of fresh water found under Earth’s surface--recharged when water at surface infiltrates into the ground ◼ Stored in under ground aquifers ◼ Discharged into rivers, springs, etc… Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 15 Infiltration - Process of water percolating through the soil and into cracks and permeable rocks. Zone of Aeration - Upper soil layers that hold both air and water. Zone of Saturation Lower soil layers where all spaces are filled with water. Water Table - Tanushree Bhattacharya. CEE101 Top of zone of 2/16/2024 module 3, BIT Mesra saturation 16  Precipitation Unconfined Aquifer Recharge Area Flowing Evaporation and transpiration Confined artesian well Recharge Area Evaporation Infiltration Runoff Well requiring a pump Unconfined aquifer Water table Less permeable material Confined aquifer such as clay Confining permeable rock layer Recharge Zone - Area where water infiltrates into an aquifer. -Recharge rate is often very slow. -Presently, groundwater is being removed 2/16/2024 faster than it can be replenished. Tanushree Bhattacharya. CEE101 module 3, BIT Mesra 17 ◼ Aquifers - Porous layers of sand, gravel, or rock lying below the water table. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 18  Water Resource Problems ◼ Too much water ◼ Too little water ◼ Poor-quality water Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 19  Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 20 According to the Water (Prevention and Control of Pollution) Act, 1974, ― ◼ water pollution means such contamination of water or such alteration of the physical, chemical or biological properties of water or such discharge of any sewage or trade effluent or of any other liquid, gaseous or solid substance into water (whether directly or indirectly) as may or is likely to, create a nuisance or render such water harmful or injurious to public health or safety or to domestic, commercial, industrial, agricultural or other legitimate uses, or the life and health of animals or plants or of aquatic organisms.  Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 22  SOURCES OF WATER POLLUTION 1, Domestic wastes 2. Industrial wastes 3. Agricultural wastes, insecticides and pesticides 4. Radioactive wastes.  Domestic source ◼ Domestic wastewater contains a great variety of pollutants, such as nutrients, oil and grease, detergents, biowastes, household chemicals, heavy metals, bathing and kitchen waste, salts, pathogens, medicinal constituents, and soluble and particulate organic matter. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 24  Causes.. ◼ Growing Population ◼ Every year we add millions of people to the world population and our country is no exception. The earth is now overcrowded and consumption habit of the people is on the rise. The growth of population gave rise to increase in wants and demands of mankind and has succeeded in creating acute problem of water pollution. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 25 ◼ Industrialization ◼ Rapid industrialization is another cause of worry as far as water pollution is concerned. Immediately after the independence, major steps were taken in our country in its stride for development in order to give its economy a big push. ◼ Industrialization along with development brought with it a danger to the human civilization- the problem of environmental pollution ◼ Urbanization ◼ big cities also developed just near the water courses particularly besides the big rivers subsequently attracted the establishment of industrial and commercial basis in and around the cities. ◼ Since many towns and cities lack a proper sewerage system, the condition worsened further. ◼ Nature of Modern Technology ◼ The nature of productive technology in recent years has been largely responsible for the generation of synthetic and non biodegradable substances such as plastics, chemical nitrogen fertilizers, synthetic detergents, synthetic fibres, petrochemical and other environmentally injurious industries and ―disposable culture. ◼ Modern Agricultural Practices ◼ Fertilizers like phosphates and nitrates cause widespread damage when applied carelessly to crops. The fertilizers can be transmitted to groundwater by leaching and to surface waters by natural drainage and storm run-off. ◼ In addition to fertilizers various kinds of pesticides and insecticide also applied. Almost all the pesticides those are used are toxic to human and animals ◼  Radioactive wastes ◼ Natural sources and man made sources like, atomic explosions and nuclear fall out. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 30  Point source and non point source Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 31  Changes in Surface Runoff ◼ Prior to 1970 about 10% of stormwater became runoff ◼ Now 55% of stormwater is transported as runoff as development exceeds 75% of the permeable soil area Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 32  Stormwater Runoff (greatest contributor to nonpoint source pollution) contains: ◼ Nutrients* ◼ Metals* ◼ Suspended solids* ◼ Pesticides ◼ Hydrocarbons ◼ Microorganisms Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 33  Types of water pollution ◼ Types of water pollution ◼ Surface water:- Water resources like huge oceans, lakes, and rivers etc. are called surface waters. Contaminants such as chemicals, nutrients, and heavy metals are carried from farms, factories, and cities into streams and rivers and then to seas and oceans. Our seas are also sometimes spoiled by oil spills. ◼ Marine pollution: Marine pollution is a combination of chemicals and trash, most of which comes from land sources and is washed or blown into the ocean. This pollution results in damage to the environment, to the health of all organisms, and to economic structures worldwide. ◼ Ground water:- Water stored underground in aquifers is known as groundwater. Groundwater gets polluted when contaminants (pesticides, fertilizers) or waste leached from landfills and septic systems make their way into an aquifer, rendering it unsafe for human use. It is virtually impossible to remove contaminants from groundwater. Groundwater can also spread contamination into streams, lakes, and oceans. ◼ Themal Pollution: ◼ Thermal pollution is defined as a sudden increase or decrease in the temperature of a natural body of water, which may be an ocean, lake, river, or pond, by human influence., thermal pollution is when an industry or other human-made organization takes water from a natural source and cools or heats it before eventually ejecting it back into the natural resource, which changes the oxygen levels, disastrously affecting local ecosystems and communities. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 34  Major type of water pollutants Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 35  Classification of pollutants Emerging water pollutants These pollutants include a variety of compounds such as antibiotics, drugs, steroids, endocrine disruptors, hormones, industrial additives, chemicals, and also microbeads and microplastics. Emerging pollutants are chemicals and compounds that have recently been identified as dangerous to the environment, and consequently to the health of human beings. Precisely, they have been labeled “emerging” because of the rising level of concern linked to them. In addition, many of these emerging pollutants have not been regulated under national or international legislation, hence posing a greater risk to our livelihood. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 36 Concept of water quality According to UNEP / WHO 1996 “Water quality” is a term used here to express the suitability of water to sustain various uses or processes. Any use will have certain requirements for the physical, chemical or biological characteristics of water, for example, if the water is for drinking purpose then contaminants should not be present, as well as the water should be acceptable, that is devoid of any colour or objectionable odour and taste. Water quality plays a pivotal role in public health, habitat protection, agriculture, and industry. Water requirements have emerged over time for drinking, hygiene, fisheries, irrigation, livestock, and industries, cooling in fossil fuel power plants, nuclear power plants, hydropower generation, and recreational activities. Drinking water supplies and specialized industrial manufacturers exert the most sophisticated demands on water qualitatively but largest demands for water quantity, such as for agricultural irrigation and industrial cooling, require the least in terms of water quality. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 37  Water quality parameters that imparts several problems in industrial water use. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 38  Type of Pollutants Oxygen-Demanding Substances ◼Dissolved oxygen is a key element in water quality that is necessary to support aquatic life. ◼A demand is placed on the natural supply of dissolved oxygen by many pollutants in wastewater. This is called biochemical oxygen demand, or BOD, ◼ Organic matter and ammonia are “oxygen- demanding” substances. Oxygen-demanding substances are contributed by domestic sewage and agricultural and industrial wastes of both plant and animal origin, such as those from food processing, paper mills, tanning, and other manufacturing processes. ◼These substances are usually destroyed or converted to other compounds by bacteria if there is sufficient oxygen present in the water, but the dissolved oxygen needed to sustain fish life is used up in this break down process. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 39  Dissolved oxygen ◼ The oxygen dissolves by diffusion from the surrounding air; aeration of water that has tumbled over falls and rapids; and as a waste product of photosynthesis. As dissolved oxygen levels in water drop below 5.0 mg/l, aquatic life is put under stress. How Dissolved Oxygen Affects Water Supplies A high DO level in a community water supply is good because it makes drinking water taste better. However, high DO levels speed up corrosion in water pipes. For this reason, industries use water with the least possible amount of dissolved oxygen. Water used in very low pressure boilers have no more than 2.0 ppm of DO, but most boiler plant operators try to keep oxygen levels to 0.007 ppm or less. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 40 Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. BOD 5 test. CBOD NBOD COD Chemical oxygen demand (COD) is defined as “a measure of the oxygen equivalent of the organic matter content of a sample that is susceptible to oxidation by a strong chemical oxidant.* ” Trivalent manganese (Mn III) is a strong, non- carcinogenic chemical oxidant that changes quantitatively from purple to faint pink when it reacts with organic matter. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 41  Oxygen sag curve Point source Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 42  Pathogens ◼ Infectious micro-organisms, or pathogens, may be carried into surface and groundwater by sewage from cities and institutions, by certain kinds of industrial wastes, such as tanning and meat packing plants, and by the contamination of storm runoff with animal wastes from pets, livestock and wild animals, such as geese or deer. ◼ Humans may meet these pathogens either by drinking contaminated water or through swimming, fishing, or other contact activities. ◼ Modern disinfection techniques have greatly reduced the danger of waterborne disease. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 43  Nutrients ◼ Carbon, nitrogen, and phosphorus are essential to living organisms and are the chief nutrients present in natural water. Large amounts of these nutrients are also present in sewage, certain industrial wastes, and drainage from fertilized land. ◼ Conventional secondary biological treatment processes do not remove the phosphorus and nitrogen to any substantial extent -- in fact, they may convert the organic forms of these substances into mineral form, making them more usable by plant life. ◼ When an excess of these nutrients overstimulates the growth of water plants, the result causes excessive growth of algae. Uncontrolled algae growth blocks out sunlight and chokes aquatic plants and animals by depleting dissolved oxygen in the water at night. ◼ The release of nutrients in quantities that exceed the affected waterbody’s ability to assimilate them results in a condition called eutrophication.  Eutrophication Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 46 ◼ Causes of Eutrophication ◼ The availability of nutrients such as nitrogen and phosphorus limits the growth of plant life in an ecosystem. When water bodies are overly enriched with these nutrients, the growth of algae, plankton, and other simple plant life is favoured over the growth of more complex plant life. ◼ How do Water Bodies Become Overly Enriched? ◼ Phosphorus is considered one of the primary limiting factors for the growth of plant life in freshwater ecosystems. Several sources also claim that the availability of nitrogen is an important limiting factor for the growth of algae. ◼ Phosphates tend to stick to the soil and are transported along with it. Therefore, soil erosion is a major contributor to the phosphorus enrichment of water bodies. Some other phosphorus-rich sources that enrich water bodies with the nutrient include: ◼ Fertilizers ◼ Untreated sewage ◼ Detergents containing phosphorus ◼ Industrial discharge of waste. ◼ Among these sources, the primary contributors to eutrophication include agriculture and industrial wastes. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 47 ◼ What Happens to the Huge Biomass of Algae in Eutrophic Waters? ◼ The excessive growth of algae in eutrophic waters is accompanied by the generation of a large biomass of dead algae. These dead algae sink to the bottom of the water body where they are broken down by bacteria, which consume oxygen in the process. ◼ The overconsumption of oxygen leads to hypoxic conditions (conditions in which the availability of oxygen is low) in the water. The hypoxic conditions at the lower levels of the water body lead to the suffocation and eventual death of larger life forms such as fish. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 48 ◼ Effects of Eutrophication ◼ Primarily, the adverse effects of eutrophication on aquatic bodies include a decrease in biodiversity, increase in toxicity of the water body, and change in species dominance. Some other important effects of this process are listed below. ◼ Phytoplanktons grow much faster in such situations. These phytoplankton species are toxic and are inedible. ◼ Gelatinous zooplankton blooms fast in these waters. ◼ Increased biomass of epiphytic and benthic algae can be observed in eutrophic waters. ◼ Significant changes arise in the species composition of macrophytes and the biomass. ◼ The water loses its transparency and develops a bad smell and colour. The treatment of this water becomes difficult. ◼ Depletion of dissolved oxygen in the water body. ◼ Frequent fish kill incidents occur and many desirable fish species are removed from the water body. ◼ The populations of shellfish and harvestable fish are lowered. ◼ The aesthetic value of the water body diminishes significantly. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 49 Ecological Effects of Eutrophication Natural standing waters range from ultra oligotrophic to eutrophic with progressive increase in productivity and related parameters. In addition to such general changes, eutrophication also affects the vertical structure of lakes with further implications for the biology of freshwater organisms. The transition from eutrophic to hypertrophic status is usually the result of human activities, and ultimately affects the whole ecological balance of the freshwater system. Decrease in Biodiversity When an aquatic ecosystem is enriched with nutrients by either natural or artificial means, the conditions become extremely beneficial to primary producers. Commonly, algae and other similar species utilize these nutrients and a huge increase in their population (algal bloom) is observed. These algal blooms hinder the flow of sunlight to the bottom of the aquatic body and also cause wide swings in the dissolved oxygen levels in the water. When the dissolved oxygen in the water reduces to an amount below the hypoxic level, many marine animals suffocate and die. This reduces the effective biodiversity of the water body. Increase in Water Toxicity A few algae are toxic to many plants and animals. When these algae bloom in eutrophic waters, they release neurotoxins and hepatotoxins. These toxins can also move up the food chain via shellfish or other marine animals and lead to the death of many animals. Toxic algal blooms can also be harmful to humans and are the root cause of many cases of neurotoxic, paralytic, and diarrhoetic shellfish poisoning. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 50 ◼ Invasion of New Species ◼ A limiting nutrient corresponding to a water body can be made abundant by the eutrophication process, leading to a shift in the species composition of the aquatic body and the ecosystem surrounding it. ◼ If a nitrogen deficient water body is suddenly enriched with it, many other competitive species might relocate to the water body and out-compete the original inhabitants of the ecosystem. One such example of a new species invading eutrophic conditions is the common carp, which has adapted to these conditions. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 51  Inorganic and Synthetic Organic Chemicals ◼ A vast array of chemicals are included in this category. Examples include detergents, household cleaning aids, heavy metals, pharmaceuticals, synthetic organic pesticides and herbicides, industrial chemicals, and the wastes from their manufacture. ◼ Many of these substances are toxic to fish and aquatic life and many are harmful to humans. Some are known to be highly poisonous at very low concentrations. Others can cause taste and odor problems, and many are not effectively removed by conventional wastewater treatment.  Thermal ◼ Thermal pollution is any deviation from the natural temperature in a habitat and can range from elevated temperatures associated with industrial cooling activities to discharges of cold water into streams below large impoundments. ◼ Heat reduces the capacity of water to retain oxygen. ◼ In some areas, water used for cooling is discharged to streams at elevated temperatures from power plants and industries. Even discharges from wastewater treatment plants and storm water retention ponds affected by summer heat can be released at temperatures above that of the receiving water and elevate the stream temperature. ◼ Unchecked discharges of waste heat can seriously alter the ecology of a lake, a stream, or estuary. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 53  Drinking water standards ◼ IS 10500 : 2012, amended in 2015. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 54  Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 55  Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 56  Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 57  Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 58  Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 59  Water Health Effects Other Effects Parameters Temperature Regulates biochemical and Affects photosynthesis, dissolved metabolic reactions. oxygen. pH Gastrointestinal irritation. Affects enzyme kinetics; corrosive; affects aquatic life. TDS Affects kidney and heart Corrosive to water-supply systems; functioning, laxative or constipation causes hardness. effects, gastrointestinal irritation. Hardness Skin irritation; worsens some health Poor lather with detergent; cloth conditions (cancer, diabetes, etc.). quality deterioration. Mg Deficiency- hypertension, cardiac Poor lather with detergent; cloth and cardiovascular diseases, quality deterioration. diabetes mellitus, osteoporosis. Ca Deficiency- osteoporosis, Poor lather with detergent; cloth hypertension. quality deterioration. Cl- Laxative effects. Corrosive; deleterious effects on plants, can clog soil pores if it is in dissolved condition. NO3- Methemoglobinemia in infants. Algal bloom; adverse impacts on aquatic life. PO43- Digestive problems. Eutrophication. SO42- Laxative effects, gastrointestinal Acid rain; associated with acid mine irritation. drainage; corrosive. Na Hypertension, heart diseases, kidney Can impart salinity hazard in soil if it related problems. is used for irrigation purpose. Al Kidney disorders, neurological Prevents nutrient intake by roots; problems. interferes with gill functioning. Heavy metals Most of the heavy metals affect liver Most of the heavy metals affects soil and kidney functioning; ATPase microbial activity; deleterious impact inhibitor; degrades enzyme on plants; ROS production (stress). transport.Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 60 Biological Oxygen High BOD levels- hazardous. Affects water quality and effluent Demand biodegradability. Chemical Oxygen Correlated to ill effect on human Hypoxic water reduces cell Demand health (algal blooms, sea food functioning, death of aquatic contamination). organisms. Bacteria Causes dysentery (Salmonella), Some aquatic animals affected similar cholera (Vibrio), typhoid to human beings; indicates DO, BOD. (Salmonella). Protozoa Causes amoebiasis (Entamoeba Affects plant growth; causes illness in histolytica), giardiasis (Giardia various animals like horse, zebra, dog lamblia). etc. Virus Causes SARS (Coronavirus), Affects various animals, plants and hepatitis A, polio (Poliovirus), even bacteria. common cold. Algae Causes Desmodesmus infection; Algal bloom; disrupts photosynthesis produces toxic compounds (e.g.- in aquatic plants and phytoplankton; Anaebaena and Nostoc). affects water colour, odour and taste. Helminths Causes schistosomiasis Many animals are hosts to such (Schistosoma japonicum), helminths such as pig, sheep etc. cysticercosis (Cysticercus cellulosae). Pathogenic Mostly harmless; diarrhoea, Mostly harmless; Can contaminate indicators (e.g.- vomiting, abdominal cramps. young plants; Animals could act as its Escherichia coli) carrier. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 61 What is Water Quality index? To get a comprehensive picture of the overall quality of groundwater or surface water, the WQI is used. WQI is defined as a rating reflecting the composite influence of different water quality parameters on the overall quality of water. The Indian standard specified for drinking water (BIS, 1991) is used for the calculation of WQI.  WQI ◼ Water Quality Index (WQI) is considered as the most effective method of measuring water quality. A number of water quality parameters are included in a mathematical equation to rate water quality, determining the suitability of water for drinking ◼ The index was first developed by Horton in 1965 to measure water quality by using 10 most regularly used water parameters. ◼ The method was subsequently modified by different experts. These indices used water quality parameters which vary by number and types. ◼ The weights in each parameter are based on its respective standards, and the assigned weight indicates the parameter’s significance and impacts on the index.  Calculation ◼ A usual WQI method follows three steps which include (1) selection of parameters, (2) determination of quality function for each parameter, and (3) aggregation through mathematical equation The index provides a single number that represents overall water quality at a certain location and time based on some water parameters. The index enables comparison between different sampling sites. The single-value output of this index, derived from several parameters, provides important information about water quality that is easily interpretable, even by lay people Calculate wqi for the following dataset ◼ pH=6.61, TDS=70, TH=70 Bicarbonate 45 Chloride 4.9 Sulphate 1.5 Nitrate 261 Fluoride 1.43 Calcium 1.60 Magnesium 0.24 Iron 1.95 All units except pH is in mg/l Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 70  Water treatment Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 71 Indian Standards for Discharge of Sewage in Surface Waters Tolerance limit for Discharge of Characteristic of Sewage in Suface Water Sources the Effluent BOD5 30 mg/L COD 250 TSS 100 mg/L  Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 73  Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 74  Wastewater Treatment Scheme Disinfectant WW effluent WW influent Preliminary Primary Secondary Tertiary sludge Sludge Treatment and Disposal Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 75  Wastewater treatment processes: ◼ Preliminary treatment is a physical process that removes large contaminants. ◼ Primary treatment involves physical sedimentation of particulates. ◼ Secondary treatment involves physical and biological treatment to reduce organic load of wastewater. ◼ Tertiary or advanced treatments. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 76 Preliminary Treatment As wastewater enters a treatment facility, it typically flows through a step called preliminary treatment. A screen removes large floating objects, such as rags, cans, bottles and sticks that may clog pumps, small pipes, and down stream processes. Coarse screens remove large solids, rags, and debris from wastewater, and typically have openings of 6 mm (0.25 in) or larger. Typical opening sizes for fine screens are 1.5 to 6 mm (0.06 to 0.25 in). Very fine screens with openings of 0.2 to 1.5 mm (0.01 to 0.06 in) Screens are generally placed in a chamber or channel and inclined towards the flow of the wastewater. The inclined screen allows debris to be caught on the upstream surface of the screen, and allows access for manual or mechanical cleaning. Some plants use devices known as comminutors or barminutors which combine the functions of a screen and a grinder. These devices catch and then cut or shred the heavy solid and floating material. In the process, the pulverized matter remains in the wastewater flow to be removed later in a primary settling tank. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 77  Screens ◼ (a) Coarse Screen :- The spacings of bars are more than 40 mm center to center. ◼ (b) Medium Screen: The spacing are less than 40mm. ◼ (c) Fine Screen: The spacings vary from 1.5 mm to 6 mm. ◼ The screens may be fixed or movable. the inclination of the screen varies from 30° to 60°. The screens are placed at designed inclination in an oblong rectangular chamber. The ends of the chamber are tapered. It is constructed with brick masonry. ◼ The inner surfaces are plastered and finished with neat cement polish. A perforated rectangular channel is provided at the top of the screen for the collection of floating debrises. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 78  Velocity ◼ The velocity of flow ahead of and through the screen varies and affects its operation. ◼ Velocities of 0.6 to 1.2 mps through the open area for the peak flows have been used satisfactorily. ◼ Further, the velocity at low flows in the approach channel should not be less than 0.3 mps to avoid deposition of solids. STP STP  Grit Removal After the wastewater has been screened, it may flow into a grit chamber where sand, grit, cinders, and small stones settle to the bottom. Removing the grit and gravel that washes off streets or land during storms is very important, especially in cities with combined sewer systems. Large amounts of grit and sand entering a treatment plant can cause serious operating problems, such as excessive wear of pumps and other equipment, clogging of aeration devices, or taking up capacity in tanks that is needed for treatment. In some plants, another finer screen is placed after the grit chamber to remove any additional material that might damage equipment or interfere with later processes. The grit and screenings removed by these processes must be periodically collected and trucked to a landfill for disposal or are incinerated. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 82  Grit Chambers Grit chambers are like sedimentation tanks, designed to separate the intended heavier inorganic materials (specific gravity about 2.65) and to pass forward the lighter organic materials Raw O Effluent wastewater I U N T L L E SETTLING ZONE E T T Z O Z O Figure : Typical View of Grit Channel N SLUDGE ZONE N E E Types of Velocity Control Devices A sutro weir in a channel of rectangular cross section, with free fall downstream of the channel A parabolic shaped channel with a rectangular weir A rectangular shaped channel with a parshall flume at the end which would also help easy flow measurement  Design of Grit Chambers ◼ Settling Velocity  Primary treatment ◼ Primary Treatment The initial stage in the treatment of domestic wastewater is known as primary treatment. Coarse solids are removed from the wastewater in the primary stage of treatment. In some treatment plants, primary and secondary stages may be combined into one basic operation. At many wastewater treatment facilities, influent passes through preliminary treatment units before primary and secondary treatment begins. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 86  Primary sedimentation ◼Primary Sedimentation With the screening completed and the grit removed, wastewater still contains dissolved organic and inorganic constituents along with suspended solids. The suspended solids consist of minute particles of matter that can be removed from the wastewater with further treatment such as sedimentation or gravity settling, chemical coagulation, or filtration. Pollutants that are dissolved or are very fine and remain suspended in the wastewater are not removed effectively by gravity settling. ◼When the wastewater enters a sedimentation tank, it slows down, and the suspended solids gradually sink to the bottom. This mass of solids is called primary sludge. Various methods have been devised to remove primary sludge from the tanks. Newer plants have some type of mechanical equipment to remove the settled solids from sedimentation tanks. Some plants remove solids continuously while others do so at intervals. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 87  Sedimentation The objective of primary settling tank is to remove the large size suspended organic solids present in the wastewater whose specific gravity is more than 1. Factors affecting settling of particles Flow velocity Shape and size of particle Viscosity Figure: Typical view of primary settling tank  REMOVAL OF OIL & GREASE Present day oil separators are provided with inclined plates (plate settlers) which improve their performance considerably. Such separators are available from several vendors to whom the size and specific gravity of the oil globules desired to be removed and their performance efficiency need to be specified. Removal of free oil and grease from a wastewater stream reduces the potential for equipment problems to occur further downstream. There are three forms of oil encountered in wastewater treatment at a refinery. They are: Free Oil or floating oil is removed by either skimming the surface in the skim tank or by gravity separation in the API separator. Emulsified Oil is comprised of oil droplets in stable suspension within the wastewater. Removal requires chemical addition to lower the pH followed Figure: Oil & by addition of dissolved oxygen or nitrogen to Grease Trap for remove the emulsified oils as they break free from Intercepting Oil and the wastewater. Grease at the Dissolved Oil is a true molecular solution within the Source water and can only be removed with biological treatment.  Coagulation and flocculation They occur in successive steps intended to overcome the forces stabilizing the suspended particles, allowing particle collision and growth of floc. If step one is incomplete, the following step will be unsuccessful. COAGULATION The first step destabilizes the particle’s charges. Coagulants with charges opposite those of the suspended solids are added to the water to neutralize the negative charges on dispersed non-settlable solids such as clay and color-producing organic substances. Once the charge is neutralized, the small suspended particles are capable of sticking together. The slightly larger particles, formed through this process and called micro-flocs, are not visible to the naked eye. The water surrounding the newly formed micro-flocs should be clear. If it is not, all the particles’ charges have not been neutralized, and coagulation has not been carried to completion. More coagulant may need to be added. A high-energy, rapid-mix to properly disperse the coagulant and promote particle collisions is needed to achieve good coagulation. Over-mixing does not affect coagulation, but insufficient mixing will leave this step incomplete. Coagulants should be added where sufficient mixing will occur. Proper contact time in the rapid-mix chamber is typically 1 to 3 or max 5 minutes. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 90  FLOCCULATION Following the first step of coagulation, a second process called flocculation occurs. Flocculation, a gentle mixing stage, increases the particle size from submicroscopic microfloc to visible suspended particles. The microflocs are brought into contact with each other through the process of slow mixing. Collisions of the microfloc particles cause them to bond to produce larger, visible flocs called pinflocs. The floc size continues to build through additional collisions and interaction with inorganic polymers formed by the coagulant or with organic polymers added. Macroflocs are formed. High molecular weight polymers, called coagulant aids, may be added during this step to help bridge, bind, and strengthen the floc, add weight, and increase settling rate. Once the floc has reached it optimum size and strength, the water is ready for the sedimentation process. Design contact times for flocculation range from 15 or 20 minutes to an hour or more. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 91 Flocs start to form during the neutralization step as particle collisions occur.... Sweep flocculation occurs when colloidal contaminants are entrained or swept down by the precipitates as they settle in the suspension. The optimal pH range for coagulation is 6 to 7 when using alum and 5.5 to 6.5 when using iron. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 92  Commonly used coagulant and flocculants The following natural products are used as flocculants: Chitosan. Isinglass. Moringa oleifera seeds (Horseradish Tree) Gelatin. Strychnos potatorum seeds (Nirmali nut tree) Guar gum. Alginates (brown seaweed extracts) Apart from these, polymers or polyelectrolytes originating from starches Tanushree Bhattacharya. CEE101 and alginates are also used 2/16/2024 module 3, BIT Mesra as flocculants. 93  Clarification Clarification is the removal of suspended solids and floc from chemically treated water, before its application to filters. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 94  Filtration –a part of tertiary treatment but used after primary treatment for municipal or industrial water supply What happens to water during filtration? The second step in a conventional water treatment system is filtration, which removes particulate matter from water by forcing the water to pass through porous media. The filtration system consists of filters with varying sizes of pores, and is often made up of sand, gravel and charcoal. The diameter of a grain of fine sand is approximately 0.1 millimetre, so only particles with diameters less than 0.1 millimetre would pass through the fine sand layer. Filtration would not be able to produce safe drinking water, if many contaminants are much smaller than 0.1 millimetre (such as viruses, which can be as small as 0.000001 millimetre in Tanushree Bhattacharya. CEE101 diameter). 2/16/2024 module 3, BIT Mesra 95 There are two basic types of sand filtration: Slow sand filtration and Rapid sand filtration Slow sand filtration is a biological process, because it uses bacteria to treat the water. The bacteria establish a community on the top layer of sand and clean the water as it passes through, by digesting the contaminants in the water. The layer of microbes is called a schumtzdecke (or biofilm), and requires cleaning every couple of months, when it gets too thick and the flow rate declines. After the schumtzdecke is removed, the bacteria must be allowed several days to reestablish a community before filtering can resume. Slow sand filtration systems have been used for many years; the first systems operated in London in the 19th century. However, slow sand filtration systems require large areas of land to operate, because the flow rate of the water is between 0.1 and 0.3 metrecube per hour. Due to the land area that is required and the down-time for cleaning, rapid sand filters, which were developed in the early 20th century, are much more prevalent today. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 96 Rapid sand filtration is a physical process that removes suspended solids from the water. Rapid sand filtration is much more common than slow flow sand filtration, because rapid sand filters have fairly high flow rates and require relatively little space to operate. In fact, during rapid sand filtration, the water flows at a rate up to 20 metrecube per hour. The filters are generally cleaned twice per day with backwashing filters and are put back into operation immediately. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 97  Equalization A well - mixed vessel with fluctuating input flow rates and / or concentration with fairly constant output flow rates and/or concentrations. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 98  Secondary Treatment After the wastewater has been through Primary Treatment processes, it flows into the next stage of treatment called secondary. Secondary treatment processes can remove up to 90 percent of the organic matter in wastewater by using biological treatment processes. The two most common conventional methods used to achieve secondary treatment are attached growth processes and suspended growth processes. If the BOD/COD ratio for untreated wastewater is 0.5 or greater, the waste is considered to be easily treatable by biological means. If the ratio is below about 0.3, either the waste may have some toxic components or acclimated micro- organisms may be required in its stabilization.. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 99  Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 100  F/M Ratio The term Food to Microorganism Ratio (F/M) is actually a measurement of the amount of incoming food ( Lbs of Influent CBOD) divided by the Lbs of Microorganisms in your system. To determine the amount of incoming food (F), you need to know the CBOD of the influent into your activated sludge(aeration) system. You also need to know the flow(MGD). So to calculate the amount of food we do the following calculation: F= Influent Flow (MGD) X Influent CBOD Concentration (mg/l) X 8.34 pounds/gallon waste water To determine the volume of microorganisms (M), you need to know the volume of your aeration system and you need to know the concentration of Volatile Solids in your aeration system (MLVSS) or Mixed Liquor Volatile Suspended Solids. M= Aeration System Volume (in Millions of Gallons) X MLVSS X 8.34 pounds/gallon waste water Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 101 Types of secondary treatment Attached Growth Processes In attached growth (or fixed film) processes, the microbial growth occurs on the surface of stone or plastic media. Wastewater passes over the media along with air to provide oxygen. Attached growth process units include trickling filters, biotowers, and rotating biological contactors. Attached growth processes are effective at removing biodegradable organic material from the wastewater. Suspended growth process In suspended growth processes, the microbial growth is suspended in an aerated water mixture where the air is pumped in, or the water is agitated sufficiently to allow oxygen transfer. Suspended growth process units include variations of activated sludge, oxidation ditches and sequencing batch reactors. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 102 A trickling filter is simply a bed of media (typically rocks or plastic) through which the wastewater passes. The media ranges from three to six feet deep and allows large numbers of microorganisms to attach and grow. Older treatment facilities typically used stones, rocks, or slag as the media bed material. New facilities may use beds made of plastic balls, interlocking sheets of corrugated plastic, or other types of synthetic media. This type of bed material often provides more surface area and a better environment for promoting and controlling biological treatment than rock. Bacteria, algae, fungi and other microorganisms grow and multiply, forming a microbial growth or slime layer (biomass) on the media. In the treatment process, the bacteria use oxygen from the air and consume most of the organic matter in the wastewater as food. As the wastewater passes down through the media, oxygen-demanding substances are consumed by the biomass and the water leaving the media is much cleaner. However, portions of the biomass also slough off the media and must settle out in a secondary treatment tank. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 103 Biotowers A biotower is used to reduce the BOD value of a liquid effluent. A biotower is an above-ground cylindrical tank or rectangular structure that contains plastic media with a high surface area, such as randomly filled polypropylene shapes or modular blocks of corrugated PVC. Effluent is pumped to the top of the tower and distributed over the surface of the media using rotating distributors, troughs, or nozzles and splash plates. The effluent trickles down over the media, which become coated with microbial films that consume the organic material. The treated liquid may be recycled over the biotower before the biological solids are settled out. Biotowers can be arranged in series with inter-stage settlement. Fan ventilation may be incorporated where the biomass must be highly aerobic, for example where nitrification is required. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 104  Rotating biological contactor The RBC process involves allowing the wastewater to come in contact with a biological medium in order to remove pollutants in the wastewater before discharge of the treated wastewater to the environment, usually a body of water (river, lake or ocean). A rotating biological contactor is a type of secondary treatment process. It consists of a series of closely spaced, parallel discs mounted on a rotating shaft which is supported just above the surface of the waste water. Microorganisms grow on the surface of the discs where biological degradation of the wastewater pollutants takes place. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 105  Suspended growth process Suspended Growth Processes Similar to the microbial processes in attached growth systems, suspended growth processes are designed to remove biodegradable organic material and organic nitrogen-containing material by converting ammonia nitrogen to nitrate unless additional treatment is provided. The suspended growth process speeds up the work of aerobic bacteria and other microorganisms that break down the organic matter in the sewage by providing a rich aerobic environment where the microorganisms suspended in the wastewater can work more efficiently. In the aeration tank, wastewater is vigorously mixed with air and microorganisms acclimated to the wastewater in a suspension for several hours. This allows the bacteria sequencing and other microorganisms to break down the organic matter in the wastewater. The microorganisms grow in number and the excess biomass is removed by settling before the effluent is discharged or treated further. Now activated with millions of additional aerobic bacteria, some of the biomass can be used again by returning it to an aeration tank for mixing with incoming wastewater. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 106  Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 107  Activated Sludge Process Activated Sludge Process - ASP Raw Effluent In Aeration Sedimentation Treated water out Sludge Recirculation Sludge withdrawal The activated sludge process, like most other techniques, has advantages and limitations. The units necessary for this treatment are relatively small, requiring less space than attached growth processes. In addition, when properly operated and maintained, the process is generally free of flies and odors. However, most activated sludge processes are more costly to operate than attached growth processes due to higher energy use to run the aeration system. The effectiveness of the activated sludge process can be impacted by elevated levels of toxic compounds in wastewater unless complex industrial chemicals are effectively controlled through an industrial pretreatment program. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 109 ASP  Upflow Anaerobic Sludge Blanket Reactor (UASB) The Up flow Anaerobic Sludge Blanket reactor (UASB) maintains a high concentration of biomass through formation of highly settleable microbial aggregates. The sewage flows upwards through a layer of sludge. The sludge in the UASB is tested for pH, volatile fatty acids (VFA), alkalinity, COD and SS. If the pH reduces while VFA increases, the sewage should not be allowed into the UASB until the pH and VFA stabilise. The reactor may need to be emptied completely once in five years, while any floating material (scum) accumulated inside the gas collector channels may have to be removed every two years to ensure free flow of gas. All V-notches must be cleaned in order to maintain the uniform withdrawal of UASB effluent coming out of each V-notch. The irregular flow from each V-notch results in the escape of more solids washout. Similarly, blocking of the V-notches of the effluent gutters will lead to uneven distribution of sewage in the reactor. Up – Flow Anaerobic Sludge Blanket Rector (UASB) Flow Anaerobic Sludge Blanket Rector (UASB) Flow Diagram Advantages UASB Requires less power than aerobic processes Biogas generated can be used as fuel or electricity. Disadvantages UASB alone does not treat the sewage to desirable limits, therefore downstream aerobic treatment is compulsory Requires very large space due to post treatment Recovery of biogas is not sufficient to produce substantial electricity in case of municipal  Description of Oxidation Ditch Oxidation ditch is an extended aeration activated sludge process. An oxidation ditch is a large holding tank in a continuous ditch with oval shape similar to that of a racetrack. The ditch is built on the surface of the ground and is lined with an impermeable lining. This allows the waste water to have plenty of exposure to the open air for the diffusion of oxygen. The liquid depth in the ditches is very shallow, 0.9 to 1.5 m, which helps to prevent anaerobic conditions from occurring at the bottom of the ditch. The oxidation ditch effluent is clarified in a secondary clarifier and the settled sludge is returned to maintain a desirable MLSS concentration. The MLSS concentration in the oxidation ditch generally ranges from 3,000 mg/ L to 5,000 mg/ L; however, this is dependent upon the surface area provided for sedimentation, the rate of sludge return, and the aeration process. Longer retention time within the ditch will allow for a greater amount of organic matter to be broken down by the aerobic bacteria. After treatment, the waste water is pumped to a secondary settling tank where the sludge and the water are allowed to separate. From there the effluent goes on to other treatment processes or disposal. The sludge that has accumulated on the bottom of the secondary settling tank is then removed and a portion of it is returned CEE101 Tanushree Bhattacharya. to the ditch to facilitate microbial activity in 2/16/2024 modulethe3,next BIT batch Mesraof sewage to be treated. 116 Lagoons A wastewater lagoon or treatment pond is a scientifically constructed pond, three to five feet deep, that allows sunlight, algae, bacteria, and oxygen to interact. Biological and physical treatment processes occur in the lagoon to improve water quality. The quality of water leaving the lagoon, when constructed and operated properly, is considered equivalent to the effluent from a conventional secondary treatment system. However, winters in cold climates have a significant impact on the effectiveness of lagoons, and winter storage is usually required. Lagoons have several advantages when used correctly. They can be used for secondary treatment or as a supplement to other processes. Treatment ponds require substantial land area and are predominantly used by smaller communities. Lagoons remove biodegradable organic material and some of the nitrogen from wastewater. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 117 Sequencing batch reactor (SBR) A sequencing batch reactor (SBR) is used in small package plants and also for centralized treatment of sewage. The SBR system consists of a single completely mixed reactor in which all the steps of the activated sludge process occurs. The reactor basin is filled within a short duration and then aerated for a certain period of time. After the aeration cycle is complete, the cells are allowed to settle for a duration of 0.5 h and effluent is decanted from the top of the unit which takes about 0.5 h. Decanting of supernatant is carried out by either fixed or floating decanter mechanism. When the decanting cycle is complete, the reactor is again filled with raw sewage and the process is repeated. An idle step occurs between the decant and the fill phases. The time of idle step varies based on the influent flow rate and the operating strategy. During this phase, a small amount of activated sludge is wasted from the bottom of the SBR basin. A large equalization basin is required in this process, since the influent flow must be contained while the reactor is in the aerating cycle. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 118  Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 119  The Use or Disposal of Wastewater Residuals and Biosolids When pollutants are removed from water, there is always something left over. It may be rags and sticks caught on the screens at the beginning of primary treatment. It may be the solids that settle to the bottom of sedimentation tanks. Whatever it is, there are always residuals that must be reused, burned, buried, or disposed of in some manner that does not harm the environment. Biosolids are processed wastewater solids (“sewage sludge”) that meet rigorous standards allowing safe reuse for beneficial purposes. Currently, more than half of the biosolids produced by municipal wastewater treatment systems is applied to land as a soil conditioner or fertilizer and the remaining solids are incinerated or landfilled. Ocean dumping of these solids is no longer allowed. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 120 Prior to utilization or disposal, biosolids are stabilized to control odors and reduce the number of disease-causing organisms. Sewage solids, or sludge, when separated from the wastewater, still contain around 98 percent water. They are usually thickened and may be dewatered to reduce the volume to be transported for final processing, disposal, or beneficial use. Dewatering processes include drying beds, belt filter presses, plate and frame presses, and centrifuges. To improve dewatering effectiveness, the solids can be pretreated with chemicals such as lime, ferric chloride, or polymers to produce larger particles which are easier to remove wastewater, still contain around 98 percent water. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 121  Incineration Incineration consists of burning the dried solids to reduce the organic residuals to an ash that can be disposed or reused. Incinerators often include heat recovery features. Undigested sludge solids have significant fuel value as a result of their high organic content. However, the water content must be greatly reduced by dewatering or drying to take advantage of the fuel potential of the biosolids. For this reason, pressure filtration dewatering equipment is used to obtain biosolids which are sufficiently dry to burn without continual reliance on auxiliary fuels. In some cities, biosolids are mixed with refuse or refuse derived fuel prior to burning. Generally, waste heat is recovered to provide the greatest amount of energy efficiency. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 122  Biosolids and its uses Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 123  Disinfection Untreated domestic wastewater contains microorganisms or pathogens that produce human diseases. Processes used to kill or deactivate these harmful organisms are called disinfection. Chlorine is the most widely used disinfectant but ozone and ultraviolet radiation are also frequently used for wastewater effluent disinfection. Chlorine Chlorine kills microorganisms by destroying cellular material. This chemical can be applied to wastewater as a gas, a liquid or in a solid form similar to swimming pool disinfection chemicals. However, any free (uncombined) chlorine remaining in the water, even at low concentrations, is highly toxic to beneficial aquatic life. Therefore, removal of even trace amounts of free chlorine by dechlorination is Tanushree Bhattacharya. CEE101 module 3, BIT Mesra often needed to protect fish and aquatic life. Due to emergency response and potential safety concerns, chlorine gas is used less frequently now than in the 2/16/2024 124 past.  Chlorination Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 125  Free chlorine and combined chlorine Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 126  Chlorine demand Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 127  Breakpoint Chlorination Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 128  Disadvantages of Chlorination The use of chlorine to disinfect water produces various disinfection byproducts, which have been classified mainly as halogenated and non- halogenated byproducts. These primary byproducts are trihalomethanes (THMs) and haloacetic acids. THMs are the byproducts of chlorination of water that contains natural organic matter. The most common THM compounds are dibromochloromethane (CHClBr2), bromoform (CHBr3), chloroform (CHCl3), and dichlorobromomethane (CHCl2Br). The sum of these four compounds is referred to as Total Trihalomethanes (TTHMs). Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 129  Ozone Ozone is produced from oxygen exposed to a high voltage current. Ozone is very effective at destroying viruses and bacteria and decomposes back to oxygen rapidly without leaving harmful by products. Ozone is not very economical due to high energy costs. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 130  Ultraviolet Radiation Ultra violet (UV) disinfection occurs when electromagnetic energy in the form of light in the UV spectrum produced by mercury arc lamps penetrates the cell wall of exposed microorganisms. The UV radiation retards the ability of the microorganisms to survive by damaging their genetic material. UV disinfection is a physical treatment process that leaves no chemical traces. Organisms can sometimes repair and reverse the destructive effects of UV when applied at low doses Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 131  Advanced treatment or tertiary treatment Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 132  Membrane filtration Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 133  Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 134  Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 135  Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 136  Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 137  Nitrogen Control Nitrogen in one form or another is present in municipal wastewater and is usually not removed by secondary treatment. If discharged into lakes and streams or estuary waters, nitrogen in the form of ammonia can exert a direct demand on oxygen or stimulate the excessive growth of algae. Ammonia in wastewater effluent can be toxic to aquatic life in certain instances. By providing additional biological treatment beyond the secondary stage, nitrifying bacteria present in wastewater treatment can biologically convert ammonia to the non-toxic nitrate through a process known as nitrification. The nitrification process is normally sufficient to remove the toxicity associated with ammonia in the effluent. Since nitrate is also a nutrient, excess amounts can contribute to the uncontrolled growth of algae. In situations where nitrogen must be completely removed from effluent, an additional biological process can be added to the system to convert the nitrate to nitrogen gas. The conversion of nitrate to nitrogen gas is accomplished by bacteria in a process known as denitrification. Effluent with nitrogen in the form of nitrate is placed into a tank devoid of oxygen, where carbon-containing chemicals, such as methanol, are added or a small stream of raw wastewater is mixed in with the nitrified effluent. In this oxygen free environment, bacteria use the oxygen attached to the nitrogen in the nitrate form releasing nitrogen gas. Because nitrogen comprises almost 80 percentTanushree air in the earth’s of the Bhattacharya. CEE101 atmosphere, the release of nitrogen into the atmosphere does module 2/16/2024 not cause 3, BITany environmental harm. Mesra 138  Biological Phosphorus Control Like nitrogen, phosphorus is also a necessary nutrient for the growth of algae. Phosphorus reduction is often needed to prevent excessive algal growth before discharging effluent into lakes, reservoirs and estuaries. Phosphorus removal can be achieved through chemical addition and a coagulation sedimentation process discussed in the following section. Some biological treatment processes called biological nutrient removal (BNR) can also achieve nutrient reduction, removing both nitrogen and phosphorus. Most of the BNR processes involve modifications of suspended growth treatment systems so that the bacteria in these systems also convert nitrate nitrogen to inert nitrogen gas and trap phosphorus in the solids that are removed from the effluent. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 139  Carbon adsorption Carbon adsorption technology can remove organic materials from wastewater that resist removal by biological treatment. These resistant, trace organic substances can contribute to taste and odor problems in water, taint fish flesh, and cause foaming and fish kills. Carbon adsorption consists of passing the wastewater effluent through a bed or canister of activated carbon granules or powder which remove more than 98 percent of the trace organic substances. The substances adhere to the carbon surface and are removed from the water. To help reduce the cost of the procedure, the carbon granules can be cleaned by heating and used again. Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 140  Ion exchange process Tanushree Bhattacharya. CEE101 2/16/2024 module 3, BIT Mesra 141