<h5 id="111-waste-water-treatment">11.1 Waste Water Treatment</h5> <ul> <li>Waste water is referred to as sewage, which can come from homes, communities, or industries.</li> <li>Sewage is difficult to treat due to the presence of antiseptics, chemicals, and high oxygen demand.</li> <li>Different industries produce unique sewage, with varying treatability; some are easily treated while others are not amenable to biological treatment.</li> <li>In India, an average individual generates 0.8 kg of waste daily.</li> <li>Treatment challenges arise from the diverse and complex nature of sewage, particularly from industries such as dairy, tannery, cannery, distillery, oil refinery, textile, coal and coke, synthetic rubber, steel, etc.</li> </ul> <p>======</p> <h5 id="1111-composition-of-sewage">11.1.1 Composition of Sewage</h5> <ul> <li>Bacteria: E. coli can cause gastroenteritis, V. cholerae causes cholera, Shigela sp results in shigellosis, and S. dysenteriae serotype 1 can cause dysentery.</li> <li>Viruses: Adenovirus is associated with respiratory diseases, enteroviruses and rotavirus can cause gastroenteritis, and Hepatitis A results in infectious hepatitis.</li> <li>Protozoa: Entamoeba histolytica leads to amoebic dysentery, Giardia lamblia causes giardiasis, and Balantidium coli results in balantidiasis.</li> <li>Helminths: Ascaris lumbricoides leads to ascariasis, Schistosoma sp causes schistosomiasis, Fasciola hepatica results in fascioliasis, and Taenia saginata causes taeniasis.</li> <li>No equations or formulae were provided in the text.</li> </ul> <p>======</p> <h5 id="1112-waste-water-disposal-plant">11.1.2 Waste water Disposal Plant</h5> <ul> <li>Sewage water treatment is essential to prevent water bodies from becoming vectors of diseases.</li> <li>The treatment aims to kill pathogenic microorganisms, prevent anoxia, raise the pH to the alkaline side, increase photosynthetic rate, and reduce organic content.</li> <li>Wastewater is treated in disposal plants through primary (physical or mechanical), secondary (biological), and tertiary (advanced) treatments.</li> <li>Primary treatment includes processes like screening, sedimentation, and centrifugation.</li> <li>Secondary treatment involves biological processes like aerobic digestion, activated sludge process, and biofiltration.</li> <li>Tertiary treatment includes advanced processes such as chemical precipitation, sand filtration, and disinfection.</li> </ul> <p>======</p> <h5 id="1113-primary-or-physical-treatment">11.1.3 Primary or Physical Treatment</h5> <ul> <li>Primary treatment is the first stage of sewage treatment, involving physical or mechanical methods.</li> <li>Screening removes bulky foreign matters like bottles and paper.</li> <li>Sewage then passes through a grit chamber with graded filters, followed by sedimentation tanks where it’s held for 2-10 hours.</li> <li>Coarse solid materials are concentrated and collected as primary sludge, which is then removed for further processing.</li> <li>The sludge and liquid effluent are processed separately during secondary treatment, with a treatment efficiency of 30-40% BOD removal.</li> </ul> <p>======</p> <h5 id="1114-secondary-or-biological-treatment">11.1.4 Secondary or Biological Treatment</h5> <ul> <li>Secondary or biological treatment of sewage aims to remove suspended organic material through aerobic or anaerobic processes.</li> <li>Aerobic secondary treatment includes activated sludge process, aerobic digestion of sludge by filters (e.g., trickling filters) and oxidation ponds, and anaerobic digestion of sludge.</li> <li>Activated sludge process involves an aeration tank and a settling tank, where sewage is aerated to maintain aerobic conditions and oxidize organic matter. The resulting sludge is then digested and recycled back to the system.</li> <li>Trickling filter process involves spraying sewage onto a bed of stones coated with a slimy film of microbes that degrade organic matter. The treated effluent is then passed to a sedimentation tank and undergoes tertiary treatment.</li> <li>Sewage oxidation ponds or lagoons are shallow ponds that allow for wind action and algal growth to oxygenate the sewage effluent. These are recommended for small communities in rural areas and can reduce BOD by 75 to 95 percent.</li> <li>Anaerobic sludge digestion involves digesting organic matter in the absence of oxygen, producing a gas mixture that can be used for power or as a fuel. The remaining sludge is dewatered and either incinerated, sold as fertilizer, or pulverized.</li> </ul> <p>======</p> <h5 id="1115-tertiary-or-advanced-treatment">11.1.5 Tertiary or Advanced Treatment</h5> <ul> <li> <p>Tertiary or advanced treatment is a process that removes non-biodegradable organic pollutants and mineral nutrients, such as nitrogen and phosphorus salts, from sewage effluent.</p> </li> <li> <p>Non-biodegradable organic pollutants are removed using activated carbon filters, while phosphorus salts are precipitated by liming, forming insoluble calcium phosphate.</p> </li> <li> <p>Nitrogen, present mainly as ammonia, is removed by volatilisation through vigorous aeration at elevated temperatures and high pH. This process can be enhanced in a metal tower with air forced upwards through the effluent.</p> </li> <li> <p>Carbon absorption, or carbon polishing, is used to remove dissolved organic compounds from the effluent. This is done by passing water through a tower packed with small particles of carbon.</p> </li> <li> <p>The final step of tertiary treatment is chlorination using sodium or calcium hypochlorite or chlorine to disinfect the effluent. The resulting effluent is clean but cannot be used as drinking water without further chemical treatment.</p> </li> </ul> <p>======</p> <h5 id="112-solid-waste-management">11.2 Solid Waste Management</h5> <ul> <li>Solid wastes can be categorized into two groups: biodegradable and non-biodegradable.</li> <li>Biodegradable wastes are generated from agricultural sector and households, and can be broken down by bacteria, earthworms, etc. into soil and organic manure.</li> <li>Non-biodegradable wastes consist of materials such as plastic, old clothes, polyesters, broken glass, chemicals, and metals, which cannot be absorbed by soil and cannot be decomposed by microorganisms.</li> <li>Different types of solid wastes include residential, industrial, commercial, construction and demolition, municipal services, process (manufacturing, etc.), and agriculture.</li> <li>Each type of solid waste has different components, such as food waste, packaging, hazardous waste, wood, steel, concrete, spoiled food wastes, and agricultural waste.</li> </ul> <p>======</p> <h5 id="1121-risks-of-solid-waste">11.2.1 Risks of solid waste</h5> <ul> <li>Decomposing organic waste can attract animals, vermins, and flies, which play a major role in transmitting faecal-oral diseases.</li> <li>Rodents can increase disease transmission and attract snakes. Mosquitoes breeding in solid waste can spread diseases like dengue, yellow fever, malaria, and microfilariasis.</li> <li>Improper solid waste management can lead to diseases like plague and dengue, affecting the environment and people’s health.</li> <li>Various waste types, when mixed with recyclable materials, can produce carcinogens and toxins when burned.</li> <li>Poor management of solid waste collection and disposal can cause leachate pollution of surface and groundwater, especially if the waste contains toxic substances near drinking water sources.</li> </ul> <p>======</p> <h5 id="1122-solid-waste-management">11.2.2 Solid waste management</h5> <ul> <li>Solid waste management involves collecting, treating, and disposing of solid material that is discarded or no longer useful.</li> <li>Effective solid waste management includes sorting waste at the generating point, recycling, and proper disposal. Organic waste can be recycled through composting, while glass and plastic waste can be reused in their respective industries.</li> <li>Construction debris can be reused as filling material under floors, and used tyres can be recycled or buried to avoid mosquito breeding.</li> <li>Community level management of solid waste involves using community refuse pits and organizing waste collection. Special solid wastes like medical, slaughterhouse, and industrial waste need expert handling and proper disposal.</li> <li>Composting is a powerful biological activity that breaks down organic waste into carbon dioxide, water, heat, and humus. It is an effective environmental tool for degrading toxic and persistent compounds present in water or soil.</li> </ul> <p>======</p> <h5 id="113-management-and-disposal-of-biomedical-waste">11.3 Management and Disposal of Biomedical Waste</h5> <ul> <li>Infectious waste: Yellow container with biohazard symbol, additional ‘HIGHLY INFECTIOUS’ marking for highly infectious waste, leak-proof non-chlorinated plastic bag, when three-quarters filled or at least once a day.</li> <li>Sharp waste: Yellow container marked ‘SHARPS’ with biohazard symbol, puncture-proof container, when filled to the line or three-quarters filled.</li> <li>Pathological waste: Yellow container with biohazard symbol, leak-proof strong plastic bag placed in a container, when three-quarters filled or at least once a day.</li> <li>Chemical and pharmaceutical waste: Brown container labeled with appropriate hazard symbol, plastic bag or rigid container, on demand.</li> <li>Radioactive waste: Labeled with radiation symbol, lead box, on demand.</li> <li>In rural areas without CBWTF, healthcare facilities dispose of biomedical waste in captive treatment or deep burial pit as authorized by SPCB or according to Biomedical Waste Management Rules, 2016.</li> </ul> <p>======</p> <h5 id="114-bioremediation-of-pesticides">11.4 Bioremediation of Pesticides</h5> <ul> <li>Azotobacter chroococcum is a bacteria that can improve the growth of maize and mustard by reducing soil pH and producing plant hormones. It also aids in the remediation of heavy metals like lead and zinc.</li> <li>Rhizobium leguminosarum is another bacteria that can enhance the growth of maize, similar to Azotobacter chroococcum. It also reduces soil pH and produces plant hormones, and aids in the remediation of heavy metals like lead and zinc.</li> <li>Rhizobium sp. is a type of bacteria that can be found in pea and lentil plants. It produces siderophores and releases hormones that aid in the growth of these plants. Additionally, it can remediate nickel and zinc.</li> <li>Notably, the text does not provide any equations or formulae.</li> <li>Examples and their solutions are also not included in the text.</li> </ul> <p>======</p>