Sewage treatment
- 1. Presented By: kavya hegade 171226 M.sc.Biotechnology SDM PG College,Ujire
- 2. what is waste water? • Used water ……includes…. • Food scraps, oil and soaps. • Human wastes. • Industrial wastes.
- 3. • Sewage treatment is the process of removing contaminants from municipal wastewater, containing mainly household sewageplus some industrial wastewater. • Physical, chemical, and biological processes are used to remove contaminants and produce treated wastewater (or treated effluent) that is safe enough for release into the environment. A by-product of sewage treatment is a semi-solid waste or slurry, called sewage sludge. The sludge has to undergo further treatment before being suitable for disposal or application to land.
- 4. Why treat wastewater? • To remove pollutants from waste water for its recycling. • To promote health concern and public hygiene. • To preserve aquatic life and wildlife habitat. • To promote recreation and quality of life.
- 5. Steps involved in the process 1. Preliminary treatment -Removal of larger objects such as leaf,timber etc.. 2. Primary treatment - removal of fine suspended organic solids 3. Secondary treatment- removes dissolved and suspended biological matter.s 4. Tertiary treatment -disinfection of treated water physically or chemically prior to discharge into stream.
- 6. Sr.Type of Treatment Type of Name of the Function Type No. Treatment Unit Units of Impurity Removed. 1Physical Treatment Physical Screens Large Suspended and Floating Matter Physical Grit Chamber Grit Physical Clarifiers Silt, Sand & Other heavier Matter 2Chemical Treatment Chemical Chemical Reactors Dissolved Chemicals 3Biological Treatment Biological Trickling filter Dissolved Activated Sludge Organic Rotating Chemicals Biological Contractors Digesters
- 7. physical treatment •Screen, Clarifiers, grit chamber are all physical treatment unit. •it uses gravitation,mechanical straining • Mechanical Straining takes place in screens • gravity Settling takes place in Clarifiers. • Clarifiers are also known as Sedimentation Basin or Settling tanks.
- 9. chemical treatment It is normally preferred when the wastewater discharge is very small like that produced by industries, which contain Chemicals. • It takes place in units which are called reactors, methods • coagulation • precipitation • oxidation • Neutralization • Ion Exchange
- 10. Primary treatment • It is aimed at the removal of fine suspended organic solids that cannot be removed in the preliminary treatment. • It basically involves the process of sedimintation or settelings. • Sedimintation is usually carried out twise before the secondary treatment. • Sometimes chemical precipitation methods are used.the chemicals used in chemical aided sedimintation are 2 types coagulants and coagulant aids. • Coagulants are the chemicals which form in soluble and gelatinous precipitates with colloidal particles.eg.alum. • Example for coagulant aids activated silica.
- 11. SECONDARY TREATMENT • Aerobic biological treatment is performed in the presence of oxygen by aerobic microorganisms (principally bacteria) that metabolize the organic matter in the wastewater, thereby producing more microorganisms and inorganic end-products (principally CO2, NH3, and H2O)
- 12. Secondary treatment •Utilizes biological treatment processes •removes dissolved colloidal and organic matter from waste water. •microorganisms convert nonsettleable solids into settleable solids. • Ex….Bacteria and protozoa • :two main approaches are there to accomplish this
- 13. 1. Aerobic process a. Activated sludge process b. Trickiling filters c. Rotating biological contactors d. Aerated lagoons 2.Anaerobic process a. Anaerobic digestion b. Anaerobic contact process(meat packing wastes)
- 14. • Micro-organisms on substrates such as rocks, sand or plastic are cultured. • Waste water is spread over the substrate . • Nutrients and organic matter are absorbed by micro- organisms as they grow in size. • Eg. trickling filters,rotating biological contactors,and sand filters.
- 15. Activated sludge • In the activated sludge process, the dispersed-growth reactor is an aeration tank or basin containing a suspension of the wastewater and microorganisms, the mixed liquor. • The contents of the aeration tank are mixed vigorously by aeration devices which also supply oxygen to the biological suspension. • Aeration devices commonly used include submerged diffusers that release compressed air and mechanical surface aerators that introduce air by agitating the liquid surface
- 16. • Following the aeration step, the microorganisms are separated from the liquid by sedimentation and the clarified liquid is secondary effluent. • A portion of the biological avtive sludge is recycled to the aeration basin to maintain a high mixed-liquor suspended solids (MLSS) level. • growth of protozoa-indicates healthy condition. • The remainder is removed from the process and sent to sludge processing to maintain a relatively constant concentration of microorganisms in the system.
- 18. Advantages • low cost&efficient • the excess &waste sludge has a higher fertilizer value Disadvantages: • large volume of sludge production -difficult to handle • High power consumption • supervission by a skilled person is necessory.
- 19. Trickling filter • A trickling filter or biofilter consists of a basin or tower filled with support porousmedia such as stones, plastic shapes, or woode slats. • Wastewater is applied intermittently, or sometimes continuously, over the media. • within 2 weeks microorganisms become attached to the media and form a biological layer or fixed film.which has a thicness of 0.1 - 2.0mm &rich in micro-organism. • Organic matter in the wastewater diffuses into the film, where it is metabolized to Carbon doxide&nitrogen.
- 20. • Oxygen is normally supplied to the film by the natural flow of air either up or down through the media, depending on the relative temperatures of the wastewater and ambient air. • film is rich in bacteria ,fungi,yeast.eg;Pseudomonas,algae-Chlorella etc. • The thickness of the biofilm increases as new organisms grow periodically, portions of the film slough off the media. • The sloughed material is separated from the liquid in a secondary clarifier and discharged to sludge processing. • Clarified liquid from the secondary clarifier is the secondary effluent and a portion is often recycled to the biofilter to improve hydraulic distribution of the wastewater over the filter.
- 21. TRICKLING FILTERS -summary •Organic material present in the wastewater is metabolised by the biomass. •Biological slime grows in thickness as the organic matter abstracted from the flowing wastewater is synthesized into new cellular material. •The liquid then washes the slime off the medium and a new slime layer starts to grow- sloughing. •The collected liquid is passed to a settling tank used for solid-
- 23. Advantages Disadvantages •Simple, reliable, biological process •Low power requirement •Moderate level of skill and technical expertise needed to manage and operate the system. •Additional treatment • may be needed to meet more stringent discharge standards. •Vector and odour problems. •Requires regular operator attention.
- 24. Rotating Biological Contactors • Rotating biological contactors (RBCs) are fixed-film reactors where organisms are attached to support media. • Consists of a series of closely spaced plastic circular disks. • In the case of the RBC, the support media are slowly rotating discs that are partially submerged in flowing wastewater in the reactor.Discs are made up of inert material such as pvc. • Oxygen is supplied to the attached biofilm from the air when the film is out of the water and from the liquid when submerged, since oxygen is transferred to the wastewater by surface turbulence created by the discs' rotation.
- 25. • Operation, biological growths become attached to the surfaces of the disks and form a slime layer over the entire wetted surface. • The rotation of the disks contacts the biomass in the wastewater ,then with the atmosphere for adsorption of oxygen. • Biomass uses the oxygen & organic matter for food thus reducing the BOD in the wastewater.
- 27. Advantages: • compact&requires moderate energy input • it has high BOD removal efficiency(90%). Disadvantages: • disposal of sludge • odour formation • requires skilled person
- 28. Aerated lagoon •An aerated lagoon or aerated basin is a holding and/or treatment pond provided with artificial aeration to promote the biological oxidation of waste waters. •There are many other biological processes for treatment of wastewaters, for example activated sludge, trickling filters, rotating biological contactors and biofilters. •They all have in common the use • of oxygen (or air) and microbial action to biotreat the pollutants in wastewaters.
- 29. Anaerobic process • It involves decomposition of organic &inorganic matter in the absence of oxygen. • used in treatment of sludges&high strength organic sewage. • eg:anaerobic digestion
- 30. Anaerobic digestion • Used for stabilization of concentrated sludges that are from industries. • It is carried out in the air tight reactor • Sludge is introduced continuously/intermittently. • Biological degradtion of organic matter of sludge occurs in 3 stages. 1. Hydrolysis -high mw compounds to low m.w compounds..eg:A.a 2. Acidogenesis-low moleclular weight comp-acidic products(lactate). 3. Methanogenesis-production of methane&carbon dioxide.
- 31. Micro-organisms 1. Acid forming bacteria • called as acidogens eg:Clostridium sp , Lactobacillus sp, E.coli etc 1. Methanogenic bacteria • conversion of acetic acid& hydrogen to methane and carbon dioxide. • eg:Methano bacterium,Methano bacillus,Methano coccus etc
- 32. Tertiary treatment • PURPOSE: Destruction of harmful (pathogenic)microorganisms,i.e.disease causing germs. • Done through: • 1.Chlorination • 2.Ozone:more powerful but unstable to store. • 3.Ultraviolet light • 4.Hydrogen peroxide:similar to ozone but activators such as formic acid is required to improve its working.
- 33. When the treatment is done… • Effluent back to stream after • a final carbon filtration and • chlorination/dechlorination • Sludge – very nutrient rich • applied directly to land as fertilizer • incinerated (good fuel after drying) • composted .
- 34. Reference • Barwal, et all (2014). "To study the performance of biocarriers in moving bed biofilm reactor (MBBR) technology and kinetics of biofilm for retrofitting the existing aerobic treatment systems: a review". Reviews in Environmental Science and Bio/Technology. Springer. • Harshman, et all (2000-12-28). "Wastewater Odor Control: An Evaluation of Technologies". Water Engineering & Management. • Khopkar, S. M. et all (2004). Environmental Pollution Monitoring And Control • Sharma et all (2012). Advances in Water Treatment and Pollution Prevention. Springer Science & Business Media. • Tchobanoglous et all Wastewater Engineering: Treatment and Resource Recovery. ,y (Fifth ed.)