Download as PDF, PPTX
Uploaded byTadviDevarshi
Wastewater engineering info
The document provides a comprehensive overview of wastewater management, detailing the sources of wastewater and the importance of its treatment in urban environments. Various methods for wastewater treatment are described, including primary, secondary, and tertiary processes such as sedimentation, filtration, disinfection, and biological treatments. Objectives of water treatment include producing safe drinking water, reducing contaminants, and ensuring environmentally friendly effluent disposal.
More Related Content
Similar to Wastewater engineering info
Wastewater engineering info
- 1. DEPARTMENT OF CHEMICALENGINEERING CHAPTER-1 “Introduction of Wastewater” PROF. DEVARSHI P. TADVI ASSISTANT PROFESSOR CHEMICAL ENGINEERING DEPARTMENT S S AGRAWAL INSTITUTE OF ENGINEERING & TECHNOLOGY, NAVSARI WASTEWATER ENGINEERING
- 2. OUTLINE • Introduction • Objectivesof water treatment • Conventional water treatment plantlayout • Various Methods of purification ofwater • Screening • Plain Sedimentation • Sedimentation aided withcoagulation • Filtration • Disinfection • Aeration • Softening
- 3. What is Wastewater? • Wastewater is a term that is used to describe waste material that includes industrial liquid waste and sewage waste that is collected in towns and urban areas and treated at urban wastewater treatment plants.
- 4. Where does wastewatercome from? • Residences ― human and animal excreta and waters used for washing, bathing, and cooking. • Commercial institution • Dairy and industrial establishment ― slaughterhouse waste, dairy waste, tannery wastewater, etc.
- 5. Where does itall go! Where does the water from the washer go? When you flush the toilet where does the contents go? By gravity flow, the waste is on its way to your local wastewater treatment plant!
- 6. Wastewater treatment • Aprocess to convert wastewater - which is water no longer needed or suitable for its most recent use - into an effluent that can be either returned to the water cycle with minimal environmental issues or reused. • Water treatment is the process of making water suitable or acceptable for an end-use. • It removes existing water contaminats and so, reduce their concentration that the water becomes fit for it’s desired application. • The amount & type of tretment process (Treatment Train) depends upon quality of Raw Water and various standards Required after treatment.
- 7. Wastewater Contaminants • Suspendedsolids • Biodegradable organics (e.g., BOD) • Pathogenic bacteria • Nutrients (N & P)
- 8. Objectives of watertreatment • Theobjectivesofwatertreatmentaretoproduce: • Waterthatissafeforhumanconsumption • Waterthatisappealingaestheticallytotheconsumer • Wateratareasonablecost
- 9. Indian Standards fordrinking water
- 10.
- 11. Functions of WaterTreatment Units
- 12. Selection of treatmentprocess-Train The types of treatmentrequired fordifferentsourcesaregiven in the following table:
- 13. WHY TREAT WASTEWATER? • Causes a demand for dissolved oxygen (lower DO levels of streams) • Adds nutrients (nitrate and phosphate) to cause excessive growth • Increases suspended solids or sediments in streams (turbidity increase)
- 14. • Reduce organiccontent i.e., BOD • Removal/reduction of nutrients i.e., N,P • Removal/inactivation of pathogenic microbes OBJECTIVES OF WWT
- 15. LEVELS OF TREATMENT •Primary – removal by physical separation of grit and large objects (material to landfill for disposal) – Sedimentation and screening of large debris Secondary – Biological and chemical treatment – aerobic microbiological process (sludge) organic matter + O2 CO2 + NH3 + H2O NH3 NO3 - aquatic nutrient Mostly dead microbes
- 17. Treatment stages -Primary treatment • typical materials that are removed during primary treatment include – fats, oils, and greases – sand, gravels and rocks – larger settle-able solids including human waste, and – floating materials
- 18. Methods used inprimary treatment • Bar screens • Grinding • Grit Chamber • Sedimentation Tank-primary Settling tank • Chlorination of effluent
- 20. Sedimentation Tank- PrimarySettling tank – Remove grease, oil – Fecal solid settle, floating material rise to the surface – Produce a homologous liquid for later biological treatment – Fecal sludge are pumped to sludge treatment plant
- 21. Secondary treatment • Biologicaltreatment – activated sludge – trickling filter – oxidation ponds
- 22. Activated sludge process •Primary wastewater mixed with bacteria-rich (activated) sludge and air or oxygen is pumped into the mixture • Both aerobic and anaerobic bacteria may exist • Promotes bacterial growth and decomposition of organic matter • BOD removal is approximately 85% • Microbial removal by activated sludge • 80-99% removal of bacteria • 90-99% removal of viruses
- 23. 5 physical components •Aeration tank • oxygen is introduced into the system • Aeration source • ensure that adequate oxygen is fed into the tank • provided pure oxygen or compressed air • Secondary clarifiers • activated-sludge solids separate from the surrounding wastewater • Activated sludge outflow line • Pump activated sludge back to the aeration tank • Effluent outflow line • discharged effluent into bay or tertiary treatment plant
- 25. Aeration and rapid mixing Settling collects sludgeon bottom Secondary process iriffuser From primary process To tertiary process
- 26. • Trickling filtersare beds made of coke (carbonized coal), limestone chips or specially fabricated plastic media • Optimize their thickness by insect or worm grazing • The primary wastewater is sprayed over the filter and microbes decompose organic material aerobically. • Low pathogen removal - Bacteria, 20-90% - Viruses, 50-90% - Giardia cysts, 70-90% Trickling filters
- 28. Stabilization or oxidation PONDS • • • • • Oxidationponds are a few meters deep, and up to a hectare in size. They are low cost with retention times of 1 to 4 weeks. Odor and mosquitoes can be a problem Pathogen removal: - Bacteria, 90-99% - Virus, 90-99% - Protozoa, 67-99% Mechanisms include the long detention time, high pH (10- 10.5) generated by photosynthesis, predation, sunlight, temperature
- 29. Continued… Stabilization ponds arethe preferred wastewater treatment process in developing countries due to low cost, low maintenance. This is balanced by larger land requirement.
- 30. When the treatmentis done… • Effluent back to stream after – a final carbon filtration and – chlorination/de-chlorination • Sludge – very nutrient rich – applied directly to land as fertilizer – incinerated (good fuel after drying) – composted
- 31. Sludge Treatment Processes Thickening(water removal) Digestion (pathogen inactivation and odor control) Conditioning (improved dewatering with alum and high temp, 175-230o C) Dewatering (pathogen inactivation and odor control) Incineration (volume and weight reduction) Final disposal
- 32. • Septic Tanks • •Constructed Wetlands Composting Wastewater Treatment Alternatives
- 33. Removes largesolids logs branches rags fish Simpleprocess mayincorporateamechanizedtrashremoval system ProtectspumpsandpipesinWaterTreatmentPlants
- 34. Plain Sedimentation Sedimentationis the removal of suspendedparticles by gravitationalsettling. Types of Sedimentation Tanks 1) Fill And Draw Type 2) Continuous Flow type
- 35. Shape of sedimentationtank 1. Rectangular tank with horizontal flow. 2. Circular tank with radial or spiral flow. 3. Hopperbottom tank with vertical flow.
- 36. SEDIMENTA TION Water flowsto a tank called a sedimentationbasin Gravity causes the flocs to settle to the bottom It would take a very long time for all particles to settle out and that would mean we would need a verylarge sedimentationbasin.
- 37. Sedimentation aided withcoagulation Sedimentation added with comprises of three step Addition of measured quantity of chemicals called coagulants to water and their through mixing ( rapid mixing ). Formation of precipitate which coagulates and forms a flow ( flocculation) Sedimentation
- 38. Coagulants AluminumSulfate Al2(SO4)3 FerrousSulfate FeSO4 Ferric Sulfate Fe2(SO4)3 Ferric ChlorideFeCl3 LimeCa(OH)2 Aluminum salts are cheaper but iron salts are more effective over widerpH range 15
- 39. Aeration Unit Work: Diffusion of Air Removes odour andtastes Oxidizes iron and manganese, increases dissolved oxygen content in water, removes CO2 and reduces corrosion and removes methane and other flammablegases. Types of Aerators 1. Gravityaerators 2. Fountainaerators 3. Diffused aerators 4. Mechanical aerators.
- 40. Gravity Aerators(Cascades): In gravity aerators, water is allowed to fall by gravity such that a large area of water is exposed to atmosphere, sometimes aided by turbulence. Aeration Unit
- 41. Injection orDiffused Aerators : It consists of a tank with perforated pipes, tubes or diffuser plates, fixed at the bottom to release fine air bubbles from compressor unit. Time of aeration is 10 to 30 min and 0.2 to 0.4 litres of air is required for 1 litre of water. Aeration Unit
- 42. Fountain Aerators: These are also known as spray aerators with special nozzles to produce a fine spray. Each nozzle is 2.5 to 4 cm diameter discharging about 18 to 36 l/h. Nozzle spacing should be such that each m3 of water has aeratorareaof 0.03 to 0.09 m2 forone hour. Aeration Unit
- 43. Mechanical Aerators flocculation are used. : Mixing Paddles paddles may be as in either submerged or at thesurface. Aeration Unit
- 44. Types of MixingDevices Mixings basins with bafflewalls
- 45. Mixing BasinsEquipped with Mechanicaldevicies
- 46. Flocculation Flocculation isa slow mixing or agitating process in which the destablished colloidal particles are brought into intimatecontact in order to promote the floc formation . Rate of flocculation dependsupon Types and amount of turbidity Types of coagulant Dosages of coagulant Mean velocity gradient inbasin
- 47. Clariflocculator Clarifier and flocculatorare provided in single unit called clariflocculator. The flocculating chamber is provided in the centre and clarifier component is formed by the peripheral space. Velocity of flowof water around 0.3 m/min. Mechanical scrapper provided to removesludge.
- 49. Filtration The process ofpassing the water through the beds of such granular material is known asfilteraton Types of Filtration Slow sand gravityfilter Rapid sand gravityfilter 1. Rapid sand gravityfilter 2. Pressure filter
- 52. Method of disinfection Physical method By heat By U.V.rays Chemical method Oxidizingchemicals Metal ions Alkalis andacids Minor method Boiling of water Treatment with excesslime Treatment withozone Treatment with iodine and bromine Treatment with ultra-violet rays Treatment with potassiumpermanganate
- 53. Water softening Wateris said to be hard when it contains relatively large amounts of bicarbonates, carbonates, sulphates and chlorides of calcium and magnesium dissolved init. Types of Hardness Temporary hardness Permanent hardness
- 54. Types of Hardness causedby dissolved Temporary Hardness- bicarbonates of Ca and Mg. -AKA ‘alkaline or carbonatehardness’ Permanent Hardness – caused by dissolved chlorides and sulphates of Ca, Mg, Fe and Aletc.
- 55. Removal of Hardness Removal of temporary hardness 1. Boiling 2. By adding lime Removal of temporary hardness 1. Lime-soda process 2. Zeolite process 3. Demineralization or De-ionizationprocess
- 56. Disinfection The filteredwater may normally contain some harmful disease producing bacteria in it. These bacteria must be killed in order to make the water safe fordrinking. The process of killing these Disinfection bacteria is known as or Sterilization.
- 57. Methods of Disinfection Boiling: The bacteria present in water can be destroyed by boiling it for a long time. However it is not. Treatment with Excess Lime: Lime is used in water treatment plant for softening. But if excess lime is added to the water, it can in addition, kill the bacteria also. Treatment like recarbonation for lime removal should be used afterdisinfection. Treatment with Ozone: Ozone readily breaks down into normal oxygen, and releases nascent oxygen. The nascent oxygen is a powerful oxidizing agent and removes theorganic matteras well as the bacteria from thewater. Chlorination : The germicidal action of chlorine is explained by the recent theory of Enzymatic hypothesis, according to which the chlorine enters the cell walls of bacteria and kill the enzymes which are essential for the metabolic processes of living organisms.
- 58. Reference • Mahajan PublishingHouse http://web.iitd.ac.in/~arunku/files/CVL100/L8.pdf http://nptel.ac.in/courses/105104102/Lecture%2020.ht m http://www.sswm.info/sites/default/files/reference_at tachments/SCHUTTE%202007%20Handbook%20for • %20the%20Operation%20of%20Water%20Treatment • %20Works.pdf -4th Water & waste water Engineering edition By
- 59.