WASTE WATER AND THEIR TREATMENT (PRIMARY, SECONDARY AND TERTIARY)
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The document discusses wastewater, which includes industrial and sewage waste, and the various treatment processes (primary, secondary, and tertiary) used to convert it into environmentally safe effluent. Primary treatment removes large objects and a significant portion of pollutants, while secondary treatment focuses on degrading organic and inorganic matter, and tertiary treatment aims at disinfecting through methods such as chlorination and UV light. The overall objective of wastewater treatment is to recycle pollutants, enhance public health, and protect aquatic ecosystems.
WASTE WATER AND THEIR TREATMENT (PRIMARY, SECONDARY AND TERTIARY)
- 1. SEMINAR TOPIC: WASTE WATER AND THEIR TREATMENT (PRIMARY, SECONDARY AND TERTIARY)
- 2. INTRODUCTION ■ 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. ■ Water treatment is the process of removing contaminants from wastewater using physical, chemical, and biological processes. ■ Its objective is to produce an environmentally safe fluid waste stream and a solid waste suitable for disposal or reuse.
- 3. WHAT IS WASTE WATER? ■ Waste water is a term that is used to describe waste material that includes…. • Food scraps • Oil and soaps. • Human wastes. • Industrial wastes. • Sewage waste that is collected from urban areas.
- 4. WASTEWATER TREATMENT ■ A process 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. ■ Aquaculture production systems have progressively intensified. Despite their high output, the intensive culture practices have adverse and negative impact on the environment. They are associated with both uncontrolled use of feed and massive production of waste which if released into the environment untreated and – • Deteriorates the water quality • Leads to eutrophication • Spreads parasite diseases and causes metals and antibiotics pollution.
- 5. 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. WASTE WATER CONTAMINANTS Suspended solids. Biodegradable organics. Pathogenic bacteria. Nutrients (N & P).
- 6. STAGES OF TREATMENT 1. Primary treatment 2. Secondary treatment. 3. Tertiary treatment. OBJECTIVES OF WASTEWATER TREATMENT Reduce organic content i.e., BOD Removal/reduction of nutrients i.e., N,P Removal/inactivation of pathogenic microbes
- 7. PRIMARY TREATMENT Removal of large objects from influent sewage. Ex. by physical separation About 25-50% of incoming biological demand(BOD), 50 to 70% of total suspended solids(TSS) and 65% of oil & grease are removed during primary treatment Removal of solid particles by- 1. Screening(for larger coarse particles) 2. Skimming(Floating Solids) 3. Sedimentation
- 8. SCREENING ■ Screening is an essential step in sewage treatment from removal of large coarse particles. This is the first treatment or operation which is carried out at the treatment plants. ■ Following are the main purposes of the screening: I. To remove the floating solids which may clog the pumps at the treatment plants and outfall. II. To remove the solids from the sewage which will form ugly sludge banks at the site of sewage disposal, when the sewage is given only primary treatment. III. To remove the solids which will clog the trickling filters and will also interfere with the aeration in the activated sludge treatment units.
- 9. SKIMMING ■ In this process skimming tanks are used for removing oil, grease and fats of the sewage. This tank is in the form of long, trough-shaped structure. Tank surface is made as large as possible, and the sides narrow down at a steep angle. Detention period of 3 min is provided in these tanks.. ■ Compressed air is circulated through out the container’s bed, so that the oily matters can rise upwards and could be collected in the side trough(beside the baffle), from where they are removed. ■ After this process remaining water is takenout from outlet.
- 10. ■ Sedimentation is a physical water treatment process using gravity to remove suspended solids from water. ■ Clarifiers are tanks built with mechanical means for continuous removal of solids being deposited by sedimentation. ■ In sedimentation process removal of suspended partical depends upon the size and specific gravity of those particles. Suspended solids retained on a filter may remain in suspension if their specific gravity is similar to water while very dense particles passing through the filter may settle. SEDIMENTATION Fig. Clarifier used for treating sewage water
- 11. SECONDARY TREATMENT ■ Removal of organic & inorganic soluble matter namely carbohydrates, fats, hydrocarbons and other material which are degraded into smaller forms like CO2, H2O ,N2O etc. ■ Methods of Secondary Treatment a. Activated Sludge I. In this process, sewage is aerated by air or by mechanical means. II. The residence time of water in this system is 1-20 hours III. Vigorous aeration is needed to prevent water from dropping down to 2-3mg/li that slows down the respiratory activity of the organisms in water.
- 12. b. Filtration • Mechanical filtration - Untreated water passes through a mesh filter that traps suspended particles on the surface or within the filter. • Biological filtration (trickling filter) - It consists of a fixed bed of rocks, coke, gravel, polyurethane foam, sphagnum peat moss, ceramic, or plastic media over which sewage or other wastewater flows downward and causes a layer of microbial slime (biofilm) to grow, covering the bed of media. c. Oxidation pond • A conventional oxidation pond contains the algal bacterial culture , which oxidizes a organic matter into CO2 ,H2O, H2S,NH3 and other decomposition products that are used as nutrients like nitrate , phosphate, sulphate. • About 85% of the suspended solids and BOD can be removed by well running plant with secondary treatment.
- 13. TERTIARY TREATMENT (DISINFECTION) ■ PURPOSE: Destruction of harmful (pathogenic) microorganisms i.e. disease causing germs. Done through: I. Chlorination II. Ozone: more powerful but unstable to store. III. Ultraviolet light IV. Hydrogen peroxide: similar to ozone but activators such as formic acid is required to improve its working.
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