ETP operation and review the process and their section
- 1. What is an ETP? INFLUENT ETP TREATMENT EFFLUENT SLUDGE • ETP (Effluent Treatment Plant) is a process design for treating the industrial waste water for its reuse or safe disposal to the environment. • Influent: Untreated industrial waste water. • Effluent: Treated industrial waste water. • Sludge: Solid part separated from waste water by ETP.
- 2. Need of ETP • To clean industry effluent and recycle it for further use. • To reduce the usage of fresh/potable water in Industries. • To cut expenditure on water procurement. • To meet the Standards for emission or discharge of environmental pollutants from various Industries set by the Government and avoid hefty penalties. • To safeguard environment against pollution and contribute in sustainable development.
- 3. Design of ETP The design and size of the ETP depends upon: • Quantity and quality of the industries discharge effluent. • Land availability. • Monetary considerations for construction, operation & maintenance. • Area dimension depends on: Quality of wastewater to be treated, Flow rate Type of biological treatment to be used . • In case of less available land, CETP (Common Effluent Treatment Plant) is preferred over ETP
- 4. Treatment Levels & Mechanisms of ETP • Treatment levels: Preliminary Primary Secondary Tertiary (or advanced) • Treatment mechanisms: Physical Chemical Biological
- 5. Preliminary Treatment level Purpose: Physical separation of big sized impurities like cloth, plastics, wood logs, paper, etc. Common physical unit operations at Preliminary level are: Screening: A screen with openings of uniform size is used to remove large solids such as plastics, cloth etc. Generally maximum 10mm is used. Sedimentation: Physical water treatment process using gravity to remove suspended solids from water. Clarification: Used for separation of solids from fluids.
- 6. Primary Treatment Level Purpose: Removal of floating and settleable materials such as suspended solids and organic matter. • Methods: Both physical and chemical methods are used in this treatment level. • Chemical unit processes: Chemical unit processes are always used with physical operations and may also be used with biological treatment processes. Chemical processes use the addition of chemicals to the wastewater to bring about changes in its quality. Example: pH control, coagulation, chemical precipitation and oxidation.
- 7. pH Control: To adjust the pH in the treatment process to make wastewater pH neutral. For acidic wastes (low pH): NaOH, Na2CO3, CaCO3or Ca(OH)2. For alkali wastes (high pH): H2SO4, HCl. Chemical coagulation and Flocculation: • Coagulation refers to collecting the minute solid particles dispersed in a liquid into a larger mass. • Chemical coagulants like Al2(SO4)3 {also called alum} or Fe2(SO4)3 are added to wastewater to improve the attraction among fine particles so that they come together and form larger particles called flocs. • A chemical flocculent (usually a polyelectrolyte) enhances the flocculation process by bringing together particles to form larger flocs , which settle out more quickly. • Flocculation is aided by gentle mixing which causes the particles to collide. Primary Treatment Level (cont…)
- 8. Secondary Treatment Level Methods: Biological and chemical processes are involved in this level. Biological unit process To remove, or reduce the concentration of organic and inorganic compounds. Biological treatment process can take many forms but all are based around microorganisms, mainly bacteria. Aerobic Processes Aerobic treatment processes take place in the presence of air (oxygen). Utilizes those microorganisms (aerobes), which use molecular/free oxygen to assimilate organic impurities i.e. convert them in to carbon dioxide, water and biomass. Anaerobic Processes The anaerobic treatment processes take place in the absence of air (oxygen). Utilizes microorganisms (anaerobes) which do not require air (molecular/free oxygen) to assimilate organic impurities. The final products are methane and biomass.
- 10. Tertiary / Advanced Treatment Purpose: Final cleaning process that improves wastewater quality before it is reused, recycled or discharged to the environment. Mechanism: Removes remaining inorganic compounds, and substances, such as the nitrogen and phosphorus. Bacteria, viruses and parasites, which are harmful to public health, are also removed at this stage. Methods: Alum: Used to help remove additional phosphorus particles and group the remaining solids together for easy removal in the filters. Chlorine contact tank disinfects the tertiary treated wastewater by removing microorganisms in treated wastewater including bacteria, viruses and parasites. Remaining chlorine is removed by adding sodium bisulphate just before it's discharged.
- 11. Flow chart for ETP
- 12. Case Study ETP Process Design for a typical Textile factory
- 13. Textile industry Share Country Value in ($ billion) Share (%) China 94.4 32.1 EU27 76.6 26.1 India 15.0 5.1 United States of America 13.8 4.7 Korea Republic 12.4 4.2 Turkey 10.8 3.7 Pakistan 9.1 3.1 Indonesia 4.8 1.6 Vietnam 3.8 1.3 Bangladesh 1.6 0.5 Rest of the World 51.7 17.5 Total 294 99.9 Source: Ghaly A. E, Ananthashankar R., Alhattab M., and Ramakrishnan V. V., Production, Characterization and Treatment of Textile Effluents: A Critical Review, J Chem Eng Process Technol 2014, 5:1, http://dx.doi.org/10.4172/2157- 7048.1000182
- 14. Textile production flow diagram
- 15. Water consumption in textile industries Fabric Water consumption (kg/kg) Cotton 250-350 Wool 200-300 Nylon 125-150 Rayon 125-150 Polyester 100-200 Acrylic 100-200
- 16. Process Water consumption (%) Bleaching, finishing 38 Dyeing 16 Printing 8 Boiler house 14 Humidification (Spinning) 6 Humidification (weaving) 9 Sanitary, Domestic 9
- 17. Emission and waste generation from textile industry
- 18. Effluent characteristics from typical textile industry Process Composition Nature Sizing Starch, waxes, carboxymethyl cellulose, polyvinyl alcohol. High in BOD & COD Desizing Starch, waxes, carboxymethyl cellulose, polyvinyl alcohol. High in BOD, COD, suspended solids, dissolved solids. Scouring Caustic soda, waxes, grease, soda ash, sodium silicate, fibres, sulfactants, sodium phosphate. Dark colored, High pH, COD, dissolved solids. Bleaching Hypochlorite,Caustic soda, sodium silicate, hydrogen peroxide, sulfactants, sodium phosphate. Alkaline suspended solids. Mercerizing Caustic soda. High pH, low COD, high dissolved solids. Dyeing Various dyes, mordants, reducing agents, acetiv acid soap Strongly colored, High COD, dissolved solids, low SS Printing Pastes, starch, gums, oil, mordants, acids, soaps. Highly-colored, High COD, oily appearance, SS finishing Inorganic salts. Slightly Alkaline, low BOD.
- 20. Important Characteristics of Wastewater from Textile Industry
- 22. Possible Choice For Wastewater Treatment And Their Sequence.
- 23. ETP Plant Operation 1. Screen chamber: Remove relatively large solids to avoid abrasion of mechanical equipments and clogging of hydraulic system. 2. Collection tank: The collection tank collects the effluent water from the screening chamber, stores and then pumps it to the equalization tank. 3. Equalization tank: The effluents do not have similar concentrations at all the time; the pH will vary time to time. Effluents are stored from 8 to 12 hours in the equalization tank resulting in a homogenous mixing of effluents and helping in neutralization. It eliminates shock loading on the subsequent treatment system. Continuous mixing also eliminates settling of solids within the equalization tank. Reduces SS, TSS. •
- 24. ETP Plant Operation 4. Flash mixer: Coagulants were added to the effluents: 1. Lime: (800-1000 ppm) To correct the pH upto 8-9 2. Alum: (200-300 ppm) To remove colour 3. Poly electrolyte: (0.2 ppm) To settle the suspended matters & reduce SS, TSS. The addition of the above chemicals by efficient rapid mixing facilitates homogeneous combination of flocculates to produce microflocs. 5. Clarriflocculator: In the clarriflocculator the water is circulated continuously by the stirrer. Overflowed water is taken out to the aeration tank. The solid particles are settled down, and collected separately and dried; this reduces SS, TSS. Flocculation provides slow mixing that leads to the formation of macro flocs, which then settles out in the clarifier zone. The settled solids i.e. primary sludge are pumped into sludge drying beds.
- 25. ETP Plant Operation 6. Aeration tank: The water is passed like a thin film over the different arrangements like staircase shape. Dosing of Urea and DAP is done. Water gets direct contact with the air to dissolve the oxygen into water. BOD & COD values of water is reduced up to 90%. 7. Clarifier: The clarifier collects the biological sludge. The overflowed water is called as treated effluent and disposed out. The outlet water quality is checked to be within the accepted limit as delineated in the norms of the Bureau of Indian standards. Through pipelines, the treated water is disposed into the environment river water, barren land, etc.
- 26. ETP Plant Operation 8. Sludge thickener: The inlet water consists of 60% water + 40% solids. The effluent is passed through the centrifuge. Due to centrifugal action, the solids and liquids are separated. The sludge thickener reduces the water content in the effluent to 40% water + 60% solids. The effluent is then reprocessed and the sludge collected at the bottom. 9. Drying beds: Primary and secondary sludge is dried on the drying beds.
- 27. FLOW CHART OF ETP Influent Screening Equalization (Lime + Alum) pH = 8.5 SS, TSS removal Disperse unit RECYCLE TANK Sedimentation tank {pH = 7.5} Sludge thickening unit Biological Treatment & Aeration {Dosing = (Urea + DAP) for O2} BOD removal ~ 90% COD removal ~ 90% Sludge Sludge discharge Fish pond Effluent Effluent discharge 60% water + 40% solids 40% water + 60% solids
- 28. SCREENING Screening is the filtration process for the separation of coarse particles from influent. Stainless steel net with varying pore size can be utilized. Screens are cleaned regularly to avoid clogging.
- 29. EQUALIZATION TANK EQUALIZATION TANK Influent from screening Spray of water coming from dyeing unit Air for diffusion Cool & Homogenous influent to pHcorrection Tank Equalization makes the waste water homogenous. Retention time depends upon the capacity of treatment plant. (Generally 8-16 hours)
- 30. PH CORRECTION pHcorrection Acid or alkali Influent from equalization tank Influent of desired to pH disperse unit In this tank pH of the influent is corrected to meet the standard. Acid or alkali is added to the effluent to increase or decrease the pH.
- 31. DISPERSE UNIT DISPERSE UNIT ( MIXING OF SLUDGE & WASTE) Sludge from recycle tank Influent from pH correction tank Mixed influent & sludge to aeration Disperse tank mixes the sludge coming from recycle tank with waste water for to proper aeration.
- 32. AERATION Function of aeration is oxidation by blowing air. Aerobic bacteria is used to stabilize and remove organic material presents in waste.
- 33. SCHEMTIC DIAGRAM OF AERATION AERATION TANK Mixture of waste water & sludge Aerobic bacteria AIR Discharge to sedimentation tank ORGANIC MATTER + O2 BACTERIA NUTRIENT CO2+ HO2 + HEAT REACTION IN AERATION TANK: O2
- 34. SEDIMENTATION TANK In this tank sludge is settled down. Effluent is discharged from plant through a fish pond. Sludge is passed to the sludge thickening unit.
- 35. SCHEMTIC DIAGRAM OF SEDIMENTATION TANK SEDIMENTATION TANK Waste water from sedimentation pack Sludge to thickening unit Effluent Effluent Discharge Fish pond Fish Pond is used to see survival of fishes to ascertain fitness of water for disposal
- 37. SLUDGE THICKENING UNIT Here sludge is dried and discharged. Partial amount of sludge is returned back to the aeration tank from thickening unit through recycle tank called return sludge tank and disperse tank.
- 38. SCHEMTIC DIAGRAM OF SLUDGE THICKENING UNIT SLUDGFE THICKENING UNIT Sludge from sedimentation unit Sludge discharge Sludge to recycle tank
- 39. DRIED SLUDGE
- 40. RETURN SLUDGE TANK Function of return tank or recycle tank is to mix water with sludge This mixture is then passed to aeration tank through disperse tank.
- 41. ADVANTAGE OF RECYCLE SLUDGE TO AERATION TANK Sludge again oxidized to minimize the pollution from sludge. Alive bacteria of sludge is again used in aeration to utilize this bacteria. SLUDGE RECYCLE TANK Sludge from thickening unit Mixing of sludge & water Sludge to aeration tank through disperse unit
- 42. PERMISSIBLE STANDARDS IN INDIA S.No. Parameter Permissible limits (disposal to inland surface water) 1 pH 5.5 to 9.0 2 TSS <100 mg/l 3 Oil & Grease <10 mg/l 4 BOD <30 mg/l 5 COD <250 mg/l