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Advanced Flotation Techniques for Industrial Pollution Control in Wastewater Treatment

This document outlines the use of flotation methods for effectively removing suspended solids, oil, and grease in wastewater treatment. Various flotation types such as dissolved air flotation (DAF) and induced air flotation systems are discussed, highlighting mechanisms, design parameters, and application in industries including petroleum, edible oil, and paper recycling. Key factors for flotation design, including pressure, recycle ratios, and retention times, are analyzed. The goal is to enable efficient separation and concentration of sludges to enhance wastewater treatment efficacy.

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Advanced Flotation Techniques for Industrial Pollution Control in Wastewater Treatment

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  1. ENVE 420IndustrialPollutionControl FLOTATION (Ref: 1- WPCF – Wastewater Treatment Plant Design 2- Eckenfelder) Dr. Aslıhan Kerç

  2. Objective of Using Flotation • Used for the removal of: - Suspended Solids - Oil and Grease from wastewater the seperation and concentration of sludges

  3. Mechanism of Flotation • If density of particle < density of water  can be separated by flotation e.g. ? Petroleum industry Edible oil industry Fiber recycling in paper industry

  4. Flotation Types • Simple flotation • Flotation with aeration • Dissolved air flotation • Electroflotation • Vacuum flotation

  5. Mechanism of DissolvedAirFlotation (DAF) • Solid particles in liquid suspension become attached to microscopic air bubbles. • Waste flow or a portion of clarified effluent is pressurized to 3.4 – 4.8 atm in the presence of sufficient air to approach saturation. • When pressurized air-liquid mixture is released to atmospheric pressure, minute air bubbles are released from the solution.

  6. Mechanism of DissolvedAirFlotation (DAF) • Agglomerate rise to the surface to join other particles and form a blanket that can be removed mechanically. • Flotation is used primarily to remove light SS. • Sludge flocs, suspended solids, oil globules are floated by the air bubbles which: • Attach to floc particles • Become enmeshed in floc particles

  7. Mechanism of DissolvedAirFlotation (DAF) • Air-solids mixture  skimmed off from the surface • Clarified liquid  removed from the bottom • A portion of the effluent  recycled back to the pressure chamber

  8. Primaryvariablesforflotationdesign • Pressure • Recycle ratio • Feed solids concentration • Retention period For clarification, retention time: 20 – 30 min loading rate: 0.06 – 0.16 m3/min-m2 For thickening: longer tR

  9. Principalcomponents of flotationsystem • Pressurized pump  elevated pressure to increase solubility • Air-injection facilities • Retention tank (saturation tank)  1-3 min • Back pressure regulation device  constant head on pressurizing pump • Flotation unit  circular / rectangular with a skimming device

  10. DAF Flow Diagram

  11. DAF Flow Diagram

  12. DAF

  13. Application of flotation • Flotation is applicable for wastewater containing high concentration of finely divided solids: - Wastes from canneries - Packing houses - Oil refineries - Laundries Recovered solids may be reusable  source of fuel

  14. Induced Air Flotation System • A submerged rotor forces the liquid through disperser openning, creating a negative pressure.

  15. Induced Air Flotation System

  16. OIL SEPARATION • Free oil is floated to the surfaceof a tank and then skimmed. • Design of gravity separators  American Petroleum Institute (API Separators) • Removal of oil particles > 0.015 cm • Effluent oil concentration : 50 mg/L • Plate separators separate oil droplets > 0.006 cm • Corrugated plates

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