APPLICATIONS OF DISSOLVED AIR FLOTATION

Applications of DAF systems in a water treatment plant

The purpose of this article is to present, in a graphic and detailed manner, the main applications of dissolved air flotation (DAF) equipment, as well as to analyze the role they play in the different stages of a wastewater treatment process.

DAF systems are commonly used in pretreatment or primary treatment stages, where their main function is to separate suspended solids, oils, fats, and other undissolved contaminants. However, they also offer high performance in other applications, such as secondary clarification and thickening of sludge from biological aeration reactors or seawater treatment in desalination plants.

Although the application is a relevant factor, the selection of the type and model of DAF to be installed will depend on other design parameters, including the flow rate to be treated and the pollutant load of the effluent.

Next, we analyze the different applications and processes that can be carried out using dissolved air flotation technology.

Pretreatment

  • Industrial effluent
  • Coarse screening / homogenization
  • SIGMA PFL
  • SIGMA DAF
  • Post-treatment
  • Network download
  • Sludge management
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1

Industrial effluent

Raw industrial wastewater

  • Effluent from process, industrial washing, mixed effluents, etc.
  • Oil & gas, pharmaceutical, cosmetics, food processing, beverages, dairy, textile, chemical, paper, etc.

2

Coarse screening / homogenization

Removal of major solids and homogenization of the flow.

  • Coarse and chunks removal screens followed by an equalizing tank to homogenize the wastewater or the different discharges, allowing a constant feed in flow and composition to the rest of the treatment. the ph is adjusted at this stage. sand removal may be included.

3

SIGMA PFL

Coagulation - flocculation equipment of unique design

  • Injection of coagulant, alkaline agent and flocculant in strategic order and positions
  • Generation of floc formed by total suspended solids, colloidal, dissolved and precipitable dissolved solids, in addition to other contaminants associated with these solids.
  • Controlled and optimized reagent dosing.

4

SIGMA DAF

Dissolved air flotation clarifier

  • Microbubble injection by depressurization of water saturated with air.
  • Effective separation of flocs and clarified water.
  • The floated flocs are dragged by scrapers on the surface of the flotation chamber and the heavier solids fall to the collection system at the bottom of the equipment. Both solid streams leave the daf and are diverted for further treatment and management.
  • Clarified water flows out of the daf, free of solids and with a constant quality.

5

Post-treatment

Post-treatment

  • The clarified product can be referred for more intensive treatment

6

Network download

Network download

  • The clarified water can be discharged into the sewage system if it complies with the current standard.

7

Sludge management

Sludge management

  • Sludge treatment consists of dewatering by decanter and subsequent transport out of the plant or energy recovery by anaerobic digestion.

2. Secondary clarifier for activated sludge

  • Biological treatment of activated sludge
  • Sigma pfl or coagulation-flocculation tanks
  • SIGMA DAF
  • Sludge recirculation
  • Sludge purge
  • Treated water
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1

Biological treatment of activated sludge:

Biological treatment

  • Removal of organic matter and nutrients by the activity of micro-organisms. in the reaction medium, called 'mixed liquor', the biomass is suspended in the water matrix.

2

Sigma pfl or coagulation - flocculation tanks

Uniquely designed coagulation - flocculation system

  • In the pfl: injection of coagulant, alkaline agent and flocculant in a strategic order and positions. if the characteristics of the mixed liquor require it, separate tanks are installed for coagulation and flocculation.
  • Generation of floc formed by the biomass.
  • Controlled and optimized reagent dosing. use of special coagulants and flocculants for biomass separation.

3

SIGMA DAF

Dissolved air flotation clarifier

  • Microbubble injection by depressurization of water saturated with air.
  • Effective separation of biomass flocs and clarified water.
  • The floated flocs are dragged by scrapers on the surface of the flotation chamber and the heavier solids fall to the collection system at the bottom of the equipment. Both solid streams leave the daf and are diverted to recirculation or purge for further treatment and management.

4

Sludge recirculation

Sludge recirculation

  • Recirculation of sludge to the bioreactor to maintain the proper biomass concentration inside the reactor.

5

Sludge purge

Sludge purge

  • The excess biological sludge, which contains approximately 5% dry matter, is sent for treatment by dewatering, with possible anaerobic digestion for energy recovery.

6

Treated water

Treated water

  • The clarified water is ready for discharge into the network or for tertiary treatment for reuse.

3. Secondary clarifier for MBBR

  • Biological treatment mbbr 'moving bed biofilm reactor'.
  • Sigma pfl or flocculation tanks
  • SIGMA DAF
  • Sludge purge
  • Treated water
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1

Biological treatment mbbr 'moving bed biofilm reactor':

Biological treatment

  • removal of organic matter and nutrients through the activity of microorganisms. in the reaction medium, the biomass grows in the form of a "biofilm" attached to the surface of floating elements calledcarriers. this allows optimal contact between the biomass and the organic matter, as well as giving the microorganisms resistance to possible sudden changes in water composition. this reactor also has the advantage that it does not require sludge recirculation.

2

Sigma pfl or flocculation tanks

Unique flocculation system design.

  • in the pfl: flocculant injection.
  • generation of floc formed by the biomass.
  • controlled and optimized reagent dosing. use of special flocculants for biomass separation.

3

SIGMA DAF

Dissolved air flotation clarifier

  • Microbubble injection by depressurization of water saturated with air.
  • Effective separation of biomass flocs and clarified water.
  • The floated flocs are dragged by scrapers on the surface of the flotation chamber and the heavier solids fall to the collection system at the bottom of the equipment. Both solid streams leave the daf and are diverted to recirculation or purge for further treatment and management.

4

Sludge purge

Sludge purge

  • The excess biological sludge, which contains approximately 5% dry matter, is sent for treatment by dewatering, with possible anaerobic digestion for energy recovery.

5

Treated water

Treated water

  • The clarified water is ready for discharge into the network or for tertiary treatment for reuse.

4. Secondary clarifier for anaerobic reactor

  • Anaerobic reactor
  • Sigma pfl or coagulation - flocculation tanks
  • SIGMA DAF
  • Sludge recirculation
  • Sludge purge
  • To aerobic treatment
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1

Anaerobic reactor

Biological treatment

  • Transformation of organic matter into biogas by the action of microorganisms in the absence of oxygen. the anaerobic biomass consortium removes organic matter from water and transforms it into a gaseous mixture of methane and carbon dioxide known as biogas, which has potential energy value in the production of electricity and/or heat or for use in the gas grid. these reactors are operated at temperatures between 35 - 40ºc. subsequent aerobic treatment is generally required to comply with discharge regulations.

2

Sigma pfl or coagulation - flocculation tanks

Uniquely designed coagulation - flocculation system

  • In the PFL: injection of coagulant, alkaline agent and flocculant in a strategic order and positions. If the characteristics of the mixed liquor require it, separate tanks are installed for coagulation and flocculation.
  • Generation of floc formed by the biomass.
  • Controlled and optimized reagent dosing. use of special coagulants and flocculants for biomass separation.

3

SIGMA DAF

Dissolved air flotation clarifier

  • Microbubble injection by depressurization of water saturated with air.
  • Effective separation of biomass flocs and clarified water.
  • The floated flocs are dragged by scrapers on the surface of the flotation chamber and the heavier solids fall to the collection system at the bottom of the equipment. Both solid streams leave the daf and are diverted to recirculation or purge for further treatment and management.

4

Sludge recirculation

Sludge recirculation

  • Recirculation of sludge to the bioreactor to maintain the proper biomass concentration inside the reactor....

5

Sludge purge

Sludge purge

  • The excess biological sludge, which contains approximately 5% dry matter, is sent for treatment by dewatering, with possible anaerobic digestion for energy recovery.

6

To aerobic treatment

To aerobic treatment

  • Clarified water may still contain amounts of dqo above the discharge limits, so further aerobic treatment is required.

5. Seawater desalination

  • Sea water intake
  • Sieves and sand separator
  • SIGMA PFL
  • SIGMA DAF
  • Multimedia filtering
  • Ultrafiltration
  • Reverse osmosis
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1

Sea water intake

Capture devices

  • The seawater is collected and stored in a homogenization tank.

2

Sieves and sand separator

Coarse and fine sieves and sand separator

  • The screens allow the removal of lumps and coarse solids, the desander removes sands, which prevents the system from clogging.

3

SIGMA PFL

Coagulation - flocculation equipment of unique design

  • Injection of coagulant, alkaline agent and flocculant in strategic order and positions
  • Generation of floc formed by total suspended solids, colloidal, dissolved precipitable solids and algae, in addition to other contaminants associated with these solids.
  • Controlled and optimized reagent dosing.

4

SIGMA DAF

Dissolved air flotation clarifier

  • Microbubble injection by depressurization of water saturated with air.
  • Effective separation of flocs and clarified water.
  • The floated flocs are dragged by scrapers on the surface of the flotation chamber and the heavier solids fall to the collection system at the bottom of the equipment. Both solid streams leave the daf and are diverted for further treatment and management.
  • Clarified water flows out of the daf, free of solids and with a constant quality.

5

Multimedia filtering

Gravity or pressure filters

  • The most common filters are gravity filters (sand, anthracite, activated carbon) and pressure filters. These systems remove clays, colloidal silica, metal hydroxide precipitates, humic and fulvic acids, algae and some bacteria.

6

Ultrafiltration

Advanced membrane treatment

  • This membrane technology allows 100% retention of colloids, suspended solids, precipitates, clays, humic and fulvic acids, algae and a large fraction of bacteria.
  • In cases of highly loaded water, multimedia filtration and ultrafiltration are applied consecutively.

7

Reverse osmosis

Advanced membrane treatment

  • This membrane technology is specially designed to remove dissolved solids from water (inorganic ions, dissolved salts, etc.), bacteria, viruses and unicellular algae.