Industrial Waste Water Treatment

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DISSOLVED AIR FLOTATION 6-1

DAF Dissolved Air Flotation Systems

Dissolved Air Flotation (DAF) is the use of micro-bubble flotation as a solid/liquid or liquid/liquid (or both) separation method that is widely used in industrial and domestic wastewater treatment processes. Dissolved Air Flotation, is a well-established separation process that uses micro-bubbles as a carrier phase to remove solids, ions, macromolecules, fibers and other materials, BOD, COD reduction and for sludge thickening. Air Flotation offers process advantages over such processes as filtration, precipitation, or adsorption using natural and synthetic sorbents and medias. The advantages include better treated-water quality, rapid startup, high rate operation, and a thicker sludge, shorter sludge residence time in a secondary clarifier stage and flexibility in changing the operation parameters as the result of active sludge separation.

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Dissolved Air Flotation (DAF) is the use of micro-bubble flotation as a solid/liquid or liquid/liquid (or both) separation method that is widely used in industrial and domestic wastewater treatment processes. Dissolved Air Flotation, is a well-established separation process that uses micro-bubbles as a carrier phase to remove solids, ions, macromolecules, fibers and other materials, BOD, COD reduction and for sludge thickening.

Air Flotation offers process advantages over such processes as filtration, precipitation, or adsorption using natural and synthetic sorbents and medias. The advantages include better treated-water quality, rapid startup, high rate operation, and a thicker sludge, shorter sludge residence time in a secondary clarifier stage and flexibility in changing the operation parameters as the result of active sludge separation.

DAF bubbles are formed by a reduction of pressure of a super air saturated water stream at pressures usually higher than 3 atm. In industrial practice, the supersaturated water is forced through precise needle valves for air control, and clouds of 0.02–0.10 mm bubbles in diameter are subsequently produced and mixed with the incoming waste stream. Once the saturated stream pressure is reduced and the two streams mixed the bubbles attach to the materials being separated and then floats to the water surface. Modern flotation devices and schemes exhibit both high throughput and efficiency.

Products removed: solids, oils, fuels (vehicle/jet), fuel oils, hydraulic fluids, immiscible machining oils, lube oil, transmission fluid, vegetable based oils, animal/vegetable by-products & many other products.

We offer many sizes in our Dinky DAF products from 5 to 50 square feet and in our large DAF line from 60 up to 600 square feet and many types of chemical pretreatment systems to float many types of solids.

Specifications

Specification Summary:
System model
Number of model sizes
Process  types
Volume range offered

Design Specification Summary

Performance
Design criteria
Influent chamber
Separation chamber
Solids hopper
Clean water effluent chamber
Water baffle
Weir plate
Surface skimmer
Float chamber
Recycle system
Cover
Fittings
Base
Lifting lugs

Materials of Construction

Tanks
Piping
Testing
Surface preparation(steel)

Coatings (steel)

 

Standards used

DAF Dissolved Air Flotation
Flotation Separation
22
Oil, solids flotation
5 – 1800 GPM

 

97% or more removal rates
API-421, 1990 &
Influent diffuser
To contain
Located under the flotation chamber
Located after separation chamber
Water flows over this baffle to exit tank
Vertically adjustable weir plate to maintain operating water level
Chain & flight design with wipers, VFD drive motor, overload safety
For temporary storage of skimmed float
Provided as DAF pump or with recycle saturation vessel
Multiple section vapor retaining, gasketed with polyethylene gasket and attached via zinc plate fasteners
NPT couplings up to 3″, 4″ & larger: 150# ANSI B16.5 FF flange
Steel skid base of channel, beam or tube construction
(4) Minimum, located at lifting points on sidewalls of tank

 

A-36 carbon steel, 304/316 SS, FRP, polyethylene, polypropylene
A-53 black steel, 304/316 SS, FRP, PVC
Dye penetrant on steel construction
Interior surfaces shall be prepared to an SSPC-SP10 near white metal blast. Exterior surfaces shall be prepared to an SSPC-SP6 commercial blast.
Interior coating shall be coated with Ameron High Build Coal Tar Epoxy Amercoat 78HB (16 mils DFT).
Exterior coating shall be coated with Ameron epoxy primer, Amerlock 2, (5-8 mils DFT).  Final coat to be Ameron Amershield Aliphatic Polyurethane Enamel coat (5 mils DFT)Surface color to be Green RT-2203.
Elements of AWS D1.1/1.1M, API, API-650, API-421, ANSI, IEC,AWS D1.6, UL, UL-508,UL-845,SSPC,ASME, CSA, NEMA, NFPA79, NEC

Dissolved Air Flotation (DAF) Theory

Is the process of removing suspended solids, oils and other contaminants via the use of air bubble flotation. Air is dissolved into water, mixed with the waste stream and released from solution while in intimate contact with the contaminants. Air bubbles form, attach to the solids, increase their buoyancy and float the solids to the water’s surface. A percentage of the clean effluent is recycled and super-saturated with air, mixed with the wastewater influent and injected into the DAF separation chamber.

The dissolved air comes out of solution, producing millions of microscopic bubbles. These bubbles attach to the solids and float them to the surface where they are mechanically skimmed and removed from the tank. The Pan America Environmental dissolved air flotation systems are designed to remove fats, oils & grease (FOG), suspended solids, food/animal production/processing wastes, industrial wastes, hydrocarbon oils/emulsions and many other contaminants. Clarification rates as high as 97% or more can be achieved using our dissolved air flotation systems. Chemical pretreatment can often help to improve the performance of contaminant removal.

Conventional DAF saturation design uses a recycle pump combined with a saturation vessel and air compressor to dissolve air into the water. Air transfer efficiency is approximately 12% @ 90% entrainment.

Pan America’s DAF design incorporates today’s “state of the art” technology in DAF design. This design simplifies the DAF process, requires less startup time, less capital cost, instrumentation, labor and maintenance. The design is process friendly, providing virtually instant saturation upon

system startup without equalization and complex startup procedures. Once the system is adjusted the system can be shutdown and started up again without any readjustment or equalization. Higher air transfer efficiencies are also realized due to higher saturation pressures with 12% @ 93% entrainment. Pan America can provide both styles of DAF design depending on application and customer preferences.

DAF sizing takes into consideration many criteria for sizing: Flow rate, Water temperature, Waste characteristics, Chemical pre-treatment, Solids loading (LBS/HR/Ft2) , Hydraulic loading (GPM/FT2), Air to solids ratio (LBS of air/LBS of Solids).

DAFs are designed on the basis of the peak flow rate expected. The flow can range from 1 to 5 gallons per minute per square foot of surface area (GPM/Ft2). Bench testing of waste stream samples is usually the preferred starting point when sizing equipment and determining proper chemical processes prior to the DAF. The chemical pretreatment will assist and improve the DAF separation process.

Chemical Pretreatment often improves DAF solids removal efficiencies. The use of chemical flocculants with DAF is based on system efficiency, application (use of DAF) and cost. Commonly used chemicals include trivalent metallic salts of iron, such as FeCI2 or FeSO4 or aluminum, such as AISO4. Organic and inorganic polymers (cationic or anionic) are often used to enhance the DAF process.

The most commonly used inorganic polymers are the polyacrylamides. Chemical flocculant concentrations used normally range from 100 to 500 mg/l. (One mg/l in 1 million gallons per day is 8.34 lbs of material.) The wastewater pH may need to be adjusted between 4.5 and 5.5 for the ferric compounds or between 5.5 and 6.5 for the aluminum compounds using an acid such as H2SO4 or a base such as NaOH. In many applications, the DAF effluent requires pH adjustment utilizing a base such as NaOH to assure the DAF effluent pH is within the limits specified by the POTW (6-9 typically).

Attachment of most of the bubbles to solid particles can be effected through surface energies while others are trapped by the solids or by hydrous oxide flocs as the floc spreads out in the water column. Colloidal solids are normally too small to allow formation of sufficient air-particle bonding. They must first be coagulated by a chemical such as the aluminum or iron compounds mentioned above and then absorbed by the hydrous metal oxide floc generated by these compounds. Frequently, a coagulant aid is required in combination with the flocculant to agglomerate the hydrous oxide flocc, increase particle size and improve the rate of flotation. Mechanical/chemical emulsions can also be broken through pH and polymer reactions.

Where the float is to be used to feed animals used for human consumption, organic compounds such as chitosan, carrageenan, and lignosulfonic acid, or their derivatives can be used. Use only compounds approved by the Food and Drug Administration (FDA) Office of Veterinary Medicine.

Float Dewatering DAF float often contains 2 to l0 percent solids. The solids may need to be dewatered before disposal to reduce the sludge volume by reducing water content. Float dewatering is usually performed by using one of the following technologies: Filter press, Belt filter press, Centrifuge, Drying bed or Vacuum precoat filter.

DAF models

DAF-5-H
DAF-10-H
DAF-15-H
DAF-25-H
DAF-35-H
DAF-45-H
DAF-50-H
DAF-60
DAF-85
DAF-100
DAF-120
DAF-150
DAF-180
DAF-200
DAF-250
DAF-300
DAF-350
DAF-400
DAF-450
DAF-500
DAF-550
DAF-600

Actual flow rates vary based on waste characteristics and chemical pretreatment.

Influent Feed System

Air operated, diaphragm pump with air controls or progressive cavity pump, sump level switches & Nema 4 control panel, base mounted, 115/230/460V power offered. Electric diaphragm pumps available.

Effluent Pumpout

Centrifugal pump with level switches & Nema 4 control panel, base mounted, 115/230/460V power offered. Effluent chamber must be expanded to accommodate pumpout or provision of an external pumpout tank.

Sludge Pumpout System

Air operated, diaphragm pump with air controls & Nema 4 control panel, auto on/off timer, base mounted, 115V/1ph/60Hz power req’d. Progressive cavity pump system also available. 1 – 100 GPM.

Float Pumpout System

Air operated, diaphragm pump with air controls, level switches & Nema 4 control panel, base mounted, 115V/1ph/60Hz power req’d. Electric gear or progressive cavity pump systems available. 1 – 100 GPM (larger if required)

Sludge Auger

Dinky DAF V-hopper can be provided with a sludge auger. System consists of stainless steel shafts with coated steel screw auger(s) driven by a slow speed gear motor drive assembly. The auger extends the full length of the solids hopper and conveys solids to the sludge outlet. A NEMA 4 on/off control box is provided, power required: 230 or 460V/3ph/60Hz.

Cover

DAF tank can be provided with a vapor retaining cover.

Freeze Protection Immersion heaters mounted through tank wall. Each heater has an independent thermocouple well, 0-100 deg. F thermostat and NEMA 1 (or optional Nema 4) housing. 230/460V/3ph/60Hz power req’d.

Oil Sight Glass

Two automatic, brass valves with tempered sight glass and protection rods mounted in oil reservoir. If glass is broken check ball stops outflow from reservoir.

External Sight / Level Glass

An externally mounted clear PVC sight tube is provided with multipoint level switch for indication or pump control of oil or water. Switch is removable for cleaning and inspection.

Elevation Stand

Epoxy coated steel stand or legs to elevate tank to desired level. Standard deck height is 30″. Full platforms & walkways with ladders or stairways can be designed where required or desired.

Alternate Tank Construction

Standard carbon steel construction can be changed to 304 or 316 stainless steel.

External Storage/Feed Tanks

A wide variety of tank volumes can be supplied for your water, product and sludge holding needs. Flat bottom and cone bottom designs constructed in polyethylene, fiberglass, steel & stainless steel can be provided.

Effluent Filter Systems

Solids filter systems can be provided to remove filterable solids from the separator effluent. Contact Pan America to determine proper filtration needs for your application.

AQAM Filter Systems

AQAM (Alkyl Quaternary Ammonium Montmorillonite) filter systems can be provided to remove trace hydrocarbons, sheens, DNAPLs, slightly soluble chlorinated hydrocarbons and high molecular weight organics from the separator effluent. Contact Pan America to determine proper filtration needs for your application. AQAM can also be used to protect and increase GAC lifespan.

Carbon Filtration Systems

(GAC) GAC carbon filters can be provided to remove contaminants after the separator. Contact Pan America to determine proper system needs for your application.

Emulsion Cracking Systems

Emulsion cracking systems can be provided to remove oil-in-water emulsions prior to the separator. Contact Pan America to determine proper system needs for your application.

pH Adjustment Systems

pH adjustment systems can be provided to maintain pH levels prior to or after the separator. Contact Pan America to determine proper system needs for your application.

Chemical Pretreatment Systems

Chemical pretreatment system can be provided to coagulate, flocculate, precipitate, oxidize, break emulsions and/or adjust pH before or after the DAF. Contact Pan America to determine proper system needs for your application.

System Containerization

DAF systems with any options can be installed in a 20 or 40’ shipping container(s) to simplify system provision and field implementation. System would include the complete mounting, piping and wiring of the system in one or more container as required by the project.

Trailer Mounting

DAF can be mounted on a trailer for system mobilization. Trailer design generally includes corner leveling jacks, bubble levels, walkway, toolbox, electric or hydraulic brakes, piping and wiring of options.

Field Skid Mounting

DAF systems can be mounted to a mobile skid with leveling for quick field mobilization.

Skid Mounted System

DAFs can be combined with our other treatment equipment and options into a fully integrated, custom designed system completely mounted, plumbed and wired to a system skid. To simplify your need to do the wiring and plumbing on site, reducing your time frames and on site costs, we design around your requirements.

Vent Scrubber

DAF vapors can be extracted and scrubbed prior to discharge to atmosphere to remove VOC content.

Level Sensors

Level sensors can be provided to detect water and oil/fuels. One or more sensor points can be provided to perform various functions such as high level, low level, pump on/off based on liquid levels and level detection for DCS controls or other functions based on your needs.

Class 1 Div 1 & 2

Systems can be designed for use in a class 1 div 1 or 2 environment. Controls, components and wiring are changed to meet the needs of these environments. Intrinsically safe relays are also used for level sensors.

Oil Monitor

an oil detection system can be provided to monitor effluent oil content and provide various actions based on the oil alarm set point. Actions might include: audible/visual alarm, redirection of influent or effluent via actuated valve, shutdown of influent pump or your custom action.

Applications

– Frac water
– Produced water
– Refineries
– Biodiesel plants
– Algae removal
– Petrochemical plants
– Dairies
– Ice cream production
– Cheese production
– Bakeries
– Drinking water pretreatment
– Sewage treatment plants
– Slaughter houses
– Rendering plants
– Vegetable processing plants
– Canning
– Poultry processing
– Pet food production
– Seafood production
– Pulp & paper mills
– Aircraft maintenance
– Ballast water
– Bilge water
– Latex removal
– Prepared foods
– Tank & truck wash

The Pan America Environmental DAF Series systems are designed to remove fats, oils & greases (FOG), petroleum oils and suspended solids. Clarification rates as high as 97% can be achieved using the DAF systems.

A percentage of the clean effluent is recycled and super-saturated with air, mixed with the wastewater influent and injected into the DAF separation chamber. The dissolved air comes out of solution, producing millions of microscopic bubbles. These bubbles attach to solids and float them to the surface where they are skimmed and removed from the tank.


Pan America Environmental, Inc
2309 N. Ringwood Rd., Ste G, McHenry, IL 60050 USA
815.344.2960   •   panam@panamenv.com