The problem of suspended solids in wastewater whether a by product of food processing such as proteins and oils, or mechanical processes where metals such as arsenic and other metals are suspended in water, and the resolution of that problem arise from the same science- and it isn’t always well explained in the best of reference materials.

Here it is: the smaller the particles, the greater the surface area, and therefore- the greater the amount of electro-chemical charge inherent to the particles is present.

Dissolved air by itself isn’t much to crow about. It rises to the top of any water it’s injected into, and escapes.

The basis of the problem, as I said and the cure, dissolved air flotation, both center on this basic physical fact.

Let’s say you have a cube that is 1 foot on each side. That’s 6 sq ft. of surface area, right? Now cut the cube in half. How much surface do you have? You retain the former area and add two more square feet. That’s 8.

Cut each piece in half again and you have 10.67, each piece contributing 1/3 x its original surface area. You grow the surface area by a substantial fraction each time you divide the original. We have a long way to go here because this can go on and on right down to the molecular level, in theory.

You turn a few sq. ft. of surface area into potentially millions when the division gets to the microscopic or molecular level.

If those billions of individual pieces have an electric charge, let’s say a positive charge, you’ve got problems because the particles now have enough charge and small enough mass that they all repel each other- Voila! suspended and unwanted particles in water. They may settle- in days, weeks, months, years… virtually never. You just may want to return the water a little cleaner than you just made it processing food or textiles, so what now?

Dissolved air, as mentioned, won’t help you alone- but you can give it its own charge too. Trace chemicals, usually based on aluminum, usually in parts per million, can be introduced to your water. Seems like more of a mess, doesn’t it?

The chemicals create their own charge and the particles now have something to which they can bond or attach electrically speaking. If you’ve got positive charges on each waste particle, you introduce negative charges on the newly introduced aluminum. A particle of aluminum may attract many waste particles and form a clump. Now we’ve got suspended clumps.

One more introduction of something in very tiny particles with a lot of surface area- and an opposite charge. Air. Not just air bubbles, but microscopic ones with an attitude (a charge) Now we’ve got action. The water is white with these very microscopic bubbles. They have little mass and buoyancy, so they’re not in a dead run for the surface. They collect plenty of your particle/aluminum clusters on their way to the top with millions of units of opposite charged surfaces. All the clusters- original waste solids, clumped in microscopic size bits around flocculant aluminum or other introduced medium, and billions of tiny air bubbles that collect around these larger particles (the air bubbles are extremely small). All rises to the top in a nice sludge the consistency of cooked oatmeal. Skim it off and you have clear water that is clean enough to send back to town without the taxi fare of pollution credits.

This operation is known as dissolved air flotation and it’s relatively cheap compared to systems that use membranes to squeeze water through under high pressure. The equipment that does this is called a DAF so that the acronym becomes a noun. A DAF uses varied techniques and DAF pumps to achieve the right balance of chemicals, charges and volume to clean the water for each application. Formulas are generally used and adjusted while the waste water flow is analyzed and the balance of flocculant and air are tweaked. The biggest expense of the operation tends to be the DAF pumps, followed by chemicals to use as flocculant. The cost of chemicals is ongoing, but when a DAF pump must be replaced, it can far outweigh what was spent on chemicals. The Keystec Air-Whip DAF pump reduces this replacement cost to a fraction because it’s both cheaper to manufacture and buy and lasts far longer than the 6 or 12 month life expectancy of most competitors.

Dissolved air flotation, the process of injecting microscopic bubbles into an influent to create a flocculant, which is skimmed away. Sounds simple, doesn’t it? It is a simple enough concept. You create small enough parts so that things can be handled on a electro-chemical level. Charges attract suspended particles whose charges are keeping them apart. Microscopic air bubbles, correctly produced, along with the right chemical agents collect all the garbage in wastewater and float it to the top- each particle surrounded by microscopic bubbles that carry each particle away. Mind you, this isn’t the large bubbles produced by some equipment that produces something like chocolate mousse. This is ultra fine microscopic bubbles that do more than just produce a coagulant. Your end result is flocculant, a more solid and “load bearing” composition of very small bubbles. Your end product is much higher in waste content, leaving nearly pure clear water.

The savings can be enormous.

Treated water is much cheaper to send to a municipality than buying pollution credits.

Are you using Hellbender DAF pumps or Edur DAF pumps or another brand that costs thousands of dollars, but wears out in short order under industrial loads? Who wants to spend $25,000 every six months on replacement DAF pumps?

Enter the Air-whip DAF pump. It’s simple- our pumps last years. Some of our first pumps, installed several years ago are still operating at full capacity today,

Our technology produces the needed micron size bubbles with a specially engineered design that uses a modified standard style pump with much higher durability. One of our pumps actually had a work shirt introduced in the influent and is still running strong after the “experience”.

Inquire now about the Air-Whip DAF pump 888-216-1231. or email dave@dissolvedair.com

Chemical if a problem arises with proper flocculation or coagulation then an adjustment in chemical dosing is determined which resolves the core problem. In some dynamic environments, chemical dosing requires constant monitoring and adjustment.

Mechanical There are relatively few mechanical components in a typical DAF. The introduction of air in proper quantities creates many of the challenges found in dissolved air flotation applications including:

• Short pump life
• High Cost
• Complexity
• Intolerance of Entrained Solids
• Difficult or Impossible Maintenance

Air-Whip DAF Pump Impeller

The science and innovation behind the Air-Whip pump addresses all of these issues and does so with lower initial cost. The price of the Air-Whip DAF pump is fractional compared to typical DAF pumps on the open market.

The Air-Whip pump is engineered to tolerate both air and entrained solids. One of the pumps actually “ingested” a shirt that was accidentally introduced into the influent and continues to operate today. The Air-Whip pump has a very long life expectancy measured in years rather than weeks and months- typical lifespans of traditional pumps. The reliability and performance of the Air-Whip DAF pump provides both flexibility in operation modes and greatly reduced maintenance costs.

Some of our pumps have been in operation since they were first installed five years ago.

Call for new or replacement Air-Whip DAF pumps for your application and water treatment success.

Call Dave Keys at 714-924-4422. The Air-Whip DAF pump price is a low cost alternative to what you have been finding on the market.

An elegant design delivered inexpensively, the KeysTec Air-Whip DAF pump.

The KeysTec Air-Whip DAF Pump

Dissolved Air Flotation | DAF Pumps

My Brother Dan and I went to visit a paper company a couple of weeks ago, here in the Los Angeles area. In East LA and Commerce there are miles and miles of industries that run various processes and you can imagine that recycling wastewater is of premium concern both for the savings of water, and the cost of disposing of waste materials.

Problem Solved with DAF Airwhip Technology

Enter the paper company. They had done some online research and called on Keystec to solve the problem that had arisen from trying to solve another problem.

The paper company produces recycled, post-consumer content cardboard, the sort that is used to package up your typical products from dry pasta to cardboard bases for shrink-wrapped goods. In an effort to recover more of the ink, clay, ash and debris from the water used in the paper making process, they had made adjustments to a chemical flocculant in the water. This seemed to work great- lots of material was floating to the surface in the processing tanks, but before very long at all, the operators realized that the flocculant was the consistency of chocolate mousse and there was lots of it. So much that it spilled over the collection tanks and processing byproduct ran onto the basement and everywhere.

It left lots of clay in the tanks too. A big mess.

We arrived on a Tuesday morning and met with the folks there and had a look at the so called DAF they were operating. It was using an old style cavitation pump, sucking air into the pump and spinning it out via centrifugal force, producing some fairly large sized bubbles. In essence, instead of creating a flocculant, they were creating big bubbles with coagulant clinging to it.

Oops! We’ve got it a little backwards here. True dissolved air flotation creates microscopic bubbles and they collect around relatively large flocculant particles and float them to the surface where the flocculant has the consistency of oatmeal, not chocolate mousse! They needed the proper three stage process of coagulation, flocculation and dissolved air flotation. Their pump wasn’t going to do the job with the single flocculation turned coagulation stage they were using, neither would it do much with a better flocculation with a two stage process because the bubbles were like beach balls compared to what’s needed for dissolved air flotation.

We recommended the Keystec Airwhip pump for its perfect application to this problem and its longevity compared to standard DAF pumps.

Soon this company will be returning much of this paper by-product back to the new product and returning clear water to their system.

Result? Savings from reduced downtime, savings from reduced sewage fees and savings from reduced disposal of paper byproducts that should be re-integrated with new product.

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New and used recycling equipment

Orange County SEO

P-TEC offers equipment and system designs to meet the exact nature of each of our clients’ needs.  Whether your flow is 5 GPM or 3000 GPM, we have a custom solution for your need. Custom Built dissolved air flotation to fit your exact application based on extensive expert experience in DAF design and innovation.  From grease removal in a restaurant to water recovery in a paper mill, we can offer the solutions that will solve your problems.  We have experience in:

During a pilot test one of the workers accidentally dropped his shirt into the whitewater. Later the shirt was retrieved from the processed water- the Keystec Airwhip® pump unharmed.

Multi-stage pumps used to make whitewater cost exponentially more. The in-use pumps at this pilot test were getting clogged within weeks. The company was producing microwave bacon. The plant had five DAFs. The Keystec trial pump that started out as a test, and then placed into service five years ago is still running strong today.

Can Your DAF pump perform like this? Are you saving hundreds of thousands on your DAF processes?

We’re talking price ranges from $2,500 to $10,000 depending on size and application. Pumps that last far beyond competitors at economic cost.

If you want serious data driven, proven information about highly efficient, fractionally priced DAF pumps, check out the Keystec Airwhip® DAF pump series at Keystec. Innovative DAF design pump specialists.

Overall dissolved air flotation related service provided by PTEC.

A true DAF generates dissolved air.  The process involves dissolving atmospheric air to the greatest saturation possible under pressure and then releasing the dissolved air in the form of microscopic bubbles with the shock developed in a back-pressure valve or valves.

Modern DAFs operate the white-water system at about 95 to 120 PSI when operated in a recycle mode to achieve the greatest practical degree of air saturation.  There are numerous ways to create the necessary interface between air and water to do this, but the most popular lately is to inject metered air into the inlet of a multi-stage pump.  A saturation tank follows the pump.  Older designs saturated the full inlet flow at about 35 PSI with a larger saturation tank and a back-pressure valve.

All “white-water” systems can be trouble due to the solids that are entrained in waste water.  They can also be very expensive with tight clearances, unable to tolerate solids passing through the pump.

Dan Keys of Keystec developed a new, solids tolerant white-water DAF pump which can work with unscreened waste streams and is low cost and very easy to repair if it’s needed.  As a DAF design engineer, it had long been one of Dan’s goals to solve this old problem.  The development is now complete and the pump is enjoying great success in every place where it has been applied.  Its ability to handle solids has made it possible to return to full flow inlet aeration and split flow inlet aeration, thus increasing the DAF throughput capacity by freeing the throughput capacity used by recycle flow.

To summarize, proper white-water is achieved by aggressive air saturation which involves maximum air to water interface under pressure and some residence time in the pressurized state to complete the saturation, followed by a high-shock back-pressure valve or valves to force the sudden release of the saturated air.

This represents a revolutionary advance in applications of Dissolved Air Flotation technology.

There are also “entrained air” systems on flotation devices.  Be aware that while this approach can work many cases, the bubbles produces by spinning discs and blowing air through porous filters have different surface charges and are often too large for good flotation.  The ideal environment is produced by 30 to 50 micron bubbles combined with good chemistry that attracts the bubbles to the flocs formed by the chemistry. If the bubbles are able to coalesce while entraped in the floc, the rise rate can increase and allow more aggressive separation.  So, chemical choices are also key to good performance.

Partners in Dissolved Air Flotation Applications

•   drinking water clarification and color removal
•   Algae removal
•   By-product recovery  (i.e. metals, etc.)
•   Dissimilar solids separation

Within Wastewater Treatment, DAF application can be divided into
•   Primary Treatment
•   Secondary Treatment
•   Tertiary Treatment

In all cases, DAF (dissolved air flotation) is used to separate fine solids (any constituents that are not dissolved) by flotation, assisted by the attachment of microscopic bubbles.  Often, solids that would normally settle are forced to the surface for removal through the attachment of those fine bubbles.

DAF is used in a wide range of situations where the suspended material  can be as little as 20 mg/l (as in algae or color removal) to tens of thousands of mg/l as in rendering or some petro-chemical oil/water separation situations.  Each case must be evaluated for size, flow, and chemical requirements.

To further complicate the issue, the general term, DAF, no longer covers all the approaches to separating solids with microscopic bubbles.  Other similar technologies that are frequently referred to as DAF are:

•   CAF (cavitation air flotation)
-Bubbles produced by a spinning disk without pressure
•   BAF (bubble air flotation)
-Bubbles produced by blowing air through a micro-filter into the water
•   SAF (saponification air flotation)
-Bubbles produced with the aid of a surfactant for more aggressive attachment
•   EAF (entrained air flotation)
-Bubbles produced with relatively low pressure and high shear, entrained in the water

Dissolved Air Flotation

DAF Pumps

DAF Design

PROCESS DESCRIPTION:

Fluid milk, cottage cheese, fruit juices, and other dairy products.

OBJECTIVES

The objective of this study was two-fold:

1. To determine the effectiveness of chemical treatment and Dissolved Air Flotation (DAF) for the removal of BOD, suspended solids, and oil and grease from the plant´s wastewater.

2. To determine coagulant and/or flocculant dosing levels required to treat the wastewater.

EQUIPMENT USED:

Plant effluent was pumped from a manhole to a 300 gallon coagulation / pH buffer tank with a flash-mix agitator. The coagulated / pH adjusted water then gravity-flowed to a 300 gallon flocculation tank with a slow-mix agitator where a flocculant was dosed. The flocculated water then gravity-flowed to a P-TEC Model MD-2442 20 GPM Dissolved Air Flotation (DAF) System. Additional ancillary equipment was also provided; (feed pumps, chemical pumps, tanks, etc.).

TESTING PROCEDURES:

Prior to each test run, the water was jar-tested to determine optimal chemical dosing rates, then the system was started-up and stabilized before sampling took place. Flow rate, chemical dosing, aeration system, etc. were monitored to insure consistent operation.

500-ml samples of the raw wastewater influent and treated effluent were taken every hour to produce daily composite samples. A sludge sample was collected for moisture analysis in order to estimate volume produced.

Sample Analyses

600 PPM aluminum chloride (AlCl3) coagulant and 10 PPM anionic flocculant.

Influent – 3930 mg/l BOD; 1420 mg/l TSS; 514 mg/l O&G

Effluent – 1870 mg/l BOD; 100 mg/l TSS; 16 mg/l O&G

Reductions – 52% BOD; 93% TSS; 97% O&G

Sludge – 15.5 % dry solids; 21.8 % O&G on a dry basis

80 ppm epi-amine coagulant, 12 PPM cationic flocculant, & 6 ppm anionic flocculant.

Influent – 2560 mg/l BOD; 796 mg/l TSS; 616 mg/l O&G

Effluent – 880 mg/l BOD; 22 mg/l TSS; < 5 mg/l O&G

Reductions – 66% BOD; 97% TSS; 99% O&G

Sludge: 39.2 % dry solids; 32.1 % O&G on a dry basis

Dissolved Air Flotation only (no chemicals).

Influent – 1420 mg/l BOD; 608 mg/l TSS; 274 mg/l O&G

Effluent – 1220 mg/l BOD; 232 mg/l TSS; 105 mg/l O&G

Reductions – 14% BOD; 62% TSS; 62% O&G

Sludge – 34.1 % dry solids; 54.2 % O&G on a dry basis

Chemical Cost Comparisons and Estimated Sludge Production

Assumptions: 100,000 Gallons per day water treated.

TSS – 941 mg/l (average of pilot test influent TSS composites)

Treatment with aluminum chloride and polymer:

600 PPM AlCl3 = 60 gal/day X 10.68 lb/gal = 640.8 lb/day X $0.20 /lb = $ 128.16 /day

10 PPM anionic polymer (non-GRAS) =8.34 lb/day X $1.75 = 14.60

142.76 /day

Sludge production:

100,000 gal. X 941 mg/l = 94 gal/day (dry)  15 % dry solids = 627 gals (wet)

Treatment with three organic polymers “3P”:

80 PPM epi-amine = 8 gal/day X 9.5 lb/gal = 76 lb/day X $1.15/lb = $ 87.40 /day

12 PPM cationic polymer (GRAS) =10 lb/day X $2.75 = 27.52

6 PPM anionic polymer (GRAS) = 5 lb/day X $2.50 = 12.50

150 PPM sulfuric acid = 15 gal/day X 15 = 225 lb/day X $0.09/lb = 20.25

147.67 /day

Sludge production:

100,000 gal. X 941 mg/l = 94 gal/day (dry)  35 % dry solids = 269 gals (wet)

NOTES: All chemical prices assume tote or pallet quantities and include estimated freight. “GRAS” – Generally Recognized As Safe (for addition to animal feed).

Note for ALL tests: The pH was maintained at between 6.0 and 7.0 using 150 PPM (by volume) of 66o Be sulfuric acid (H2SO4) during the “3P” and DAF only trials. Little or no acid was required for the aluminum chloride and polymer trial because the 600 PPM dose of aluminum chloride itself lowers the pH to ~6.5. Average influent pH was approximately 9.0, but was observed as low as 4.5 and as high as 11.5.

Dissolved air flotation

Dissolved air flotation is an effective application for removal of BOD, suspended solids, oil and grease from wastewater used in Ice Cream production and other Dairy processes. P-TEC ran a pilot test study for this application while determining the coagulant and dosing levels for specific reclamation.

In this test, plant effluent was delivered to a 1100 gallon coagulation pH buffer tank. The coagulated, pH adjusted water then was introduced to P-TEC Model MD-2442 20 GPM Dissolved Air Flotation (DAF) System with an integrated flocculator. Here, flocculant was dosed.

Each test was preceded by jar testing to determine the usual needed chemical dosing rate. During each test, monitoring included, dosing, flow rate, aeration, etc. Hourly samples of influent and effluent were taken in 500ml amounts as well as sludge samples to to estimate produced volume.

Results:

DAF Pilot Test Results - Dissolved Air Flotation