Not By Flocculant Alone – How Dissolved Air Solves A Paper Recycling Problem

Inquire about the Keystec pump: Call Dave Keys at 714-924-4422.

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

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Dissolved Air Flotation DAF Solutions For The Dairy Industry, BOD & TSS Removal In Milk Wastewater

Here is a summary of an actual recent pilot test study.  The pilot test demonstrated the effectiveness of DAF treatment of fluid milk wastewater.

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 | Can DAF Solve The Ice Cream Problem?

Can DAF (dissolved air flotation) solve the wastewater problem for ice cream plants? Success is obtained in Dairy Pilot testing.

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

Need A Pilot Test? Dissolved Air Flotation • DAF Solutions and Design

THE P-TEC MOBILE DAF PILOT SYSTEM Complete with the following:

• Mixed Equalization Tank
• DAF Feed Pump
• Flowmeter
• Flocculator
• DAF System
• Sludge Collection Tank
• Sludge Pump
• pH Controls and Pumps
• Coagulant Pump
• Polymer mix tanks with mixers
• Polymer Pumps
• Electrical Control Panel
• Jartesting Lab

Pilot System Cost: $ 2,500/week including PTEC Field Engineer
Plus travel expenses and Freight

**Contact PTEC for a formal Pilot Rental Agreement at 770-530-8313

Dissolved Air Flotation DAF Pumps and DAF Pump Design

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