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Innovative Cost Saving Solutions To Waste Water Problems

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