Effective Wastewater Treatment for Dairy Ice Cream Industry. Dissolved Air Flotation DAF Test

The following is a summary of an actual pilot test study that demonstrates the effectiveness of DAF treatment of ice cream wastewater.

PROCESS DESCRIPTION:

Ice Cream 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 1100 gallon coagulation / pH buffer tank with a flash-mix agitator. The coagulated / pH adjusted water was then pumped to a P-TEC Model MD-2442 20 GPM Dissolved Air Flotation (DAF) System with an integrated flocculator where a flocculant was dosed. 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 

24 HOUR COMPOSITE SAMPLE: 

Raw water........... 9865 mg/l BOD, 11159 mg/l COD, 1267 mg/l TSS, 855 O&G

Treated water.......4385 mg/l BOD, 5373 mg/l COD, 48 mg/l TSS, 15 mg/l O&G

Reductions........56% BOD, 52% COD, 96% TSS, 98% O&G

SLUDGE ANALYSES:

7/16, 10 AM........… 22.2% dry solids

(fresh off DAF)

7/16, 5:30 PM........ 34.0% dry solids

(fresh off DAF)

7/17, 3:15 PM...... 46.6% dry solids, 2.82% FFA, 32.9% dry basis, 48.0% fat dry basis

(decanted 24 hrs, refrigerated)

7/17, 1:15 PM............ 44.8% dry solids, 4.18% FFA

(decanted 24 hrs at room temp.)

24 HOUR COMPOSITE SAMPLE:

Raw water..................…16146 mg/l COD, 1900 mg/l TSS, 878 mg/l O&G

Treated water................ 7599 mg/l COD, 42 mg/l TSS, 13 mg/l O&G

Reductions.................53% COD, 98% TSS, 99% O&G

SLUDGE ANALYSES:

7/23, 6 PM........... 33.0% dry solids

7/24, 6 AM........... 46.9% dry solids