Dairy process byproducts from fluid milk, juice, and cheese operations were so excessive that the dairy paid surcharges for failing to meet required sewage discharge effluent requirements. They were required to improve pre-treatment of their wastewater before discharging to the city collection system or face possible shut-down of operations since the city's waste treatment plant could not handle the overloading of the effluent which contained shock loads of CIP sanitizers.
The average daily influent of the wastewater had a BOD5 of 4000 mg/l and TSS of 3000 mg/l. The dairy operated an activated sludge system with two aeration tanks in series. Total detention was designed at 24 hours. Each tank contains a 25 hp turbine aerator with a 7.5 hp blower and diffuser system to provide supplemental oxygen in the first tank. A 12 feet deep cone-shaped tank with a top stirrer serves as a rough clarifier. The sludge from the bottom of this tank is returned to the first aeration tank. The dairy was required to reduce BOD5 to 300 or lower. Freeze dried bacterial strains had previously been tried without success.
For this particular operation, Alken-Murray Corporation suggested a customized dry powder blend of Alken Clear-Flo® 4003, specially formulated to provide optimal performance in degrading dairy byproducts, and Alken Clear-Flo® 7002, to effectively and safely degrade CIP sanitizers. The operator introduced the blend of non-pathegenic microorganisms to the dairy's activated sludge system. Following suggested dosage guidelines, a fluffy settleable biomass was produced in 10 days. Protozoa which had never before been present in the system flourished and after 15 days, effluent BOD averaged 500 mg/l. Dosage levels were adjusted slightly and with careful control of the MLSS (Mixed Liquor Suspended Solids), pH, and solids wasting, the effluent BOD5 levels were further reduced within 2-3 weeks, to an average of 120-240 mg/l.
Problems and solutions:
1) Excessive MLSS growth from daily fresh solids.
A program to waste 3% of the daily sludge flow was set up to stabilize MLSS at 8000 ppm.
2) The breakdown of acid whey caused the MLSS pH to become acidic when BOD5 dropped below 500 ppm.
Additions of 25 ppm of Alken® Treatment 479 raised the alkalinity. As MLSS was increased, the caustic dosage was decreased.
3) Whey dumping caused odors which made it unpleasant for employees. The instantaneous dumping of whey was causing an immediate oxygen demand on the system.
This was initially improved by additions of Alken® 895 (NaNO3) during whey dumping., but was later switched to Alken Enz-Odor 9.
4) The effects of shock loading upsets and bio- population kills caused by the presence of CIP sanitizers.
This was overcome by continuing treatment with Alken Clear-Flo® 4003 and 7002.
The demands of oxygen by a waste often causes the growth of filamentous organisms in activated sludge. The special blend of bacterial strains in Alken Clear-Flo® 4003 are microaerophilic* and successfully out compete other organisms for the available organic nutrients in the wastewater. A thirty minute settling test had zero settling before the application and has steadily shown a 100-300 ml of sludge since bringing the system under control with Alken Clear-Flo® 4003 and 7002.
*Microaerophilic: Bacteria which thrive optimally at 2 ppm dissolved oxygen (DO) but will perform in a pure oxygen system.
**Note: Other blends are customized and suggested when appropriate.