Crush the Crust

About the author:

Chris French is a freelance writer on water, environment and renewable energy issues. French can be reached at [email protected].

Throughout Ohio there is a large a number of meat and food processing plants and municipal sites whose wastewater system is plagued by fats, oils, greases (FOG) and debris. Many of these may already have some sort of pump or mixer — perhaps sold on the basis of it being non-clog — but staring down at a tank crusted over so badly that wastewater cannot be seen, is an immediately tell that this is not the case. Chances are that the odor from the tank and collection system is so bad that even a new visitor to site — blindfolded — could locate it in seconds.

A classic example of this came to light when a leading meat processor — bogged down by reoccurring costs, foul odors and poor performance of its wastewater treatment system — looked for a cost-effective, long-term solution. The problem at this particular site was so bad that one could (not that anyone in their right mind would) walk on or jump up and down on the layer of the tank’s crust because it was so thick.

To combat the ongoing crust, odor problem and loss of capacity in its 300,000-gallon equalization tank, the meat processor considered the use of chemicals to tackle the wastewater, and was also trying to get things moving in the tank by hiring a contractor four times a year to blast the crust apart with a basic portable pump. This rather primitive, nasty job not only caused a temporary major increase in odors, but also cost $5,000 per visit.

As with all meat and food processors, wash-down of the plant at the end of the work day presents a test for the on-site wastewater treatment system — in this case two dissolved air floatation (DAF) units as they suddenly have to deal with bringing a large volume of particles to the surface. Fat removal is essential for discharge consent, to protect the local water courses en route to the local municipal wastewater treatment facility, and to keep effluent costs as low as possible.

At this Ohio plant, removed fat also provides a revenue stream as it is sold on for use in other manufacturing industries.

Finally, with the odor-generating permanent presence of fat in the equalization tank and a lack of capacity adversely affecting the whole treatment process led the meat plant’s facilities manager — who described the situation as “extremely troublesome; especially the odors” — to seek help via his chemical vendor.

An inquiry was made to Smith Environmental, initially for a propeller mixer, but upon learning more about the tough application, the Columbus-based wastewater consultant knew immediately that a more robust solution would be required.

“Never Seen a Tank So Crusted Up”

“Over the years we’ve seen some very clogged up lift stations,” said Paul Matrka of Smith Environmental. “Every municipality across America seems to have at least one very labor-intensive sewage lift station that causes major problems, but while all meat processors have the same issue with waste fat to deal with, I have to admit that in this case, in my over 25 years’ experience in the industry, I’ve never seen a tank so crusted up.”

Representing a carefully selected range of equipment from top-line manufacturers, Smith Environmental had experienced positive outcomes with a chopper pump that not only has an external knife system to prevent solids from entering its casing, but one that — when fitted with a Venturi nozzle — acts as an effective mixer to distribute air throughout the tank.

In keeping with its firm policy of designs driven with what is the best long-term solution for the community, Smith Environmental proposed a trial of the AeriGator from Landia.