Knowing What’s Coming

Industries are not the only sources of discharges that can upset treatment plants. Residential abusers can have big impacts, too.
Knowing What’s Coming
Cooking oil enters a clarifier and rises to the surface.

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It seems many wastewater operators don't get the opportunity to go out into the community and visually inspect the collection system that conveys sewage to their plant.

We drive to the treatment plant on the surface of roads that cover the gravity sewer lines and force mains buried below. During our shift at the plant, we treat the entering waste flow without really knowing where it came from, who sent it to us, or even what's in it.

Several treatment plants I worked at would get various colors of wastewater (red, black, pink) entering the headworks. We kept small plastic sample bottles near the bar screen to capture the unusual waste for lab analysis. Of course, industrial and commercial users contribute all kinds of interesting waste to the collection system, but what about the residential users?

Being a regular contributor to TPO Lab Detective allows me to share some of the more unusual situations I have experienced. In this installment, I'll share a few short stories that allowed a few friends and me to put on the Lab Detective cap and get to know the dischargers.

Happy Thanksgiving!

As deep fat turkey fryers become more popular each year, residents sometimes face the dilemma of what to do with 7 to 8 gallons of used cooking oil once the Thanksgiving holidays have passed. Some ingenious homeowners have discovered that the 3-inch PVC clean-out cap sticking up in the yard is conveniently connected to the local sewer system.

What better way to dispose of all that used oil? Down the drain goes all that oil and chunky food waste. Some folks say, "It's only a few gallons — what harm could it do once it's mixed with millions of gallons of wastewater?" The fact is that many residents dispose of cooking oil down clean-outs and sink drains, and this accumulation of oil and grease is very detrimental to the wastewater collection system and treatment plant.

When the oil reaches the treatment plant, it collects on the surface of aeration tanks and the primary and secondary clarifiers, and it can also coat the fragile membranes of today's membrane bioreactor (MBR) treatment units. Once oil and grease enter a plant, problems can arise: foaming in the aeration tanks, excessive Nocardia spp. bacteria growth, turbid effluent, equipment malfunctions, and more. Aerobic and anaerobic digesters experience excessive foaming and frothing as well.

How to stop this crisis? Public education, developing and enforcing local sewer use ordinances, and grease trap inspection and pumping programs are just a few places to start, but beware: this is a never-ending battle!

Got meth?

Here in America we continue to see a rise in the use of drugs, both legally prescribed and illegally manufactured and sold. Enter the do-it-yourself meth lab. Ordinary household chemicals and cold medicines are being converted into methamphetamine, or meth for short.

Some wastewater operators in the heartland of America have asked me what the dumping of meth lab waste would do to the treatment plant biomass. They see the effects of these toxic mixtures on the treatment plant, especially after the police have raided suspected home labs.

In doing research for this article, I learned quite a bit about methamphetamine. It appears that a change in manufacturing processes used in small home labs require much less of the chemicals that might be used by larger meth labs producing drugs on a mass scale. The term 'shake and bake' is often used to describe the use of small plastic bottles to produce meth crystals.

In the past, large quantities of chemicals were needed to make the same amount of the drug, and the disposal of the waste product into the sanitary sewer system seemed to be causing difficulties at treatment plants. Anhydrous ammonia used as fertilizer on farmland was one of these chemicals, and theft of ammonia from tanks left on farmer's fields has increased.

The high levels of waste ammonia discharged into the sewer system along with other hazardous substances create a high-strength, or even toxic waste to the fragile microorganisms.

Seeking remedies

How do you detect or verify that meth chemicals are affecting your treatment plant? Have an open discussion with your local law enforcement officials. Tell them your concerns; ask if they think the possibility of a meth lab exists and where they suspect it might be located.

Next, if the indicated location is on the municipal sewerage system, collect samples from nearby manholes and check for elevated levels of the suspected pollutants. A portable composite sampler that fits into a manhole works great for this purpose, and you can rent one from a local lab or wastewater supply house.

Alternatively, you can set up a sampler at a nearby lift station, or collect a series of manual grab samples and combine them into a composite sample. If you find the suspected pollutant (ammonia, for example) at higher levels than in background samples, you have narrowed down your source location.

Share this information with law enforcement officials or local environmental regulatory agencies, especially if the illegally dumped waste is affecting the treatment plant's operation.

These are just two of the many stories operators from all over the country have shared with me. Whatever your particular situation may be, take heed: You are probably not alone! Please feel free to share your stories with me at the email address below.

About the author

Ron Trygar is senior training specialist in water and wastewater at the University of Florida TREEO Center and a certified environmental trainer (CET). He can be reached at rtrygar@treeo.ufl.edu.



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