FOG Pretreatment

Grease interceptors have different weaknesses and points of failure depending on what they’re made of. Those materials affect how durable a particular grease trap is, and often affect how it’s designed. Design choices, in turn, also affect the reliability and durability of a grease trap.

If concrete and fiberglass have problems, it seems as though it might make sense to use something stronger to construct the grease interceptor. Something like steel. But steel grease traps come with their own problems, and often have very short lifespans compared to other options.

Since concrete has so problems with corrosion, a substance such as fiberglass, which doesn’t have those problems, might seem to be a better choice. While fiberglass doesn’t experience the corrosion problems that steel and concrete grease traps do, it has some other challenges.

Fiberglass' rigidity and the use of other materials for inlet and outlet connections can create problems.

Grease traps – at least most grease traps – don’t last forever. Understanding why some fail might help keep your current interceptor running efficiently. If you’re in the market for a new grease interceptor, understanding why they fail might help you make a smarter choice.

Today we take a look at why concrete grease traps fail.

Concrete grease traps are the oldest type of grease interceptor still in common use, but they have a number of inherent problems that lead to failure.

If you read our post on how emulsions can lead to fats, oil and grease (FOG) escaping a grease interceptor, you know that some grease will inevitably get into the wastewater system.

While the amount of grease getting through each day doesn’t seem that large, it constitutes what many feel is the greatest threat to the world’s sewer systems. 

You might wonder why it would be a problem if the fats and oils have been emulsified — broken into tiny particles — through physical emulsion or, via soaps and detergents, chemical emulsion. And what that has to do with grease interceptor design.

Even if a commercial kitchen has an effective grease interceptor properly installed and maintained, fats, oils and grease (FOG) can still escape into the wastewater system.

While no grease removal system is 100 percent effective, a properly maintained, modern grease trap can still remove more than 99 percent of FOG found in kitchen effluent. One of the biggest obstacles to grease removal, though, is the invisible thief called emulsion.

Emulsion is a “fine dispersion of minute droplets of one liquid in another in which it is not soluble or miscible.” So what does that mean in plain English? And what can you do about it?

It happens every year during the holidays: Home cooks rev up their ovens and deep fryers and in go millions of turkeys in preparation for Thanksgiving day feasts.

The following day, and sometimes even the same day, plumbers and sewer district workers get called out to deal with blockages, back-ups and overflows. It’s messy and expensive. And it’s all completely unnecessary. 

But, as someone who works in wastewater treatment, you knew that. 

The question is, how do you eliminate, or least reduce the impact of, the annual Thanksgiving grease-apocalypse. The goal, obviously, is to convince as many people as possible about the dangers of dumping turkey grease down the drain.

Many local sewer ordinances require that food service establishments make their grease interceptors available for periodic inspection to ensure they’re working correctly, keeping fats, oil and grease (FOG) out of the wastewater system.

And the tool of choice for many pretreatment coordinators and other professionals is the dipstick (or popularly, the Sludge Judge, a specific brand of dipstick). It’s a long, clear plastic tube that enables anyone to quickly measure how much grease a grease interceptor has accumulated.

While dunking a dipstick into a grease interceptor may allow you to quickly determine whether or not it needs to be emptied, it doesn’t really tell you how well the interceptor is keeping grease out of the wastewater system. 

Across the country and around the world criminals are targeting a new kind of “liquid gold” — used cooking oil.

The headlines say it all:

“Three charged in Harford in $1 million scheme to steal used cooking oil”

“Huh? Thieves stealing used cooking grease to turn into quick cash”

“Theft of grease for biofuel gets stickier”

In 2014, two brothers, both in their 70s, pleaded guilty to federal charges of conspiring to sell and transport used cooking oil stolen from restaurants in Rhode Island and Massachusetts. The FBI wiretapped a federal informant to bring the pair to justice, and prosecutors said the two men stole grease worth more than $120,000 over the course of two years.

Businesses and local authorities, though, are fighting back.

The American Society of Mechanical Engineers (ASME) developed standards in the 1990s to govern passive hydromechanical grease interceptors. The standard was developed in collaboration with the Plumbing & Drainage Institute, and is referenced by the Uniform Plumbing Code, the International Plumbing Code and the National Standard Plumbing Code.

The standard — ASME A112.14.3 — is the measure by which passive grease interceptors (including many of Thermaco’s products) are measured. If it meets the standard, then the interceptor can be used in many installations. If it doesn’t, then it’s a non-starter. 

So how, exactly, does one test a grease interceptor to see if it meets the ASME standard? 

Fats, oils and grease (FOG) in wastewater are one of the biggest challenges facing wastewater systems around the world. Grease, sometimes along with solids, can build up into a solid mass that can narrow or even block wastewater pipes. When that happens, sewers overflow, pipes break, and local authorities are forced to clean up the mess and make repairs.

In the United States alone, the Environmental Protection Agency estimates that as many as 47 percent of all wastewater system blockages are caused by the buildup of grease. In New York City alone, those annual repairs cost nearly $5 million. Other large cities also rack up multi-million dollar bills for repairs and emergency service.

Cities are adopting a number of tactics to keep grease out of their wastewater systems.