• July 22, 2014

Grease a daily challenge for WCID-1

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Posted: Friday, December 14, 2012 4:30 am

Cloise “Homer” Graves grows microscopic “bugs” in Killeen’s sewage for a living.

Treating sewage is a biological process, said Graves, an operations manager at Bell County Water Control and Improvement District No. 1. The bacteria-consuming organisms naturally clean the sewage, which flows into the plant with each flush of a toilet.

The sewer mains carry different materials, which threaten the plant’s infrastructure, including debris, soap, dirt, rags, hair, heavy metals and toxic chemicals.

It takes about 10 days for a gallon of wastewater to be cleaned and reintroduced from the WCID-1 treatment plant into Nolan Creek.

“We can have a different biomass in 24 hours,” Graves said. “It is a very delicate process.”

Graves said the biggest challenge for the WCID-1 wastewater treatment plant is a chronic problem: grease. “It shocks the system.”

Grease increases the plant’s electrical and chemical costs, and half of each workday is spent cleaning grease out of plant infrastructure, said wastewater superintendent Wayne Lovett.

The cost of treating grease is higher than the cost of treating soap, trash, dirt, or any other material except massive amounts of blood, said WCID-1 General Manager Jerry Atkinson.

System overflow

Two 50-by-20-foot drying beds holding 24,000 pounds of solid grease sat in the sun last week at the WCID-1 north wastewater treatment plant, waiting to be loaded into hazardous materials trucks and taken to the landfill.

This grease is not from the north plant.

WCID-1 has transported the grease from the smaller south plant into these beds because it has run out of places to store it.

Although the south plant is half the size, it receives 55 percent more grease, Atkinson said.

Over the last year, WCID-1 has spent $130,000 dealing with grease.

If the water that WCID-1 releases into Nolan Creek does not meet guidelines set by the Texas Commission on Environmental Quality, it can face fines as high as $16,000 a day.

“If we don’t do something about it now, well, guess what will have to happen to the cost to customers,” Atkinson said.

A greasy process

At the plant, grease is found in each of the five main treatment processes.

Wastewater enters the plant through the headworks, a tall metal structure that separates trash and debris from the water through large metal filters and plastic brushes.

At least that is how it is supposed to work.

With each wave of wastewater coming into the plant, grease deposits coat the filters, forming mounds of debris or grease balls, which jam up the infrastructure before the wastewater has entered the treatment process.

To clear the filters, Graves uses a hot-water power washer, which melts the grease into a liquid and passes it on to the next stage.

“What costs the plant the most money is the grease you can’t see,” Graves said. “Once grease is in the system it doesn’t get out unless you take it completely out.”

Even in the second stage of aeration, grease gums up the infrastructure.

In this stage, the water is pushed through a series of diffusers, or thin rubber membranes that transfer air into the sewage to speed up the biochemical process.

In 2009, a few thousand of these diffusers were eaten up by grease at the south plant, Atkinson said.

“It ate all of this up and air was not able to go through,” Atkinson said. “I have never seen grease eat plastic like that in my life.”

The incident resulted in a $954,000 fine paid by the city of Killeen and was the impetus for the city’s 2010 Fats, Oils and Grease law.

“Not only that, but we lost our ability to treat our water,” Atkinson said.

Atkinson has taken a hard line on compliance with the city’s grease ordinance, urging more restaurants to comply with the law and spreading awareness to residents about the problem. Currently 49 of the city’s 255 restaurants are complying with the ordinance.

“Grease is the biggest enemy of the plant,” Atkinson said. “We have to have more compliance.”

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