By the end of this year, the Altoona Water Authority will have brought in about $2.3 million in revenue from treating landfill leachate.

But it will be scaling back on accepting the material, because nitrogen from processing the runoff that was discharged to a stream this year has exceeded the authority’s permitted limit, forcing it to purchase nitrogen credits.

Moreover, the authority’s new digester will soon begin impinging on the Westerly sewer plant’s excess treatment capacity.

“The past year we pushed the plant as far as it could go and consumed all the nutrient credits,” Wastewater Treatment Director Brad Kelly said at a recent authority meeting. “We’ll need to buy credits at the end of the cycle.”

He’s not sure how much the authority will need to buy.

Conversely the authority is under the limit for phosphorus and has some credits available, according to General Manager Mark Perry.

Despite the nitrogen overage, it was the right decision to take the leachate, according to Perry.

The authority this year has been accepting about 5 million gallons per month of the landfill runoff, according to Kelly.

And while the need to buy credits might offset about $300,000 of the leachate revenue, the authority will still be “$2 million to the good,” Kelly guessed.

Further, processing the contaminated water, which is created when rain filters through landfill trash before being collected, helps the environment, Kelly said.

Last year, the authority broke even with nitrogen, which was ideal, he said.

This year, in going over the limit, “we found where the threshold was,” he said.

The threshold is dependent not only on leachate quantity, but on contaminant concentration, Kelly said.

He has had to refuse leachate from a couple haulers because the concentration of their loads was too high, he said.

The threshold will also need to be adjusted because of the digester.

The dewatering of liquid sludge that will be brought in from other sewer plants for the digester creates “centrate,” a nitrogen bearing liquid that will go to the head of the Westerly plant for treatment, according to Kelly.

That means there will be less leachate leeway.

The authority started seeding the digester with sludge about two months ago and in September was expecting soon to begin producing biogas, according to Kelly.

It’s necessary to heat the digester contents to between 96 and 100 degrees to produce the biogas, and thus, the authority has a startup boiler that runs on gas from the grid, Kelly said.

This month, there should be enough biogas created to justify starting a “flare” to burn off the excess, Kelly said.

In December, the authority will begin bringing in high-strength food waste from restaurant grease trap haulers, snack food makers and dairy product plants to feed the digester.

A separate biogas boiler will take over the digester heating for the startup boiler when there’s enough biogas to supply it.

Biogas will then run a sludge dryer.

The sludge dryer can treat both the sludge produced by the authority and sludge imported from other authorities, creating mulch dry enough that the authority can give it away or sell it, eliminating the difficult and expensive problem of getting rid of wetter sludge.

Mirror Staff Writer William Kibler is at 814-949-7038.