David Casaletto, Executive Director, Ozarks Water Watch

 

Last Thursday I attended the "Putting Green to Work" luncheon held at the Paul R. Noland Wastewater Treatment Plant in Fayetteville, AR. Our topic this month was Fayetteville's Biosolids drying facility. During the process of wastewater treatment, most of the treated water is cleaned and can be returned directly to the environment. But some water and the solids left over, called sludge, have to be disposed of in some manner. The sludge, even after being dewatered by a belt filter press, still contain nutrients, harmful microbes and 82% water. Up until 2003, Fayetteville land applied the sludge on fields, a very common practice.

 

Example (from the web) of sludge being land applied Note: Fayetteville had a much nicer truck!

 

In 2003, the city's hay fields receiving the sludge became over-saturated with nutrients and the city started hauling the sludge to a landfill for disposal. Over time, with rising transportation costs and tipping fees, the landfill option became very expensive and officials started looking for a better way.

 

Three truckloads of sludge a day arrive to be dried

 

Across the country many municipalities will dry the sludge to a "Class A" biosolid. This product still contains nutrients but the harmful microbes are killed and the water content is reduced drastically. A common drying method in southern hot climates is solar while other cooler areas will use a thermal dryer that utilizes fuel such as electricity or natural gas. After much research and study, Fayetteville decided on a combination of solar and thermal drying.

 

Wet sludge being spread to dry in solar house.

 

Almost 3 semi-truck loads a day of wet (82% water) sludge arrive at the drying facility. In the summer the sludge is spread out in 6 large computer controlled solar buildings where it will stay for 8 days and be dried to 40%. An automatic machine called a mole rakes and turns the sludge for even drying.

 

A "mole" rakes and turns the sludge.

 

The solar dried product is then loaded into a large hopper to be fed into the thermal dryer. The dryer is fueled by natural gas and will heat a batch of solar dried biosolids for 45 minutes at 370 degrees until the water content drops to 10% and all microbes are killed. In the winter when solar is not available, the wet sludge is fed directly into the thermal dryer and heated to 433 degrees for 3 hours. At this point the biosoilds are considered "Class A" and can be safely added to the soil as a fertilizer. What once weighed 120# wet now weighs 20# dry.

 

Natural gas dryer removes water and kills microbes

  

Testing has shown that the finished product contains 7% nitrogen, 7% phosphorous and 1% potassium. Fayetteville has had no problem selling their Class A biosolids at $15 a ton (soon to go to $20) as the equivalent cost for that amount of commercial nutrients would be $117 per ton. 

 

A few handfuls of the finished product.

 

Not only does the biosolids drying facility allow Fayetteville to lower their costs, it is the "green" thing to do. It lowers the carbon footprint and recycles the nutrients instead of taking them to the landfill. The Fayetteville Wastewater Treatment Plants and the Biosolids Management Site are operated and maintained by CH2M HILL.

ADEQ issues permits and guidelines instructing farms on the proper disposal of animal waste. This particular operation is near Big Creek, a tributary of the Buffalo River. There is concern, that despite regulatory requirements, waste from the thousands of animals could eventually find its way into the Buffalo. The Buffalo River is unquestionably a treasure, both for Arkansas and for America. As our country's first national river, it has been a source of Natural State pride for generations. As you can imagine, my office has received numerous calls and e-mails from Arkansans worried about the potential environmental harm the hog farm could have on the Buffalo and its tributaries.

First let me say that, based on previous legal interpretations, neither I nor my ADEQ director has the legal authority to unilaterally halt a properly permitted farming operation, or to declare an executive moratorium on such farms near certain bodies of water. When concern began to grow about the C&H Hog Farm, I had ADEQ officials review the entire permitting process to ensure that the farm's owner had followed all state requirements and procedures. And he had. The farm has plans in place to manage waste disposal and undergo regular testing and monitoring. However, while the state may not have the authority to stop the operation of a legally permitted farm, we do have the authority to go above and beyond the required diligence for environmental monitoring. Next month, I will ask the Arkansas Legislative Council to authorize $250,000 to establish additional testing in areas on and near the C&H Hog Farm.