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Making compost from wastewater is a piece of “cake”

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By Renae Counter, Editorial Assistant

BIG SKY – When the Big Sky Water and Sewer facility opened in 2004, it set out to be a 100 percent self contained treatment facility. In order to achieve this goal, nothing could go to waste, not even the waste.

“The district chose to make compost instead of trucking the sludge to the Logan Landfill, which would have been a greater cost,” said Peter Bedell, operator at the facility.

Since its opening, Big Sky Water and Sewer has been making compost during the summer months, converting all of the waste from the municipal wastewater sludge in the facility’s ponds into land application compost.

The process takes roughly three weeks from start to finish. The end product is compost that is safe and meets EPA standards.

Compost made from wastewater may sound disgusting, but Big Sky Water and Sewer maintains such an efficient operating and cleaning system that by the time the wastewater is converted to compost it resembles nothing of its previous state, not even the smell. For the most part, the wastewater and compost has no smell at all.

To start the process of making compost, waste is pulled from the holding ponds to undergo a series of treatments. First, all garbage, debris and other obstructions are removed from the wastewater. Next, the water is sent to two holding basins where it undergoes a six hour treatment of agitation and rest. This treatment allows microorganisms to begin breaking down the waste. During the resting stages, the wastewater settles to the bottom of the basins and the remaining water rises to the top. After it’s separated, the top water is pumped to the Big Sky Golf Course and Yellowstone Club course for watering; it has never been sent down the Gallatin River.

The remaining wastewater is stored in two digester basins. From there it’s brought through pipes to the composting building, where excess water is rung out and the remaining waste is formed into a “cake.”

“For conversational terms, this is poop,” Bedell said while holding a piece of cake in his gloved hand.

The cake is sent through a series of conveyor belts before it eventually lands in a large mixing bin. Wood chips and sawdust are added to the mixture before it goes up another conveyor belt to one of five Environmental Compost System vessels. Once full, the ECS vessels are hooked up to two air pumps which circulate both hot and cold air. This air treatment allows aerobic microbial activity to break down the leftover waste. For three days the compost is kept at 55 degrees Celsius, in order to kill any remaining pathogens. To finish off the treatments, the mixture is kept at 45 degrees Celsius for 14 days.

After leaving the vessels the compost is screened to remove large leftover wood chips, which can be reused in another batch. Finally, the compost is stored in bins, ready to be picked up and sold to the public at $20 per yard.

With bare hands, Bedell handles the compost to examine. I took a whiff and got it dangerously close to my mouth and nose before replacing it in the bin.

Bedell laughed. “It’s perfectly safe and nothing a tough Montana girl can’t handle.”

All the operating systems at the facility are controlled by computers to ensure safety of the operation and product. Compost that doesn’t meet the operation and EPA standards is not sold to the public.

Currently, Big Sky Water and Sewer makes compost whenever it begins to run low or sees an increased need for it from the public. Now, with the summer months fast approaching, compost will be readily available and can be picked up at the treatment facility.

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