PIA experiments with 'sludge' composting
Kyle Clayton / Petersburg Pilot
The sludge is constantly being aerated to increase bacteria productivity in the digester at the wastewater treatment plant.
The stuff you flush down the toilet might spruce up town if Petersburg Indian Association's new compost plan works out.
"It's a lot less gross than you think," said Jason Wilson, PIA tribal resource director.
Justin Haley, wastewater-operating supervisor, and his staff calls it sludge and Wilson took a tour of the facility earlier this week.
"Sludge is what we refer to it as until we take the water out," Haley said.
Haley said an average of 400,000 gallons of sludge per day flows from Petersburg's pipes into the treatment facility.
Sludge includes material from toilets and kitchen sinks to rain runoff. Last Tuesday, after the heavy rains, 1.3 million gallons flowed into the plant.
After the material goes through screening processes that remove larger particles, the sludge goes into a clarifier and then the 'digester'-a pool holding a brown bubbling bacterial all-you-can-eat buffet.
"We're giving them air so they can live," Haley said. "Eventually they run out of food. There's a limited amount and they start consuming themselves. As they die off more will eat them, they kind of turn into food for the others. So we're reducing the volume of sludge through digestion."
The leftover material is pressed where the water gets squeezed out. Not all the liquid gets pressed out-about half of what remains is water.
"The remaining half is volatile material that can be composted, broken down further and turned into base components like nitrogen, phosphorus and carbon," Haley said.
Those are the bio-solids that, if PIA staff can pull it off, will be used for compost that the tribe will give to the borough or possibly sell to the state.
"If it's good enough, it won't just stay in Petersburg," Wilson said. "We could sell it to the DOT or various agencies. If they're building roads they could use it for fill or a top layer of soil. As of now our only intention is to see if it works and see if we can do something helpful for the city."
Within two months, Wilson hopes to have a testable product. He'll then send a sample to the University of Alaska Fairbanks where it will be tested to determine whether or not it's viable.