Bugs, Bioreactors and Birthday Cake
It’s not every day you get to celebrate a birthday for billions of bugs—but that’s exactly what happened at Cross Generating Station on July 2.
Team members marked a key milestone in the commissioning of the new Effluent Limitation Guidelines (ELG) Wastewater Treatment System with the addition of microscopic organisms—commonly referred to as “bugs”—to the system’s bioreactor tanks. And in true celebratory fashion, there was even cake to honor the moment.
These tiny organisms may be small, but they play a big role in the plant’s biological treatment process. Their job is to help remove nitrates and selenium from the flue gas desulfurization (FGD) wastewater that flows through the system.
The bugs are first grown in a lab, frozen, and transported to the site in powdered form. On arrival, they’re rehydrated with water and poured into seven Stage 1 and 20 Stage 2 bioreactor tanks—two bags per tank for Stage 1 and four for Stage 2. The same process also took place at Winyah Generating Station.
Inside the tanks, the bugs attach to beds of granulated activated carbon and begin to grow. With proper nutrition, thanks to a carefully measured nutrient feed, they multiply over several days and become capable of treating the wastewater at designed flowrates.
“The addition of the bugs is a major milestone, marking the start of the system doing what it was built to do,” said Julia Talley, Sr. Engineer of Capital Projects. “After years of planning and construction, it is exciting to see the biological treatment process come to life.”
This step marked the transition from construction to operation for the ELG system—a major accomplishment for the team, and a sign that full system start-up is just around the corner.
