ROBERTS -- Jan. 1 and the considerably more stringent phosphorus discharge limit are right around the corner for the Village of Roberts.
The good news is, four of the 10 new photobioreactors constructed to meet and exceed that limit are now running green injected with the algae required to remove phosphorus (and other pollutants) from the village’s wastewater.
Six additional photobioreactors await the process of commissioning, testing with clean water to make sure there are no leaks and that all of the mechanical, technical and digital components of the system are functioning properly, to be followed by inoculation, the introduction of the algae into the system to commence the photosynthetic cleaning process.
Initially anticipated to be fully operational by sometime in August, construction of the Advanced Biological Nutrient Recovery system has been slowed by manufacturing delays related to the pandemic and subsequent scheduling conflicts with contractors.
“Part of the problem has been, when you do need parts, you can’t get them. The delays to get what we need have been frustrating. Unfortunately with COVID-19, a lot of these manufacturers don’t have these parts sitting on the shelves anymore. The lack of inventory means that, when you order them, you have to wait for them to be built. But it is exciting to finally see green,” said John Bond, the Roberts Public Works director.
CLEARAS Water Recovery Inc. designed and engineered the ABNR system, the first of its kind in the world. Nearly all of the new technology is in place.
The Clearas team is hoping manufacturing flaws in the valves on the pumping units which prevented them from opening and closing properly leading to leaks and the necessity to rebuild the valves will be the final hurdle.
The photobioreactors are constructed in pairs known as fences. To keep the project moving forward, three fences (six photobioreactors) were taken offline to repair the flawed valves while crews inoculated the two remaining fences by adding 10 pounds of algae to the wastewater circulating through the reactors to begin the process of increasing the total suspended solids or TSS.
Once the valves are repaired for fences 1, 2 and 3, fences 4 and 5 will be taken offline so their valves can be rebuilt.
The system currently operates as a closed loop recirculating the same water and requiring the addition of “food,” phosphorus and nitrogen, to grow the algae. The idea is, that as each photobioreactor reaches the correct TSS, the next reactor is brought online and the process starts again until all 10 reactors are functioning at the proper density.
“By the beginning of November, we should have algae in fences 1, 2, and 3, while we are converting 4 and 5. By the middle of November, we hope to have algae in all five of them,” said Autumn Fisher, regional director of project delivery for CLEARAS. “There might still be a period of acclimation where we have to get the TSS up a little bit higher, but that would be about the time we would begin the continuous flow treatment,”
Continuous flow signals the point at which the loop is opened and wastewater will begin to flow continuously into the photobioreactors from a retention tank. At that point, the wastewater will provide the phosphorus on which the algae will feed and the supplemental feeding will stop.
“It takes the algae time to grow. So we only put about 10 pounds of algae into the tubes initially. With that small amount of algae, the pipes are barely green to the naked eye. So every day that algae replicates, it multiplies, so you slowly get more total suspended solids, and the tubes turn more green. When the algae reaches the TSS for normal operation, it’s going to be a very, very dark green. It will look almost black,” Fisher said.
Once the algae growing process begins, it must continue 24/7 so lights that emit a red and blue wavelength are strategically located along the photobioreactors to keep growing conditions optimal even at night.
Once the ABNR system is fully functional, wastewater will flow continuously from the retention tank to the mix tank where it is mixed with a biodiverse blend of algae and other microorganisms. That mixture flow is then pumped into the photobioreactors where it is circulated for about 50 minutes promoting photosynthesis, allowing the algae to consume the phosphorus and other pollutants. The effluent then exits the reactors and flows through membranes that separate the clean oxygenated water from the algae biomass.
The clean water is discharged and part of the algae biomass is rerouted back into the mix tank. The other portion of the biomass enters a centrifuge which further separates the algae into a byproduct for sale.
The whole system is automated by a computerized control panel which also provides remote oversight by Public Works personnel.
The ground-breaking project represents a sizable financial investment by the village and return for CLEARAS, but is even more so about proving the ABNR concept and what it means for the future of clean water everywhere.
“I’ve got about seven years of my life invested in finding this technology to meet these limits. So I’m this close now to proving this is the right technology. I’m looking forward to that day. When we prove that this is the right technology, this will open up a lot of opportunities in the state of Wisconsin and beyond for a lot of treatment plants,” Bond said.