From space, it is easy to understand why our earth is called the ”blue planet.”
Twenty-nine percent of its surface is occupied by land, 71 percent by the oceans that contain more than 97 percent of the earth’s total water.
The remaining 3 percent makes up the only fresh water on our planet and of that, 2.5 percent is in frozen form.
By 2050, the earth’s human population is expected to approach nine billion. Of that .5 percent of fresh water, growing food uses 70 percent while industry uses another 22 percent. Excluding marine life, the remaining 8 percent of the world’s fresh water must be shared by every living being on earth.
That’s why the fight to secure fresh water by us living beings is so important.
And that’s why the technology being tested in Roberts, Wisconsin, could have a huge impact not only here in St. Croix County, but across the state, the nation and the entire globe.
That new technology looks like some contraption from the future, a work of fiction, a network of glass tubes filled with flowing green liquid flooded with ultraviolet light out of which pours water clean enough to drink.
Sounds too good to be true?
On Dec. 1, 2010, the Wisconsin Natural Resources Board adopted new stricter limits governing the allowable levels of phosphorus in treated water. The Department of Natural Resources (DNR) revised effluent level limits for phosphorus regulated via the Wisconsin Pollutant Discharge Elimination System (WPDES) permitting process.
It was generally acknowledged at the time the new limits were adopted that the technology to actually remove enough phosphorus from water to meet the new standard did not exist, nor did the tools required to measure such finite detection.
Luck of the draw has put the St. Croix County community of Roberts at the head of the line, making it one of the first communities around the state to comply with the new Phosphorus Water Quality Standard beginning in 2018.
The Roberts wastewater treatment plant is considered a minor utility designed to treat an average flow of up to 465,000 gallons per-day. The old limit for allowable phosphorus in treated water for Roberts was 1 mg/l with a cap of 880 pounds per-year. The new limit, using the same 800-pound annual cap, is .04 mg/l.
Two months ago, finding a solution to meet the new standard, let alone the astronomical funding it would likely take to construct such a new technology, seemed a pipe dream.
Then at the Oct. 10 village board meeting, Roberts Public Works Director John Bond told board members the phosphorus removal pilot plant the village had been testing for two weeks had, so far, exceeded expectations in a big way.
The samples tested from the village pilot program had exceeded the DNR-mandated limits showing up as “zero detect,” according to Bond. Testing of additional samples were being sent to an independent third party lab to verify those results last week.
“Every batch that we have run through this plant, the final product has come back with zero detect for any nutrients. Another micro-filtration pilot program we ran, which was a mechanical process, got us to the limit for phosphorus, but nothing other than phosphorus and the cost was prohibitive. With this process, we are not only achieving no detect on phosphorus, it’s taking care of nitrogens, the BODs, the suspended solids, and the trace elements like copper,” said Bond.
Advanced Biological Nutrient Recovery (ABNR) could offer a long-term, cost-effective, sustainable recovery solution to meet or exceed the DNR-mandated limits for phosphorus and other nutrients.
The technology, developed by Clearas Water Recovery out of Missoula, Mont., uses algae grown by photosynthesis to feed on targeted nutrients like phosphorus and nitrogen present in the effluent of typical wastewater treatment facilities.
The ABNR system starts by mixing phosphorus and nitrogen-loaded wastewater (effluent) with a “bio-diverse” blend of algae and other micro-biology. The liquid mixture is fed into a “photobioreactor,” a network of plastic or glass tubing where it is circulated while being exposed to ultraviolet light sources causing photosynthesis to occur.
During photosynthesis, the algae feeds on the phosphorus and nitrogen and other nutrients in the effluent. The wastewater effluent, now free of phosphorus, nitrogen and other nutrients, is separated from the algae using a sophisticated filter system generating oxygenated clean water for reuse and a biomass recycle stream which is returned to the mix stage to re-initiate the treatment process.
Clearas technician Kellen Triplett explained how the system works.
“Clearas systems work in three phases: a mixing phase, an actual recovery phase and then a separation phase. In the mixing phase, the wastewater effluent mixes with the algae culture, one part algae to one part wastewater. We inject CO2 because the algae needs a carbon source and also to regulate the PH level of the water. When the algae cells are in the recovery phase, they are creating oxygen in an enclosed environment, the tubes, which increases the PH level of the water. The recovery phase happens in our photobioreactors. This is where the party, photosynthesis, actually happens. Depending on the size of the system, the algae effluent mixture either circulates or operates as a one pass system. The algae cells pick up photons from sunlight during the day and from LED lighting at night if necessary so the system can operate 24 hours per day. As the algae cells grow, they ingest the nutrients in the effluent. The algae cell mixture is added to the effluent proportional to the nutrient level in the effluent. In the separation phase, the algae effluent mixture is pushed through a honeycomb-like filter, which allows clean water to pass through while the algae remains trapped in the filter. Then the clean water is pumped into one tank and the algae into another tank,” said Triplett.
During the course of testing the Clearas technology, the wastewater treatment plant still had to meet its existing phosphorus limit, so the testing initially used effluent which contained the chemicals the plant currently uses to combat phosphorus.
Over the final days of testing, Bond and Triplett upped the challenge by using completely untreated effluent devoid of any chemicals to see if the process could handle the additional load of pollutants.
“When my effluent normally leaves the plant, I’m at about 0.5 - 0.6 mg/l phosphorus. So that’s what he’s growing right now. If I don’t add chemical, I’m about 4 mg/l - a huge difference. That untreated effluent will be what we test Thursday,” said Bond.
By increasing the amount of algae in proportion to the load of phosphorus, Bond and Triplett expect the same no detect results. The implications of that kind of success are large.
“If it reacts like we think it will, there are three parts that are huge factors for the Village of Roberts. One - we could eliminate chemical feed, and that’s roughly $18,000-$20,000 per-year that we spend. That goes away. When you use chemicals, the solids, like phosphorus cling to the chemical additive which becomes heavier than the water and they sink to the bottom into the sludge. We have to ship that sludge to Ellsworth and pay to have it treated. Two - our sludge production would decrease, saving us money on that whole process. Finally, three - there is a market to which you can sell the algae. Potentially it looks like we could, between the savings on chemical, the savings on the sludge, and the sale of the algae, have a process that may pay for itself. In wastewater, that’s unheard of,” Bond said.
Too good to be true?
The results from the third party testing came back and they confirmed no detect at all levels of effluent tested.
Clearas executives are scheduled to meet with city officials from Roberts sometime the end of this year or beginning of next to present all of the exciting possibilities.
As for the need to perfect this type of technology for the benefit of all mankind?
It’s being played out right here in Roberts, Wisconsin.
From space, it is easy to understand why our earth is called the ”blue planet.”