Can a nanotech product be the solution to a challenge as daunting as removing phosphorus (P) from the watershed?
Ed Weinberg is optimistic it can.
He’s hoping the Chippewa First Nation pilot-scale demonstration of nanotechnology mitigating dissolved P in surface runoff and tile drainage (edge of field) will provide the necessary data to spark a sustainable, reusable circle economy.
Why it matters: Phosphorus is considered one of the main problem pollutants going into Lake Erie, causing algal blooms.
Weinberg, president of ESSRE Consulting, has spent the last 14 years creating an engineered solution for sustainability and renewable energy projects.
As part of the Chippewa First Nation pilot project for innovative watershed scale approaches to pollutant phosphorus reduction, Weinberg went big by going small – really small.
Without getting too heavy into a math equation, one milligram of quartz sand and 100 microns is equivalent to nine square centimetres and 100 particles of absorption surface. Grind that to one micron, and it increases to three square metres of surface area and one billion particles. But Weinberg goes further.
“If you were to take that, with nano-manufacturing, to 10 nanometres, now you are up to 300 square metres, a couple of more orders of magnitude to 100 trillion particles,” he said. “Now you have all these surface sides to capture dissolved phosphorus.”
The beauty is the highly porous nano-enhanced Phosphorous Absorptive Materials (PAMs) are commercially available and allow water to flow through, negating concerns around flooded fields or blockages in media, said Weinberg.
In the Chippewa study, Weinberg used two different products, the Po4 Sponge and the SmartSpongeHM by AbTech Industries.
The PO4 sponge uses MetaMateria as the supplier seeded with 20 to 100 nanometres of phosphorus-binding iron oxide crystals within the rust-coloured cube.
The SmartSpongeHM is a commercial stormwater product designed to absorb heavy metals (HM), but Weinberg enhanced its PAM ability with nano-impregnated wood.
At the Chippewa and Woodstock project sites, Weinberg used a donut ring style deployment around Hickenbottom Tubes with the outer wood-filled layer working as a sediment trap and the inner ring containing either the SmartSpongeHM or the Po4 Sponge.
In Woodstock, a five cartridge unit filled with Po4 Sponge was installed at the base of a Hickenbottom Tube to measure dissolved P capture rates as water flowed toward the drain.
Finally, filter socks of SmartSpongeHM and stacked baskets of coupon-shaped Po4 Sponges were fitted in the edge-of-field tile drainage inlet, capable of allowing 400 gallons-per-minute flow in a storm event.
The results showed the Hickenbottom Tube media far outshone the tank media by pulling approximately 41 milligrams of P out of 152 grams of media, where the tank cumulatively removed 18 milligrams with a shorter media life expectancy.
“When we look at that tank arrangement on the tile drainage, you could see much less pick up, much greater acreages and doubling of costs,” he said. “Which gives us an indication that we should really go after where the phosphorus is most concentrated, which would be at the surface.”
Compared to other best management practices for removing phosphorus, the Chippewa project costs $119 per project-acre, nearly equivalent to forest buffers at $108 per acre. The nearest traditional cost-per-pound of dissolved P removal was growing energy crops for biofuel conversion.
The Woodstock Hickenbottom drain media cost $43 and $11 per-project-acre respectively, which is relatively equal to the more traditional management of P via cover crops costing $27 per acre and grass buffers at $17 per acre.
The open-drain media cost the most at $353 per-project-acre and was the least effective in dissolved P removal.
“Theoretically, if I treated 618 acres with that (Hickenbottom) PAM media, I would get a break-even on fertilizer savings (at a total investment cost of $75,542),” Weinberg said.
The potential exists to apply the media to remove dissolved P from manure, biosolids and digestate before land application and has urban applications within municipal drain collection, sewage treatment and legacy P.
Weinberg said if farmers were charged 20 per cent of the original price and municipalities’ drain collection or sewage treatment plants were charged 80 per cent, the break-even point would be 15 per cent.
“All those provide a compelling case for a circular economy built on phosphorus removal,” he said. “This ESSRE RePleNish program using the nano-enhanced PAM is a viable watershed-scale solution for direct removal of dissolved phosphorus in all these cases.”