Features Aquaponics Education Research
Doors open at Lethbridge College

In their desire to expand, or even get up and running, RAS operations face challenges with effluent content. However, new tools are in development to help with this, using cutting-edge RAS research equipment at the Aquaculture Centre of Excellence/Centre for Sustainable Food production at Lethbridge College in Alberta, Canada.

“We are very excited to have a new, state-of-the-art facility and an extensive range of equipment we’re testing and developing for aquaponics, RAS and hydroponics research,” says Centre chair John Derksen. “For fish studies, this includes aerobic bioreactors, our own revolutionary biofilters, dewatering disc filters for fish sludge, and automated microclimate control systems, with pilot-scale RAS and 51 experimental aquaponics modules from 80 to 700 litres in size.”

He adds that “to enhance our research capacity, we have also developed 42 micro-aquaponics units that are vertical and shelf-based. Simple to operate, these systems have already provided valuable data for us for our mass balance studies, which define where the nutrients go when fish are fed (i.e. fish mass, dissolved nutrients, suspended and settled solids, and plant tissue).”

The team designed and constructed its own RAS system, incorporating its research findings into the design.

Five fish species have been studied so far and mostly in aquaponics: tilapia, rainbow trout, coho salmon, barramundi and grass carp, with carp tilapia and rainbow trout being the principal species for performance testing in RAS systems. Studies include treatment methods for fish water, waste and mortalities, refining biofilter systems and production of fertilizer from fish waste. Projects to come will include fish feed testing and containerized aquaponics production.

“Aquaponics production is the future, in my view,” says Centre researcher Dr. Nick Savidov. “Its circular nature is extremely sustainable, and I believe we’ve globally only scratched the surface of its potential.” Derksen adds, “we know that fish waste issues are holding back the expansion of aquaculture in Canada and elsewhere, and in a recent meeting with personnel from the Department of Fisheries and Oceans, we told them aquaponics is the answer, not constructed wetlands.”

Savidov explains that in addition to all their other projects at the Centre, “we are creating a really robust new simulator so that fish farmers who want to expand can do so confidently through aquaponics as a fish waste solution. The simulator will determine how much phosphorus or other nutrients they will be producing at various levels of expansion and calculate the size of greenhouse required to use these nutrients. It’s very exciting that they can make money with their fish waste and produce even more local, fresh food. We’ve shown that about three grams of fish feed is all that’s needed to support one m3 of plant growth.”

One well-established North American aquaponics operation is Superior Fresh in Wisconsin, where they’ve been growing organic greens and Atlantic salmon since 2017. The operation has a semi-decoupled RAS system, with interconnected but separate greenhouse and aquaculture operations. The same water usually flows through both, then is cleaned and recirculated.

In Canada, a new aquaponics company called Stack Industries is doing things a little differently. At their large facility in British Columbia near the US border currently under renovation, they will cultivate organic rainbow trout and a highly-nutritious crop called water lentils, with first harvest expected in early 2024. Water flow will be decoupled in that the fish RAS system and water lentils system will have their own process flows. There will be very limited mixing and different temperatures maintained. Fish waste will spend 15 days in a biodigester and then added to the water lentil tanks. After waste removal, the filtered water will go through a UV system and a moving-bed bioreactor where bacteria will convert ammonium from the fish waste to nitrite and nitrate.

Bioreactors at Lethbridge
In the early 2000s, for the first time in the world, aerobic bioreactors for aquaculture use were proposed, designed and proven in an aquaponic facility at Crop Diversification Centre South in Brooks, Alberta. They were further modified and improved at the Aquaculture Centre of Excellence through an aquaponics project that ended in 2021.

Centre for Sustainable Food Production

The Centre has computer-controlled aerobic bioreactors at its disposal, which achieve complete conversion of all the solid fish waste produced. Liquid solids are turned into a high-value liquid fertilizer in three weeks using a proprietary process. In addition to fish waste, mortalities and offal can also be added to the bioreactors, after going through the Centre’s industrial grinder.

With regards to the quality of their fertilizer product, Derksen points out that not all fish fertilizer is equal. “Most are smelly, ours is odourless,” he says. “The level of plant-available nutrients is generally lower in other products, where our nutrients are 100 per cent plant-available, in mineral form. Ours is also completely stable and very safe, without any human pathogens, like E.coli or Salmonella. We’ve shown it has no biological activity even after a year, so there’s no risk of containers exploding or change in available nutrient levels. We are close to selling the intellectual property to a company that will commercialize the process.”

In addition, further automation of the bioreactor is coming. “We’re automating so that every time the drum filter backwashes, it fills a reservoir that goes into the bioreactor and there’s no handling of backwash needed,” says Derksen. “Also, the Opto22 platform that automates the hydroponics is being set up to control our fed-batch bioreactors. It’s a very user-friendly platform that allows modifications to easily be made.”

Biofilters
Another innovation at the Centre is the high-efficiency black carbon water-polishing trickling biofilters that achieve very high water quality.

Black carbon bed

For almost 20 years, Savidov had been testing black carbon (made using a process called pyrolysis, that converts all biological material into charcoal) as a soilless growing media for hydroponic plants, and he wondered how it would work to filter fish waste. Savidov, Derksen and others have been working on their black carbon biofilter aquaculture beds for about four years, and found that they are extremely effective and reliable as both a fine mechanical filter and biofilter.

“The black carbon possesses dramatically more surface area for bacterial colonization than any other material or product available,” Savidov explains. “Black carbon is amazing because it’s so stable and has an incredibly large pore area. In one gram, less than a teaspoon, you have a surface area of 2,000 to 3,000 square feet. The microscopic nanopores offer great buffering capacity, the larger micropores can host legions of beneficial bacteria and the still larger mesopores retain particulates. And the black carbon never has to be replaced or backwashed. We have created something unique in the world.”

The water quality is truly outstanding. “It’s crystal clear, even in the tilapia tanks, and we get better dissolved oxygen too,” says Savidov. “We went from an 80-micron to 30-micron drum filter that takes most of suspended solids out, and anything that gets mineralized is removed by the trickling filters. We don’t even have to use a fluidized sand filter, so the black carbon filters have a dual role. This is incredibly important because many aquaponics operations have failed because they didn’t handle the solids effectively. And the cost is nothing compared to other biofiltration systems.”

Only about 10 per cent of flow goes through the trickling filter, in a side loop. The carbon filter nitrifies 95-100 per cent of the ammonia, at a rate of 64 litres per minute (total facility volume: 80,000 litres). And while the bed does take up floor space, Derksen, Savidov and their colleagues have also created vertical systems. To keep the entire bed aerobic, they’ve injected oxygen into every layer, but oxygen-rich water can also be forced to flow through the layers.

In a real-world application, Derksen and Savidov recently gave some of their ‘activated’ carbon to a Red Deer, Alberta aquaponics company called NextGen Aqua to which they provide consulting. “We put some black carbon in a barrel on the side of our system for about four weeks to let the bacteria grow, and then gave it to this client for use in their biofilter bed,” Derksen explains. “It worked perfectly for them since day one. It was totally seamless for them, with ammonia levels completely controlled from the start.”

Savidov adds that “the water is so clean that we don’t need to add water to backwash our drum filter (we use the water from the black carbon filter), and we don’t need to discharge. This again reduces the environmental footprint and it’s another huge step closer to a zero-waste aquaponics system.”

Unique approach
Savidov explains that the Aquaculture Centre of Excellence pursues an “ecosystem approach” to design the most efficient food production system that will not pollute the environment with phosphorus or other wastes. 

Post-carbon filtration

This approach is different from so-called decoupled systems, where two monoculture systems, hydroponics and aquaculture, are simply combined to utilize just a part of nutrients produced by fish.

These decoupled systems represent what Savidov calls a “hydroponic approach,” where the water is not recirculated back to the fish. In this case, the biofiltration ability of plants to remove such pollutants as phosphorous and nitrogen is not fully utilized for the benefit of fish production.

What is even more important, he says, is that decoupling interrupts the natural development of beneficial organisms, which form the ecosystem. 

“That’s why it can be called a hydroponic approach as opposite to an ecosystem approach,” he says. 

“Unfortunately, the hydroponic approach is often the result of the lack of understanding how aquaponics really works. In the decoupled systems, the water (containing residual minerals) still needs to be discharged, while in aquaponics the same water can be recirculated indefinitely, without discharging.”

Savidov is proud that the Centre has nine small aquaponics systems which have been continuously recirculated for 19 years. 

“With our filter beds, bioreactor use, production of the best fertilizer possible and our ecosystem approach,” he says, “we are bringing aquaculture to its potential through aquaponics, to be the first animal protein production system that’s zero waste.”