Biosolids modeling: helping engineers extract more value from sludge

Better, faster, cheaper. It’s the mantra of wastewater treatment plant engineers around the world. That’s why more of them are focusing attention on unlocking the full potential of anaerobic digestion: using the biogas produced to generate electricity and transforming sludge into valuable fertilizer.

Now, an Ontario collaboration funded by SOWC is giving them the design tools they need to do exactly that. In a civil engineering lab in Hamilton’s McMaster University, Dr. Younggy Kim believes the key lies in high-temperature (“thermophilic”) pre-treatment. “We want to develop a new model for the pre-treatment of wastewater sludge,” he says.

Hydrolysis — the first stage of anaerobic digestion — is the rate-limiting step, explains Kim, a Canada Research Chair in Water and Health. Turning up the thermostat to 50°C or higher makes it happen faster. Not only that, it also enhances the breakdown of sludge, increasing the amount of biogas a plant can generate and therefore boosting electricity production. Meanwhile, those faster speeds and greater efficiencies mean plants can use smaller digester tanks, cutting their capital equipment costs.

But to effectively incorporate thermophilic pre-treatment into the digestion process, engineers need numbers. That’s where Kim comes in. For the past year, he and his students have ben testing sludge breakdown at various temperatures and measuring the results as invisible microorganisms worked their digestive magic.

The challenge, Kim says, is that sludge varies from day to day, so they needed a big data set to come up with robust constants. But after painstakingly repeating their experiments with sample after sample, they’ve determined the kinetic constants that describe how fast anaerobic digestion can proceed. Now, they’re ready to hand over a wealth of data to Oliver Schraa.

Building better design tools

Schraa is Chief Technology Officer at inCTRL, a small consulting company in Oakville that specializes in monitoring, modelling and control of wastewater treatment systems. The company sells SIMBA#: simulation software aimed at wastewater plant engineers.

The drag-and-drop simulator allows engineers to build detailed models of wastewater treatment plants, optimizing the design of things like sludge lines, aeration systems, biogas operations and more. And thanks to Kim’s data, inCTRL will soon have a new thermophilic pre-treatment module for their platform. “We want engineers to be able to design these systems accurately and confidently,” says Schraa.

Meanwhile, Kim’s team is also developing sophisticated bioanode sensors to monitor the performance of pre-treatment, generating data that can feed into a process control system.

Safe, nutrient-packed fertilizer

But the collaboration doesn’t end there. In addition to reaction data, Kim is providing inCTRL with information on how higher temperatures can also deactivate disease-causing pathogens — a crucial step for turning sludge into a beneficial agricultural resource.

“In order to use the digested sludge as land fertilizer, we have to make sure the digested sludge is safe,” says Kim.

Farmers look for fertilizers that are free of waterborne pathogens, so the McMaster researchers are analyzing the inactivation reactions of representative microorganisms (e.g., E. coli) that take place during digestion under high temperature conditions. That information will help engineers maximize the beneficial utilization of treated wastewater sludge.

A win-win collaboration

The McMaster/inCTRL collaboration is backed by an Advancing Water Technologies (AWT) Program grant from SOWC. The program connects small and medium-sized water technology businesses in the province with academic experts, leveraging Ontario’s R&D expertise to help companies succeed in the global marketplace.

Kim has plenty of praise for the AWT program. In addition to supporting his research, the grant gives his students the satisfaction of seeing their work applied in the real world.

Schraa shares Kim’s enthusiasm. As a small startup, inCTRL doesn’t have its own lab facilities or the resources to gather the research data for their software. McMaster provides that. Meanwhile, the grant funds a one-year engineering internship at inCTRL. Having co-op student Jerome Remigio on board provides a big boost to the three-person team, as well as training a bright young student for a career in the wastewater industry.

The project also complements another AWT-funded project, run by GE Water & Process Technologies. At a wastewater pilot facility at the University of Guelph, GE has developed a full-scale, “energy-neutral” demonstration system that uses advanced anaerobic digestion technology to enhance the production of biogas, inactivate dangerous microorganisms and extract nutrients for fertilizers. What GE lacked were hard numbers and modelling tools to take their technology to market — key pieces they will have thanks to Kim’s data and inCTRL’s simulation software.

It all adds up to a win-win collaboration. But Schraa expects the benefits of this particular project to continue long after the new SIMBA# module hits the market.

Kim’s data will prove beneficial for other inCTRL projects, while the newly forged partnership opens the door for future co-operation. “It helped us establish this relationship and collaboration with Prof. Kim and McMaster,” he says. “That’s one of the big, long-lasting values of the project.”

2017-10-12T18:25:04+00:00 October 10th, 2017|Features|0 Comments

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