Speaking at WEFTEC 2025 this week in Chicago, Nick Butson, an engineer with Geosyntec Consultants, shared a case study in which his company helped a Canadian potato processor reduce its water use by more than half. Butson said the processor set a goal of reducing its water consumption by 50 to 80 percent due to the rising costs of water from the local utility.
The project faced three main constraints. The first of which involved treatment residuals. “So, if we did generate, say, a concentrate from a high-pressure membrane system, what are we going to do with that?” Butson asked.
The other constraints were costs and regulations.
In Canada, food plants are regulated by the Canadian Food Inspection Agency (CFIA). The rules are simple to state but tricky to apply: water used in food production cannot introduce biological, chemical or physical hazards.
Instead of treating all reuse water to the same level, they applied a fit-for-purpose approach. Lower-quality reuse water could go to the wastewater treatment plant itself or to boilers. Higher-quality reuse water could be directed to potato washing or rinsing lines.
Butson stressed that this was a water reuse system not a potable water reuse system.
“It wasn't going to be commingled with any potable water within the facility that got into plumbing codes. That was a lot more of a mess than what we or the facility wanted to sign up for,” he said. “So this is all reused water that wasn’t going to be used in sinks or toilets or anything like that.”
The processor’s initial treatment system included a primary treatment, anaerobic digestion to reduce organics, and a membrane bioreactor (MBR) for nutrient removal and UV disinfection.
According to Butson, the plant’s choices for additional treatment were ultra-filtration, nano-filtration or reverse osmosis (RO). They ultimately went with nano-filtration because they didn’t need to produce water that was RO permeate quality.
The processor also went with a separate distribution system to keep reuse water completely isolated from the facility’s potable supply.
This design struck a balance between performance and cost, while also keeping operations simple for plant staff.
Butson said projections show that such a nano-filtration system can achieve a maximum recovery of 75% without significant issues.
The next steps for the plant could be a general validation protocol (GVP), including 16 weeks of challenge testing before full-scale implementation.