A waste water expert from…

A waste water expert from OOWA informed the following comment:

The proposed phosphorus removal strategy—chemical precipitation followed by filtration—is a well established and widely used treatment approach in Ontario. While many facilities historically used sand filters, cloth disc filters such as those proposed here are also proven technologies and can achieve comparable performance with a smaller footprint. The effluent phosphorus limits proposed for this facility are stringent, but with a properly designed and operated system, they are technically achievable.

The expert review provided two relevant Ontario examples using similar Napier Reid SBR systems with chemical precipitation and filtration:

• Havelock WWTP
o Technology: Napier Reid SBR + chemical precipitation + sand filtration
o Dry season TP limit: 0.14 mg/L
o 2020 performance: 0.07 mg/L average TP
o Operating at ~65% of rated capacity

• Teeswater Formosa WWTP
o Technology: SBR + chemical precipitation + sand filtration
o TP objective: 0.1 mg/L
o TP limit: 0.15 mg/L
o 2024 performance: 0.1 mg/L average TP
o Operating at ~74% of rated capacity

These examples demonstrate that the proposed effluent phosphorus limits are theoretically achievable with this type of treatment process.

However, the expertise emphasized that achieving these limits depends heavily on the accuracy of the influent flow and concentration assumptions used in the design. As noted in earlier comments, the influent BOD, TSS, TKN, and TP values appear to be underestimated, particularly given that approximately half of the wastewater flow will originate from restaurants and commercial kitchens, which are known to produce significantly higher strength wastewater.

If influent concentrations are higher than assumed, this will directly affect:

• chemical dosing requirements
• sludge production
• filtration loading
• SBR cycle performance
• the plant’s ability to consistently meet low TP limits

For these reasons, I respectfully request that MECP require the proponent to:

1. Reassess influent concentrations, particularly BOD, TSS, TKN, and TP, to reflect the substantial contribution from commercial food service operations.

2. Demonstrate that the phosphorus removal system is adequately sized for realistic influent conditions.

3. Confirm that the proposed filtration system can reliably meet the effluent TP limits under peak flow and peak loading scenarios.

These steps are necessary to ensure that the phosphorus removal system performs as intended and that the receiving watercourse is adequately protected.