The Design Brief describes…

The Design Brief describes the influent as “typical domestic wastewater.” However, based on the concentrations presented in Table 5 of the report, the proposed influent characteristics align more closely with weak to medium strength domestic sewage according to standard wastewater literature. The report does not explain whether these values were derived from actual monitoring at the existing facility or whether they are purely assumed. This lack of clarity is concerning given the nature of the proposed development.

A significant portion of the projected wastewater flow—approximately half—will originate from commercial uses, including restaurants and a conference centre. These types of facilities are well documented to produce wastewater with substantially higher concentrations of:

• Total Suspended Solids (TSS)
• Biochemical Oxygen Demand (BOD)
• Total Kjeldahl Nitrogen (TKN)
• Total Phosphorus (TP)
• Fats, Oils, and Grease (FOG)

Commercial restaurant wastewater can have BOD concentrations in the several hundreds to thousands of mg/L, depending on food type, cooking practices, dishwashing procedures, and grease management. In contrast, the design basis used in the report assumes an influent BOD of only 110 mg/L, which is typical of weak domestic sewage and does not reflect the expected contribution from commercial kitchens.

The expert review concluded that the influent concentrations used by the proponent and Napier Reid are likely underestimated for a facility with this level of commercial activity. If 50% of the daily flow originates from restaurants and food service operations, all influent design concentrations (BOD, TSS, TKN, TP, FOG) should be re evaluated and increased to reflect the higher strength wastewater expected from these sources.

Underestimating influent strength has direct implications for:

• Nitrification performance and the ability to meet ammonia limits
• Aeration requirements and blower sizing
• Alkalinity demand
• Sludge production rates
• SBR cycle timing and tank sizing
• Tertiary filtration loading
• Overall treatment reliability

If actual TKN concentrations are higher than assumed, the plant may not achieve the required ammonia removal, and the treatment equipment may be undersized for real world conditions.

Given the sensitivity of the receiving watercourse and the importance of accurate influent characterization, I respectfully request that MECP require the proponent to:

1. Clarify the basis for the influent concentrations used in the design (measured data vs. assumptions).
2. Reassess influent strength to account for the substantial contribution from restaurants and commercial kitchens.
3. Demonstrate that the treatment system is adequately sized for realistic BOD, TSS, TKN, TP, and FOG concentrations.

These steps are necessary to ensure the WWTP is designed to handle the actual wastewater characteristics expected from the proposed development.

THIS IS A MAJOR FLAW