Monitoring Kawartha sewage treatment effluent

Early studies

In 2006 that we had some students at Fleming College in Lindsay undertake a study of the sewage treatment plants discharging into the Kawartha Lakes, under the tutorship of Sara Kelly. This excellent program allows groups like ours the opportunity to undertake small studies that might take a semester to complete, for little or no budget. Here keen teams of 3 to 4 students are matched with an equal number of ‘employers’ to the optimal extent for all concerned.

Our project for that year required the students to get statistics on rated capacity of the sewage plants, typical output quantity, and a few key parameters such as phosphorus.

The results of that study indicated that there have been vast improvements made over the years, especially at Lindsay, but some issues remained.

Such was the case with Bobcaygeon, where phosphorus discharges were excessive and the effects were seen as producing algal pea-soup conditions in Pigeon Lake.

Overall, the need to reduce the excessive weed growth seen recently, as well as, perhaps, the unappealing growth of the algae mougotia called for a reduction in controllable phosphorus.

Phosphorus outputs in 2008

Studying reports from a few sewage plants, what we saw was that the Lindsay plant continued to remain well under its reasonably stringent permitted requirements, especially for phosphorus. The two Bobcaygeon plants did likewise, but not as well, and their requirements are not nearly as tight.


  • Lindsay is allowed to discharge 0.2 mg/l of phosphorus in its effluent to the lakes, at the mouth of the Scugog River.
  • In 2008, the overall average was 0.049 mg/l, just under a quarter of what they are allowed.
  • Lindsay continues to grow however, and the total amount of phosphorus may be going up.
  • The removal rate was 97% and the total loading to the lake was an average of 0.866 kilograms of phosphorus per day.


  • Bobcaygeon is allowed to discharge 1.0 mg/l at either plant, which is five times the allowable concentration of Lindsay.
  • It in fact it discharged about 0.34 mg/l overall average from both plants.
  • The overall removal rate was about 86 and 90%, and the total average loading rate was 0.70 kilograms per day.
  • This is close to the amount of Lindsay’s contribution and yet Lindsay treats about 15 times the sewage volume. Clearly, this is a relatively large contribution in comparison, and one that strongly suggests that we can do better.
  • This may also be an important contributor to the higher levels of phosphorus we now see downstream of Pigeon Lake.


  • This plant which is actually a lagoon system produces an excellent quality effluent with a discharge of phosphorus in the 0.09 range.

Fenelon Falls

  • We await the Fenelon report.

If Lindsay and Lakefield can do it, why not the others? We will monitor this situation and see what we can do to improve the situation.  Fenelon Falls remains a bit of a mystery as to what is occurring in that vicinity.

Phosphorus levels are quite high in the north end of Sturgeon Lake, quite similar to the rest of the lake.  It might be the result of sewage plant issues.


This year we again engaged Sara Kelly and her team of students in another project, this time investigating the storm sewer systems in City of Kawartha Lakes.   Their study of what is draining out of storm sewer outfall pipes into the Scugog River had surprising results.  Is human sewage getting into the Scugog, the source of Lindsay’s drinking water?


Monitoring and Sustaining the Health of the Kawartha Lakes

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