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| Satellite image of Noelville sewage lagoons off of highway 64. The town of Noelville is to the left of the lagoons. |
Noelville Sewage Treatment Lagoons |
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There are serious problems with the Noelville sewage treatment lagoons. The problems have existed for some time and the effects are now being seen in downstream waters. There is a serious problem with algae on the river, which is the backbone of our local economy. The factors that led to this situation have occurred over a long time and it will take time to remedy the situation. It is important to take immediate actions to minimize future nutrient loading. Only then will remediation efforts make sense. The Noelville Sewage Treatment Lagoons are probably not the only source of nutrient loading into Wolseley Bay, but they do appear to be the largest.
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| Satellite image of Noelville sewage lagoons off of highway 64. The town of Noelville is to the left of the lagoons. |
The Noelville lagoon is a two cell facultive system. These are very simple systems where waste water is held while biological activity cleans the water. Such systems can efficiently remove organics, nutrients and suspended solids from waste streams. Two lagoons are required to work opposite of each other, one fills while one sits and treats the water. Treated water is discharged into the environment prior to refilling. Lagoons are designed to be discharged during traditional high water events in the spring and fall to facilitate dilution of the effluent. The schematic below shows the water levels in an ideal lagoon that fills for six months sits for five months and has one month for analysis and discharge. The total combined capacity of the lagoons is theoretically the total amount of waste that can be properly treated in a year, however, rain water and seasonal and yearly variations mean that lagoons must operate below this theoretical maximum.
Due to my efforts as science officer for the French River Stewardship Council, the Municipality of French River ordered a septage plan review, which was presented to council in February, 2010. A representative of the engineering firm Trow Associates summarized the report to council, identifying water infiltration from non-sewage sources (rain) as a source of water that was stressing the lagoon system and left no reserve capacity for development. Council seemed satisfied that if the rainwater infiltration could be addressed then the system would provide some reserve cpacity.
Problems with the reviewUnfortunately, there where two significant problems with the report presented to Council by Trow Associates, as outlined below. I have delivered a more detailed report clearly documenting these problems and the underlying causes to Mayor Bourgeois, CAO Michel Monette and to each of our municipal councillors. A copy of my report to council can be seen here.
The rated capacity of the lagoon is too high
The Noelville facility is two 220 m2 lagoons with a capacity of about 72 600 m3 each at a depth of about 150 cm (5 feet). If they were operated as described above the lagoons would therefore be able to handle 2 X 72 600 / 365 = 398 m3/day. This is well below the 477 m3/day rated capacity cited by the MOE, which would fill the lagoons in 300 days. Why the difference? I believe there was an error caused by confusion between holding time in a batch treatment lagoon system such as ours and the retention time in a continuous flow filtration system. According to the Certificate of Approval, a lagoon with a 300 day retention time was approved, which is simply the combined 150 day holding time of the two lagoons. Each year we should be holding waste in the lagoons for a total of 300 days (150 each), as described above. The error was made when the 300 day holding time was used to calculate the capacity of a 143 200 m3 continuous flow filtration system, which would be able to handle 477 m3/day, but is not the kind of system we have in Noelville. That is why nobody has been able to explain how our lagoons could handle 477 m3/day over a full year, they cannot. The true capacity is 398 m3/day, well below the 437 m3/day that it is currently receiving! This is why the lagoons had to be discharged early three times in three years from 2007-2009, rather than following the seasonal regime.
Unfortunately, The French River Stewardship Council submitted a follow-up report to Municipal Council in March that repeated the error. I have tried to explain their errors to them but they are reluctent to admit that the system is over capacity. Could it be that the Municipal councillors who sit on the Stewardship Council are more interested in development than advocating true environmental responsibility? :-(
There is no indication that the health of the receiving system was considered
The purpose of any waste water treatment is to minimize the effects of the effluent on downstream ecosystems. Acceptable discharge levels depend on characteristics of the receiving waters and can vary greatly between sites. The MOE sets the maximum allowable concentration of nutrients and contaminants for discharge from any sewage lagoon in Ontario. This does not mean that levels lower than the limit are insignificant or even 'acceptable' from an ecosystem perspective, just that discharges above these levels are illegal. Although some people are reassured by the fact that discharges don't usually exceed regulated levels, this is a mistake. The amount of rainwater entering the system can dilute the effluent in the ponds so that the levels appear acceptable even though there has been little to no significant treatment. Imagine you have a glass of water that tests above some limit. Dilute it with excess rainwater and the numbers may be OK and now you can dump it in the river even though the amount of contamination has not changed. Dilution is still pollution and it bypasses the purpose of the lagoons. This is the situation that has prevailed at the Noelville lagoons for years. For facultive lagoons to properly serve the environment the waste must be held for 150 days of treatment time AND contaminants must be at acceptable levels before discharge. The failure to adequately hold the lagoons is now starting to affect the French River, as outlined here.
Municipal Council's response to the problem; worse than I could have imagined.Council is focused on economic growth, working on the mistaken assumption that the lagoon system is working fine. This is quite remarkable, given that two of our councillors are directors of the French River Stewardship Council (which claims "to protect and improve the overall water quality of the French River") and have been aware of the problems for years. However, at the same meeting on February 3rd where Trow Associates informed council that there was no reserve capacity in the system, our Municipal Councillors passed a recommendation (Rec. 2010- 52) to proceed with a 25% extension of the current municipal sewage system. I presented my report to council and staff on February 9th, hoping somebody would take the situation seriously.
Unfortunately, our representatives ignored my advice, as well as the advice of Joe Dippong of the French River Stewardship Council, when on February 17th they passed resolution 2010-90 to resume development. The resolution displays an amazing degree of incompetence and confirms that they simply do not understand the system they are charged to operate.
Noelville Sewage Treatment Lagoons |
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