Expanded Outfall from the Duffins Creek Sewage Plant

Access the Regions' Phase 2 EA Draft Report HERE

The Duffins Creek sewage plant (illustrated at right, officially known as the York-Durham Water Pollution Control Plant) is located on the shores of Lake Ontario on the Pickering side of the Ajax-Pickering border. It is one of the largest in Canada. It is at the end of the 'Big Pipe' from York Region. It currently dumps about 340 million litres a day (mL/d) of effluent into the lake. 80% of this is from York Region. All waste receives secondary treatment which means that while it may look clean, it still contains a lot of nutrient chemicals. When testing reveals that phosphorus levels are too high, then and only then, does the plant apply tertiary chemical treatment to reduce the phosphorus to 'acceptable' levels.

For an explanation of sewage treatment, click here for an excellent slide show entitled 'Waste Water 101' prepared by York region, which explains the terminology and processes. It is quite a large file, so it may take a minute or so to load.

The plant has been expanded several times and the latest expansion gives it a theoretical capacity of 630 million litres per day. The effluent is discharged through a giant pipe, 3 meteres in diam (approx 10 ft) that extends about a kilometer under the lake where it is released through numerous 'diffusers' approx 9 metres below the lake surface. In theory, the massive amounts of lake water will dilute the remaining pollutants to the point where they will not be noticeable. The Ministry of the environment has defined an acceptable dilution ratio as 1:20 in the immediate vicininty of the diffusers under calm conditions. However studies have shown that the Duffins outfall would not meet these standards at the full 630 mL/d outpyut and so, the Ministry has imposed a 520 mL/d limit on the plant capacity.

Note that there are long term plans to expand the Duffins Creek facility to close to a billion litres a day.

The Regions are currently conducting an Environmental Assessment on modifications to the outfall in order to meet the dilution guidelines at higher capacities.The plan they are concentrating on is the installation of duck bill diffusers on the existing outfall pipes. These are designed to increase the jet velocity of the outflow thereby increasing the dilution.

However, the Town of Ajax maintains that even the current outfall is polluting the water around its shoreline, leading to algae blooms which wash up on the shore and rot producing a very unpleasant stink. (picture at left). The Town of Ajax rightfully suggests that this impacts the usability of the Ajax waterfront.

The issue is phosphorus, a nutrient in sewage which encourages the growth of Cladophora, a strain of algae which is a problem wherever there are high concentrations of phosphorus. The Regions maintain that the current outfall is providing sufficient dilution and that the problem along the Ajax shoreline is not due to the outfall.

However, the Regions have included 2 maps on the FAQ page for the EA (http://www.durham.ca/works.asp?nr=/departments/works/duffincreek/faq.htm...) which suggest otherwise:

You can see that there is an area of higher phosphorus concentrations around the sewage plant outffall. On both maps there is also elevated levels around the Ajax shoreline which the Regions attribute to the flow from the local creeks. IT SHOULD BE NOTED, that just prior to the dates this data was collected, there were major storm, where fertilizers from lawns and farms, were washed into the creeks upstream. SINCE these events occur infrequently, their contribution to the lake level of phosphorus is not constant, as with the sewage plant's outfall. Phosphorus levels during normal flows in the creeks has never been shared with the public. It is expected that data would clearly show the sewage plant's outfall IS the major contributor.

The levels of phosphorus further out in the lake are 3 micrograms/litre, while the discharge from the plant at 500 micrograms/litre is 170 times that. Technology exists today to take phosphorus down to 1.5 micrograms/litre, why wouldn't the Regions opt for such tertiary treatment? Likely because it would cost more.

While there are plenty of other sources of phosphorus in the map (local streams, zebra mussels) which certainly need to be addressed, it is a reasonable conclusion that the phosphorus from the Sewage Plant Outfall is drifting back to shore in Ajax and causing the Cladophora blooms.

The Regions want to accelerate this EA (why?) and the Town of Ajax is opposing that on the grounds that there are a couple of studies currently underway (due to be finished in 2014) that may shed further light on the problem.

Here is a graph of the outfall volume - actual and projected. The light blue line is actual sewage growth over the last 9 years - no significant growth at all. Beyond that there are 2 projections based on population and water usage: 330 litres per capita per day (lcpd) and 386 lcpd. Even if you accept the least optimistic of these (red squares) there is no need for expanded outfall capacity until 2019. However, given what the actual flow has been, expansion seems unlikely to be needed until 2030 or beyond. In light of that, why not take the time to do the necessary studies and actually solve the phosphorus and algae problems properly once and for all? Why spend a couple of million dollars on duck bill diffusers when they may not solve the problem?

(Note that the graph above bears a remarkable similarity to the projections that Durham made in order to justify the garbage incinerator in Courtice. By 2012 it was evident that the Region would be unable to continue to feed the burner AND meet its recycling commitments. Like in the graph above, waste has declined and the projections have to be redrawn.)

DurhamCLEAR is assisting a new citizens group, PACT-POW, which was formed to fight the Duffins plant outfall proposal or, at least, to slow it down until we get all the answers. PACT-POW is an acronym of Pickering Ajax Citizens Together - Protect Our Water.

There are alternatives:

  • more of the phosphorus should be removed from the effluent before it is dumped into the lake. The northern part of York Region dumps into Lake Simcoe and ever since phosphorus levels there went off the scale in the 80s, all sources of phosphorus including sewage treatment plants have been subjected to stringent controls. Phosphorus is routinely precipitated from the effluent prior to discharge, If York can do that to its Lake Simcoe discharges, why can't the Duffins Creek plant do the same for discharges into Lake Ontario.
  • York Region needs to take greater responsibility for the volume of its sewage - all other options should be explored before dumping it on a neighbour:
    • it could do more to limit water volumes - aggressive retrofits of low volume toilets
    • it should explore the use of minimal or zero water toilets (composting toilets which process human waste in situ to compost that you can put on your garden like any other compost - no sewage connection required.)
    • aggressive repair schedule on its sewage piping to correct the huge volumes of ground and rain water that are infiltrating the sewage system
    • it could build sewage plants which use the phosphorus-rich effluent for farm irrigation (the soil cleans the effluent while the effluent helps grow food)
    • it could build advanced sewage treatment plant which could discharge clean effluent directly back into local rivers and stream (York is building just such an advanced treatment plant that will discharge into the East Holland River - it should consider doubling the size of that plant.)

Durham Region needs to draw a line in the sand - we can no longer be a dumping ground for York's waste (both human and garbage). York needs to accept responsibility for its waste so that there is no need for further expansion of the Duffin Creek plant.