The Harbour Gets Loaded

Halifax Harbour cannot be made clean by Primary Sewage Treatment Plants and combined sewers.

It can be made cleaner, but not clean.

In the vain hope that Peter Kelly would go swimming for the cameras the day after a severe thunderstorm, I kept a bit quiet for a while on this issue. Now that it looks like he won't get some cool tropical disease, I might as well spill the news. The truth is, we spent millions of dollars on work to change where we put our poop into the environment, and to take some of the easy to remove things out, and that's all we did. The work on the Halifax Harbour Cleanup shut off many of the existing outfalls along our now well used and appreciated waterfront, and consolidated all those little problems into three big ones. It is doing what the engineers intended it to do.

From the rudimentary treatment plants we built, we put special, long outfall pipes out into our harbour so that the pollution is injected into the harbour at a place where it can be more easily flushed out to sea by the tides and currents in the harbour. That makes it all seem better because it is "all gone away".

What no one bothered to explain to the media (which didn't seem to try to understand the project anyway) was just how tough it is to clean up sewage flow when the sewers are combined sewers - they carry both flushed things from homes and businesses, as well as any rain that falls on our streets and roofs. So if it rains in Halifax (I have it on good advice that it does so on occasion) then an immediate, and very high volume (compared to the sewage) flow of runoff whooshes down the pipe, diluting the sewage, sometimes making it over 100 times the flow, and also making it colder than it was.

A huge, cold, dilute organic waste is very very difficult to treat. And to remove a high percentage of the pollutants, especially the organic ones (poop) is almost impossible. Organic waste is treated by biological processes that need some time, which at a high flow means massive tank storage to give the bugs time to eat the poop. Those bugs operate at a speed that is pretty much regulated by temperature - the colder they are, the slower they work, like me. When it rains, the system we now have really does not remove very much of the organic pollution because it would simply be too expensive to build such a massive treatment plant where the sewage has been collected.

But, there are two things that the media has yet to identify and understand, and that therefore mostly remain a mystery to the residents of HRM. First, when it rains, not only can we not treat the huge flow of dilute sewage, our pipes are not big enough to even take it to the new, better discharge sites we put a lot of the investment into creating. At some point, the pipe backs up (hello again, finless brown!) and is dumped directly into the harbour, usually via the old outfall pipe we thought was no longer in service.

The second thing is the real kicker, though. What do our environmental regulators do about this problem? When it rains, the harbour cleanup project allows most of the pollution to run out to the ocean the same as it always did. The total amount of material that causes environmental problems is not really reduced by any normal sewage treatment removal percentage. If, say 100,000 kilograms of poop went to the harbour before we spent all out money on the project, on a rainy day, maybe 75,000 (a wild guess just for demonstration purposes) kilograms of the poop goes to the harbour.

How is this possible given that they had to have a permit from Nova Scotia Environment, with the tacit approval, and funding from Environment Canada (plus DFO has to OK it) to continue to discharge this deleterious substance? Well, have you not heard the old axiom, "The solution to pollution is dilution." ?? That's how. The permit would authorize HRM to discharge as much sewage as they want up to a certain concentration of poop (I heard it was 50-60 ppm when every other Municipality in NS has to meet maximum 30 ppm for an ocean discharge). As long as there is enough rainwater diluting the poop, the regulators can look the other way, and the politicians can pretend they did something.

The sewage coming from a house before dilution has about 250 to 300 ppm of BOD. Stormwater dilution of sewage in a combined sewer is often up to ten times. Discharging more than 50 ppm when diluted 10 times would then be impossible, because it would be at 30 ppm, on average, with no treatment at all! You'd have to add poop (staff toilets in the treatment plants are not that big) to not meet the Approval. So the overflows meet permit with no treatment, because the permit is a bit, well, soft.

Sweet, eh?

Of course, the ecosystem in the harbour does not see it quite the same way. Most of that part of the equation is simply looking for food (poop to us), to live from, and they then strip oxygen from the water to support themselves, to the detriment of other things we might prefer to have live in the harbour.

Most countries regulate discharge of sewage in terms of the amount, or load in kilograms, of BOD per day that a receiving water body is subjected to, no matter how high, or low, the concentration of the discharge. We have ignored the logic of this, and regulate in mg/L or parts per million of BOD (by the way, for the purposes of this discussion, BOD (Biochemical Oxygen Demand) can be considered a laboratory based scientific way of saying "poop".) A two year old having a pee pee off a wharf might not meet the permit because the ammonia discharge in the effluent stream would be too high, but all of peninsular Halifax's sewage running untreated after a storm is just peachy.

This concentration versus loading concept can be explained in terms most Haligonians would understand. If we were out drinking, and I had ten shots of scotch, and you had ten beers, you'd have consumed a lot more liquid than me, but we'd both still be loaded. We all know that it is the alcohol loading that causes us to be loaded, not the water in the drink.

Yes, the harbour is still getting loaded every time it rains.

Cheers!