About 20 years ago my girlfriend and I were enjoying a walk along scenic Point Pleasant Park, which overlooks part of Halifax Harbour. The beach ranges from sand in some areas, to fist-size rocks, to car-sized boulders in other areas. We were jumping from one such boulder to another when my girlfriend happened to look down and commented, “I wonder who would climb up on this boulder and then change tampons.” There was a pastel-shaded plastic tampon applicator at her feet. Within seconds we realized that during our walk along the beach and then vigourous exercise of boulder-hopping we had failed to notice the shoreline was littered with thousands of pastel pink, blue, or yellow plastic tampon applicators. We were shocked and startled, to say the least. Definitely killed the rest of our hike.
Halifax dumped raw sewage into the Harbour, depending on the fact that human pathogens (such as coliform bacteria) will be killed or at least strongly diluted by seawater and ocean currents. When residents and tourists complained about a sewage smell, the city’s response was to move the outfall pipe further from shore. Prior to the G7 summit in Halifax in 1995, I remember the city even put out a plea to residents to not flush tampons, applicators, or condoms, to keep such articles from floating along such scenic harbour sites such as the Bluenose II.
I don’t mean to dump on Halifax (pun intended). It’s a great city, I loved most aspects of living there, and feel London would do well to emulate some features of Halifax.
Halifax has cleaned up its act since then. In February 2008, a $300 M primary sewage plant began screening its sewage to keep larger objects from entering the harbour, and removing much of the polluting aspect of its sewage. (I’ll write more about Halifax’s progress in a future piece). So much for the stuff you can see (but shouldn’t) on our beaches . . . it’s what you don’t see that can be scarier.
Sodium hypochlorite (laundry bleach) is often added to partially treated sewage to kill bacteria and viruses. Many Canadian cities treat their sewage with chlorine, which is cheaper than using either of the preferred methods: ultraviolet (UV) irradiation or ozone.
Chlorine bleach is powerful stuff. Don’t be fooled by fact you can buy a 4-liter jug of the stuff for $2- $3. Chlorination of the relatively clean water before distribution to the tap is quite safe, and indeed essential for killing pathogenic microorganisms in our drinking water. When combined with an organic “soup”, like sewage, the oxidizing effect of the hypochlorite is quite effective in killing most (though not all) pathogens, be they bacterial, viral, or fungal. This is good. However, chlorine also reacts with many organic molecules to produce some nasty by-products. This is bad. Some of these nasty by-products include carbon tetrachloride and chloroform, both of which are toxic and, since 1979, have been listed by the US Environmental Protection Agency (EPA) as carcinogens (cancer-causing chemicals). Other toxic by-products include N-nitrosodimethlylamine (NMDA), which is particularly toxic to the liver and also a suspected carcinogen. Other by-products of chlorinated sewage include chloramines (particularly when mixed with the amine compounds in urine). Chloramines are also secondary disinfectants, though less effective than hypochlorite, and give swimming pools their characteristic “chlorine”smell. They are also irritating to the eyes. It is not exactly clear what are the effects of these and lesser-characterized by-products on freshwater and marine ecosystems. Discussing their effects on fish here would be opening another can of worms . . . (but it will be the subject of a future blog post).
The City of London does not chlorinate the sewage treated at its Pollution Control Plants (see the summary of London’s PCP operations here). However, you may inadvertently chlorinate sewage do so when you use laundry bleach. As I said above, bleach is powerful stuff. The brand I use recommends using 1 cup per load of laundry. I believe this to be overkill (and a way for the bleach companies to boost sales) – certainly not warranted with the vast improvement in today’s laundry detergents. I use less than a quarter cup per load, and then only when disinfecting laundry say during flu or norovirus season. A 4-liter jug of bleach usually lasts our household for over a year.
Upcoming posts of Sewage Ain’t Sexy in the queue are:
Combined Sewage Overflows: A Bad Combination
Dead Zones
E. coli – my favourite bacterium
Filters
. . . it should now be obvious from the post titles that I’m working my way through the alphabet.
Peter Ferguson
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