Victoria has had great difficulty moving ahead with centralized sewage processing because of concerns about cost, odour and unsightliness.
If we encourage our engineers to think outside the box, there may be an answer to these problems. There are many different primary and secondary treatment approaches. One city in the U.S. does it with a fountain in the desert, for example, although most use a form of sewage lagoon, often with large rotating paddles.
In all cases the basic objective is to aerate the waste stream so that aerobic bacteria, which neutralize the biological matter (human waste, food waste, soaps and detergent), can continue to receive oxygen and continue multiplying. Then the treated sludge is removed to landfill sites so that the plant doesn’t fill up and overflow, and the treated liquid is released.
In plants discharging into highly sensitive ecosystems like small inland lakes, tertiary treatment to help with disinfection is often incorporated prior to discharge.
One new idea is to turn our existing sewer infrastructure into an enormous primary and secondary treatment plant by injecting oxygen and microbes. Turbulence in the pipes would allow the bacteria to touch everything in them and thoroughly clean the waste. We could introduce the oxygen and microbes far upstream so that there is sufficient time to enable complete bacterial treatment.
All of the sewer infrastructure would be underground, underwater and invisible. There would be no need to change the existing equipment at Clover Point and Macaulay Point. There would be no smell. The capital cost would be low.
The operating cost would be negligible, because there would be no need to collect and remove the treated sludge to a landfill (which drives the operating cost of the currently proposed sewer plants up to $25 million per year). It would be deposited on the sea floor just like the silt from every creek and river flowing into the ocean. It is all natural.
The injection equipment could be installed in existing houses or in other buildings. Camouflaged utility buildings are normal.
Probably all of this could be accomplished for less than $50 million rather than the currently proposed $1 billion, and we can move ahead quickly because the public’s concern about plant location will disappear. I don’t advocate tertiary treatment in our situation (usually accomplished via the addition of chlorine or other chemicals) because it isn’t environmentally necessary, however, if eventually deemed important it could be added later.
I do think we should continually remind ourselves to reduce the chemicals and drugs we flush down the drain. Estrogen, for example, is a real problem. Victorians are concerned about the environment as is indicated by our litter-free streets and our heavily used blue box program. We will be careful about the sewer as well if we understand the harm our chemicals can cause to the creatures in the sea.
With a little prompting, out-of-date medicines and drugs will be returned to pharmacies for proper disposal. Also, the use of detergents, shampoos and other household products with problematic ingredients will be reduced if a list is distributed that ranks them according to these chemicals.
David Black, Civil Engineer, MBA
(David Black is owner of Black Press, which publishes the Gazette)