Tag Archives: domestic sewage

“It’s a dirty bird that fouls it own nest”

Agricultural pollution...Wairarapa New Zealand. Photo source: Wikimedia Commons.

So far I have been looking at the amount of water we use, and hopefully, managed to convey the idea that some things we do use a lot of water in a rather unsustainable way.

Luckily for us, the fresh water system is generally cyclic and renewable. However, there are some practices we as humans do, that have the potential to seriously (and irreversibly) damage the environment, and consequently harm ourselves. Today I’m going to introduce you to the issue of water pollution.

Now, this is a large topic, but arguably the main contributors to fresh water pollution are:

  • Domestic Sewage
  • Industry
  • Agriculture
  • Urban runoff

Domestic Sewage

It has to go somewhere, doesn’t it? While in New Zealand there is legislation in place regarding the treatment of your toilet bowls before it is pumped out to our rivers and oceans, many other countries are not so lucky. The United Nations  tells us the 2 million tons of human waste are disposed into water courses daily. That isn’t treated waste, or dirty water, that’s what comes out of us, and into our rivers and oceans.


Again, we are lucky to have regulations in New Zealand, but many developing countries do not. Having to treat waste before discharging it is expensive, so there is an attraction for factories to be built in places that are unregulated, therefore decreasing operating costs. Industrial processes often include by products such as PAH’s (more to come on this), oils, ores, acids, particulates (both organic and inorganic), pharmaceuticals, dyes, detergents, plastic, and more! In some places these contaminants flow out of a pipe and straight into the nearest river.


Stock effluent is high in nitrate and ammonium, and this combined with phosphate based fertilizers set up a perfect environment for eutrophication to occur. Eutrophication refers to nutrient enrichment, which typically promotes algal growth, decreases oxygen supply in the water, and damages the ecosystem. Eutophication may kill organisms including phytoplankton and fish, while toxic algae may harm humans and other large mammals (we often hear of dogs dying after they have been in contact with toxic algal blooms).

Urban Runoff

Our urban environment promotes runoff rather than infiltration, as buildings and roads create impervious surfaces requiring storm water drains to remove rain water, rather than natural processes. Heavy rain has the effect of washing away contaminants which have built up on the road surfaces. This typically includes by-products of transportation, such as petrol and oil, as well as heavy metals including copper zinc and lead.

It sounds dreadful, doesn’t it?

But really, we are in no position to vilify these polluters. We must stop and ask ourselves: Whose toilet is it that flushes into the rivers? Who buys the products from those who pump their industrial waste into waterways? Who demands cheaper produce from the supermarket? And finally, whose cars drive around the cities emitting noxious particulate pollutants?

Yes, we must take some responsibility for these issues. But! There is hope. By changing our perceptions, and telling those who make the decisions that we will not support poor environmental practices we do have the chance to put some of these wrongs right.

It is my belief that this is a very significant subject, and to gloss over it would be to do it an injustice. So, for my next few blogs, I aim to discuss each of these pollutant issues, looking at what is going wrong, and most importantly, what we can do about it.  

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