University of Canterbury’s Department of Civil and Environmental Engineering associate professor Ricardo Bello Mendoza told The Front Page that many wastewater plants in New Zealand are under strain due to ageing sewer networks.
“It looks like the origin of the problem was having rain in recent days, and that increases the volume of wastewater coming into the treatment plant. Most plants aren’t able to deal with these peaks in wastewater flows. So, in most cases, they will have to bypass at least a portion of the wastewater to go straight into the outfall and then into the ocean without any treatment,” he said.
“In this case, quality is not a big issue because there is dilution due to the rainwater. There still needs to be some screening, some preliminary treatment to remove big stuff in the water, but organics and solids will still be in the water, and that will be discharged.
“That is something that happens, I wouldn’t say regularly, but from time to time, in most wastewater treatment plants in New Zealand, because simply they are not designed to treat rainwater.
“But, in this case, when they decided to do this bypassing, it looks like there was a blockage in the outfall pipe, and then the water just backed up. Basically, huge volumes of water were just coming back into the treatment plant, and that flooded the plant and the equipment.
“We are talking about wastewater. Even though it was diluted with rainwater, it is still a hazard. So they need to be careful with that, and they need to then look at the damage that has caused to the equipment.”
The chronic underfunding of our wastewater systems around the country means that councils are constantly “catching up” after breakdowns rather than upgrading ageing infrastructure proactively, Mendoza said.
“I think wastewater is one of these critical infrastructures that we actually probably don’t think about. So even though it is quite important for our daily lives, we just flush it and then forget about it. Out of sight, out of mind.
“That usually leads to decision makers just putting it behind in their priorities. Quite often, it’ll be the things that are more visible. And that happens everywhere, not only in New Zealand.
“If you ask people what their priorities are, they will probably talk about hospitals, the situation of the roads, transport, and so on. Probably only a few of them will be saying we need to improve our wastewater infrastructure because nobody sees it, so we all assume it’s working well.
“I think it’s important to make a national assessment of priorities and then start investing wisely in what is actually needed,” he said.
Mendoza said the new national wastewater standard, which became law last December, aims to coordinate decisions and reduce inconsistent council-by-council management – a “step in the right direction”.
Listen to the full episode to hear more about:
- Systemic infrastructure challenges
- Lessons and future decisions
- A change in our priorities
- Planning problems.
The Front Page is a daily news podcast from the New Zealand Herald, available to listen to every weekday from 5am. The podcast is presented by Chelsea Daniels, an Auckland-based journalist with a background in world news and crime/justice reporting who joined NZME in 2016.
You can follow the podcast at iHeartRadio, Apple Podcasts, Spotify or wherever you get your podcasts.
