Thread: Microplastics: The latest human scourge on the environment.

The title may be a bit inaccurate as this form of pollution has likely been around for quite some time.

But a recent article* in the BBC News Science section brought it back to my attention. The story seems pretty nasty.

This problem is probably going on everywhere, and much of this material may be found in the oceans, causing troubles for many creatures that filter-feed on "micro-foods".

Does anyone have a link to a good overview on this problem from a global perspective? Would like to catch up.


"Wastewater is 'polluting rivers with microplastic'"

* https://www.bbc.co.uk/news/science-environment-57092135

One thing I learned when I was a service gas fitter was to not drink the hot water from a hot water heater storage tank. That’s one that stores hot water and heats it also. For one thing there’s a sacrificial magnesium anode inside the tank which deteriorates while protecting inside of tank. There is also what’s called a dip tube of which I’ve replaced hundreds, a plastic conduit that takes cold water to the bottom of tank to be heated.

These dip tubes also deteriorate over time and eventually break off, split or disappear altogether. There are literally millions of these tanks currently in use around the world. Doesn’t matter if gas or electric water heater. I never hear them mentioned when the micro plastics in water topic comes up. A new dip tube doesn’t necessarily mean the old one is removed so some tanks are breaking down two or three dip tubes at same time.

https://www.hot-water-heaters-review...-dip-tube.html

Originally Posted by zinjanthropos

These dip tubes also deteriorate over time and eventually break off, split or disappear altogether. There are literally millions of these tanks currently in use around the world.

That certainly sounds like a source for some microplastics. One might imagine that the dip tubes are made of hard plastic, which is brittle and can fracture down to the micron size. I suspect those dip tubes may be PVC, and simply disintegrated over time, the fragments getting flushed into the waste stream. It seems unlikely that the people investigating these particulates could tell exactly what their source is. From that BBC story, they were sourced to raw sewage.

It seems that, over time, most plastics would get hard and brittle, potentially providing a major source for microplastics from many objects. But what is the mechanism for micronizing them? Perhaps that is how all plastics thrown into the environment end up, slowly disintegrating into microplastic particulates by various means. Their half-lives in the environment would depend a great deal on their composition. PVC would likely last a long time. Others, many not so long. The threat of so many of them seems real enough.

Originally Posted by Double Helix

That certainly sounds like a source for some microplastics. One might imagine that the dip tubes are made of hard plastic, which is brittle and can fracture down to the micron size. I suspect those dip tubes may be PVC, and simply disintegrated over time, the fragments getting flushed into the waste stream. It seems unlikely that the people investigating these particulates could tell exactly what their source is. From that BBC story, they were sourced to raw sewage.

It seems that, over time, most plastics would get hard and brittle, potentially providing a major source for microplastics from many objects. But what is the mechanism for micronizing them? Perhaps that is how all plastics thrown into the environment end up, slowly disintegrating into microplastic particulates by various means. Their half-lives in the environment would depend a great deal on their composition. PVC would likely last a long time. Others, many not so long. The threat of so many of them seems real enough.

My water heater is 20 yrs old and I’ve replaced the dip tube couple times* One was split and the other still in tank. If they’ve been in there long enough they can easily crumble in your hands when removed and dry. With constant heat/cool cycles they can just disintegrate. These tanks/dip tubes have been around for decades.

Instantaneous water heaters (no dip tube)have made inroads in NA in last 20 years but are expensive. If you see a domestic storage water heater with hot & cold connections at the top then most likely there’s a plastic dip tube inside. Cold water inlet connection at bottom of tank, particularly in a commercial appliance, likely an indication of no dip tube. I think the idea was to save on copper used for water lines on a domestic tanks.

*Tip: How do you know dip tube is shot? Best indicator is the shower. If shortly after starting shower the hot water suddenly turns cooler and you have to turn faucet dial towards hotter, then most likely the cold water that’s usually directed by dip tube to bottom of tank is mixing with hot water being drawn from top of tank. Dip tube either disintegrated, broken off or split. Tube itself is cheap but labor costs, unless you know how to solder copper/brass, could be high.