Hello. We're here with Lutra TV.
I'm Jemma Henneveld.
I'm the summer intern here at Lutra, and I'm here with Tim Miskimmin
to talk a bit about UV treatment.
Yeah, so. Tim. Kia ora.
What is UV treatment?
UV treatment. So UV stands for ultraviolet light.
Ultraviolet light is in the family of electromagnetic radiation,
so its the same as microwaves and visible light
and all those sorts of things.
Ultraviolet light can be used in water treatment
to deactivate microorganisms in the water.
UV treatments found all across New Zealand,
it's becoming increasingly popular.
I think the reason for that is it's
extremely effective at treating protozoa.
So it's an effective and compact way
of getting your protozoa log credits, which are required for treatment.
You can also use it for bacteriological compliance.
So the mechanisms for treating protozoa and bacteria, the UV light
applies itself to these microorganisms and scrambles their DNA
and effectively it makes them sterile.
So they can't multiply in the water.
That's the primary use in water treatment, in New Zealand.
It's also used in a process called advanced oxidation.
With advanced oxidation, you are dosing hydrogen peroxide
upstream of the UV and blasting it with tons of UV light.
This breaks down taste and odour compounds,
and other nasty organics into the elemental form.
So it's another real good use for UV
It's also used in waste treatment in a similar fashion to the water
treatment side, where it's taking the final effluent
from a wastewater treatment plant and getting rid of lots
of the pathogenic nasties in it so that it's not in the discharge.
Cool, what source water is UV primarily used on in New Zealand?
Source water, so primarily it's used on ground waters.
And the reason for that is groundwaters typically have a low and stable turbidity,
and a really high UVT, which is UV transmittance.
The reason you want both of those
in your raw water quality is because
effectively turbidity is looking at the amount of particulates in the water.
So you have a really high turbidity, you've got lots of opportunities
for the microorganisms to be shielded from the UV light.
So if you've got a low turbidity, you'll have low solids.
With UV transmittance, UV transmittance effectively,
is a measure of how well the UV light can travel through the water.
So if you've got a really high UVT, then it loses its strength, less.
Effectively, if it travels through the water.
So you what more of that.
With surface water, you have
much more variability in those two parameters.
So there's periods where it's much harder to treat
and make it applicable for UV treatment.
It is doable and you see it around.
It just means that you normally need some upstream filtration to facilitate the UV.
Yeah, so you need to pre-treat it before the UV treatment?
Yes, exactly.
You'll see it common enough in New Zealand,
but it's just much easier with groundwater sources. Yeah.
How will the proposed changes to the drinking water standards
going to change UV treatment in New Zealand?
So Taumata Arowai have put out the new drinking
water quality assurance rules, in draft form.
So the latest one of those went out in December 2021.
We are now filming this in February of 2022.
So they are a draft form.
But the most recent exposure draft looks like
the UV treatment is going to go to 4 log credits, from 3.
So it's quite a big change.
So if you wanted to get 4 log treatments and a water treatment plant
in New Zealand with the old drinking water standards, you'd typically have to use
a conventional coagulation sedimentation filtration plant
or you'd have to use UV in conjunction with some upstream filtration.
So let's say it changes to 4 log.
For new plants
that means that if you're source water requires 4 log treatment of protozoa,
the UV is going to do that all on its own.
You don't need any upstream filtration. If your turbidity is good, and your UVT is
good, then the UV is going to be able to do that on its own.
For existing plants which already have upstream filtration.
This means that they can probably remove those,
so if there are cartridge filters that need a lot of servicing.
Suppliers might be able to remove them from service
and save themselves some operational cost.
So it's pretty positive, but we're going to have to see
what happens with the next iteration of the standards.
So I say all of that looking primarily at the treatment side of things.
The other thing that needs consideration is what's happening in the source water.
So the Taumata Arowai water quality assurance rules also talk about those
and it looks like there's going to be a change
to the log treatment requirements, for the source water as well.
So it's kind of an odd scenario where there's going to be a lot of plants
where the treatment requirement for their source water goes up to 4 log,
and the UV also goes up to 4 log, and it's a wash at the end of the day.
It depends on, I guess, the scenarios for each of the plants.
When you say that the UV treatment
is going up from 3 log to 4 log,
does that include an increase in UVT or is that just a way of categorizing it?
Like what does that really mean?
Yeah, so that's a good question.
There's nothing actually physically changing on the plant.
There are some nuances around the rules that are going to change,
which we can talk about.
But in terms of the physical equipment, on-site, there's really no difference.
It's just a way of categorizing it and
looking at the validators and saying, okay, they've done enough to prove
that these reactors can treat to this level.
So there will be no physical change on the on the plant itself.
Are there any other changes to the standards that will affect UV treatment in New Zealand?
Yeah, so there's quite a small basket of changes that are going to be applied across the plants.
So it's not just UV treatment.
The main one being for large suppliers is that the compliance period
is going to be moved to one day for online monitoring,
as opposed to one month.
So UV treatment for large supplies used to be one month compliance period.
So you collect your data over a month
and you'd see if your comply at the end of the month,
based on the rules and the old drinking water standards.
Now that's getting changed from midnight to midnight,
which means that the window for having
non-compliant water go through your UV is much shorter.
So for example, the process requirement for UV dose is the same.
For bacteriological compliance, you need 40 millijoules per centimetre squared,
for more than 95% of the compliance period.
If you look at that over a month, if you've got 5% to be outside
of that window. That's quite a lot of time.
Now we're looking at a day.
So the window for being low on UV dose is much smaller.
So it's going to be quite a bit tighter around that.
So these's an updated change
to turbidity as well, which makes things a little bit easier for suppliers.
So in the previous standards, you had to be below 1 NTU
for more than 95% of the compliance period.
And you couldn't be more than 2 NTU
for more than one 3 minute consecutive period.
So both those rules are going to go, and there's going to be one rule put in,
which is you can't exceed 5 NTU for any 15 minute
period, so it's just one block rule for turbidity.
Depending on what your source water does.
For some people that's going to make that a little bit easier,
which I suspect will be the case.
And for other people it might make it a little bit harder.
But yeah, it'll be a case by case basis.
So if you’re non-compliant around midday, do you have 24 hours after that
or do you have until midnight to become compliant?
So you have to look at the whole period as a whole 24 hour block,
as soon as you've exceeded the criteria
for becoming non-compliant, for that 24 hour period,
you can't turn back, that one periods going to be non-compliant.
However, talking about treating water.
It's a public health issue.
So you always have an incentive to treat the water as best you can.
You don't just throw your arms in the air and say, Oh, we're no good.
So it works on a 24 hour basis.
But the way that Taumata Arowai's currently set up is at
the end of the year, you have to report on all your days as well.
So it's that whole picture that they'll be looking at as well as the
smaller periods of non-compliance.
Cool, thanks for that Tim.
If you have any questions about UV treatment or water
treatment in New Zealand, don't hesitate to get in contact with Lutra.
Thank you.