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Here's a thread about water treatment for wading pools, e-mails back and forth with engineer Jes Clauson-Kaas in Copenhagen

From: Jes Clauson-Kaas
Date: Fri, Apr 17, 2009 at 9:24 AM
Subject: Wading pool

Dear sir/madam,

I am presently working on a project for the Danish Ministry of Environment about health aspects of recreational waters.

I find the setting of your wading pool very nice and would like to know:

a) what is the water source

b) how is it managed during summer? (chlorination, recirculating through filters, any rain water draining to the pond to reduce drinking water consumption, etc.)

Thank you very much for any assistance.

Best regards

Jes Clauson-Kaas
Senior project manager
Water and Wastewater
COWI A/S
Parallelvej 2
DK-2800 Kongens Lyngby
Denmark

From: Jutta Mason
Sent: Friday, April 17, 2009 5:29 PM
To: Jes Clauson-Kaas
Cc: akoropes@toronto.ca

Subject: Re: COWI Copenhagen wading pool inquiry

Hello Jes -- the park staff referred this e-mail to me. I'm glad to see you're still working on this. However I think you will do better than we do, if your company can get such water recirculation projects integrated with children's fun in Copenhagen and elsewhere. Since COWI is so huge, maybe you will be successful, and others can copy you.

Toronto wading pools do not recirculate water at all -- each morning the wading pools are filled with 100% drinking water, lots more chlorine is added, and then the water is dumped down the city sewer at the end of every day (i.e. the wading pools are completely drained every day).

During a recent summer of drought, we had the irony of a huge amount of water being drained from park wading pools into the lake every evening, while nearby trees were dying of thirst.

Toronto is located right beside freshwater Lake Ontario, so it's easy to be prodigal with water. Toronto's Parks Division has a big project (almost $10 million, 2008-2018) of renovating many neighbourhood wading pools, but as far as I know, the re-use of the wading pool water -- even just to give water to the park vegetation -- is not a consideration in those projects.

I have cc'd the Director of Parks, Andy Koropeski, above, in case you would like to contact his office directly for more information.

Good luck -- children do love such wading pools, and they create wonderful social spaces for the parents/caregivers as well.

Jes Clauson-Kaas wrote:

Dear Jutta,

So very nice that you answer, I did'nt know you were such a water expert.

Thank you for the detailed explanation, I get a fine idea of how the water system works. All I need now is to come at have alook at it, Toronto is an exiting city I know. Mybe I can find someone here to finance a study tour.

Concerning chlorination I am seeking methods of avoiding that. Chlorine is not the best to get into a biological wastewater treatment plant.

Concerning use of drinking water, this is of course the safest way. However, the wading pools should serve the dual purpose of storing rainwater, which is overloading the wastewater system.

Our project will finish around the end of the year and during spring 2010 we will produce articles in English on our conclusions. You will be on the mailing list.

Best regards

From: Jutta Mason
Sent: Monday, April 20, 2009 4:01 PM
To: Jes Clauson-Kaas
Subject: Re: COWI Copenhagen wading pool inquiry

Hi Jes,

I am certainly no water expert but one interesting thing about chlorination is that the chlorine vanishes very quickly on hot days and also when sand gets mixed in with the water (the wading pool is right beside our wonderful sand-pit where the children play and get sand all over themselves and then run into the wading pool). This, I gather, is the nature of chlorine -- it breaks down fast, yes? What this means in practical terms is that the park staff have to re-chlorinate the water often when many children are using it (i.e on every hot sunny day in the summer).

It also means that at the end of the day, the chlorine levels in the water are very low as the water is going down the drain. I think it also means that the pool water ought to be reused to water the park, and can be used without covering the park with chlorine. But there's no system for that kind of re-use at the moment. I'm hoping you can invent one! Maybe if someone sponsors your trip here, you'll be inspired.

Jes Clauson-Kaas wrote:

Hi Jutta,

I will mail you an interesting article on water and sustainability from your city.

Concerning chlorine it does not disappear, it is attached to other compounds(impurities) in the water. Only if there is free chlorine it can desinfect, i.e. kill bacteria, virus, etc. As imourities are added to the water the free chlorine is consumed and more chlorine must be added. As chlorine is a desinfectant it will not be good to water plants with chlorineated water. Chlorine can also in combination with organiv acids form carcinogenic substances, so if chlorine can be avoided it is the best. In wastewater treatment plants you sometimes chlorinate the effluent, but before discharging you dechlorinate to avoid toxic compounds in nature.

From: Jutta Mason
Sent: Monday, April 20, 2009 7:56 PM

To: Jes Clauson-Kaas
Subject: Re: COWI Copenhagen wading pool inquiry======

Thanks Jes -- I've printed off pages 79-84 and wil see if I can grasp what it says, I see there's a graph attributed to Barry Gutteridge, who used to work for the City as an engineer until (I think) a short and perhaps unhappy period as a city manager. I see also that you're in the bibliography, more evidence that you are an expert in this field.

We (park staff and park users) were quite concerned about the carcinogenic possibilities of chlorine, and the wading pool staff used to try and wait as long as possible before adding more (closing their eyes a little). But then somebody did a secret test and our particular wading pool was on TV as having high levels of e-coli and low levels of chlorine. We did do some reading about chlorine and other alternative additives but every other possibility seemed to be very expensive.

It's not so easy to understand. For example, I've put two statements in red in your text below -- you seem to be saying two incompatible things, i.e. that when chlorine attaches to the sand in our wading pool water, it will no longer disinfect, but that the used-up (dirty with sand) water at the end of the day shouldn't be used on plants because it disinfects them. I'm sure that there is a further explanation -- maybe another project for you could be to write a simple primer of wastewater use?

And of course another area of research is the actual effects on people -- when there was the panic around here about low chlorination and high e-coli, parents were very puzzled -- their children play in the pool all the time and they never seem ill after, they said.

Lots of puzzles!

From: Jes Clauson-Kaas
To: Jutta Mason
Subject: RE: COWI Copenhagen wading pool inquiry
Date: Thu, 23 Apr 2009 10:16:27 +0200

Hi Jutta,

We have quite an interesting discussion.

I am interested to hear why there is e.coli in your wading pool. Do they come from the children playing there accidently spilling a little dirt or maybe from dogs jumping into the water?

Concerning chloride: when the free chlorine han formed compounds with other substances in the water the water becomes salty. The trees, bushes and grass in your park cannot cope with these compounds in the water, the roots will be destroyed. If you planted coconut, mangrove etc. which can sustaine in saline waters, then it would be ok. However, I guess you don't have that kind of plants in the park.

Best regards