Cisterns: But I Have City Water, Right?

I was doing a routine reverse osmosis maintenance yesterday for a client of mine in Strathcona County. Anyway, they do a lot of water testing for this facility as they rent this particular hall out for parties, weddings and other group gatherings. They were having problems passing the microbiological tests because the water in their cistern (for those not familiar with this concept, if you don't have municipal water piped into your home and you don't have a well, the alternative is to have a buried storage tank that gets filled by delivery trucks filled with city water to run your property) kept showing bacteria.

The client had been performing regular cleanings (something most cistern owners rarely do) and they have spent a LOT of money sealing the cistern so leaves, dirt, bugs, mice, etc don't find their way in. Despite these steps, the tests kept coming back FAIL... Douglas Environmental Solutions was called in a little over a year ago to make recommendations.

The client initially was inquiring about ultraviolet (UV) sterilization to take care of this. Sounds good, but there are certain water quality requirements that must be met for that to work. The water must be:

- filtered to finer than 5 microns - sediment creates shadows and places for bacteria to "hide"
-there cannot be any colour, turbidity, iron, H2S or manganese present. (This is normally not a problem with city water supplies.)
- less than 7 grains hard (Edmonton/Sherwood Park water is HARD, between 9 and 12 grains, so that won't work)
- there must be minimal "turbidity" (basically a murkiness in the water) that prevents light from passing through and can inhibit UV's effectiveness at killing germs.

Needless to say, since raw city water doesn't meet these requirements, if they wanted UV, they'd need to filter and soften the water. Because of particular installation confinements at this facility (its so incredibly tight) we opted instead to create a potable water supply using reverse osmosis. This treatment would filter, soften and clean up the water effectively removing bacteria from the supply.

As added protection, we incorporated a UV sterilization chamber for the product water - just in case something physically happened to the RO system, the UV would still be there as back up and sterilize any germs.

The system has been operating for over a year now and even though the cistern is continually cleaned and the seal on the cistern rivals the one my grandma used when she made jelly, "stuff" is still getting into the tank.

How do I know? When we change the filter, you can see all the organics that are trapped by the prefilter. When new, these filters are pristine and white. The post filters (final stage of filtration before the water goes to the faucet) still look nice and white - although when wet, you can see the black carbon behind it, kind of like when you get a t-shirt wet - but that's another story...

Anyway, we've had to cut the filter change time in half for this facility and we're still getting a great deal of staining on the pre-filter. That's what its there for though - you can see by the post-filter the organics are not making it through the system.

We employ Total Dissolved Solids (TDS) Monitoring at this location as well. TDS is a measure of purity of the water. A meter reads impurities in the water and gives a number. The closer to zero the number, the better the water. When we installed the system last year, we were getting ZERO TDS water; indicative of very high quality. A year later, the meter still reads ZERO. The system is still doing its job - despite all the 'stuff' in the cistern.

I literally cringe when I hear people telling me they can drink water from their cistern because its "pure city water." Those people have, I guarantee you, either not cleaned their cistern, or not WATCHED the cistern getting cleaned. What comes out of there is enough to make you sick - just by looking at it. Its not uncommon to see frogs, mice and all kinds of organic material just decaying in there. That is running into your home and out the tap - unless you take measures like our clients!