When UV and TOCs don’t mix
The blue activated carbon filters in this mobile plant for UBC work to remove TOCs before water enters the UV unit
Our technical sales guy Mike Beeney has been tearing his hair out lately and he doesn’t have much left to spare. He is seeing more cases of communities wanting to upgrade their water system to UV, because of their water quality not meeting Canadian guidelines.
“I’m just not comfortable giving a project estimate on a UV-only system for these communities,” says Mike. “Honestly, I’m worried about the health of the community being compromised. If the potable source water has high total organic carbons (TOCs) – especially dissolved TOCs, and you’re blasting them with UV, it’s suddenly creating a situation where you’re turning a bowling ball into ping pong balls – now all of a sudden you’ve got more surface area requiring even more chlorine to treat the TOCs, with the result being higher trihalomethanes (THM),” which are known as possible carcinogens.
“I can see it being a maintenance nightmare with constant alarms going off. The system won’t be getting the proper dosage of UV or chlorine.” The solution is to pre-treat the water before UV with filtration or an ion exchange unit, and this adds to the cost of a system upgrade. While the cost for UV may be going down, adding an additional filtration system will add to the maintenance and system cost, but it is easy to maintain and install, and will save on chlorine costs.
And filtration may well be worth it. At BI Pure Water we invariably use filtration in all our systems, as an efficient, non-chemical method to treat the water. And it’s remarkably similar to the way nature treats water by filtering through sand and earth.
“The result is the community is in limbo because of the cost…either those communities go to household carbon filters or they’re looking at paying more for their water if they want healthy water in today’s world,” says Mike.
Canadian drinking water guidelines for TOC in raw water call for 4ppm or below, and for treated water, below 2ppm. If below 2ppm TOC the Canada Health guideline of 0.1 mg/l trihalomethanes (THM) will not likely be exceeded.