Testing Water Shouldn’t Cost (or Taste Like) the Earth
Posted on March 20th, 2020
Have you ever left a glass of water out for a bit too long and found that it tasted a bit earthy? If you haven’t, lucky you. It’s gross.
You may not know that it is geosmin you’re tasting. We have a strong limbic response to its smell and flavour, likely evolved to prevent us from drinking potentially pathogen ridden water.
Some people are hyper sensitive to geosmin. So sensitive that the human nose can detect it to 5 parts per trillion. To put this into context, it’s the equivalent of an amount of geosmin with the volume of a single pea, in a whole reservoir of drinking water!
Its prevalence in water tends to be seasonal with warm weather stimulating algae blooms and increasing concentrations when water levels are low. Increasingly warmer weather is causing it to be more widespread, less regional and less predictable.
While it’s not toxic in the kinds of concentrations we’re talking about, it still represents a major headache for the water industry, particularly the ones that are situated in grassy landscapes like moorlands or the fens.
Complaints are expensive…
In the mind of the drinker, the taste and odour that geosmin brings to water is a marker of poor quality and people rightly complain when theirs starts to taste nasty.
The Drinking Water Inspectorate will issue fines based on the number of complaints they receive, so water companies test for it routinely to limit its impact as quickly as possible. Making sure they hit their sample turnaround times while maintaining the required sensitivity is mission critical.
…So is treatment
Once geosmin is found, water companies tend to treat the water aggressively for the rest of the season to limit its impact. This is an extremely expensive way of working and inevitably leads to a lot of powdered activated carbon (PAC) being wasted, treating nothing at all. Unfortunately, it’s a difficult situation to avoid.
With the increased prevalence across the country, water companies are all looking for more efficient ways of testing and treating water for geosmin.
One approach is to install in-situ testing equipment that takes samples more frequently and analyses them on site as and when they are prepared. This allows them to use analytical data to more accurately monitor both, geosmin, and 2-methlyisoborneol (MIB) and so dose more effectively. This is a fairly radical approach but is possible and the potential benefits of virtually real-time monitoring are massive.
Dosing only when geosmin and MIB is found, rather than seasonally has the potential to save these companies hundreds of thousands of pounds annually from reduced PAC usage and the costs incurred from fines.
Another improvement is to simply cut sample turnaround times.
We’ve seen early success at one of our customers in testing for geosmin and MIB. In short, their system allows them to prepare samples overnight and run them in the lab first thing in the morning. This drastically cut their turnaround time while ensuring excellent data and sensitivity.*
We have previously seen the savings which were made by Affinity Water using their on-line Metaldehyde solution. They found that the savings from the reduced GAC regeneration alone paid for their system within 12 months.
They didn’t expect to see a return for two years. Read more about that here.
We’re working on a system that can apply this technique to the analysis of geosmin and MIB. We’re excited by the early data we’re getting and an application note is on the way.
Sign up to e-apps to get it and other relevant application notes directly to your inbox as and when they are released.
*An earlier version of this blog erroneously included an Anatune client.