Friday, July 12, 2013

Water testing strips: a quick and easy way to monitor water quality

To most people unfamiliar with water quality monitoring (WQM) techniques, testing your water may sound like a frightening proposition, filled with scientific jargons, chemical names and strange equipment.

Fortunately, there is a quick and easy way to test your water without sending your water samples to a commercial lab which can bite off a chunk of your budget and take time from submitting your samples and receiving your data.

If you have been holding your breath, here is your answer - water testing strips. The instructions look simple to follow. No messy and hazardous chemicals to handle. No heating and special sample preparation needed. Most strips simply require you to dip them into your water sample, take out and wait for some time (typically a minute or so) to the colour to develop. Match the resultant colour against a colour chart and viola! Instant water quality data. (The longest time I waited was about 10 minutes for the chloride test. I have not used the bacteria strips but most still need the typical incubation time e.g. 48h.) If this sounds like your DIY urine glucose testing strips, you are absolutely right.

On-site tests can be done with these guys with no lag time that can allow reactions to interfere with your results.

There are various suppliers for these strips but the one I tried came from Hach - a well recognised company for water analysis. There are strips for pH, hardness, alkalinity, iron, copper, ammonia, nitrate, phosphate, chlorine, chloride and even arsenic and bacteria. But in case we get too carried away with the WQ parameters that can be tested with these strips, keep in mind that WHO drinking water guidelines have about 200 parameters so there are still many parameters not available for testing on strip.

Another limitation of strips is the precision of your results. It may only give you a range of say, 0-5, 5-15, 15-30 ppm (parts per million). For the strips testing for bacteria, the result is a simple present or absent. Sometimes that is not good enough to tell you whether the water is safe, tolerable or plain dangerous. And for research purposes, you need a more definite figure to plot your trends or perform your statistical analysis.

Nevertheless, if you keep in mind their limitations, water testing strips are a great (quick and easy) method to test your water. Use them for preliminary tests or perhaps as screening tools to check if further and more precise analyses are necessary.

Figure: Water testing strips normally come in bottles like these. This make them extremely mobile - no bulky equipment and chemical containers to cramp the space in your travel bag. Each bottle usually has a colour chart on it exterior. Notice the colour chart on the leftmost bottle.
Figure: 5-in-1 testing strip. Each coloured square tests for a separate WQ parameter.


Unknown said...

This is a great idea and convenient as well as we don't have to send the results to a lab. I like the idea that it would only take some minutes to get the results but are the results accurate? How often do we have to use these testing strips?

CK said...

The results are reasonably accurate though you have to check the instructions for possible interferences. However, as mentioned in the blog post, they are not precise e.g. a range of values is given instead of a single value.

Frequency is the same as for usage of instruments or any other form of monitoring. It depends on your statutory requirements, resources, environmental conditions, purposes etc.

kiat said...

hi, where do you buy the strips in Singapore?

CK said...

These strips are from the water testing company Hach and distributed by Fluke South East Asia Pte Ltd in Singapore