How to test water quality? Here are some low-cost, low-tech options

Sustainable Development Goal 6 (SDG6) calls for “universal and equitable access to safe and affordable drinking water” by 2030, which is quite different from access to an “improved” water source, which has been our primary focus with the Millennium Development Goals. This makes water quality monitoring essential: how can we assess progress towards #SDG6 without knowing whether water is safe to drink? 

When you have limited resources, water testing methods need to be low-tech, affordable, and simple .  They also need to be reasonably accurate. Single-use tests can sometimes fit the bill, but many are still too costly for large-scale deployment.  Generally speaking, these tests trade some of the accuracy, precision, and quality control of the analytical lab setting for practicality: they’re portable, easy to use with little or no training, and many have eliminated the need for a power supply, refrigeration, or precise temperature control. 

The availability of commercial water testing products varies from one country to the next, and supply chain issues may make local products more practical than test kits from abroad.  What’s more, low-tech water quality testing is an area of active research, especially for microbial tests.  New options may be available every few years, either through collaborations with developers or as new products are commercialized. 

We provide here a brief overview of low-tech water quality monitoring options. 

Let’s begin with testing by physical characteristics.

In the absence of water testing tools, people use color, odor, taste, and cloudiness to assess whether water is safe to drink.  Unfortunately, these physical characteristics are an imperfect guide: water that will make you sick may seem fine, and water that is unappealing may in fact be safe .   Because physical characteristics may cause consumers to reject certain water sources, it can be helpful to monitor them. 

• Turbidity - Turbidity is not just cosmetic: increasing turbidity decreases the effectiveness of chlorination. A turbidity tube is a low-tech approach to measuring how cloudy (“turbid”) the water is.  It’s just a long plastic tube: you look down through the tube as you gradually fill it with water.  When you can no longer see the pattern printed on the bottom of the tube, you check the water level and read the turbidity from the markings on the side. For an even lower-tech method with a “yes/no” outcome, you can look down through a clear plastic 2L bottle that has been filled with water and check if you can see something printed in large text placed underneath (for more information, see the CAWST manual). 
• Color, taste, and odor - These characteristics may be recorded from simple observation (with the caveat that it is unwise to taste water of unknown quality!).  There are also standard solutions that can be used for color comparisons.
• Temperature - Water temperature affects microbial activity, dissolved oxygen levels, and ecosystem function.  It is easy to measure with a normal thermometer (digital or not). Modern probes for water quality monitoring typically include a temperature sensor. 

In future blogs, we’ll talk about chemical tests and microbial tests on water quality. Stay tuned!