Field Analysis Guidelines Enhance Water Test Results

Water quality is often tested in the field to meet federal, state, and local requirements as well as for process control and emergency response. Using established guidelines can improve field analysis results. 

When true analytical chemistry began to be applied to water quality concerns in the late 1700s and early 1800s, the goal wasn’t to detect potentially harmful substances in the water so they could be avoided but to identify beneficial agents in the water.

At the time, the concept of hydrotherapy as a cure for a wide variety of health problems was in vogue. Gradually, it became apparent, as was obvious to many ancient cultures, that water also had the potential to be the source of contaminants that could cause sickness and disease.

For example, in 1854, London was undergoing a cholera epidemic, but no one knew the cause of the disease at the time.

One man, John Snow, was convinced that water contaminated with sewage was the culprit. Snow’s efforts eventually led to one of the first experiments in the young science of epidemiology and directed attention to contaminated water as a source of disease. 

Now, as knowledge of potential water threats increases, the number and types of parameters that need to be monitored also increase. Metals, pesticides, industrial chemicals, disinfection by-products, and microorganisms are just a few of the parameters that need to be measured.

Recently, parameters that have become important include those of environmental concern, such as nutrient loading levels, and security concerns involving acute toxins and bioagents. 

FIELD ANALYSIS GUIDELINES
Initially, most water analysis was done in a laboratory, but today it’s known that some measurements are more efficiently and conveniently done in the field, with more precise results.

The criteria detailed here are useful in judging an analytical method’s worthiness for field testing as well as how such methods are used. The method should be usable by anyone who can read.

This concept is based on the diversity of skill levels found in the water and wastewater industry. The skill levels of field-test users in the municipal water industry vary from those with a chemistry degree to part-time city employees with lower levels of education.

Simplify.
Keeping a procedure simple without compromising analytical integrity is a difficult but achievable goal. Fortunately, a variety of analytical methodologies for most parameters of common interest is available, developed to serve various user communities, from easy-to-use test strips to field-portable gas chromatograph/mass spectrometer systems. However, simplicity should always be favored.

Even highly trained and proficient operators can make mistakes when trying to operate equipment or perform procedures in emergency situations.

Know Your Procedures.
It’s prudent to have a good understanding of an analytical procedure before attempting it in the field. Often, analytical procedures have subtle nuances and depend on technique. It’s important to recognize a procedure’s intricacies and understand the underlying chemistry or biology involved.

A thorough understanding of the science involved, including where a test can go wrong (interfering substances, environmental conditions such as temperature and light, as well as issues such as sample selection), can help alleviate problems. 

Practice, Practice.
Beyond having an intellectual understanding of a procedure, the adage of “practice makes perfect” is appropriate concerning field testing. Dry runs of the testing procedure should be practiced in conditions as close to fieldlike as possible, as many unexpected variables can come into play in field conditions.

Noninstrumental procedures that rely on matching colors or recognizing a colorimetric endpoint, such as a titration, should be practiced with special diligence, because many people have difficulty recognizing a specific color. The method should be rapid and easy to use. Three main reasons call for performing water tests in the field. All three relate in some way to a desired speed in obtaining a result, and ease of use is often directly correlated with speed.

Accuracy.
Water quality measurements often change with storage regardless of preservation steps. Some parameters, such as pH, dissolved oxygen, oxidation–reduction potential, and chlorine residual, change rapidly with time. If time is spent transporting samples to a laboratory for analysis, these and other transient parameters may change enough to diminish the value of the results.

In these instances, it becomes easier—indeed crucial—to perform measurements in the field to ensure accurate readings. Convenience. Field analysis allows users to generate results at a site so action can be taken. Often, processcontrol decisions rely on data generated on-site.

Although process instrumentation has advanced to the point that many of these decisions can be automated by routing the process analytics data through a supervisory control and data acquisition system, accurate measurement is needed before control measures can be taken.

Field analytics play a crucial role in calibrating and verifying analytical measurements performed by process instrumentation. When process instrumentation isn’t used or isn’t practical, the field results themselves can be used to adjust and control a system. For example, some small water treatment systems can’t afford continuous online instrumentation and use field analysis to adjust chemical feed rates.

Field analytics play a crucial role in calibrating and verifying analytical measurements performed by process instrumentation. When process instrumentation isn’t used or isn’t practical, the field results themselves can be used to adjust and control a system. For example, some small water treatment systems can’t afford continuous online instrumentation and use field analysis to adjust chemical feed rates.

Speed
It’s often necessary to get analytical results on which decisions can be made as quickly as possible. A prime example of this is emergency response to a water supply’s accidental or deliberate contamination.

In such situations, the keys to an appropriate response are speed (the quicker action is taken, the fewer people will be affected) and accuracy (false positives aren’t acceptable when remedial action involves high-consequence activities such as turning off water supplies and issuing public warnings). Field analytical procedures, if properly chosen and used, can be an important way to gather knowledge and gain confidence in that knowledge. 

Read the full Article at AWWA - here.

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Taxonomy

• Water Quality
• Test & Measurement
• Water Quality Monitoring
• Test Equipment
• Field Instrumentation