Checking for contamination is important, but knowing about fouling and the ageing of the well are critical too.
By Michael Schnieders, PG, PH-GW
Discuss with the lab your goals for testing ahead of time to avoid frustration for all parties. All photos courtesy Water Systems Engineering Inc. in Ottawa, Kansas, except where noted.
Testing is often conducted in the groundwater industry because we must do so as part of regulatory requirements.
Testing is typically targeted towards “water quality,” a term loosely based on the National Primary and Secondary Drinking Water Regulations. These regulations were born out of the Clean Water Act and its reauthorization, the Safe Drinking Water Act, to establish potable water source guidelines in the United States.
The Journal of Environmental Quality defines water quality as “the chemical, physical, biological, and radiological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and/or to any human need or purpose.”
The last aspect of the definition—purpose—is so often forgotten. As I mentioned, groundwater industry professionals typically test because they must—which has aided in the delivery of safe water to millions of people within our borders.
But what about well health?
Unfortunately, there remains a great misunderstanding in the role of water testing and the definition of a contaminant. The confusion in testing spans the entire industry—everyone from the well owner to the contractor to the engineer and even the regulator.
While testing for the more than 90 contaminants on the National Primary and Secondary Drinking Water Standards list is necessary in evaluating a water source initially and when contamination is suspected, it does little to tell us about fouling occurring or the ageing of the well.
Understanding the Issues
In a dynamic well system, complex physical, chemical, and biological activities can occur slowly over time or quickly. As these reactions and interactions occur, they can impact the operation of the well, the efficiency of the well, and at times, the produced water quality or usability of the well.
With maintenance and operational issues, water testing is generally targeted at identifying the potential for mineral scale development, the occurrence of corrosion, and an evaluation of the microbial community.
A large Protozoa, reflective of surface water influence, identified during microscopic evaluation. The water sample containing the Protozoa was “total coliform negative.”
While the focus and parameters are different for regulatory purposes, regulatory and maintenance testing generally use the same methods for analyses of a sample.
Regulatory testing requires specific collection methods, the use of special containers and preservatives, and has strict limits regarding holding times prior to testing. Maintenance testing generally has different procedures for sample collection and submittal, partially reflective of the well or any specific problems occurring.
When attempting to understand an issue with the well, it is wise to discuss the observed problems with a lab so that a specific sampling procedure can be developed. Similarly, the necessary parameters can be discussed to provide insight into the problems being experienced. A simple 15-minute conversation can save time and money, not to mention alleviate frustration for both sides.
In evaluating water chemistry from a well for troubleshooting or maintenance, the primary concern is for scale formation and corrosion. Useful parameters for evaluation include pH, alkalinity, total dissolved solids (TDS), conductivity, hardness level, calcium, magnesium, iron, manganese, and the oxidation-reduction potential.
These parameters help to characterize the water, identify the likelihood of scale development, and give insight into the type of scale expected. Additionally, it can provide useful information with respect to corrosion. This information can also help you select the right type of chemical and mechanical response and provide you with monitoring parameters during treatment.
Crystalline debris identified during microscopic evaluation used to assess formation influence and identify the cause of degradation of the pump.
Often, biological testing is used as an end or fail point. This mainly occurs because of our industry relying on the total coliform test as the sole means of assessing the microbiological community. While this test is a regulatory necessity for many wells, it does little to assess the downhole community or identify biofouling potential.
When conducting biological analyses, it is advised you first quantify the population. Think of this like a census to see whether the microbial community falls within a normal range. Historically, the heterotrophic plate count (HPC) has been used for this purpose. The challenge with plate counts is to confirm the test method and range to ensure that groundwater bacteria will respond, and you have a means of interpreting
The adenosine triphosphate (ATP) test is another method that quantifies all living bacteria within a sample, including both aerobic and anaerobic species. In addition to identifying the size of the resident bacterial population, it is recommended you test for the presence of anaerobic bacteria.
Anaerobic bacteria are a collective group of bacteria that do not require oxygen, and as such, produce a dense form of biofilm. Testing for anaerobic growth is useful in identifying areas of heavy fouling as well as the development of environments for more problematic organisms such as sulfate-reducing bacteria (SRBs).
SRBs are common in heavily fouled wells or older, stagnant systems. They have a distinctive rotten egg type odor as hydrogen sulfide gas is produced by the bacteria.
In addition to the evaluation of anaerobic growth and the presence of SRBs, testing for the presence of iron bacteria is recommended. Iron-oxidizing bacteria are a common problem in wells, occurring in approximately 47% of troubled wells evaluated by our lab.
A mass of iron bacteria and iron oxide entrained biomass, a common problem in shallow alluvial wells.
They commonly occur in alluvial aquifer settings or wells with low carbon or galvanized steel completions. Often misidentified as iron-reducing bacteria, iron oxidizers are typically identified by the iron-oxy-hydroxide deposits they develop during their life cycle.
If you suspect a coliform problem, in addition to the aforementioned tests, it is advised you confirm the coliform occurrence and also rule out the presence of E. coli-specific coliforms. In addition, quantifying the coliform presence and having the dominant species identified can help further understand the problem and identify whether the issue is a fouled well or contamination.
In addition to chemical and biological concerns, physical fouling, often referred to as mechanical fouling, can occur. This can be the result of material physically blocking or impeding flow in the well, filter pack, or adjacent boreholeaquifer interface zone.
Oftentimes, these problems present themselves at start-up with turbidity or sediment occurring. While traditional testing may not help in identifying these issues, a lab can still provide insight. If a sample shows signs of turbidity, sediment, or settling solids, it is advised the sample be evaluated microscopically.
Microscopic evaluation of a sample under low power (20 to 400 times magnification) can help in identifying the influence of clay, silt, and fine grain size sediment on a well system. The evaluation can also be used to identify corrosion byproducts and surface water influence.
In addition to a water sample, evaluation of mineral scale, slime, or sediment can be useful. Analyzing actual material extracted from the well or pump can give you unique insight into the fouling mechanisms present. However, be careful. While a deposit can be an excellent representation of fouling— it can also be specific to one part of the well and not accurately portray the problems downhole.
Using Other Tools
Calcium carbonate scale buildup occurring in a well and associated piping, readily identifiable by hardness levels. Photo courtesy Thom Hanna, PG.
It is important to note that laboratory testing should not be the only tool used when investigating a well problem. Records review, site inspection, video survey, power evaluation, and operational observations are necessary procedures that can help identify problems or increase the understanding of an issue.
Reviewing what information the customer and county and state offices have on file can give insight into the age of the well, materials of construction, stratigraphy, and possible issues faced during construction.
Physical inspection of the wellhead at the surface can help identify degradation or damage that has occurred. Conducting a video survey helps to assess the nature of fouling, degree of impact, and location of problems while providing some insight into the structural stability of the well.
Evaluating the electrical components can provide insight into efficiency, corrosion, and pump operation. Discussing the quality of the produced water with the homeowner or operator can help to identify when issues occur, which can give insight into the nature of many well problems.
Laboratory analysis provides valuable insight into problems and potential challenges experienced by a variety of wells and water systems found in residential, municipal, industrial, and environmental use.
Laboratory analysis helps to lessen the unknowns of what is occurring downhole and can be an integral part of the evaluation and diagnostic process used to interpret problems. Chemical and biological water analysis helps to identify and pinpoint problems that cause fouling and production loss, determine the severity of the problem, and the level of response.
Regular water analysis helps to maintain efficient function, prolong the life of the well system, and ultimately protects water quality.
Find Books on Water Treatment in NGWA Bookstore
There are several books available in the NGWA
Bookstore that focus on matters relating to water treatment, water well technology, and more. Included is Operational Stage of the Well
, whose coauthor is Michael Schnieders, PG, PH-GW, the author of this article. The book goes over various factors of well deterioration and how they impact well operation and maintenance. Visit the NGWA Bookstore section on water treatment
Michael J. Schnieders, PG, PH-GW, is a professional geologist serving as the principal hydrogeologist and president of Water Systems Engineering Inc. in Ottawa, Kansas. Schnieders’ primary work involves water resource investigation and management, specializing in the diagnosis and treatment of fouled well systems. Schnieders served as The Groundwater Foundation’s 2017 McEllhiney Distinguished Lecturer in Water Well Technology. He can be reached at email@example.com.