News - Water Quality Parameters (WQPs)


In my blog post several weeks ago, I wrote about the Lead Copper Rule (LCR). I mentioned that from time to time, the metals can leak from water pipes or fixtures into the water system by corrosion. The corrosion is a process through which metal has oxidized to form a cation. The cation is water soluble thus it can migrate from the metal surfaces into water. Most of metals can be corroded to some degree which takes place in the same way as to how a battery functions when two different metals are connected through a media called electrolyte. However, the rate and extent of the corrosion depends on the metal, media and environment. In the case of a water system, the corrosion can be affected by the following conditions:

1. pH. Either low pH or high pH can both cause corrosion. At a low pH, the water is acidic under which most of the metals whose redox potentials are low can be oxidized. At a high pH, the water may become vulnerable to bacteria (such as sulfur reducing bacteria) induced corrosion.

2. Dissolved solid (TDS). The water that has low TDS is called soft water. The corrosion can occur in soft water due to lack of dissolved cations, such as calcium and magnesium in the water because the presence of those minerals tends to form a coating on the metal surface thus slowing down the dissolution of the metal from metal pipe. Water contains a high level of TDS when there is large amount of sodium, chloride or other ions present. High TDS water means it has high conductivity thus promoting corrosivity.

3. Chloride to Sulfate. The mass ration of two (CSMR) along with alkalinity is related to galvanic corrosion. An elevated CSMR can increase the potential for galvanic corrosion of water system. In fact, research conducted by Dr. Edwards from Virginia Tech concluded that it was a change of CSMR ratio that caused the deterioration of metal corrosion in the Flint water crisis. Prior to water crisis, the city of Flint, Michigan had switched water treatment materials from sulfate-based aluminum to chloride based in order to save money.

Under Lead Copper Rule (LCR), the parameters like pH, conductivity, ion concentrations, and TDS are used to evaluate the quality of the water flowing through the distribution system. TCEQ requires all Public Water Systems (PWS's) with a population over 50,000, new PWS's of all population and any PWS's that have exceeded the action levels (0.015 mg/L for lead and 1.3 mg/L for copper) to test for the water quality parameters (WQPs). Orthophosphate is a common chemical used as an inhibitor for water treatment. If it is used for water treatment, it is also required to be included in the testing of WQP.

In compliance with LCR, TCEQ published public water system guidance in terms of how to do monitoring and sampling for WQP testing. TCEQ will use WQP results to evaluate if drinking water is corrosive and determine effectiveness of the water treatment program in order to prevent corrosion.

The info about WQP can be found on the TCEQ website at:

https://www.tceq.texas.gov/drinkingwater/chemicals/lead_copper/lead-copper.html

1. How many WQP samples are needed if required

System Size

Number of sites for

Initial/Routine monitoring

Number of sites for Reduced monitoring:

More than 100,000

25

10

10,001 to 100,000

10

7

3,301 to 10,000

3

3

501 to 3,300

2

2

101 to 500

1

1

100 or fewer

1

1

2. When should you do it?

Sample twice quarterly within a 6-month monitor period.

3. Where do you get the containers for WQP sample?

From TCEQ approved and/or accredited labs.

4. How do you get the data of pH and temperature?

pH and temperature must be obtained in the field by sample collector. Prior to measuring those on-site data, PWS's must have documented approval from TCEQ.

5 The other requirements about sample collection, preservation and labeling can be found from the link shown below:

https://www.tceq.texas.gov/assets/public/permitting/watersupply/pdw/chemicals/lead_copper/PWS_WQP_Sampling_Guidance.pdf

Should you have questions or need additional information on Water Quality Parameters (WQPs) or need water testing services, please contact us at 903-984-0551. Ana-Lab Corp. has been been providing superior analytical lab services since 1965.


Bill Peery

Bill Peery is the Vice President of Technical Services and has been with Ana-Lab for over 30 years. He holds a Bachelor of Arts degree in Biology and Chemistry from the University of Texas at Austin and a Bachelor of Science degree in Software Engineering from Lamar University. He also earned his Master's degree in Computer Science and Chemistry from the University of Texas at Tyler.