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Water Quality Parameters

There are several water quality parameters that could be affected with the presence of oil and gas in the water. These include:

• Turbidity: Turbidity is a water quality parameter that indicates how transparent water is. The less transparent water is, the more turbid it is - or the more "stuff" it has in it. Causes of turbid water can include runoff from the land that that carries sediments, discharge from pollution sources, phytoplankton, and algae. Turbidity is measured by units called " Nephelometric Turbidity Units" or NTUs. You can measure turbidity with an instrument called a nephelometer or turbidimeter, or you can use a device called a secchi disk to measure NTUs in standing water. Turbidity can be affected by oil presence the water as it sit on top of the water column and affects visibility, or suspends within the column itself.

• Conductivity: "measure[s] of the capability of a solution such as water in a stream to pass an electric current. This is an indicator of the concentration of dissolved electrolyte ions in the water. It doesn't identify the specific ions in the water. However, significant increases in conductivity may be an indicator that polluting discharges have entered the water...The basic unit of measurement for conductivity is micromhos per centimeter (µmhos/cm) or microsiemens per centimeter (µS/cm)." (http://www.fosc.org/WQData/WQParameters.htm)) Conductivity is often measured with a probe or a meter which can test the electrical capacity of water by measuring the voltage that passes between two electrodes. Oil, gas, and byproducts of the industry such as lubricants, heavy metals, and salts can cause an increase in the conductivity in contaminated water.

• pH: "Level of pH can indicate chemical changes in water, and the biological availability of nutrients in water. The pH scale ranges from 0 to 14. A safe level of pH of water ranges between 6.5 and 8.5 units. pH levels higher than 8.5 become highly basic, while pH levels below 6.5 become highly acidic for water quality." (www.cvc.ca) "The most common method for measuring pH is with a meter, which involves a pH-sensitive electrode and a reference electrode. Acid-base indicators change color in response to different pH values. Litmus paper and pH paper are used for quick, relatively imprecise measurements. These are strips of paper that have been treated with an indicator. A colorimeter may be used to measure the pH of a sample. A vial is filled with a specimen and a reagent is added to produce a pH-dependent color change. The color is compared against a chart or standard to determine the pH value." (www.thoughtco.com) Contamination of oil and gas often changes the pH of water.

• TDS (Total Dissolved Solids): Total Dissolved Solids "refer[s] to any minerals, salts, metals, cations or anions dissolved in water" (waterreseach.net). TDS can relate to the conductivity and the turbidity of the water, but is often harder to determine as a water quality parameter. TDS is measured as a volume of water with the unit milligrams per liter (mg/L), or parts per million (ppm). Oil and gas contamination can often cause high levels of TDS.

• Temperature: temperature is also a water quality parameter that can change with the presence of contamination. Thought it should be noted, that temperature can also be affected by many other factors.

Water Quality Sensors

One of the tools for collecting measurements of these water quality parameters is through digital/electronic sensors. These sensors come in roughly three categories: - Expensive, lab-grade sensors: these sensors cost hundreds or thousands of dollars and have clear procedures in place for collecting and calibrating data as well as a high degree of accuracy.
- Cheap, consumer sensors: these sensors cost tens of dollars, and are primarily used by people wanting to measure their swimming pools and aquariums. These consumer sensors seem to be limited to temperature, pH, conductivity, and TDS and generally don't have clear, documented procedures for testing and calibration. - DIY electronics sensors: these sensors are not self-contained and require additional hardware and programming to use, usually something like an Arduino or a Raspberry Pi.

We have documented the use of a set of liquid sensors from DF Robot with our Simple Water Sensor Platform.

Methods/Activities

Questions

Current Challenges and Next Steps

• Research and document accessible techniques and procedures for calibrating water quality sensors.
• Research and document ways of knowing /where/, /when/, and /how/ to collect water samples and water data that is relevant to oil and gas contamination.
• Collect stories of people's experiences with oil and gas pollution, water monitoring, data collection, organizing, advocacy, etc...
• Continue to test, prototype, and document the Simple Water Sensor, including:
  • Test and document calibration procedures for the whole set of DF Robot liquid sensors
  • Rewrite sensor platform software to allow users to calibrate their sensors without needing to change/upload Arduino code
  • Create a "troubleshooting" document collecting common difficulties and pitfalls for building and using the sensor platform
  • Research and document procedures for using these sensors, including tips for collecting usable data, common pitfalls, and rough guidelines about the limitations of these sensors
  • Test these sensors in comparison to known, lab-quality equipment