Environmental Water Quality Testing

Water is one of our planet’s most valuable resources. As populations grow, environmental water quality testing is vital to detect changes and protect aquatic ecosystems.

What Is Water Quality?

Water quality defines how suitable water is for specific uses such as drinking, swimming, irrigation, or power generation. It reflects physical, chemical, and biological characteristics that can change by location and season.

Surface and groundwater interact at the water table, meaning each can affect the other’s quality. Continuous monitoring helps detect contamination from both natural and human sources before serious impacts occur.

Accurate Field Calibration

Field calibration ensures reliable results.

Before sampling: Calibrate instruments using fresh standards.
During testing: Perform mid-day checks for long projects.
After sampling: Do a post-calibration check for instrument drift. Always clean probes and use uncontaminated buffers for accuracy.

Key Water Quality Parameters

1. pH

Definition: Measures hydrogen ion concentration on a 0–14 scale (acidic → basic).

Ideal Range: Typically 6.0–8.0 (acceptable 5.0–9.0).

Why It Matters: Extreme pH levels can stress or kill aquatic life.

Measurement: Use a portable pH meter and field electrode for precise readings.

Calibration Procedure:

Choose buffer solutions bracketing expected pH (e.g., 1.00 and 4.01).
Fill beaker with ~75 mL buffer.
Immerse electrode, stir gently, and wait for a stable reading (≥ 5 s).
Rinse between points; use at least two calibration points.
Rinse with deionized water and store per manufacturer’s guide.

2. Temperature

Range: −50 °C to 150 °C (−58 °F to 302 °F) using thermistor technology.

Importance: Affects oxygen solubility, photosynthesis, and biological activity.

Factors: Sunlight, runoff, flow rate, and industrial discharge (thermal pollution).

Calibration: Most meters are factory calibrated; verify yearly in a lab.

3. Conductivity (EC) / Total Dissolved Solids (TDS)

Definition:

EC: Ability of water to conduct electricity (mS/cm).
TDS: Total dissolved substances in mg/L, ppm, g/L, or ppt.

Importance: High EC or TDS can indicate pollution from sewage, runoff, or salts. Acceptable levels vary with water use.

Calibration Procedure:

Inspect the EC sensor for debris.
Fill a 100 mL beaker with ~75 mL conductivity standard.
Rinse the probe in a second beaker of standard.
Place probe in calibration beaker, remove bubbles, and confirm stable reading (≥ 5 s).
Rinse with deionized water and store properly.

4. Dissolved Oxygen (DO)

Definition: Concentration of oxygen in water (mg/L = ppm).

Ideal Levels: ≥ 2 mg/L for corrosion protection; < 10 mg/L for boiler systems.

Why It Matters: DO levels indicate ecosystem health. The low DO often signals pollution or excess organic matter.

Influences: Photosynthesis, temperature, turbulence, and runoff.

Calibration (100 % DO):

Place sensor in a moist, closed beaker (or wet sponge) for 10–15 min.
Warm up instrument and confirm stable reading (≥ 5 s).

Calibration (0 % DO):

Immerse in ~75 mL 0 % DO solution.
Wait for stability (≥ 5 s).
Rinse completely before sampling.

5. Turbidity

Definition: Optical measure of water cloudiness caused by suspended particles like algae, silt, or bacteria; expressed in NTU (nephelometric turbidity units).

Why It Matters: High turbidity reduces light penetration, slows photosynthesis, and can carry toxins or heavy metals.

Measurement Methods: