Physical and Chemical Water Parameters
Physical and Chemical Parameters
Routine parameters provide rapid information about water quality and treatment performance. Reliable results depend on correct measurement range, calibration, sample handling and method limitations.
## 1. Field and bench measurements | Parameter | Measurement principle | Important quality checks | |—|—|—| | pH | Potential difference across a glass electrode system | Buffer calibration, slope, temperature and electrode condition | | EC | Electrical conductance between electrodes | Cell constant, standard solution and temperature compensation | | TDS | Residue after evaporation or meter estimate from EC | State whether gravimetric or estimated; conversion factor is water-dependent | | Turbidity | Light scattering, commonly nephelometric | Calibration standards, clean cell and bubble control | | DO | Optical luminescence quenching or electrochemical response | Probe condition, calibration, temperature and stabilization | | Alkalinity | Acid titration to defined endpoint | Standardized titrant, endpoint and sample handling | | Hardness | Complexometric titration or instrumental determination | Standardization, endpoint and interference control | | Chloride | Argentometric titration or ion chromatography | Blank, standardization and matrix effects |
## 2. Measurement versus sample preservation Parameters such as pH, temperature, EC and DO can change quickly after collection and are often measured in situ or promptly. Other analytes may require cooling, chemical preservation, filtration or digestion. Always follow the selected method’s instructions.
## 3. Calculation examples TDS by gravimetry: determine the mass increase of a prepared residue dish, correct for the blank where required, and divide by the analyzed sample volume. Report the final concentration with the correct unit.
Hardness as CaCO₃: calculate from standardized EDTA titrant consumption, titrant concentration and sample volume using the method-defined conversion.
Alkalinity as CaCO₃: calculate from standardized acid consumption to the prescribed endpoint, with the method’s equivalent-weight factor.
## 4. Common sources of error - Dirty or contaminated probes and glassware. - Calibration standards beyond expiry or outside the working range. - Temperature mismatch or incorrect compensation settings. - Inadequate mixing, settling or sample homogenization. - Reporting a meter-derived TDS estimate as a gravimetric measurement. - Failing to record whether a result was measured in the field or laboratory.
## 5. Minimum measurement record Record sample ID, location, date/time, instrument ID, calibration check, temperature, method, result, unit, analyst and any deviation.