Source Water and Water Quality
A Class III operator must read a source before treating it. Know the difference between groundwater (stable temperature, low turbidity, often high hardness, iron, manganese, and sometimes nitrate or radionuclides) and surface water (variable turbidity, seasonal algae, color, pathogens, temperature stratification). Understand watershed influences: runoff, agricultural nutrients, road salt, upstream discharges, and algal blooms that raise pH and produce taste-and-odor compounds.
Key water-quality parameters to master: turbidity (NTU), pH and alkalinity (buffering), hardness, conductivity/TDS, temperature (affects coagulation and disinfection), dissolved oxygen, and the pathogens of concern (Giardia, Cryptosporidium, viruses, bacteria). Know how alkalinity and pH constrain coagulation and how temperature changes reaction rates.
Traps: confusing alkalinity with pH (a water can be well buffered at high pH or low pH); assuming low turbidity means safe (Cryptosporidium oocysts occur in clear water); treating a single grab sample as representative when source quality swings diurnally and seasonally. Also watch unit and definition questions-turbidity is optical, not a mass measure.
Rule of thumb: track source turbidity and alkalinity daily and watch the trend, not just today's number. If raw turbidity doubles and alkalinity is low, expect to adjust coagulant dose and possibly add alkalinity before the filters see the change.
Worked example: Raw alkalinity 40 mg/L as CaCO3 and pH 6.5. A metal-salt coagulant consumes alkalinity; at 40 mg/L you have little buffer, so expect pH to drop sharply and coagulation to suffer. Anticipate feeding a base (lime or caustic) to hold pH in the coagulation range.