Source Water Characteristics and Protection
Start with the water, not the plant
Every downstream decision - coagulant dose, filter run length, disinfectant demand - is dictated by raw water quality. Candidates must be able to compare surface water (variable turbidity, color, algae, pathogens, temperature-driven swings) with groundwater (stable chemistry, low turbidity, but often elevated iron, manganese, hardness, sulfide, nitrate, and low dissolved oxygen). Know that GWUDI - groundwater under the direct influence of surface water - is regulated as surface water.
Understand what each raw-water parameter signals: turbidity (particulate load and pathogen risk), alkalinity (buffering capacity - not the same thing as pH), hardness (dissolved calcium and magnesium, largely an aesthetic issue), pH, temperature, TDS, and specific contaminants such as nitrate (recent pollution from fertilizer, manure, or septic systems), iron and manganese (reduced groundwater, or reservoir turnover), and algal metabolites (MIB, geosmin) that cause taste and odor.
Learn source protection: delineating a wellhead protection area and controlling land use and backflow within it, sanitary surveys, watershed inspection, and reservoir stratification and turnover, which produce sudden turbidity, manganese, and taste-and-odor spikes each spring and fall.
Traps: confusing alkalinity with pH; assuming groundwater is always pathogen-free (it is not - GWUDI and poorly sealed wells exist); calling hardness a health hazard; forgetting that nitrate points to recent contamination.
Worked example: hardness of 120 mg/L as CaCO₃ converts to grains per gallon by dividing by 17.12: 120 ÷ 17.12 ≈ 7.0 gpg - a moderately hard water.