How is silica measured in power plant water systems?

Silica measurement in power plants: colorimetric method using molybdate reagent forming blue silicomolybdate complex measured photometrically. Critical for boiler water because silica volatilizes at high pressure, deposits on turbine blades causing efficiency loss and damage. Measurement points: raw water, demineralizer effluent (ppb levels), boiler blowdown, and steam. Online analyzers automate reagent addition and measurement; accuracy typically +/-2% or +/-2 ppb. Considerations: phosphate interference (requires masking), proper sample conditioning (temperature, flow), and regular calibration. Silica limits depend on boiler pressure - high-pressure boilers require very low levels (<5 ppb).