acidity

Acidity as a Water Quality Indicator Analysis

Definition and Measurement

Acidity characterizes the total concentration of hydrogen ions (H⁺) in water, quantified through pH:

pH scale: 0-14 (at standard conditions of 25°C)

Acidity determination: pH < 7.0 (neutral water pH = 7.0)

Detection method:

Electrode method (GB/T 6920-1986) accuracy ±0.01pH

Methyl orange titration method (total acidity determination)

Key Influences on Water Treatment

pH Range Water Quality Characteristics Treatment Process Risks

＜6.5 Increased Corrosivity Metal pipe corrosion rate ＞ 0.5 mm/a

6.5-7.5 Ideal Operational RangeOptimal coagulant performance range

> 7.5 Scale tendency increased CaCO₃ saturation > 300%

Industrial control requirements

■ Drinking water: pH 6.5-8.5 (GB 5749-2022)

■ Wastewater discharge: pH 6-9 (GB 8978-1996)

Boiler feedwater: pH 8.5-9.2 (for scale inhibition and corrosion prevention)

Acidity control technology

Acidic water treatment

Alkali addition: Ca(OH)₂ / NaOH (theoretical addition ratio 1 mg of acidity requires 0.74 mg of CaCO₃)

Aeration decarbonation: CO₂ stripping rate > 80% (pH increased to 8.3)

Alkaline water treatment

CO₂ acidification: pH controlled precisely ±0.2 (addition of food-grade CO₂)

Weak acid resin desalination: total alkalinity reduced by ≥90%

All about water...