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Potable Water Disinfection: Calcium Hypochlorite vs Sodium Hypochlorite vs TCCA 90

Compare Calcium Hypochlorite 70%, Sodium Hypochlorite 15%, and TCCA 90% tablets. Dosing calculations, stability, and KEBS drinking water compliance in Kenya.

Author: Kiki's Chemical Engineering Team•Published: 2026-02-16•8 min read
DisinfectionCalcium HypochloriteSodium HypochloriteTCCA 90Drinking Water

Quick Answer — Potable Water Disinfection: Calcium Hypochlorite vs Sodium Hypochlorite vs TCCA 90

Drinking water disinfection utilizes three primary chlorine donors: Calcium Hypochlorite 70% (high-strength solid powder/granules ideal for remote or high-volume dosing without transport water weight), Sodium Hypochlorite 10-15% (liquid bleach ideal for automated metered pump dosing in established plants), and TCCA 90% (slow-dissolving stabilized cyanuric acid tablets ideal for continuous pool and small-scale water chlorination).

Chlorine water disinfectants are chemical chlorine donors that yield Hypochlorous Acid ($HOCl$) upon dissolution in water, penetrating bacterial cell walls to achieve complete microbial inactivation.

Key Facts

  • •Hypochlorous Acid ($HOCl$) is 80 times more effective at pathogen kill than the Hypochlorite ion ($OCl^-$), making pH control (pH 6.5 - 7.5) crucial.
  • •Calcium Hypochlorite 70% contains 70% available chlorine by weight and retains shelf stability significantly longer than liquid bleach.
  • •KEBS standards require a free residual chlorine level of 0.2 to 0.5 mg/L at the consumer tap.

Primary Use Cases

Municipal and community water supply chlorinationBottled water processing raw water pre-disinfectionCommercial swimming pool and resort water treatmentDisaster relief and emergency field water purification

Protecting Public Health & Industrial Water Disinfection

In water treatment plants, flower farms, beverage factories, and residential communities throughout Kenya, water disinfection is the non-negotiable barrier protecting consumers and processes from waterborne pathogens (*E. coli*, *Vibrio cholerae*, *Giardia*).

While ozone and ultraviolet (UV) radiation provide excellent point-of-use disinfection, chlorine chemistry remains the global gold standard because it provides a durable **residual chlorine protection** that prevents recontamination during distribution and storage.

Comparison Matrix: Physical & Chemical Characteristics

| Chemical Property | Calcium Hypochlorite (HTH) | Sodium Hypochlorite (Bleach) | TCCA 90 (Trichlor) |

|---|---|---|---|

| **Commercial Form** | White Granules / 200g Tablets | Clear Yellow Liquid | White Powder / 200g Tablets |

| **Active Available Chlorine** | 65% – 70% | 10% – 15% | 85% – 90% |

| **pH Impact** | Slightly Alkaline (pH 10-11) | Strongly Alkaline (pH 12-13) | Acidic (pH 2.8 - 3.2) |

| **Shelf Life Stability** | Excellent (Years if dry) | Poor (Degrades in weeks) | Exceptional (Years if dry) |

| **UV Resistance** | Unstabilized (Fades in sunlight) | Unstabilized (Fades in sunlight) | Self-Stabilized (Cyanuric Acid) |

| **Storage Requirement** | Cool, dry, non-combustible store | Dark, vented poly drums | Cool, dry ventilated store |

The Disinfection Chemistry: Hypochlorous Acid ($HOCl$) Balance

When any chlorine donor dissolves in water, it forms Hypochlorous Acid ($HOCl$), the active biocidal molecule:

$$ ext{Cl}_2 + ext{H}_2 ext{O} ightleftharpoons ext{HOCl} + ext{H}^+ + ext{Cl}^-$$

$$ ext{HOCl} ightleftharpoons ext{H}^+ + ext{OCl}^- quad (pK_a = 7.53)$$

  • **At pH 6.5:** Over 90% of available chlorine exists as active $HOCl$.
  • **At pH 7.5:** Exactly 50% exists as $HOCl$ and 50% as the weaker $OCl^-$ ion.
  • **At pH 8.5:** Less than 10% exists as active $HOCl$.

**Key Takeaway:** If your water pH exceeds 8.0, chlorination efficiency drops by over 80%. Always adjust pH to 6.8-7.4 prior to or during chlorination.

Calculating Required Dosage for Municipal & Factory Tanks

To calculate chemical requirements:

$$ ext{Required Active Mass (g)} = rac{ ext{Volume (m}^3 ext{)} imes ext{Target Concentration (mg/L)}}{ ext{Fractional Chemical Purity}}$$

  • **Example:** Treating a $500 ext{ m}^3$ (500,000 Liter) reservoir to $3.0 ext{ mg/L}$ free chlorine using **Calcium Hypochlorite 70%**:

$$ ext{Active Chlorine Needed} = 500 ext{ m}^3 imes 3.0 ext{ g/m}^3 = 1,500 ext{ grams}$$

$$ ext{Calcium Hypochlorite Mass} = rac{1,500 ext{ g}}{0.70} = 2,142.8 ext{ grams (approx. 2.14 kg)}$$

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