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Disinfection factors; bleaching powder 5 ML/day

Short answer

Key factors include organism type, disinfectant concentration and contact time, temperature, pH, turbidity, and chemical demand. For5 MLD at0.6 mg/L dose and30% chlorine, daily chlorine=3.00 kg/day, so bleaching powder=10.00 kg/day.

Discuss the factors affecting disinfection. Calculate the quantity of bleaching powder required per day for disinfecting 5 ML per day. The dose of chlorine has to be 0.6 ppm and the bleaching powder contains 30% of available chlorine.

Factors affecting disinfection

  1. Type and number of organisms: viruses, spores and cysts are more resistant than vegetative bacteria; high numbers need more disinfectant.
  2. Nature and concentration of the disinfectant (dose): CntC^n t = constant.
  3. Contact time: longer contact gives greater kill (at least 30 minutes).
  4. Temperature: warm water speeds up the reaction; cold water needs more time.
  5. pH: chlorine is more effective at lower pH, since more HOCl is present.
  6. Turbidity and suspended solids: they shield microbes and use up the disinfectant, so disinfect after filtration.
  7. Chemical quality: organic matter, ammonia, iron and manganese consume chlorine (chlorine demand).
  8. Mixing and uniform distribution of the disinfectant.

Bleaching powder required

Flow = 5 ML/day =5×106= 5\times10^6 l/day; dose = 0.6 ppm; available chlorine = 30 %.

Chlorine=0.6 mg/l×5×106 l/day=3×106 mg/day=3.00 kg/dayBleaching powder=3.000.30=10.00 kg/day\begin{aligned} \text{Chlorine} &= 0.6\ \text{mg/l}\times5\times10^6\ \text{l/day} = 3\times10^6\ \text{mg/day} = 3.00\ \text{kg/day} \\ \text{Bleaching powder} &= \frac{3.00}{0.30} = 10.00\ \text{kg/day} \end{aligned}

Answer: 10.00 kg of bleaching powder per day.

✓ Answer checked by Claude Opus 5.5 (high effort)

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