---
title: "Bleaching powder for 2 MLD, 30% chlorine"
subject: "Water Supply Engineering"
chapter: 6
key: "semester_5/water_supply_engineering:bleaching-b79"
source: https://www.bctengineer.com/q/semester_5/water_supply_engineering/bleaching-b79
site: BCT Engineering
---

# Bleaching powder for 2 MLD, 30% chlorine

Water Supply Engineering · Chapter 6: Water Treatment

- Asked in: 2079 Bhadra, 4 marks
- Video: [Chlorine Dosing Calculation|How to calculate chlorine Dosing & Consumption|How to Prepare solution.](https://www.youtube.com/watch?v=COtK4Y62yzQ) — ETP, ZLD Plant Technical knowledge
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/water_supply_engineering/bleaching-b79
- Whole chapter: https://www.bctengineer.com/md/semester_5/water_supply_engineering/chapter-6

## Question

Calculate the quantity of bleaching powder required to be added in the treatment plant to disinfect 2 MLD of water if the dose of chlorine is 0.5 ppm and 30% chlorine is available in bleaching powder.

## Short answer

For2 MLD flow and0.5 mg/L chlorine dose with30% available chlorine, chlorine need=1.00 kg/day, so bleaching powder required=3.33 kg/day.

## Answer

Flow = 2 MLD $= 2\times10^6$ l/day; chlorine dose = 0.5 ppm $=0.5$ mg/l; available chlorine in bleaching powder = 30 %.

$$
\begin{aligned} \text{Chlorine required} &= 0.5\ \text{mg/l}\times 2\times10^6\ \text{l/day} = 10^6\ \text{mg/day} = 1.00\ \text{kg/day} \\ \text{Bleaching powder} &= \frac{1.00}{0.30} = 3.33\ \text{kg/day} \end{aligned}
$$

**Answer: 3.33 kg of bleaching powder per day.**

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. For 2 MLD of water and a dose of 0.5 mg/l, how much pure chlorine is needed per day?
   A. 0.25 kg/day
   B. 1.00 kg/day
   C. 10 kg/day
   D. 100 kg/day
   Answer: B. 0.5 mg/l x 2x10^6 l/day = 10^6 mg/day = 1 kg/day. (Key point: Unit conversion for dose)

2. Why is the pure chlorine quantity divided by 0.30 to get the bleaching powder quantity?
   A. Bleaching powder contains only 30% available chlorine, so more powder is needed
   B. 30% of the powder is lost during mixing
   C. Bleaching powder is 30% stronger than chlorine gas
   D. Only 30% of the flow is disinfected
   Answer: A. Only 30% of the powder's mass is available chlorine, so powder = chlorine / 0.30. (Key point: Available chlorine)

3. What quantity of bleaching powder per day is required?
   A. 0.30 kg/day
   B. 1.00 kg/day
   C. 3.33 kg/day
   D. 6.67 kg/day
   Answer: C. 1.00 / 0.30 = 3.33 kg/day. (Key point: Final result)

## Related in Water Supply Engineering

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