GATE CE 2020 Set 1 — Question 47
Go beyond PYQs with Success TrackerAI-powered personalised practice and doubt support. Unlimited practice on eligible plans; AI usage limits apply.MCQ+2 / -0.67HardChlorinationDrinking Water TreatmentEnvironmental Engineering
Environmental Engineering → Drinking Water Treatment → Chlorination
Last updated
Question
A water supply scheme transports 10 MLD (Million Litres per Day) water through a 450 mm diameter pipeline for a distance of 2.5 km. A chlorine dose of 3.50 mg/litre is applied at the starting point of the pipeline to attain a certain level of disinfection at the downstream end. It is decided to increase the flow rate from 10 MLD to 13 MLD in the pipeline. Assume exponent for concentration, . With this increased flow, in order to attain the same level of disinfection, the chlorine dose (in mg/litre) to be applied at the starting point should be
Correct answer
(C) 4.75
Solution
The level of disinfection is maintained constant, which implies that the product of remains constant, where is the chlorine concentration, is the exponent for concentration, and is the contact time.Given:
Initial flow rate,
Pipeline diameter,
Pipeline length,
Initial chlorine dose,
Exponent for concentration,
New flow rate,
Convert to Litres:
We need to find :
Substitute the values:
Rounding to two decimal places, the required chlorine dose is approximately .The closest option is (C) 4.75.The final answer is .
Initial flow rate,
Pipeline diameter,
Pipeline length,
Initial chlorine dose,
Exponent for concentration,
New flow rate,
1.Calculate the volume of the pipeline (V):
Convert to Litres:
2.Calculate the initial contact time ():
3.Calculate the new contact time () for the increased flow rate ():
4.Apply the constant disinfection level relationship ():
We need to find :
Substitute the values:
Rounding to two decimal places, the required chlorine dose is approximately .The closest option is (C) 4.75.The final answer is .
Continue learning with Success Tracker
A step still unclear? Work through it with support
Use Success Tracker to ask about the reasoning, then try another GATE CE question to check your understanding.
AI-powered practice· Unlimited practice on eligible plans
- PYQs with solutions
- Attempt available previous-year questions, then compare your reasoning with the worked solution. Coverage varies by stream.
- Practice that adapts
- Choose a topic, work on weaker areas and bookmark questions to revisit. Your attempts feed your progress tracking.
- AI doubt support
- Ask follow-up questions about a step or concept while practising, instead of stopping at the final answer.
Unlimited practice is available on eligible plans. Free practice and AI usage have limits; check the current plan allowances before choosing.
This page stays readable without an account. AI responses can be wrong; check them against the solution and source material.
More questions on Drinking Water Treatment
2026 Set 1 Q21A rapid sand filter bed of depth m has % porosity during service cycle. It is…2026 Set 1 Q22The settling velocity of inorganic particles in the sedimentation tank of a water treatment plant…2026 Set 1 Q25Which of the following components is/are NOT removed in the secondary treatment of sewage?2026 Set 2 Q27Column I presents common air pollutants, and column II presents treatment technologies commonly…2026 Set 2 Q28One-third of the solid matter in a sludge containing water is composed of fixed mineral…