Preparing Environmental Engineering -1 Water Supply Engineering

Posted by under Civil Engineering on October 30, 2018

This blog is the 6th article in a series of GATE preparation tips blog articles for Civil Engineering Students. The blog author, Rohit Sachdeva has secured AIR 93 in GATE 2017 and is currently studying at IISc Bangalore. You can read the rest of the articles under the CE section for GATE blogs at

Preparing Environmental Engineering 1 Water Supply Engineering.

Environmental Engineering is a very vast and important subject in Civil Engineering. In this blog, I will be discussing how to prepare for PART 1 of Environmental Engineering: Water Supply Engineering (PART 2 & 3 to follow).  It carries a high weightage in GATE exam. This subject should be studied thoroughly and should not be skipped at any cost.  It includes theory & numericals, but, we can observe that questions have been following a similar trend through years. Since there are many topics to be covered & formulas to be memorized, try to revise this subject maximum number of times.

A rough breakup of questions of various topics in last 30 years in GATE is as follows:

SR No.  Topic No. of Questions
1 mark 2 marks
1 Water Demand 1 1
2 Water Quality Control 22 20
3 Plain Sedimentation 1 12
4 Coagulation 5 6
5 Filtration 2 8
6 Disinfection 5 4
7 Misc. Water Treatment 4 3
8 Distribution Systems 1

An analysis of last 5 years of GATE papers shows that Environmental Engineering (all parts together) carries 10-12 marks.

Time required for preparation (Part 1)

12-15 days (if you have 8-10 month of preparation) with 3-4 hours daily
6-7 days (if you have 4-5 months of preparation) with 6-8 hours daily

Equal weightage of 1-mark and 2-mark questions can be expected, with fewer number of NAT questions.  There is lesser to practice than to remember, so 2 rounds of revision are suggested. The textbook(s) to be referred are mentioned in BLOG-3 which you can utilize.
Let’s start our topic-wise discussion (most important concepts are bold & italics):


Population forecasting methods (Arithmetic, Geometric, Incremental & Decrease in Growth Rate, Logarithmic), Variations in water demands (hourly, daily, weekly, monthly, etc), coincidental draft.  Practice 1 numerical each for population forecasting method.


This is the most important chapter in water supply and there will be a sure question.  This chapter has following three parts:

  1. Physical characteristics:  Temperature, color, turbidity, taste and odor. The measurement methods/equipment and permissible values/ranges for these should be studied.
  2. Chemical:  This is the most important section.  Solids (Total, dissolved, volatile, etc), pH (& pOH), Acidity, Alkalinity, Hardness, Chlorides, Sulphates, Dissolved Oxygen, Flourides, Nitrogen compounds, toxic chemicals.  Clearly understand the concept of alkalinity & indicators, temporary (carbonate) & permanent (non-carbonate) hardness.  Practice lot of numerical questions relating alkalinity and hardness as there will be sure questions from this concept.  Also practice numericals on pH & pOH.
    Limits/ranges of different metals allowed in water should be learnt (make short notes), most important being nitrogen compounds.
  3. Biological:  Qualitative and quantitative test for E.Coli, MPN and E.Coli index.  Also read about different water-borne diseases.


This is also important chapter from point of view of 2 mark & NAT questions.
Type-1 settling, terminal velocity & Stoke’s law, sedimentation tank – types and design, design parameters (surface overflow rate, detention time, loading rate and flow-through velocity), particle removal efficiency (Vs > Vo) are important. Also practice numerical questions.


Different types of coagulants (alum, copperas, chlorinated copperas, sodium-aluminate, remember chemical equation & note in formula sheet) and their application can be asked.  There can be match the following questions. The dosage and action (alkalinity) of alum (and lime); optimum dosage of coagulant are also important.
Design of clariflocculator (detention time & velocity gradient), relation b/w turbidity, alkalinity and coagulant dosage.


Mechanism of filtration, classification of filters, comparison and design of slow sand & rapid sand filters, filter kinetics, operational troubles in rapid sand filters, pressure filters & multi-media filters (theory).


Mechanism of disinfection, various methods of disinfection (physical and chemical).  Chlorination: Understand in detail the action of Chlorine (chemical equation, different forms, their % and pH range of their formation); chlorine demand of water, physical forms in which Chlorine is available (hypochlorite, chloramines, chlorine gas & chlorine dioxide) are important.  
Types of chlorination is important; understand the concept of residual chlorine (its graph) and break-point chlorination.  Practice numericals to calculate chlorine demand based on this.  Also practice few numericals for kinetics of chlorination.


Aeration, softening (chemical requirements, Zeolite process, remember chemical equation & note in formula sheet), desalination of water (reverse osmosis, electro-dialysis, distillation), fluoridation & defluoridation (Nalgonda method), color removal are included in this chapter.  Understand these processes and the reactions involved.


Type of water distribution system (gravity, pumping, combined, their advantage/disadvantage), storage capacity of reservoir, layouts of water distribution, types of valves.  In-depth study is not required for this topic.

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