Quality of water

Impurity                                                                Causes

Suspended impurities

a) Silt, Clay                                                          -Turbidity

b) Bacteria                                                                             

i) Pathogenic                                                        -Typhoid, Paratyphoid, Cholera, Bacillary, Dysentery        

ii) Non-Pathogenic                                                 1.Slim forming bacteria

                                                                                2.Iron Bacteria-cause pitting, turbidity

                                                                                3.sulpher bacteria-acidity, corrosion

c) Virus                                                                   1.infectious hepatitis (Jaundice)

                                                                                2.Poliomylities

d) Algae and Protozoa                                           -  Colour, turbidity, odour, taste, acidity, 

                                                                                   and amoebic dysentery  

e) Helminthes                                                         -Tape worm, Round worm

Dissolved Impurities         

a) Ca(HCO₃)₂, Mg(HCO₃)₂                                            Alkalinity, Hardness, Laxative effect,

                                                                                   Corrosion

   CaSO₄, MgSO₄, CaCl₂, MgCl₂                                                                                                                                                        

b) Na₂SO₄                                                                 -Foaming in boilers

c) NaF                                                                        -Fluorosis

d) Iron and Manganese                                              -Red,Brown/Black Colour, Taste Corrosion

e) Lead                                                                       -Cumulative Poison, Plumbo solveny

f) Nitrates                                                                   -Methamogloninemia (Blue Babies)

g) CO₂                                                                        -Acidity, Corrosion

h) H₂S                                                                        -Acidity, Corrosion and foul smell

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Objective question set-I (Water Supply Engineering)

                 1.       The device installed for drawing water from the source are called

                  -Intake

                2.       Factors considered in selection of site for intake is that it should be

                  a. nearer to the treatment plant  

                  b. in pure zone of the water source

                   c. upstream of the point of disposal of waste water  

                   d. all of the above^*

                 3.       Gravity water supply system starts from

                    -Intake

                 4.       “Puits devlopee” is generally provided in case of

                   -well

                  5.       Infiltration gallery is a horizontal well

                  6.       Minimum depth of infiltration gallery is 2m

                  7.       The aquifer having least water  bearing capacity is

                  -Perched aquifer

                  8.       Water shed control method is used to control

                  -Sedimentation in reservoir

                   9.       Shrouding is the process of filling gravel, bajri etc. in

                  -Slotted tube well

                  10.   The radius of influence of well varies with

                -rate of pumping

                  11.   Coefficient of permeability is maximum for

                 a. Clean gravel^*

                 b. Clay

                 c. Fine Sand

                d. silt

                   12.   An aquiclude is – a confined bed of impervious material between aquifer.

                   13.   A perched aquifer generally occurs

                 -above the water table

                   14.   The specific retention is least in the soil type

                  a. Clay

                  b. Sand

                  c. Silt

                  d. Coarse gravel^*

                    15.   To determine velocity of flow of underground water, the most commonly used            non-imperial formula is

              -Dracy’s formula

                    16.   The location of a well is considered to be good, if it is sunk into

                 -Coarse gravel

                    17.   The dug well or open well

                  a. has diameter 1 to 4m

                  b. suitable for small discharge of about 20cum/hr

              c. are cheap in construction

                  d. all of the above ^*

                    18.   Specific yield of wells is expressed as

                  -m3/hr

                     19.   The most widely used tube well in Nepal is

                 -Strainer well

                    20.   For insignificant effect on the water table,the tube wells are be spaced as one in every

                 -1.5Km

                    21.   The interference of well depends upon

               a. no. of well

               b. spacing between wells

               c. types of well

              d. all of the above^*

                22.   Strainer type tube well are considered unsuitable for

              -Fine sand strata

                23.   Break pressure tank is generally provided in rural water supply scheme if static head           exceed

           -60m

               24.   The type of form work provided for ferro cement tank in rural water supply scheme is

            -HDP Pipe

               25.   Sickness of tube well indicates

           -Reduction in yield

               26.   The relation between porosity, specific yield and specific retention is

          -Porosity= Specific yield+ Specific retention

               27.   For good test a desirable temperature of water is,

          -Less than 11^oC

              28.   Permissible colour for drinking water is not more than

          -5 units

               29.   Turbidity is measured by,

          -Intensity of light scattered when light is passed through.

               30.   Units of turbidity are

           a. mg/l

           b. Ntu^*

           c. Pcu

           d. Threshold number

                31.   The standard unit of turbidity is produced when,

             a. 1mg of silicon dioxide is dissolved in 1 litre of distilled water.

             b. 1mg of platinum is dissolved in 1 litre of distilled water.

              c. 1mg of sodium chloride dissolved in 1 litre of distilled water.

              d. 1mg of cobalt being dissolved in 1 litre of distilled water^*

                 32.   Conductivity represents the concentration of the following in the water sample

             a. total solid                                                        b. dissolved solid^*

             c. volatile solid                                                   d. fixed solid

                 33.   Conductivity is standardize at

            =25^oC

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