Test: Quality of Water - Civil Engineering (CE) MCQ

The permissible limit for copper in water 0.05 mg/L.
As per IS 10500-2012, General Parameters Concerning Substances Undesirable in Excessive Amounts (Table 2):

Odour and taste
It is one of the parameters which define the physical property of water
The odour in water is measured by a device known as osmoscope and expressed in terms of Threshold Odour Number (TON)
TON is a dilution ratio at which odour is just detectable

Where,
A = Volume of water sample tested in 'ml'
B = Volume of distilled water used in dilution in 'ml'
Capacity of osmoscope = A + B = 200 ml
There is no test for taste but senses of odour and taste are closely assosciated with each other. When water smell bad it also tastes bad.
The taste is expressed in terms of Flavoured Threshold Number (FTN) 

According to Drinking water standard TON < 3

Nitrogen in water:
The nitrogen in water indicates organic contamination of water i.e when water is contaminated by sewage then nitrogen compounds are traced in water. We can trace the following compounds,

• Ammonia nitrogen
• Organic nitrogen or Albuminoid nitrogen
• Nitrites
• Nitrates

Nitrogen compounds are measured by colorimetry
Total Kjeldahl nitrogen (TKN): 
It is the sum of organic nitrogen, ammonia (NH3), and ammonium (NH4+) in the chemical analysis of soil, water, and wastewater.
To calculate Total Nitrogen (TN), the concentrations of nitrate-N and nitrite-N are determined and added to the total Kjeldahl nitrogen
Kjehldahl Nitrogen = Organic nitrogen + free ammonia

The permissible limits of various compounds are as follows:

For geometric increase method,
P_n = P × (1+r)ⁿ
Where
P_n = Future Population, P = Latest known population and n = numbers of years


P₄ = 10000 × (1 + 0.2885)¹ = 12885
∴ The population of the city in the fourth continuous year will be 12885. 

As per IS 10500: 1991, what is the permissible limit in the absence of alternative sources for the total hardness of drinking water is 600 mg/l.
The permissible limits of various compounds are as follows:

Various methods for population forecasting as suitable for that city, considering the growth pattern, are as follows:

• Arithmetical increase method:
  • In this method assumed that the population is increasing at a constant rate.
  • This method is suitable for a large and old city with considerable development.
• Geometrical increase method (or geometrical progression method):
  • In this method, the percentage increase in population from decade to decade is assumed to remain constant. 
  • This method gives higher values and hence should be applied for a young and rapidly increasing city, but only for a few decades.
• Incremental increase method:
  • This method is a modification of arithmetical increase method and it is suitable for an average size town under the normal condition where the growth rate is found to be in increasing order.
• Logistic curve method:
  • This method is used when the growth rate of the population due to births, deaths, and migrations takes place under normal situation and it is not subjected to any extraordinary changes like an epidemic, war, earthquake or any natural disaster, etc.

The permissible limits of various compounds are as follows:

Fluoride or fluorine deficiency is a disorder that may cause increased dental caries (or tooth decay) is the breakdown of dental tissues by the acidic products released by the bacterial fermentation of dietary carbohydrates.
Excess of nitrates is harmful to infants and causes Methemoglobinemia or Blue baby disease.
Lead in excess is toxic to many organs and tissues including heart, kidney, bones, intestines, reproductive system and nervous system. Excess lead causes anemia.

Some important points about screens in the screening process

• The coarse screen consists of parallel iron rods are placed vertically or at a slight slope at about 25 to 50 mm apart
• The fine screen is usually made of woven wire mesh with an opening not more than 6 mm square
• The spacing between two bars in medium size screen ranges from 15 to 40 mm
• The clear spacing between the bars may be in the range of 15 mm to 75 mm in case of a mechanically cleaned bar screen
• However, for the manually cleaned bar screen, the clear spacing used is in the range 25 mm to 50 mm
   

The permissible limit of total dissolved solids (TDS), (in mg/l), in drinking water in the absence of an alternate source, is 2000 mg/l
As per IS 10500 : 2012, the following are the various permissible limits for different parameters: