Problems On Water
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1) Calculate the quantity of bleaching powder required to disinfect the following well with diameter. 5 mtr, depth 10 mtr with 20% available chlorine to give1 ppm.
Solution: Volume of the water = r2 h
= x x 1 0
= x x 10
= 196.4 m3
Approximately 0.7 mg is applied for disinfection of 1 lts of water with chlorine content 33.3%.
For 20% available chlorine = 1.65 mg
0.7 x 1.65 mg of 20% chlorine is necessary for 1 lt of water for 196.4 m3.
1 m3 = 1000 lt
For 196 m3 = 196 x 1000 lts
So 196 x 1000 = 196 x 7 x 165.
= 226380 mg of bleaching should be applied to disinfect the well.
= 2263.8 gm of chlorine should be applied.
10) A rectangular well measuring length 20 mts, breaths,4 mts, depth 5 mts is to be disinfected. The horrock’s test shows blue colouration in 415 cup onwards. Calculate the bleaching powder demand of water.
Solution:
Volume of the water = L X b x l
= 20 x 4 x 5
= 400 m3
1 m3 = 1000 lts
400 m3 = 400000 lts
455 lts = 8 gm
4,00,000 lts = ?
x =
= 7032.9 gm of bleaching powder is required to disinfect the water
11) Interpret the significance of the following data in a sample of drinking water.
Albuminoid ammonia = 0.14 ppm
Free ammonia = 0.07 ppm
NO2 = 6.5 ppm
NO3 = Traces
Give the normal standards of drinking water for the above items
Solution:
Given water Normal valves
Albuminoid ammonia 0.14 ppm 0.1 ppm
Free and saline ammonia 0.07 ppm 0.05 ppm
NO2 6.5 PPM Traces
NO3 Traces 1 ppm
The given water is not potabl :
The level of albuminoid ammonia and free ammonia is high. This ammonia in the environment originates from metabolic, agricultural and industrial processes and from disinfection with chloramine. Ammonia in the water is an indicator of possible bacterial, sewage and animal waste pollution.
Ammonia also causes odour and tests problems.
Nitrites and nitrates are the part of nitrogen cycle. It’s level will be increased in intensification of faming practices. But the nitrate level in drinking water should be less then 10 mg/lt. Because of the possibility of the occurrence of nitrates and nitrites in water simultaneously for drinking water the sum of the ratios of the concentration of each of the guideline values should not exceed i.e. Any way this component of the given water is in safer level.
12) With the help of a flow diagram, describe briefly the water supply to Davangere city.
13) Following are the results of 2 samples of water analysed at district public health leb. Davangere.
Sample A Sample B
Sparklingly clean Turbid
Nitrites traces Nitrites absent
Chlorides- 500 ppm Chloride – 1 ppm
E.coli – 12 / 100 ml E.colic 1 / 100 ml
Comment on quality of water. Are the samples fit for drinking
Solution:
Sample A :
Sparklingly clean – Acceptable
Nitrites traces – Acceptable
Chlorides – 500 ppm – normal 250 mg / L – Not acceptable
E.coli – 12/100 ml : normal nil – not acceptable
Even though the water is acceptable physically chlorides. 500 ppm which is very high when compared to normal standard level. It adds to salinity of water, alters tests and causes common of pipes.
Bacteriologically it is not acceptable since presence of even one coliform organism indicates the fecal contamination of water. Since it has greater resistance, the possibility of presence of other intestinal pathogens con not be ruled out.
Sample B :
Turbid – Not acceptable
Nitrotes absent – Acceptable
Chloride – 1 ppm, acceptable
E.coli – 1/ 100 ml – Not acceptable
Since the water is turbed, the turbidity is due to presence of practicable matter or resuspension of sediment in the distribution system. It may also be due to inorganic matter made the water non poteble. Even biologically the presence of even, E-coli should suspect the fecal contamination of water, and this water is not potable
14) Comment on the following
a) One need not bother about fluoride, nitrates, chlorides and PAH (Polynuclear aromatic hydrocarbons) in water analysis.
Solution:
Fluoride :
Exposure to fluoride from drinking water depends on the solution. Level is normally maintained less than 1.5 mg / lt. The acceptable level of fluorine level is 0.5 – 0.8 mg/lt.
If it is less, leads to dental caries.
If it is >5 mg / lt – causes skeletal and dental fluorosis which is a crippling disorder.
Nitrates :
They constitute the part of Nitrogen cycle. The normal safe level of nitrates in drinking water should be 10 mg/l. When it exceeds 50 mg/lt, it leads to metahemoglobineemia.
Chlorides :
Chlorides causes increased salinity of the water. It alters the teste of water and causes corrosion of pipes. So it is important to known the normal range of chloride level. It is 200 mg/lt. maximum permissible level is 600 mg/lt.
PAH :
They are derived in the environment from the variety of combustion and pyrolysis sources.
Benzopyrene which constitute the minor fraction of total PAH, have been found to be carcinogenic in mice.
So it is necessary to check for the chemicals in the drinking water.
b) O2 dissolved level can be upto10mg / L in a sample of water.
The dissolved O2 content of water is influenced by the raw water temperature, composition, treatment and any chemical or biological processes taking place in the distribution system. Depletion of dissolved O2 in water supplies can encourage microbial reduction of nitrate to nitrite and sulphate to sulphide giving rise to odour problem. It can also cause on increase in the concentration of ferrous iron in solution.
No health based guideline volume has been recommended.
c) KmNO4 is not a good water disinfectant
KmNO4 is a good water disinfectant. But it causes change in colour of water to reddish brown and causes disagreeable taste and odour of the water. It makes the water not acceptable. Hence it cannot be used for disinfection of water.
15) Comment on the quality of water heaving the following date
Normal values
Total solids 250 ppm 1000 ppm
Total hardness 180 ppm 100 ppm
Free ammonia 0.244 ppm 0.05 ppm
Acbuminoid ammonia 0.8 ppm
Nitrites 0.005 ppm Traces
Nitrates 21 ppm 1 ppm
Chlorides 45 ppm 200 ppm
Coliform count 15/100 ml of water Nil
Solution:
This water is not potable because the hardness of water is more causes corrosion of pipes and inturn contamination. Free ammonia is also high, indicates possible bacterial, sewage and animal waste pollution and also nitrates and nitrates. Bacteriologically cotiform count indicate local contamination
1) As medical officer of a PMC, what measures will you take during a jatra in a village to prevent gestro-intestinal disease.
i) Collection of following base line data
- Name of village
- Name of primary health, centre / subcentre
- No. of people population
- No. of people expected to come from other places
- Source and adequency of water supply
- Availability of sanitation facilities
- Number of under 5 children and their immunization status.
Following preventive strategies will be adapted
1) Provision for safe
Water is the most important vehicle of transmission of cholera. Facilities will be selected and installed for the ultimate aim for precision for piped water supply on a permanent basis and elimination of the alternative unsafe water source. If this is not possible, atlest herogen tablets will be supplied each tablet of 0.5 mg for 1 lts of water / health education will be given for drinking the boiled water.
2) Food sanitation :
Since food is also an important vehicle of infection, steps will be taken to improve food sanitation. Same of foods in unhygeine condition will be bound. Health education must stress the important of eating cooked not food and proper individual food handling techniques.
Sanitation :
The people should be instructed to use shallow trench latrine, which are build 1 for 100 people. They are instructed to close the faecal matter with mid time they use it. Adequate water supply will be provided for washing their hands after defection. Health education will be given to wash with soap and water before touching food items.
Immunization :
Immunization against measles particularly will be made same in the children since with their immunization 25% of diarrhaoe deaths in children <5 will be prevented.
If any child who is not immunized, will be immunised with measles atleast 15 days before the Jothre. SF any child with malnutrition is found, they are also immunized with measles vitamin A is also given to the children.
Indenting for ORS pockets :
Adequate number of ORS packets will be indented from the DHO.
Health education : Regarding the sanitation, hygienic measures will be given.
Fly control : By appropriate measures like with the use of insecticides primary health care approach for control / prevention of diarrheal diseases involves the delivery of package of curative and preventive services at the community level. An intersectional approach central upon primary health care involving activities in the fields of water supply and excreta disposal, communicable disease control, MCH, nutrition and health education.
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