Page 114 - GRIHA Manual Volume IV - Introduction to National Rating System
P. 114
Building planning and construction 105
b) For water in a distribution system:
(i) E Coli count in 100 ml of any sample must be zero (0).
(ii) Coliform organisms should not be more than 10 per 100 ml in any sample.
(iii) Coliform organisms should not be present in 100 ml of any two consecutive samples or
more than 5% of the samples collected for the year.
Choosing a water treatment system based on contaminants
In order to ensure safe drinking water, it needs to be treated before use to bring it to desirable
drinking water standards. The choice for selecting technology for treatment depends on several
factors such as the following.
1. Kind of contaminant,
2. Extent of contamination,
3. Simplicity of the system and durability,
4. Low maintenance,
5. Power consumption,
6. Affordability.
Precautionary note: Only when the TDS levels in water crosses the 500 mg/litre mark, one should opt
for Reverse Osmosis (RO) water purifier. RO systems should otherwise be avoided as such systems
waste water at the rate of 2–3 litres for every litre of purified water. Also, they reduce essential
mineral content in drinking water, which is otherwise required for good health.
The following table gives a list of various treatment systems that could be used for each type of
contaminant.
Table 2 List of various treatment systems that could be used for each type of contaminant
Physical parameters Turbidity/transparency Slow sand ilter
Candle system
Cloth iltration
Coagulation
Sedimentation
Odour Aeration/oxidation
Activated carbon ilter
Charcoal
Resin
Boiling
Colour Charcoal
Activated Carbon ilter
Slow sand ilter
Resins
Chemical parameters Fluoride Activated alumina
Nitrate Reverse osmosis
Ion exchange
Distillation
Ammonia Chlorine
Boiling
Iron Oxidation and settling
b) For water in a distribution system:
(i) E Coli count in 100 ml of any sample must be zero (0).
(ii) Coliform organisms should not be more than 10 per 100 ml in any sample.
(iii) Coliform organisms should not be present in 100 ml of any two consecutive samples or
more than 5% of the samples collected for the year.
Choosing a water treatment system based on contaminants
In order to ensure safe drinking water, it needs to be treated before use to bring it to desirable
drinking water standards. The choice for selecting technology for treatment depends on several
factors such as the following.
1. Kind of contaminant,
2. Extent of contamination,
3. Simplicity of the system and durability,
4. Low maintenance,
5. Power consumption,
6. Affordability.
Precautionary note: Only when the TDS levels in water crosses the 500 mg/litre mark, one should opt
for Reverse Osmosis (RO) water purifier. RO systems should otherwise be avoided as such systems
waste water at the rate of 2–3 litres for every litre of purified water. Also, they reduce essential
mineral content in drinking water, which is otherwise required for good health.
The following table gives a list of various treatment systems that could be used for each type of
contaminant.
Table 2 List of various treatment systems that could be used for each type of contaminant
Physical parameters Turbidity/transparency Slow sand ilter
Candle system
Cloth iltration
Coagulation
Sedimentation
Odour Aeration/oxidation
Activated carbon ilter
Charcoal
Resin
Boiling
Colour Charcoal
Activated Carbon ilter
Slow sand ilter
Resins
Chemical parameters Fluoride Activated alumina
Nitrate Reverse osmosis
Ion exchange
Distillation
Ammonia Chlorine
Boiling
Iron Oxidation and settling
