Page 73 - GRIHA Manual Volume IV - Introduction to National Rating System
P. 73
64 Griha Manual: Volume 4
Rainwater runoff from the following catchments should be avoided.
# Tar felted roofs: Such roofs are often a source of biological and heavy metal contamination.
# Asbestos sheets: Weathered and leached fibres of asbestos are highly toxic and should, therefore,
be avoided for harvesting rainwater.
# Chemically treated roofs: Roofs that have been chemically treated for water proofing or reflective
coating should be checked for possible contamination with heavy metals and other harmful
chemicals and at best be avoided.
# Water from kitchen and bathrooms should not be used for harvesting.
# Any other contaminated runoff (industrial or domestic wastewater) should not be used for
harvesting.
Filtration system
Filtration is one of the essential components of rainwater harvesting system and required for
purification of water. It usually involves allowing water to pass through a filter media—sand. Filtration
essentially involves removal of suspended and colloidal impurities present in water. Depending
upon the type of filtration, the chemical characteristics of water may be altered and the bacterial
content may be considerably reduced. Selection of a filter system should be based on the following.
1. Type of catchment
2. Amount of silt load
3. Quality of runoff
4. Purpose of storage
5. Type of recharge structure
Some of the commonly used filters are as follows.
1. Cloth filter
2. Sand filter
3. Reverse sand filters
4. Dewas filter
5. Varun filter
6. Desilting chambers
Maintenance
Quality control and maintenance of catchment areas before monsoon and cleaning of storage and
recharging structures are a very important underlying factors, extremely essential to reap benefits
from rainwater harvesting. Following care should be taken while harvesting rainwater.
# Keep all catchments neat and clean.
# Do not allow contaminated water to flow into the system.
# Put iron/nylon mesh/fine cloth on inlet and outlet pipes and chambers to prevent solid debris
from getting into the system.
# Clean open drains regularly by removing deposits of sand and gravel.
# Make available a layer of soil beneath the recharge structure to ensure natural filtration.
# Provide first-flush to drain runoff from initial spell of rain.
# Drain and clean storage tanks thoroughly before every monsoon.
# Change the filter media every year.
# Remove algae from the roof tiles and asbestos sheets before the monsoon.
Rainwater runoff from the following catchments should be avoided.
# Tar felted roofs: Such roofs are often a source of biological and heavy metal contamination.
# Asbestos sheets: Weathered and leached fibres of asbestos are highly toxic and should, therefore,
be avoided for harvesting rainwater.
# Chemically treated roofs: Roofs that have been chemically treated for water proofing or reflective
coating should be checked for possible contamination with heavy metals and other harmful
chemicals and at best be avoided.
# Water from kitchen and bathrooms should not be used for harvesting.
# Any other contaminated runoff (industrial or domestic wastewater) should not be used for
harvesting.
Filtration system
Filtration is one of the essential components of rainwater harvesting system and required for
purification of water. It usually involves allowing water to pass through a filter media—sand. Filtration
essentially involves removal of suspended and colloidal impurities present in water. Depending
upon the type of filtration, the chemical characteristics of water may be altered and the bacterial
content may be considerably reduced. Selection of a filter system should be based on the following.
1. Type of catchment
2. Amount of silt load
3. Quality of runoff
4. Purpose of storage
5. Type of recharge structure
Some of the commonly used filters are as follows.
1. Cloth filter
2. Sand filter
3. Reverse sand filters
4. Dewas filter
5. Varun filter
6. Desilting chambers
Maintenance
Quality control and maintenance of catchment areas before monsoon and cleaning of storage and
recharging structures are a very important underlying factors, extremely essential to reap benefits
from rainwater harvesting. Following care should be taken while harvesting rainwater.
# Keep all catchments neat and clean.
# Do not allow contaminated water to flow into the system.
# Put iron/nylon mesh/fine cloth on inlet and outlet pipes and chambers to prevent solid debris
from getting into the system.
# Clean open drains regularly by removing deposits of sand and gravel.
# Make available a layer of soil beneath the recharge structure to ensure natural filtration.
# Provide first-flush to drain runoff from initial spell of rain.
# Drain and clean storage tanks thoroughly before every monsoon.
# Change the filter media every year.
# Remove algae from the roof tiles and asbestos sheets before the monsoon.
