improved and inovative rural water supply design concepts [email protected]
TRANSCRIPT
IMPROVED AND INOVATIVE
RURAL WATER SUPPLY
DESIGN CONCEPTS
THE NEED FOR WATER TREATMENT
The purpose of water treatment is to provide a continuous supply of safe, palatable/potable drinking
water
RRPN Ratnayake
Free of unpleasant characteristics
Free of Disease-causing (biological) contaminants
Free of chemical contaminants
Colour
Turbidity
Taste and odour
Free of plants like algae
All the above physical and chemical characteristics are mainly due to suspended matter or dissolved chemical constituents in the water
RRPN Ratnayake
In simple terms Water treatment is the removal of Unwanted suspended /dissolved matter (solids, liquids or gases) from water
SLS 614 USEPA drinking Water Regulations
Particle Size & Settling Rates
Type ofParticle
Particle Size(mm)
Settling Time through1 m of Water
Gravel 10 1 second
Sand 1 10 second
Fine Sand 0.1 2 minutes
Clay & Silt 0.01 2 hours
Bacteria 0.001 8 days
Colloid 0.0001 2 years
Colloid 0.00001 20 years
Colloid 0.000001 200 years
RRPN Ratnayake
TRAY AERATOR
4Fe2++ O2+10H2O 4Fe(OH)3+8H+
When PH above 7.5
2Mn2++ O2+2H2O 2MnO2+4H+
(Better if PH >9.0 for Mn oxidation)
Trays filled with coke, crushed stone, lime stone or plastic media up to a depth of 300-450mm.
RRPN Ratnayake
INDUSTRIAL POLLUTANTS
Slow sand filtration
Plain sedimentation for >8 days
Slow sand filtration
Roughing filtration
Aeration
Aeration
Turbidity< average of 5 NTU, Algae (Chlorophil <.05µ)g/l,Colour, Taste, Odour, Iron<.3mg/l, Manganese<0.05mg/l, Algal toxins (to be tested) Slow sand
filtrationTurbidity< average of 20 NTU and maximum up to 50 NTU, Algae (Chlorophil <.05µ)g/l,Colour, Taste, Odour, Iron<.3mg/l, Manganese<0.05mg/l, Algal toxins
Slow sand filtration
Aeration
Turbidity< average of 20 NTU and maximum up to 200 NTU, Algae (Chlorophil <.05µ)g/l,Colour, Taste, Odour, Iron<.2mg/l, Manganese<2mg/l, Algal toxins, fluoride<0.8mg/l
Roughing filtration
Turbidity< average of 60 NTU and maximum up to 500 NTU, Algae (Chlorophil <.05µ)g/l,Colour, Taste, Odour, Iron<.2mg/l, Manganese<2mg/l, Algal toxins, fluoride<0.8mg/l
TREATMENT PROCESS SELECTION
Plain sedimentation for 8 days
Slow sand filtration
Roughing filtration
Aeration/Ozonation
Granular Activated carbon
Turbidity< average of 60 NTU and maximum up to 500 NTU, Algae (Chlorophil <.05µ)g/l,Colour, Taste, Odour, Iron<.2mg/l, Manganese<2mg/l, Algal toxins(high), fluoride<0.8mg/l
To Storage
Filter Bed No. 1
Influent Structure
Filter Bed No. 2
Collection Pipes
A
Section A
WaterCollection Manifold
Sand
Perforated Pipe
SLOW SAND FILTER
Scrape off the top 2-5cm sand layerfor cleaning after cloggingTimber planks should be used to move on sand bed
RRPN Ratnayake
RRPN Ratnayake
Floating intake
One square kilo meter of 1 meter thick humus layer can store about 400,000 cubic meters of rainwater