b) Rainwater harvesting: Introduction to rainwater
Transcript of b) Rainwater harvesting: Introduction to rainwater
a) Water distribution system: System of water supply- Continuous and intermittent system. Different distribution systems and their components. ESR- Design of ESR capacity. Wastage of Water- Detection and Prevention. b) Rainwater harvesting: Introduction to rainwater harvesting, need of rain water, methods of rainwater harvesting, components of domestic rain water harvesting system, design of roof top rainwater harvesting system. c) Introduction to Packaged WTP in townships, big commercial plants, necessity (On-site water treatment). Introduction to process description of RO, Pressure Filters
* Water Distribution System
Purpose: To convey water from WTP to the individual consumer, in sufficient quantity and with adequate pressure
Basic requirements: Functional: Configuration of pipes Location & type of valves,
Hydraulic: Adequate residual pressure even at peak hours
Methods of distribution: governing factors? Topography: key factor; if favourable topography – gravity supply possible through tunnels / pipelines else pumping or pumping + gravity flow required
Water Distribution System
Continuous Supply
24 hrs water supply :possible when water in sufficient quantity available
Losses? May be
Intermittent water supply
Most of cities have this kind of supply
Storage @ consumer end required
Chances of contamination during Non Supply Hrs (NSH)
Special efforts required to restore supply during NSH Large no of valves required to be operated (start / shut of supply; to cutoff a particular area)
Flow of water merely by gravity
Water may be supplied to different reservoirs within the city by gravity. System is economical as no pumping is required
Mumbai – treated water from Pise Panjarapur --pumped (40 m) --- supplied to all reservoirs by gravity
* Gravity Supply
Uses mechanical – electrical energy Water is supplied to consumers and / or reservoirs under pressure Raw water mains --- Bengaluru Distribution mains --- Ahmedabad (few years back)
Combined gravity & pumped system • Storage reservoirs: used to maintain adequate pressure (elevation); filled during non-peak hours --- water supplied through them along with regular pumped water supply during peak demand
* Pumped Water Supply
Basis of classification:
* Water Supply Systems
Based on hrs of supply Based on type of flow
Continuous Gravity – Parvati WTP to old parts of Pune city
Intermittent Pumping: olden days – Ahmedabad
Combination (p + g) ; Water pumped to ESR during n p hrs
• Distribution network: Series of interconnected pipes distribution network (DN)
• Various networks possible • Network to be adopted depends on place, orientation of roads, local conditions
• Various possible types include 1. Dead end system
2. Grid iron system
3. Ring system
4. Radial system
* Water Distribution Networks
* Dead End System / Tree System / Branching System
Structure – similar to tree Trunk / main line: main source of Water Supply
service mains / sub-mains – connected to mains
Branches – connected to sub mains
Network adopted for older towns that have developed in haphazard manner, without proper planned roads (almost all cities and towns in India, except a few)
Advantages: Easy to analyze and calculations are more accurate
Less no of sluice valves are required to be provided
Pipe lengths are short & hence laying is easy
Cheap, simple and easy extension possible
* Dead End System
Bacterial growth possible at dead ends. scour valves must at dead ends
During maintenance all D /S consumers suffer as water reach to them through the same pipe During fires flow diversion is not possible and
therefore can be troublesome
Due to extensions, pressure drop may occur and its difficult to restore as no connectivity. Only solution is lay parallel pipes / mains / sub mains which is costlier
* Disadvantages of Dead End System
* Grid Iron System
Most convenient for towns with proper road networks
e.g. Chandigarh Each point gets water ( or major part of the city) from more than 1 points, hence very useful during emergencies
No dead ends no stagnation of water reduced chances of bacterial contamination / otherwise Disadvantage / challenge?
* Grid Iron System
Advantages:
• Each point gets water ( or major part of the city) from more than 1 points
• In case of repairs, very small area devoid of complete supply, as at least, some supply will be reaching at the point from other route
• Continuous circulation of water, hence not liable to pollution
• During fire more water can be diverted towards affected point
Disadvantages:
• The length of pipe required is more and number of sluice valve also increases.
• Its construction is costly
• The design calculations are difficult. Determination of size of pipes and pressure at key points is tedious job.
* Circular / Ring System
Circular / Ring System
• A closed ring, either circular or rectangular, of the main pipe is formed around the area to be served.
• This system is suitable for well planned towns and cities
• For higher demand areas the ring system is used with grid iron system
* Radial System
Radial System
All above systems are helpful during emergencies
No dead ends no stagnation of water reduced chances of bacterial contamination / otherwise; No of valves to be operated are more
Head loss (valves; pipes’ friction; bents; meters) etc.
“Effective head available” imp. Factor for “design”
Normally in design: 7 m residual pressure. Considered @ consumer end for single storied; 12 m -2 s, 17 m – 3 s
Distribution reservoirs Balancing reservoirs: quantity for balancing variations in
demand & supply, buffers, mass curve to be used
Break down: pumps may fail / power failure; main source of w s may get damaged
Fire reservoirs: quantity to be kept reserved for fire fighting --- fire demand formulae Fire reserve = (f – c) t --- f = fire demand; c = fire pumping
capacity; t = duration of fire;
* Pressure In Distribution System
Reservoirs that store treated water for supplying water during emergencies (fire, power failure, repairs)
To cater for fluctuations in hourly demand as well as to maintain adequate pressure Types: Based on material: steel / RCC / masonry
Location : surface / elevated
Surface reservoirs either circular or rectangular constructed at G L or below G L; generally constructed @ highest pt in the city --- Malabar Hills in Mumbai If city area is undulating: more than one reservoirs are provided & zoning pattern is followed;
From G S R: water is sent to d/s in case of gravity flow
* Distribution Reservoir / Service Reservoir
Shape: rectangular / circular / oval
Constructed above g l @ some ht & is supported on supporting structure suitable for areas where combined gravity + pumped supply is made
Material: R C C , Steel Different sizes & shapes are possible (especially in RCC); also its cheap & requires less maintenance. hence RCC ESR are more common these days
Intz type, egg shaped, spherical / bulb, semi – spherical etc.
Stand pipe
* E S Rs (ELEVATED STORAGE RESERVOIRS)
* Stand Pipe
• Either G S R / E S Rs without Support Structure • Height 15 to 30 m,dia.-10 to 15 m • Were common in older days
* Determining Storage Capacity Of A Reservoir
Total storage capacity = ς (balancing storage + breakdown storage + fire storage)
Balancing storage: main function of distribution reservoir: to satisfy fluctuations in demand by acting as a buffer thereby ensuring constant supply Quantity required to be stored in the reservoir for equalizing variable demand balancing storage / balancing reserve / storage capacity of a balancing reservoir
Breakdown storage: emergency repairs / power failures Fire storage: uncertain, general consideration @
01 lpcd is 9668: 1980
* Methods to Determine Storage Capacity of A Reservoir
Mass curve method (diagram on board) A mass diagram: plot of accumulated inflow (i.e. Supply)
or outflow (i.e. Demand) v/s time. The mass curve of supply (i.e. Supply line) is, therefore, first drawn and is superimposed by the demand curve. The procedure to construct such diagram is as follows: From the past records, determine the hourly demand for all
24 hours for typical days (maximum, average and minimum). Calculate and plot the cumulative demand against time, and
thus plot the mass curve of demand. Read the storage required as “the sum of the two maximum
ordinates between demand and supply line as shown in fig.” Repeat the procedure for all the typical days (maximum,
average and minimum), and determine the maximum storage required for the worst day.
Hydrographs – refer your hydrology & irrigation (~ for water) Analytical method --- thr’ numericals
b) Rainwater harvesting: Introduction to rainwater harvesting, need of rain water, methods of rainwater harvesting, components of domestic rain water harvesting system, design of roof top rainwater harvesting system.
Necessity of Rain Water Harvesting
1) In areas where there is inadequate groundwater supply, rainwater harvesting offers an ideal solution.
2) It helps in utilizing the primary source of water and prevents the runoff from going into sewer or storm drains.
3) It reduces urban flooding.
4) Recharging water into the aquifers help in improving the quality of existing groundwater through dilution.
Harvesting System
Broadly rainwater can be harvested for two purposes
1)Storing rainwater for ready use in containers above or below ground
Harvesting System
2)Charged into the soil for withdrawal later (groundwater recharging)
Where to harvest rain
Rooftops
Paved & unpaved areas
Water bodies
Storm water drains
Whether to store rainwater or use it for recharge
Rain Water Harvesting
a) Individual House Rain Water Harvesting
Recharge Trench with Bore Method
Borewell with Settlement tank
Open well method with filter bed
Bore well with settling tank
b) Group Houses
ROOF TOP RAIN WATER HARVESTING
Component Parts
1) Catchment
2) Coarse Mesh
3) Gutters
Steel
Wood
Plastic Gutter
Aluminium Gutter
4) Down Pipe and First Flush Pipe
5) Filter Units
Charcoal Filter
Sand Filter
Dewas Filter
Rainwater Harvesting1
Rainwater Harvesting2
c) Introduction to Packaged WTP in townships, big commercial plants,
necessity (On-site water treatment)
Introduction to process description of RO, Pressure Filters
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