Water Supply Flashcards
Why integrate the 3 water?
- strategic planning
- recognises inter-relationships
- integrates financial planning
Stormwater and wastewater network performance issues in dunedin:
- flooding due to localised network capacity being exceeded
- water enters pipes through crack leading to overflows
- saltwater enters network and can affect biological wastewater treatment process
What are some water supply sources?
- groundwater bores
- reservoirs
- stream/ rive offtakes
- lakes
- de-salination
- roof water
- process water reuse
(source determines level of treatment required)
Christchurch water supply system:
- water taken from wells
- pumps keep mains pressurised
- reservoirs on hills
- where no hills, pumps are kept running for water pressure
Auckland water supply system:
- water supply 100% from dams
- high location of dams allow gravity flow
What are the key design consideration of water supply system design?
- water quality
- hydraulic capacity
- structural strength of system
- fire supply
- “fit for purpose” service life
- seismic resistance
- corrosion/ degradation resistance
- life cycle costs
- capacity for future extension
- networking, redundancy and security of supply
For what customer/ users is quantity and quality of water supply user specified?
- industrial
- commercial
- agricultural
Breakdown of water use in NZ home:
- 30% baths and showers
- 30% toilet
- 20% kitchen
- 20% laundry
Amount of water used per person per day
180-250 L
+ water used outside
Industrial water use:
40% of non residential water use
- food processing
- beverages
- textiles
- semi-conductor manufacturing
- pulp and paper
What needs to be calculated for design flow and pressures?
- minimum water demand (250L/p/d for residential)
- peak flow
- fire water demand
Important aspects of network design:
- models to access combination of pipe size, pressure and layouts
- check ability to add future connection
- looping to provide flow security
- incorporate valves for maintenance/ fault isolation
- design pressures
- rate pipes for 1.5 times operating pressure
Typical fittings in pipes:
- sluice valves
- backflow prevention
- scour valves
- air valves
- thrust and anchor blocks
- meters
What are two basic causes of backflow?
- sudden drop in pipe pressure causing water to siphon back into the system
- water supply is directly connected to equipment which is at a higher pressure than the water supply system, forcing water into the supply system
What is backflow prevention design based on?
Contamination risk
High - toxic
Medium - endangers health
Low - nuisance
