Zhuo CHEN1, Huu Hao NGO1(), Wenshan GUO1, Xiaochang WANG2
1. Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, Sydney 2007, Australia; 2. School of Municipal and Environmental Engineering, Xi’an University of Architecture and Technology, Xi’an 710055, China
Recycled water provides a viable opportunity to partially supplement fresh water supplies as well as substantially alleviate environmental loads. Currently, thousands of recycled water schemes have been successfully conducted in a number of countries and Sydney is one of the leading cities, which has made massive effort to apply water reclamation, recycling and reuse. This study aims to make a comprehensive analysis of recycled water schemes in Sydney for a wide range of end uses such as landscape irrigation, industrial process uses and residential uses (e.g., golf course irrigation, industrial cooling water reuse, toilet flushing and clothes washing etc.). For each representative recycled water scheme, this study investigates the involved wastewater treatment technologies, the effluent quality compared with specified guideline values and public attitudes toward different end uses. Based on these obtained data, multi criteria analysis (MCA) in terms of risk, cost-benefit, environmental and social aspects can be performed. Consequently, from the analytical results, the good prospects of further expansion and exploration of current and new end uses were identified toward the integrated water planning and management. The analyses could also help decision makers in making a sound judgment for future recycled water projects.
3) level 1 water restriction on the use of recycled water
water quality requirement
current recycled water can be safely used without any quality improvement
additional advanced treatment (e.g., membrane technology) is required to recycle backwash water
current recycled water can be safely used. Level 1 restriction includes no use of sprinklers or other watering systems (excluding drip irrigation) as well as no hosing of hard surfaces and vehicles at any time
water quantity
laundry generally requires 20% of total water use. Given the total water use is 5.5 × 109 L·a-1 in Rouse Hill, this option can save around 1.1 × 109 L·a-1 of fresh water
there are three community swimming pools in Rouse Hill. Given the water use of 8 × 104 L·d-1 for each one, this option can save around 8.76 × 107 L·a-1 of fresh water
due to STP failure and maintenance, 15% of the water sold as recycled is clean drinking water. Level 1 restriction can result in 12% reduction of water demand, saving up to 2.64 × 108 L·a-1 of recycled water. This equals to save 3.96 × 107 L·a-1 of fresh water
risk
the risk is even lower than recycled water used for toilet flushing because of less exposure
although the exposure to recycled water is high, the improved quality can sufficiently reduce the risk
reduced recycled water consumption can reduce its exposure to human and the environment to some extent
environmental considerations
reduced effluent discharge and freshwater use
reduced effluent discharge and freshwater use
high water use efficiency and low ecological footprint
community attitudes
60% of respondents in Sydney agree this option
13% of 116 householders agree this option
public acceptability is low as the frequencies of washing hard surfaces, using sprinklers are significantly high in households
costs and benefits
need to add extra taps in dual reticulation systems for washing machines. No additional costs on water quality improvement
need to add extra taps in dual reticulation systems for swimming pools. Additional costs on water quality improvement are required
neither additional taps nor costs on water quality improvement are required
references
[19]
[4,16]
[20]
Tab.2
key criteria
primary weighting /%
sub-criteria
sub weighting /%
scores of options
1
2
3
water supply
20%
water quantity and security of supply
50%
+ 4
+ 3
+ 2
water quality
50%
+ 3
+ 4
+ 3
risk related issues
15%
treatment technology
50%
+ 3
+ 4
+ 3
reliability, robustness and safety
50%
+ 3
+ 4
+ 3
Operability
10%
ease of operation
55%
0
–1
0
system flexibility to upgrade and extend
45%
0
+ 1
0
environmental considerations
25%
volume of waste generated
20%
+ 2
+ 1
+ 1
footprint of plant and infrastructure
20%
+ 1
+ 1
+ 2
energy use
15%
+ 1
+ 1
+ 2
greenhouse gas emission
15%
+ 2
+ 1
+ 1
impact on local ecology
20%
+ 1
+ 1
+ 1
impact on groundwater
10%
+ 1
+ 1
0
social/community considerations
15%
aboriginal, cultural and non-cultural heritage
15%
0
0
0
aesthetics
20%
0
+ 1
0
traffic disruption
20%
0
–1
0
community/social acceptance
25%
+ 3
+ 2
–2
community education opportunities
20%
+ 4
+ 3
+ 1
costs and benefits
15%
capital cost
50%
–1
–2
0
operating cost
50%
–2
–1
0
total
100%
1.50
1.48
1.22
Tab.3
Fig.2
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