What Are the Main Options for Applying the Multiple-Use Water Services Paradigm? - Rethinking Infrastructure Design for Multi-Use Water Services - page 28

Lookout Grey water policies and proper regulation are of key importance to
reinforce public acceptance and awareness, economic viability and imple-
mentation of grey water reuse practices, aiming at reducing water demand and
improving water sustainability (Yu et al. 2013 ). Economic incentives, such as
subsidies, provided by water utilities can be valuable tools to promote grey
water reuse technologies. Tucson Water, in the city of Tucson, Arizona,
through the Gray Water Rebate Program offers rebates up to $1,000 per
household for the installation of grey water irrigation systems for both ret-
ro ts and new buildings ( www.tucsonaz.gov/water/rebate ).

2.2 Why Grey Water Recycling?

Reduction of water demand from public water supply for non-potable uses,
leading both to lower household water bills and wider community bene

￿

ts.

Reduction of ef uent discharge and thus energy reduction for wastewater treatment.

￿

Household water savings can reach a level of 50 % through grey water reuse for
toilet

￿

flushing and garden irrigation (Maimon et al. 2010 ).

3 Urban Green Spaces

Green spaces in the cities include private gardens, parks, green parking lots, squares
and streets, community forests, etc.

3.1 What Is the Cost-Bene t?

Planting and maintaining trees and vegetation can be costly. The main costs
associated include initial planting and ongoing maintenance, such as for irrigation,
pruning and pest control, administration, etc. Nevertheless, the bene

ts derived

(direct and indirect) can exceed the overall cost.

Facts A study on the functioning and value of street and park trees in ve

US cities from different States (McPherson et al. 2005 ) showed that for every
dollar invested in tree planting and ongoing maintenance, bene ts returned

annually ranged from $1.37 to $3.09. More speci cally annual costs ranged

-

from around $15 $65 per tree, while total revenues including energy savings,

atmospheric CO 2 and storm water run-off reduction, air quality, aesthetics and
other bene

ts were about $31 - $89 per tree. Regarding costs, pruning was