Page 84 - Build 161

Departments/Research
By Lee Bint, BRANZ Sustainable Building Scientist, Amber Garnett, BRANZ Research Scientist, Roman Jaques, BRANZ Senior Building Environment Scientist,
and Alma Siggins, Senior Scientist, ESR
Harvested and recycled water use
Could we harvest more rainwater and recycle more greywater in our commercial buildings? A BRANZ study of eight buildings found water tari s are the major driver to uptake, and these vary by location.
FUTURE STRAINS on water networks are fore- cast as the population continues to increase and urbanisation and per capita water use grows. Compounded by climate change, the future stability of the freshwater resource in New Zealand is a growing concern.
Adopting rainwater and greywater tech- nologies could help reduce the burden on our water networks. BRANZ has completed a 3-year study to understand the feasibility of rainwater harvesting and greywater recycling in commercial buildings.
Drivers and barriers to uptake
Online surveys of industry representatives showed cost and environmental reasons were the main drivers for installing rain- water harvesting and greywater recycling systems. Resilience was a secondary driver.
Cost, education and storage were perceived as the biggest barriers to installing rainwater harvesting systems in New Zealand buildings.
For greywater recycling, the biggest barriers were education and cost.
Water quality, health and waterborne disease were the primary concerns respondents had with rainwater and grey- water systems.
For greywater quality, health, general quality, cross-contamination with potable water, cleanliness of the system and soci- ety’s perception of dirtiness were recurring concerns.
Eight buildings assessed
Eight commercial buildings across New Zealand with an operational rainwater harvesting and greywater recycling system were investigated. Despite varying building use, size and location, these buildings all used the rainwater and greywater for the ushing of toilets and urinals.
Assessments of these systems involved monitoring water consumption and rain- water and greywater use (Figure 1). The systems’ operational e ciency was inves- tigated as well as building managers’ and maintenance sta learnings in the design, operation and maintenance of the systems.
23% of water use non-potable
Rainwater use in the eight commercial build- ings monitored ranged from 45–1,147 kL in summer to 22–1,039 kL in winter. The annual water use was 309–23,525 kL.
The average proportion of total water use that comprised non-potable, non-contact end uses (toilets and urinals) was 23%.
Little or no potential human health risk
Since health is a concern, a water quality study was commissioned with the Institute of Environmental Science and Research (ESR). This found there is likely to be little or no potential human health risk in using rainwater or greywater for toilet and urinal flushing. However, only five buildings formed this part of the study, and the results are not representative.
As well as the drivers and barriers listed, some regulations are considered prohibi- tive. These can create a barrier to installa- tion and effective utilisation, highlighting the need for education to enable effective water reuse.
82 — August/September 2017 — Build 161