Rainwater harvesting is becoming an integral part of the toolkit for sustainable water management. This study indicates that office-scale rainwater harvesting systems offer significant water and cost savings, and emphasises the importance of monitoring data.
Rainwater harvesting is increasingly becoming an integral part of the sustainable water management toolkit, and provides significant water savings for toilet flushing in offices, for example.
However, despite numerous studies modelling the feasibility of utilising rainwater harvesting (RWH) systems in particular contexts, there remains a significant knowledge gap in respect of detailed empirical assessments of performance.
Domestic systems have been investigated to a limited degree in the literature, including in the UK, but there are few recent longitudinal studies of larger non-domestic systems. And there are few studies comparing estimated and actual performance.
Here researchers at the University of Exeter present the results of a longitudinal empirical performance assessment of a non-domestic RWH system located in an office building in the UK.
They compare actual performance with estimated performance based on two methods recommended by the British Standards Institute: the Intermediate (simple calculations) and Detailed (simulation-based) Approaches.
The results highlight that the average measured water saving efficiency (amount of mains water saved) of the office-based RWH system was 87% across an 8-month period, due to the system being oversized for the actual occupancy level. Consequently, a similar level of performance could have been achieved using a smaller tank.
Estimated cost savings resulted in capital payback periods of 11 and 6 years for the actual oversized tank and the smaller optimised tank, respectively. However, more detailed cost data on maintenance and operation are required to perform whole-life cost analyses.
These findings indicate that office-scale rainwater harvesting systems can offer significant water and cost savings, although greater innovation in types of RWH systems is required.
The study also emphasises the importance of monitoring data, and that a transition to the use of Detailed Approaches (particularly in the UK) is required to both minimise the oversizing of storage tanks, and to build confidence in rainwater harvesting system performance.
Water Research, Volume 46, Issue 16, 15 October 2012, Pages 5127–5134.
