Globally, water resources are under immense and increasing pressure. This, coupled with the threat of climate change, has increased global interest in water reuse. However, global water reuse remains limited because of public opposition. This paper thus examines public perceptions and attitudes to water reuse across the world. It finds that results from studies of water reuse acceptance have tended to be context specific, although claims can be made about the universal relevance of some predictors, underscoring the need for individual water reuse schemes to carefully consider their local context. Disgust remains a constant in the public psyche, while public trust in delivery agents as well as how water reuse is communicated vis-à-vis perceptions about the quality and safety of recycled water are also critical. The latter particularly highlights public concerns about the indeterminate health risks associated with water reuse.

As climate change and agriculture burden water resources globally, there is a need for more efficient water use including irrigation with recycled water in greenhouses. While research has proven that properly treated recycled water can be safe for use, many growers still express concern. Underlying most studies on growers' perceptions is the assumption that they understand recycled water the same way scholars and policy makers do—as municipally treated wastewater. We question this assumption and explore whether the ways in which growers conceptualize recycled water is associated with the ways they perceive its usability. Our findings reveal that growers define recycled water in four different ways—captured water, treated water, recirculation and in a general sense as ‘reuse’. These definitions do appear to suggest trends in the way recycled water is perceived by growers. While these definitions do not significantly affect growers' willingness to use, other factors such as prior experience using recycled water appear to be significant.

We conducted an isotopic analysis of groundwater in Orange County, California, USA, around the Talbert Seawater Injection Barrier to determine if recycled water, used to artificially recharge local aquifers, carries a unique isotopic signature that can be used as a tracer. From September 2014 to April 2015, we collected groundwater from six privately owned wells within the coastal groundwater basin, along with various surface waters. All water samples were analyzed for their stable isotopic composition (δ18O, δD), the δ13C and 14C signature of the dissolved inorganic carbon (DIC) pool, DIC concentration, pH, and salinity. The DIC of groundwater mixing with recycled water is enriched in 14C above natural background levels, with varying signal strength through time, depleted in δ13C, and low in DIC concentration. Water isotopes further suggest that recycled water is a mixture of Colorado River water and regional groundwater. In contrast, groundwater found further away from the injection barrier has carbon and water isotope composition consistent with regional groundwater and Santa Ana River water. Our findings imply that recycled water injected through the Talbert Barrier is isotopically unique, and that 14C enrichment may be used as an intrinsic tracer of artificial recharge within the basin.