There is a Chinese proverb that goes “when drinking water, remember the source.” In Singapore, where clean water can be obtained at the turn of a faucet, it is easy to take for granted how much resources are needed to ensure our water security. Additionally, although Singapore has advanced water purification and recycling technologies allowing for the economical production of clean water for day-to-day consumption, the environmental costs associated with the use of such technologies remain poorly understood.
“Water recycling in industries can help to reduce overall water consumption. However, as water recycling can be resource-intensive, the environmental impacts of using recycled water versus that of public water supply should be considered to prevent unintended trade-offs,” explained Ms. Cadence Hsien, a Research Engineer at A*STAR’s Singapore Institute of Manufacturing Technology (SIMTech). “To be able to make this comparison for informed decision making, we first need to quantify the environmental impact of water supply in Singapore.”
Hsien and colleagues thus conducted a life cycle assessment of Singapore’s national water sources, including water derived from desalinated seawater, treated stormwater and recycled water, better known as NEWater. As Singapore’s water supply system is complex and comprises numerous components, such as rivers, reservoirs, desalination plants and water distribution networks, the group decided to begin the life cycle assessment by first evaluating the environmental impact of each activity involved in the water supply.
The group used eight indicators selected from the ReCiPe method to measure environmental impact. They reported that the production of NEWater and tap water had similar impacts on particulate matter generation, fossil fuel depletion, photochemical oxidation and human toxicity. This is because NEWater production and desalination involve the use of similar chemicals and materials in the maintenance of the membrane and reverse osmosis processes.
However, NEWater production had a greater direct impact on ozone depletion than tap water production, owing to the emission of nitrous oxide from the water reclamation process. The researchers thus highlighted that better removal of biological nutrients in the water reclamation plants could reduce the environmental impact of NEWater production.
They also noted that some treated water from water reclamation is not further purified into NEWater and ends up being discharged into the sea. This represents a form of waste and inefficiency, which could be weeded out from the water supply chain.
“Our study quantifies the environmental impact of producing tap water and NEWater in Singapore using life cycle assessment. These results can be used to support decisions on water use and water recycling. Additionally, the insights provided by the life cycle assessment points to improvement potentials of the Singapore water system in terms of environmental impact,” Hsien concluded.
The A*STAR-affiliated researcher contributing to this research is from the Singapore Institute of Manufacturing Technology (SIMTech).