From seawater to tap or from toilet to tap? Joint Desalination and Water Reuse is the future of sustainable water management
In an era of increasing water scarcity, coupled with continued population and industrial growth, climate change and environmental degradation, we need to conserve water, as well as creating new sources of high quality water to sustainably meet future water demands.
Desalination combined with water reuse are essential components of our vision towards a water wise world. Water reuse and desalination offer climate-independent, locally controlled water sources that are beneficial to communities and cities. Potable reuse of treated wastewater is still marginal, whereas desalination is now widespread with over 18,000 plants in 150 countries around the world.
Potable reuse can be “direct”: water produced in an advanced wastewater treatment facility is introduced into the raw water supply immediately upstream of a drinking water treatment facility, or directly into a drinking water supply distribution system. The latter has successfully been in place for decades in Windhoek, Namibia. Potable reuse can also be “indirect”: highly purified water is introduced into an environmental buffer before being withdrawn for potable purposes. The buffer provides an additional barrier for the protection of public health, storage and means of transport. It may be a groundwater aquifer, like in Orange County, California, or a surface water reservoir, like in Singapore.
In many cities, desalination is chosen over potable reuse. Is this because of cost? Of energy efficiency? Or because of public perception?
How do potable reuse costs compare to seawater desalination? The cost of treatment depends on many localized factors. The costs discussed here include both annualized capital costs and operation and maintenance costs, including energy. Costs for advanced water treatment, including Reverse Osmosis, which is needed for direct potable reuse, range between $0.45 and $0.75 /m3. Costs are lower for advance water treatment without reverse Osmosis, ranging from $0.32/m3 to $0.55/m3. Costs for desalination of seawater for large facilities varies from $0.50/m3 to $1.80/m3, dependent upon energy cost and location. So the cost analysis would often weigh towards potable reuse, though handling of concentrates or managing the buffer could tip the balance the other way.
Let’s take a look at energy consumption. An advanced water treatment facility requires .95 kWh/m3, whereas the state of the art desalination plants require about 3.3 kWh/m3 . The energy required for potable reuse is significantly lower than for desalination, and the carbon footprint of desalination is three times higher.
So why don’t we have more potable reuse projects? It’s often because the public acceptance towards reuse is harder to obtain for city or government officials. Would you drink recycled toilet water? How do you get the citizens and the regulators to embrace that?
We need to build water wise communities – the inhabitants, the professionals, the policy makers and the leaders, who can make the right decisions for a water wise world. Desalination is still needed as a source of raw water in many places, but given its cost and its energy consumption, we should consider a combination of desalination and potable reuse.
In the IWA Principles for Water Wise Cities, to be launched at the World Water Congress & Exhibition, in Brisbane, People, the “water-wise communities”, are the overarching level of action. We need each actor of the city to be water-wise if we are to achieve sustainable urban water, which underpins the resilience and sustainable growth of cities.
IWA and IDA recognize that successful water reuse and desalination are critical for our future. Respective sponsors of the IWA Congress in Brisbane and IDA Conference in Nice, we aim to build water wise professionals and together influence city leaders, regulators, industry, citizens … only then can we ensure a sustainable water future for all.
The IDA International Conference on Water Reuse and Recycling – Turning Vision into Reality, in Nice, is an opportunity to build water wise professionals. Pioneers and leaders of water reuse will share worldwide success stories, including the City of Windhoek in Namibia; OCWD Orange County Groundwater Replenishment System; PUB Singapore program of New Water; eThekwini water reuse in Durban and Sulaibiya in Kuwait.
Join us to contribute to the debate on joint technologies for Desalination and Water Reuse, learn on the key to success of water reuse-desalination and shape the vision for the future.
The IWA World Water Congress & Exhibition in Brisbane offers water professionals broader perspectives on water management, including reuse and desalination at the Desalination Pavilion.
Those interested in the future of urban water and building sustainable, resilient cities, can participate in the City Leaders Forum and Cities Pavilion, both of which will inspire City leaders to start the journey to water wise cities