Published on IDRA Global Connections Summer 2021 Issue

By Mr. Graham Bateman, Chief Technical Officer, Hydro Industries Ltd., UK

Predicted rates of global population growth combined with the anticipated impacts of climate change have been and will continue to be the driving force to develop ever more sustainable approaches to manage global water resources.

What is SDG6 and why is it so important?

Sustainable Development Goal 6 (SDG6) is one of 17 Sustainable Development Goals established by the United Nations General Assembly in 2015 to “ensure availability and sustainable management of water and sanitation for all.” The goal has eight targets to be achieved by at least 2030, progress against which will be tracked by eleven global indicators. Two targets of particular relevance within the context of this article
are as follows:

SDG Target 6.3 directly calls for more water recycling: “By 2030, improve water quality by reducing pollution, eliminating dumping and minimizing release of hazardous chemicals and materials, halving the proportion of untreated wastewater and substantially
increasing recycling and safe reuse globally”. SDG6 Target 6.4 calls for sustainable withdrawals and supply of freshwater: “By 2030, substantially increase water-use efficiency across all sectors and ensure sustainable withdrawals and supply of freshwater to address water scarcity and substantially reduce the number of people suffering from water scarcity”.

The future of desalination for highly developed economies is expected to be more like Singapore – desalt seawater once but reuse it several times.

Many forecasts indicate that by the middle of this century half the world’s population will live in a water stressed zone. The human population is using more water than the water resources available globally. There often exists the notion that more water can be extracted from our environment to meet demand. This is not the case. We need to reduce the quantity of water being consumed. If this cannot be achieved, the distribution of water will change.

To meet the current and future challenges in water (resource) management, the required actions can broadly be categorised under the following headings:

1. Conservation.
2. Reuse.
3. Desalination.

In terms of dissolved solids, the following typical concentrations are a reminder of the relative energy requirements involved depending on the final water quality required.

• Wastewater – 1000 mg/l
• Seawater – 35,000 mg/l
• Gulf seawater – ≥40,000 mg/l

Water stressed locations tend to be those places where people want to live, often cities and often near the coast, resulting in hot-spots for potential reuse. Increased demand leads to an increased uptake in demand for reuse as part of the supply, as does climate change. The future of desalination for highly developed economies is expected to be more like Singapore – desalt seawater once but reuse it several times. As much of the world’s population lives in cities on or near the coast, using the sea as a truly sustainable base load water source makes sense, but it then becomes too valuable to dispose of, leading to water reuse. In Singapore, a lot of treated water is much more valuable to industry than the domestic customer because it is desalinated, i.e., much lower dissolved solids. This has helped fuel the significant growth in the
industrial sector there.

There will be increased uptake of holistic water resource management, e.g., industrial and municipal link-ups will become regarded as win-win scenarios, the ‘logical’ course of action.

Water Reuse and Water Recycling 

The terms water reuse and water recycling have often been used interchangeably and can mean different things to different people. To date, a lot of research has been
carried out to gauge as well as influence public perception of these terms. When we think of what is included under this banner, it typically includes but is not necessarily limited to the following:

• Domestic wastewater treatment and reuse/ recycle for non-potable.
• Domestic wastewater treatment and reuse/ recycle for potable.
• Greywater treatment and reuse/recycle for non-potable.
• Greywater treatment and reuse/recycle for potable.
• Rainwater treatment and reuse/recycle for non-potable.
• Rainwater treatment and reuse/recycle for potable.
• Industrial wastewater treatment and reuse/ recycle for non-potable.

Note: potable reuse/recycling can be direct or indirect.

There is evidence to suggest that “reused water” has been perceived as a lower quality product than “recycled water”, shifting the move towards the greater adoption by governments, authorities, and water providers of the term “recycled water”.

Reuse has gained growing acceptance due to political practice and recognised professionalism. It is important to have recognised professional practice – reasonable and consistent consensus amongst professional practitioners. This has been an enabler for rapid adoption/ application from city level and broader community level, particularly in the US. There has been an exponential growth in successful reuse programmes and an increased rate of acceptance of this practice in the community.

Policy and Legislation

Since the early pioneers of reuse from Namibia, Singapore, Australia, and the USA in particular, the world is waking up to the reality that much greater steps to conserve and better manage the quality and quantity of water we use must be taken. To make more ambitious strides in this direction the significance of policy development and legislation cannot be understated.

A wealth of research challenging traditional approaches to obtaining sources of water in a more sustainable way has taken place in recent years. There have been novel approaches incorporating innovative technologies to recognised and generally accepted treatment trains as well as novel approaches to combining well-understood/ proven technologies in different configurations to achieve demanding water or effluent quality standards much more sustainably.

Sustainable water supply, water reuse and desalination

A significant opportunity to achieve sustainable supplies of both potable water and energy exists with the growth of solar-powered desalination. This is due to the reduction of production costs for both desalination and renewable energy systems in recent years. Achieving this goal will
require a shift away from overdesigned, large desalination plants to smaller, decentralised plants. In addition, energy recovery from wastewater treatment facilities needs to become the norm rather than the exception, and we should expect to see an increased emphasis on nutrient recovery from wastewater, such as nitrogen, phosphorus, and organic carbon.

The most significant advances in desalination technology (for brackish and potable reuse) in the near future will be in the sphere of the enhanced recovery technologies. These technologies will become increasingly common, both in terms of incorporation into new reverse osmosis (RO) facilities and as retrofits to existing desalination plants. Applications will be driven by either 1) the need for increased water production; and/or 2) the need to reduce concentrate volume.