在线英语听力室_免费在线英语听力学习网站

Wastewater Key to Sustaining Life

The world population is growing rapidly and is expected to reach 9 billion by 2050. While efforts are underway to ensure there’s enough food, one scientist is warning there may not be enough water.

Professor Stanley Grant said billions of people don’t have adequate water supplies. That number will only get bigger, he says, unless something is done immediately.

“There are drought conditions across the U.S. and in many parts of the world. So as our planet gets warmer we need more fresh water and as populations grow we also end up using more fresh water. So that’s kind of the big picture backdrop,” he said.

Grant is a professor of environmental engineering at the University of California at Irvine. He’s the author of a new study called Taking the Waste out of Wastewater for Human Water Security and Ecosystem¹ Sustainability.

“The focus of this particular paper is really on moving toward a paradigm² shift away from where we really have been for years, which is just simply trying to get more sources of water all the time. And that’s kind of a flawed approach. Eventually you run out of new sources of water. You can’t tap into rivers that are already dry. You have to come up with a new approach. And the new approach really is focused around improving the productivity of the water that you already have. And that means basically getting more value out of that water,” he said.

Water is essential for life, which is why it’s at the heart of tensions in many regions. For example, many countries draw water from the Nile River and there’s often disagreement over how much each should get.

“The Nile is an interesting example. It’s one of a number of examples. Colorado River in the United States, the Yellow River in China would be other examples. These major rivers have been tapped out so much that basically they’re dry by the time they get to their deltas,” he said.

Grant said important ecosystems³ that rely on those and other rivers could be destroyed and people downstream won’t have enough water.

He added limited fresh water supplies make recycling wastewater and sewage effluent necessary.

“That can involve using highly treated wastewater for activities where you don’t need really high quality water, like landscape irrigation, for example. Or it can involve using super advanced methods to treat the water to sometimes better than potable standards and actually drinking it,” he said.

It’s already being done in some places.

“Israel is kind of leading the world in terms of using recycled wastewater for agricultural purposes. In Singapore, for example, wastewater recycling is being used to provide water for industrial applications. In the U.S. we have a couple of wastewater reclamation⁴ facilities. For example, the Orange County water District in Orange County near where I live is recycling wastewater using very advanced techniques. And then essentially⁵ infiltrating⁶ it into the groundwater basin here and that groundwater eventually is extracted and put back in the potable water supplies,” he said.

Residents of Melbourne, Australia have also begun to conserve⁷ and recycle water as a result of a prolonged drought. Stanley says much of the world should be doing the same.

“If the trajectories⁸ for global climate change continue as they appear to be headed, we could see in our lifetime some really tragic⁹ situations where, for example, megacities essentially run out of water and have to be abandoned. That almost happened in Chennai, India a couple of years ago where there was a prolonged drought and at some point water wasn’t coming out of taps and there was no ground water to be had. And the city planners had to begin think about drawing up plans for evacuating¹⁰ the city,” he said.

The University of California professor added that megacities that are expected to emerge in coming years, in Africa for example, could face similar problems. Grant says the technology exists to recycle and treat wastewater. However, the big hurdle¹¹ will be to convince Western nations that such water can taste good.