Living things cannot survive without water.

Yet more than 700 million people worldwide have trouble getting clean, safe water. That number comes from the Water Project, a non-profit group. It estimates that one in nine people do not have access to safe and clean drinking water.

Governments, non-governmental organizations (NGO) and charities sent representatives to Stockholm, Sweden earlier this month for World Water Week activities. The subject for this year's water week campaign was "water and waste, reduce and reuse."

The United States Geological Survey defines wastewater as used water. It is the water that comes out of pipes from peoples' homes — from their bathrooms, washing machines and dishwashers. It can contain substances such as human waste, food pieces, oils, and chemicals. Businesses and industries also use water that must be cleaned.

Wastewater can also have harmful substances that wash off roads, areas where motor vehicles are kept, and tops of buildings when it rains.

Todd Gartner of the World Resources Institute spoke with VOA from Stockholm by Skype. He says only a small amount of wastewater is being reused for other purposes.

"Something like, I think it's only four or five percent of wastewater is being recycled for any useful purpose. And over 90 percent of wastewater is just raw water. Right, you obviously have some nutrients and some metals you have to filter out, but the technology is increasingly becoming available to treat and reuse that wastewater."

Gartner says the simple step — reusing water — could make a big difference. He notes that recycling is already happening in some places.

"Even for potable water, there is a lot of places where they are treating the water to drinkable standards. And if you think about that as an option, it dramatically reduces our need to think of using fresh water each time."

Treating wastewater is good for human beings because it provides fresh water for us. But it also helps the environment by keeping waste out of rivers and oceans.

"Eighty percent of wastewater around the world is not treated at all. Which means that it is running into oceans and bays."

Another problem is that people are using more clean water than our planet has. Sarah Feakins, a professor at the University of Southern California, spoke with VOA by Skype. She says agriculture is reducing the amount of water in the ground.

"It is well known that the water table level is dropping because of all the water being used for agriculture, so that means we can not keep doing what we are doing for a very long time. We actually have to change what we are doing."

Todd Gartner believes there are two kinds of solutions. One is low technology, like reforestation, or planting trees, and fixing pipes that leak. More high-tech solutions include better watering methods for agriculture, and factories to remove salt from salt water.

On average, the world uses about 10 billion tons of water a day. And while 75 percent of our planet is covered with water, only about two percent is fresh water — that comes from rivers, lakes, ice and snow.

The rest, 98 percent of the water, is in seas and oceans. It is too salty to drink. This is where desalination businesses come in.

The International Desalination Association, an industry group, says there are more than 19,000 desalination plants worldwide. They process more than 92 million tons of water every day. But they require a lot of energy. Currently, desalination operations are found mostly in coastal nations with large energy supplies. Examples are found in the Middle East.

Researchers are working to create a less costly technology. They are studying a process called membrane desalination. It moves water through special membranes that keep the larger salt molecules from passing through.

Nikolay Voutchkov is president of Water Globe Consultants. He says other technologies, such as using membranes with enzymes and nanoparticles, may cut the cost of using desalination for large amounts of water. He spoke to VOA by Skype.

"This type of structure, if we could imagine that we could generate that structure that looks like a honeycomb, we would increase production about 20 times to what we have today."

Scientists say finding a less costly desalination process would mean less pressure on natural sources of clean water.

And Todd Gartner says everyone should have access to clean water.

"Water is a human right and we want to make sure that everyone has access to clean, pure plentiful water, right now, we are not allocating it in a way that suggests it is a human right and everyone deserves their equal share."

But for now, the world still faces each day with not having enough water for everyone.

I'm Anne Ball.

Kevin Enochs and George Putic reported on this subject for VOANews. Anne Ball adapted their reports for Learning English. George Grow was the editor.

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charity – n. the act of giving money, food, or other kinds of help to people

recycle – v. to make something new from something that has been used

filter – v. to pass something like a liquid through a filter to remove something unwanted

option – n. the opportunity to choose something or to choose between two or more things

desalination – v. to remove salt from something like water

plant – n. a building or factory where something is made

membrane – n. a thin sheet or layer

enzyme – n. a chemical substance in animals and plants that helps to cause natural processes

nanoparticle – n. a microscopic particle whose size is measured in nanometers

honeycomb – n. a group of wax cells with six sides that are built by honeybees in their hive and that contain young bees or honey

allocate – v. to divide and give out something for a special reason or to particular people, companies, etc.