The World Health Organization says nearly 40 percent of the world's population still live without proper bathroom facilities. That includes many families in rural China, who have scant indoor sanitation or underground sewage systems.

One researcher has developed a vacuum toilet system for residents of Chentang, a village in East China’s Jiangsu province.

In the fourth episode of CCTV Rural Recovery series, reporter Feng Xin discovers the history of sanitation across three generations there and tells how a revolution has taken place.

This wooden bucket was part of Fei Xiaoliu’s dowry when she married in this village four decades ago.

Wooden buckets were a necessity for every household. They served as chamber pots at night, because no family had indoor toilets. Fei used to scrub the buckets out each morning at the river that was a quick walk from her house.

"In the old days, we had to use the wooden buckets and poured the waste into a tank. Then we built a new house and installed a flushing toilet. But we still used both," said Fei Xiaoliu, Chentang village resident.

The area around the Yangtze River estuary is often called “China’s Venice” because of the large number of villages that interwoven with rivers and lakes. With no underground sewage systems, many families had to find their own ways, if they ever wanted to have indoor sanitation.

68-year-old Wang Yuanyuan was the first person in Chentang to install a flushing toilet at home. But unlike those in modern apartments, Wang’s toilet created bad smells and new problems.

"I’ve had this toilet for 26 years. We didn’t have running water back then, so I dug a tank just outside my house to store the waste. Later, we had tap water, but the toilet had to waste too much water for flushing," he said.

Official numbers show that only 15 percent of China’s rural population has modern sanitary facilities. A more serious problem, though, is that 90 percent of China’s villages have no sewage treatment facilities at all. Much more than just installing modern toilets in rural areas needs to be done.

Researcher Fan Bin grew up in a similar village in Jiangsu province. He believes that rural sanitation problems need to be solved in different ways than in cities.

“Unlike urban areas, where sewage treatment facilities are quite large, rural living areas are smaller, and people live in small density. So, we can use some small or even micro units to deal with rural wastewater,” he said.

Fan Bin started a sewage project in Chentang in 2011. And Wang Yuanyuan, again, became the pilot to experiment with Fan’s design.

Wang installed the new toilet just opposite to his old one. As he pushes a button, the device vacuums away waste, using only one cup of water.

The waste is sucked into a sewer system via pipes outside his house. The sewage is then sent to an underground tank that's connected to an electricity-powered vacuum system. The tank is where the waste is processed and converted into solid and liquid fertilizer.

“Conventional sewage treatment methods mix all the different wastewater together and drain it to a centralized facility by using huge amounts of water," Fan said.

"A lot of useful substances in human excrement and kitchen garbage can hardly be reused. What we do is separate the different waste waters from their origins, based on their densities. Without using any more water, we can process the waste into fertilizer and apply it on farmland. “

The liquid fertilizer is sprayed directly onto the farmland through tubes while the solid waste fertilizer will be collected a couple of times a year and also applied to the land.

Twenty-three families in Chentang have now installed vacuum toilets. Fan plans to use the same technology to soon process kitchen waste as well.