The makeshift toilets once used by residents of Jindan, a village in Xiangyun county, Yunnan province, were unbearably dirty and fetid, especially during summer when they were plagued by flies and mosquitoes, posing a health risk.

To address the problem, the locals decided to dig simple communal toilets a few minutes' walk from the village. Although the new facilities reduced the health risk, they were inconvenient and children had to be escorted to them at night because they were afraid of the dark.

The situation began to change in June last year, when the local government started a pilot project using the CHtank, a sewage-disposal facility designed and made in China.

While the 566 households in the village couldn't afford to build a dedicated sewage treatment facility, the CHtank, a small, independent unit that can be used by individual households, offered a cheaper solution to the problem.

The tank has two chambers, one for solids and one for liquid waste. Four types of bacteria are used to clean liquid waste-which is then used to irrigate fields - and break down solids, which are stored in the tank before being collected and taken away.

Li Shizhao's family is one of 55 households that have benefited from the facility, which was provided free of charge as part of a demonstration project.

"Our toilet used to smell really bad. Every two months, I had to spend about an hour emptying and cleaning it before transporting the waste to my farmland using buckets and a carrying pole," the 43-year-old farmer said.

"After the CHtank was installed in our compound, we built a new toilet at home. The tank transforms wastewater from the toilet into clean, odorless water," he said. "It's convenient to use, and we don't have to keep driving away the flies."

Produced by Shenzhen Hexu Environmental Technology, the CHtank costs about 60 yuan ($8.70) a year to operate.

According to Hao Lei, manager of the company's branch in Xiangyun, a county in southern Yunnan, it would be prohibitively expensive to build a network of sewers in the rural areas of the mountainous province because the dwellings are scattered across a wide area.

The CHtank may provide a solution. Its bio-treatment technology transforms liquid waste into water that can reach grade I, the highest level of a three-tier assessment system for treated water, which is the same quality as the water in ponds, lakes and rivers.

At the end of last year, Shenzhen Hexu signed an agreement with the Xiangyun government to invest 400 million yuan to build an industrial park to manufacture about 300,000 CHtanks a year.

The provincial government wants to develop Jindan into a demonstration village to promote the device and showcase its ability to transform the rural environment, said Dong Xuehui, director of rural construction at the Xiangyun department of housing and rural-urban development.

The biggest obstacle to the plan is the cost; each Chtank costs 8,000 to 10,000 yuan to manufacture and install.

"We hope the higher-level government will provide financial support for the promotion," Dong said.