A NUMBER of cities are in talks with Shenzhen authorities about using our man-made wetland technologies to help them trim costs in treating sewage.More than 10 sewage treatment plants from Shanghai Municipality, Fujian Province and other regions have approached the Shenzhen Environmental Science Research Institute (SESRI), complaining of fund shortages in building sewage treatment facilities to cope with soaring urban household sullage. They were happy to learn the construction of artificial wetlands was only half that of a sewage treatment plant with operational costs only one fifth, SESRI head Lei Zhihong said Sunday.With limited funds, the wetland technologies would help them greatly boost their sewage treatment capacities.The Honghu Park wetland project in Luohu District in Shenzhen was rated by the State as a model project in sewage treatment.Shenzhen began a trial using artificial wetlands to treat sewage under a cooperation project with the European Union in 1997. By screening more than 300 plants, SESRI researchers found wetland cultivated with a combination of six tropical and subtropical plants, including reed and canna, offered maximum effect in absorbing and decomposing pollutants and nutrients in water running through it.After passing through wetlands the water has been found to be up to surface water standards set by the State, SESRI said.The man-made wetland in Honghu Park is now integrated with the neighboring ecological system, and has become a habitat for various birds. The park also saves up to 1 million yuan (US$121,000) each year using water purified by the wetland to water the park.(Roger Lin)