Symposium no. 24 Paper no. 355 Presentation: oral 355-1

plants in China at the end of 1999 and produced about 15,000 tones of sewage sludge per day. The production of sewage sludge has been increasing sharply in order to treat 40% of the municipal sewage in 2005 as planned by central government. The main sludge disposal method is landfill owing to heavy metal contamination, but it presents an attractive potential for agricultural land application. Experiments were carried out to study the simultaneous metal removal and sludge stabilization by hyper-accumulator plants. The sludge samples were collected from Datansha Wastewater Treatment Plant of Guangzhou, it contained excessive Cu and Zn compared with the Chinese National Standard for Agricultural Use of Sewage Sludge. A Zn high-accumulating and high growth rate plant (Alocasia macrorrhiza) in Guangzhou was selected from 30 sludge plants and grown on sludge beds under field experiment conditions. The water, organic matter, heavy metals and nutrients contents, the E. coli number and the cress seed germination index were monitored for the sludge samples collected monthly. The plant growth parameters and its heavy metals contents were also determined. The sewage sludge treated by plants could be stabilized at about 5 months, the E. coli number was significantly decreased and the cress seed germination index attained 100%. Crop of the high-accumulating plants on sludge could ameliorate the sludge drying. The Zn and Cd hyper-accumulator Thlaspi caerulescens was also successfully grown on the sludges. The metals taken up by the hyper-accumulator were under determination. The experiments are continuing to find out the appropriate plant combination for simultaneous sludge stabilization and metal removal for an acceptable period. Comparisons between the proposed processes and other m..