Application of Municipal Sewage Sludge in Tea Garden in Wuxi

The municipal sewage sludge (MSS) was applied to tea garden to assess its effectiveness and safety. The level of heavy metals in MSS from five wastewater treatment plants in Wuxi was measured. MSS was applied in the tea garden. The bud density, mass per hundred buds, and heavy metal in tea leaves were determined. A large difference in the level of heavy metals in MSS from five plants was identified. There might be a high risk if MSS from each wastewater treatment plant was applied individually. However, the safety degree could increase if the MSS from five plants were mixed before their application. After two consecutive years’ application of MSS in tea garden, bud density and mass per hundred buds were 1 385 unit/m² and 54.2 g respectively, the increase being 29.2% and 33.5% respectively compared with the control group. After the sewage application, the lead and copper content in the tea leaves increased to 3.23 and 21.1mg/kg from the initial values of 2.81 and 18.3 mg/kg. So it is not recommendable to apply MSS in tea garden in consecutive years.