Variations of metal distribution in sewage sludge composting Sabiene Nomeda a , Paulauskas Valdas a , Shen-Yi Chen b , Jih-Gaw Lin c, * a Environmental Institute, Lithuanian University of Agriculture, Studentø 11, LT-4324 Kaunas-Akademija, Lithuania b Department of Safety, Health and Environmental Engineering, National Kaohsiung First University of Science and Technology, 2 Jhuoyue Road, Nanzih, Kaohsiung 811, Taiwan c Institute of Environmental Engineering, National Chiao Tung University, 75 Po-Ai Street, Hsinchu, Taiwan Accepted 25 June 2007 Available online 11 September 2007 Abstract In the study, the variations of heavy metal distributions (of Cu, Mn, Pb, and Zn) during the sewage sludge composting process were investigated by sequential extraction procedures. The total content of Cu and Zn in the composted mixture increased after the compo- sting process. Mn and Zn were mainly found in mobile fractions (exchangeable fraction (F1), carbonate fraction (F2), and Fe/Mn oxide fraction (F3)). Cu and Pb were strongly associated with the stable fractions (organic matter/sulfides fraction (F4) and residual fraction (F5)). These five metal fractions were used to calculate the metal mobility (bioavailability) in the sewage sludge and composted mixture. The mobility (bioavailability) of Mn, Pb, and Zn (but not Cu) increased during the composting process. The metal mobility in the com- posted mixture ranked in the following order: Mn > Zn > Pb > Cu. Ó 2007 Elsevier Ltd. All rights reserved. 1. Introduction The rapid increase of world population leads to signifi- cant amounts of waste discharge. At present, environmen- tally friendly and cost effective methods of waste utilization have received much attention. The European Union (EU) Waste Framework Directive (91/156/EEC amending 75/ 442/EEC) confirms the waste management hierarchy. Pref- erence is given to waste prevention, followed by waste reduction, re-use, recycling, and energy recovery. In 1980, the main solid waste management option in the USA was landfilling, and only a minor part was incinerated, or other- wise utilized. However, the extent of waste utilization stea- dily increased, and it is estimated that almost 35% of all waste in the USA will be utilized in 2010 (USEPA, 1997). In order to improve the wastewater control process, the Taiwan Government has decided to raise the populariza- tion of sewer systems by a rate of 3% per year. Due to the expansion of population, the number of municipal sew- age treatment plants (MSTP) is increasing rapidly, and a great amount of sewage sludge will be produced. It is esti- mated that 832 tons of sewage sludge per day will be gen- erated in 2010. Surveying the reports of sewage sludge production worldwide shows that the total amount of sew- age sludge produced in 15 EU countries increased to at least 9.4 million tonnes of dry matter in 2005 (EEA, 2005). Therefore, the disposal of waste sewage sludge will become an environmental issue in the future. Not only in European countries, but all over the world, scientists and producers make every effort to reuse sewage sludge as a valuable bio-fertiliser. The sewage sludge usually contains a high content of organic matter and nutrients, and there- fore it can be used as a fertiliser for land application. Although such application may be beneficial to soil, its negative impacts, such as groundwater pollution, pollutant accumulation in soil, etc., should be considered (Veeken and Hamelers, 2002; Peigne and Girardin, 2004; Wei and Liu, 2005). Analysis of EU Environmental Legislative doc- uments (Directives, Regulations in force and projects) showed that the requirements of sewage sludge, composted 0956-053X/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.wasman.2007.06.022 * Corresponding author. Tel.: +886 3 5722681; fax: +886 3 5725958. E-mail address: jglin@mail.nctu.edu.tw (J.-G. Lin). www.elsevier.com/locate/wasman Available online at www.sciencedirect.com Waste Management 28 (2008) 1637–1644