Low temperature conversion of some Brazilian municipal and industrial sludges H. Lutz a , G.A. Romeiro b , R.N. Damasceno c , M. Kutubuddin a , E. Bayer a, * a Institute of Organic Chemistry, University of T ubingen, D-72076 T ubingen, Germany b Universidade Federal Fluminense, Departamento de Qu  õmica Org^ anica, Niter oi, CEP 24210-150 RJ, Brazil c Universidade Federal Fluminense, Departamento de Geoqu  õmica, Niter oi, CEP 24210-150 RJ, Brazil Received 20 May 1997; received in revised form 20 July 1999; accepted 8 January 2000 Abstract Three Brazilian municipal and industrial sludges were subjected to the Low Temperature Conversion (LTC) process. They in- clude activated, digested and lacquer sludges. The activated sludge recorded the highest yield of LTC oil (31.4%), followed by lacquer sludge (14.0%) and the digested sludge 11%. 1 H-NMR studies of the oils indicated that they consisted mainly of aliphatic and ole®nic compounds, while the concentration of aromatics was below 2.5%. The major hydrocarbons in the oils were penta- decane and heptadecane. The distribution pattern of hydrocarbons present in the oils was similar to what is known from the conversion of other sludges. In addition the LTC oil from activated sludge contained 26% fatty acids, while the oils from digested and lacquer sludge contained only about 3% fatty acids. Recovery studies on the fate of heavy metals in the sludges indicated that they were accumulated in the char. Partial gasi®cation studies of the LTC chars resulted in active carbons with quite low iodine and methylene blue numbers. However, even if their use is limited the production of active carbon together with the recovery of LTC oil constitutes a complete disposal of the sludges. Ó 2000 Elsevier Science Ltd. All rights reserved. Keywords: LTC; Sludges; Oil; Char 1. Introduction Wastewater treatments have recently found renewed attention in Brazil. This is accompanied by the problem of sludge management. Low Temperature Conversion (LTC), a thermocatalytic method simulating the natural process of oil formation developed by Bayer and Ku- tubuddin (1981, 1982, 1988), has been used to recover raw materials in the form of oil and char from these kinds of wastes. The process is carried out at 300±420°C in the absence of oxygen and can be applied to various kinds of organic waste materials. The products can be used as chemical and energetic feedstocks which are both easy to handle and store (Bridle and Hertle, 1988). In general the oil contains aliphatic and ole®nic hydro- carbons and fatty acids, together with lesser amounts of a number of other compounds. The residual char can be deposited, burned or activated by partial gasi®cation. This paper, therefore, considers the LTC of three Brazilian sludges from municipal and industrial waste- water treatment plants, including the chemical charac- terization of the conversion products. 2. Methods 2.1. Collection of sludges Activated and digested sludges were collected from a wastewater treatment plant in Rio de Janeiro, Brazil, while the third sludge, called `lacquer sludgeÕ, was col- lected from a treatment plant of the printing industry. These were stored in plastic bags at 4°C and dried to constant weight prior to analysis and conversion. 2.2. Low temperature conversion Low temperature conversion was carried out batch- wise in triplicate on 250±500 g samples in a laboratory reactor at 380°C for 3 h (Fig. 1). The sludge samples (2) were ®xed in the tube by glasswool (3), put into the furnace (1), and heated under nitrogen (5) (heating rate about 10 K min À1 ) to the ®nal temperature. The volatized compounds were condensed (6) into a separa- Bioresource Technology 74 (2000) 103±107 * Corresponding author. Tel.: +49-7071-292-437; fax: +49-7071-295- 246. 0960-8524/00/$ - see front matter Ó 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 0 - 8 5 2 4 ( 0 0 ) 0 0 0 1 1 - 0