Kinetics of anaerobic treatment of slaughterhouse wastewater in batch and upflow anaerobic sludge blanket reactor Jes us Rodr  ıguez-Mart  ınez * , Ivan Rodr  ıguez-Garza, Estaban Pedraza-Flores, Nagamani Balagurusamy, Gerardo Sosa-Santillan, Yolanda Garza-Garc  ıa Department of Biotechnology, Chemistry Faculty, Universidad Autonoma de Coahuila, Blvd. V. Carranza and J. C ardenas V. Saltillo, Coahuila, ZC 25280, Mexico Received 3 July 2001; received in revised form 4 June 2002; accepted 5 June 2002 Abstract The kinetics of anaerobic treatment of slaughterhouse wastewater in batch and upflow anaerobic sludge blanket (UASB) reactors was investigated. Different concentrations of organic matter in slaughterhouse wastewater did not change the first order kinetics of the reaction. In batch digesters, methane and nitrogen production stopped after 30–40, 20–30 h, respectively, and in UASB reactors it was terminated after 30–40 days. The constant of velocity was 3.93 and 0.23 h 1 respectively, for methane and nitrogen pro- duction. The yield coefficient, Y p was 343 and 349 ml CH 4 per g of chemical oxygen demand at standard temperature and pressure conditions for batch reactors and UASB reactor, respectively. Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Slaughterhouse wastewater; Anaerobic treatment; Kinetics denitrification; Methanogenesis 1. Introduction Anaerobic treatment is widely employed for treat- ment of most of the industrial wastewaters containing high concentrations of soluble organic matter (Jeris, 1983). The advantages of anaerobic treatment are widely reported by many workers (Fiestas, 1984; Olthof and Oleszkiewick, 1982). Conventional anaerobic treatment of slaughterhouse wastewater has also been reported by several workers (Rodr  ıguez-Mart  ınez et al., 1997; Borja et al., 1995; Polprasert et al., 1992; Sayed et al., 1984, 1987). Borja et al. (1993) investigated the influence of different supports on the kinetics of anaerobic puri- fication of slaughterhouse wastewater. The kinetics of various processes of anaerobic digestion, viz., denitrifi- cation, sulfate reduction and methanogenesis in batch reactors as well as upflow anaerobic sludge blanket (UASB) reactors fed with slaughterhouse wastewater is not yet fully investigated. As nitrate and sulfate are present in considerable quantities in slaughterhouse wastewater, it is important to assess the influence of these substrates on biometha- nation of this wastewater. It is well known that presence of sulphate is inhibitory to methanogenesis in marine and fresh water sediments (Balderston and Payne, 1976) and in anaerobic digesters (Lawrence et al., 1966). The toxicity of sulfide or free H 2 S produced by microbial reduction of sulphate and competition for electron do- nors between sulphate-reducing bacteria (SRB) and methanogens are considered to be two important factors responsible for this inhibitory effect (Kristjansson et al., 1982; Kroiss and Wabnegg, 1983). The aim of this present work was to carry out a kinetic study on various processes that occur during anaerobic treatment of slaughterhouse wastewater in batch and UASB reactors. 2. Methods 2.1. Wastewater and inoculum The wastewater used in this study was collected from the municipal slaughterhouse of Saltillo, Coahuila (Mex- ico). The wastewater production was approximately Bioresource Technology 85 (2002) 235–241 * Corresponding author. Tel.: +52-844-4100-722; fax: +52-844-4155- 752. E-mail address: jrodrigu@alpha1.sal.uadec.mx (J. Rodr  ıguez- Mart  ınez). 0960-8524/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII:S0960-8524(02)00141-4