Performance of a commercial inoculum for the aerobic biodegradation of a high fat content dairy wastewater Lyliam Loperena a , Mario Daniel Ferrari a , Vero ´ nica Saravia a , Daiman Murro a , Cynthia Lima a , Lucı ´a Ferrando b , Ana Ferna ´ndez b , Claudia Lareo a, * a Dept. Bioingenierı ´a, Instituto de Ingenierı ´a Quı ´mica, Facultad de Ingenierı ´a, Universidad de la Repu ´ blica, J. Herrera y Reissig 565, 11300, Montevideo, Uruguay b Ca ´ tedra de Microbiologı ´a, Facultad de Quı ´mica, Universidad de la Repu ´ blica, Gral. Flores 2124, 11800, Montevideo, Uruguay Received 23 May 2005; received in revised form 10 April 2006; accepted 10 April 2006 Available online 21 June 2006 Abstract The effectiveness of a commercial inoculum for degrading a dairy wastewater with high fat content was evaluated, and compared with an activated sludge inoculum from a dairy wastewater treatment pond. Both inocula reached similar chemical oxygen demand removal in batch experiments. The population dynamics was also studied by determining heterotrophic counts. Predominant microorganisms were differentiated by colony morphology and genomic fingerprinting (BOX-PCR) analysis. The higher population diversity and the wider range of CO 2 production rate observed in batch reactors inoculated with activated-sludge, indicated that microorganisms from this inoc- ulum were well adapted and may have had synergic activity for the degradation of the dairy effluent. When the bioreactor was operated with the commercial inoculum in continuous mode, according to its microbial growth kinetics, other microorganisms became predom- inant. These results showed that inoculated microorganisms did not persist in the open system and periodic addition of microorganisms may be needed to achieve a high performance treatment. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Bioaugmentation; Biodegradation; Biological treatment; Milk fat; Respirometry 1. Introduction The use of bioaugmentation strategies, such as the addi- tion of external microorganisms with high degradation capacity of specific compounds, can improve the overall performance of biological wastewater treatment systems (Huban and Plowman, 1997; Timmis and Pieper, 1999; Van Limbergen et al., 1998). Several types of commercial biological products exist in the market (inocula). Most of them consist of mixed microbial populations which can include components such as enzymes or nutrients (Ferrari et al., 2002; Wakelin and Forster, 1998). Such microorgan- isms should meet the desired criteria: (i) capable of degrad- ing target pollutants under in situ conditions, (ii) competitive and persistent after inoculation, and (iii) com- patible with the indigenous microbial community, comple- mentary and/or synergic for the degradation of an effluent type or specific compounds (Yu and Mohn, 2002). Various bioaugmentation studies on biodegradations of fats and oils have been reported in the literature. Some researchers did not find differences in biodegradation per- formances between natural acclimatised activated sludge and bioaugmented processes treatment (Mendoza-Espi- noza and Stephenson, 1996; Wakelin and Forster, 1997). However, others have found promising results in fats bio- degradation performances using bioaugmentation (Huban and Plowman, 1997; Keenan and Sabelnikov, 2000; Louki- dou and Zouboulis, 2001; Tisinger and Drakos, 1996; Zou- boulis et al., 2001). In this work, the ability of a commercial inoculum to degrade fat-containing dairy wastewater aerobically was 0960-8524/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2006.04.030 * Corresponding author. Tel.: +598 2 7110871; fax: +598 2 7107437. E-mail address: clareo@fing.edu.uy (C. Lareo). Bioresource Technology 98 (2007) 1045–1051