Journal of Environmental Management 85 (2007) 927–935 Effects of feeding time and organic loading in an anaerobic sequencing batch biofilm reactor (ASBBR) treating diluted whey Leonardo H.S. Damasceno a , Jose´ A.D. Rodrigues b,Ã , Suzana M. Ratusznei b , Marcelo Zaiat a , Eugeˆnio Foresti a a Departamento de Hidra´ulica e Saneamento, Escola de Engenharia de Sa˜o Carlos, Universidade de Sa˜o Paulo (USP), Sa˜o Carlos-SP, Brazil b Departamento de Engenharia Quı´mica e de Alimentos, Escola de Engenharia Maua ´, Instituto Maua ´ de Tecnologia, Caetano do Sul-SP, Brazil Received 28 June 2005; received in revised form 23 October 2006; accepted 1 November 2006 Available online 20 December 2006 Abstract An investigation was carried out on the performance of an anaerobic sequencing batch biofilm reactor (ASBBR) treating diluted cheese whey when submitted to different feed strategies and volumetric organic loads (VOL). Polyurethane foam cubes were used as support for biomass immobilization and stirring was provided by helix impellers. The reactor with a working volume of 3 L treated 2 L of wastewater in 8-h cycles at 500 rpm and 30  C. The organic loads applied were 2, 4, 8 and 12 gCOD L 1 d 1 , obtained by increasing the feed concentration. Alkalinity was supplemented at a ratio of 50% NaHCO 3 /COD. For each organic load applied three feed strategies were tested: (a) batch operation with 8-h cycle; (b) 2-h fed-batch operation followed by 6-h batch; and (c) 4-h fed-batch followed by 4-h batch. The 2-h fed-batch operation followed by 6-h batch presented the best results for the organic loads of 2 and 4 gCOD L 1 d 1 , whereas the 4-h fed-batch operation followed by 4-h batch presented results slightly inferior for the same organic loads and the best results at organic loads of 8 and 12 gCOD L 1 d 1 . The concentration of total volatile acids varied with fill time. For the higher fill times maximum concentrations were obtained at the end of the cycle. Moreover, no significant difference was detected in the maximum concentration of total volatile acids for any of the investigated conditions. However, the maximum values of propionic acid tended to decrease with increasing fill time considering the same organic load. Microbiological analyses revealed the presence of Methanosaeta-like structures and methanogenic hydrogenotrophic-like fluorescent bacilli. No Methanosarcina-like structures were observed in the samples. r 2006 Elsevier Ltd. All rights reserved. Keywords: ASBBR; Feeding time; Organic loading; Whey 1. Introduction Cheese whey possesses a high organic load with concentrations of approximately 60–80 gCOD L 1 . This characteristic, combined with others such as low alkalinity and high biodegradability, make anaerobic treatment in high rate reactors difficult (Malaspina et al., 1996; Yan et al., 1988). Alkalinity present in the system is quickly consumed due to rapid conversion of lactose into short- chain volatile acids, making it necessary to constantly monitor alkalinity as well as pH (Backus et al., 1988). Supplemental addition of alkalinity as bicarbonate, carbo- nate or hydroxide may also be necessary (Lo and Liao, 1986; Wildenauer and Winter, 1985). Factors that may significantly affect ASBR performance according to Zaiat et al. (2001) include feed strategy, agitation, reactor configuration and initial ratio between substrate and biomass concentrations (F/M). In batch or fed-batch operated reactors the influence of feed strategy is related to the F/M ratio. According to Angenent and Dague (1995), increase in feed time would cause a reduction in total volatile acids (TVA) and consequently increase reactor performance, since by supplying substrate within a longer time, availability to microorganisms will be less, occasioning less accumulation of these acids. Bagley and Brodkorb (1999) corroborated the assumptions of Angenent and Dague (1995) in easily ARTICLE IN PRESS www.elsevier.com/locate/jenvman 0301-4797/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvman.2006.11.001 Ã Corresponding author. Tel.: +55 11 4239 3148; fax: +55 11 4239 3131. E-mail address: rodrigues@maua.br (J.A.D. Rodrigues).