Biodegradation of p-chlorophenol by a microalgae consortium Sofia A.C. Lima, M. Filomena J. Raposo, Paula M.L. Castro, Rui M. Morais* Escola Superior de Biotecnologia, Universidade Cat ! olica Portuguesa, Rua Dr. Ant ! onio Bernardino de Almeida, Porto 4200-072, Portugal Abstract An aquatic community was recovered from a waste discharge container fed with several aromatic pollutants. After 3 months of selective enrichment with p-chlorophenol and p-nitrophenol, two microalgae species, Chlorella vulgaris and Coenochloris pyrenoidosa, were recovered from the microbial consortium. As an axenic culture, this microalgae consortium was able to remove p-chlorophenol under different photo-regimes. Cultures grown under a 24 h light regime were capable of biodegrading 50 mg l 1 of p-chlorophenol within 5 days. Addition of zeolite, an adsorbing material, did not improve the p-chlorophenol removal. However, when p-chlorophenol at 150mgl 1 was fed to the culture supplemented with zeolite, the growth rate of the consortium improved, but the lag phase was longer (16 against 14 days in the absence of zeolite). Keywords: Adsorption; Biodegradation; p-chlorophenol; Microalgae; Zeolite Halogenated compounds represent one of the most predominant environmental pollutants, due to their widespread usage as biocides, fungicides, disinfectants, solvents and other industrial chemicals. Biodegradation of chlorinated phenols has been studied with pure and mixed bacterial cultures [1,2]. Only a few studies have shown that microalgae are able to biodegrade aromatic compounds [3]. Chlorella sp. was found to decolourise certain azo dyes and use them as carbon and nitrogen sources [4]. Semple and Cain [5] reported the degrada- tion of phenol by Ochromonas danica. Luther [6] has reported that the alga Scenedesmus obliquus was able to utilise naphtalenesulphonic acids as a source of sulphur for their biomass, releasing the carbon ring into the medium. Three species of Chlorella were found to degrade pentachlorophenol [7], one of the species mineralised up to 13.8% of [UL- 14 C] PCP to 14 CO 2 within a 11-day incubation in a light-dark photo-regime. The biotransformation of 2,4,6-trinitrotoluene by an Anabaena sp. has been described [18]. The study of the role of microalgae in biodegradation systems is scarcely reported. A common approach used to treat organic compounds is a combination of biodegra- dation and adsorption processes. Adsorbing material, like zeolite or activated carbon, may be added to a biological process in order to improve the overall performance of the system and to increase the removal of the most recalcitrant organic material from waste- water [8,9]. Furthermore, zeolite has found parti- cular significance in aquaculture, as it has a positive influence on the growth of the marine microalgae Nannochloropsis sp. —75% higher cellular yields re- ported when cultivated in the presence of zeolite at 10mgl 1 [10]. An axenic microalgae consortium was isolated from a waste discharge container fed with several aromatic pollutants. The capacity of the microalgae consortium to degrade and to grow on p-chlorophenol under different light regimes, was studied. Adsorption of p- chlorophenol onto zeolite is described and its effect on Abbreviations: p-CP, p-chlorophenol; Chlorella vulgaris, Chl. vulgaris; Coenochloris pyrenoidosa, C. pyrenoidosa *Corresponding author. Tel.: +351-225580001; fax: +351- 225090351. E-mail address: rmorais@esb.ucp.pt (R.M. Morais). Introduction