Monitoring of effluent DOM biodegradation using fluorescence, UV and DOC measurements Ibrahim Saadi a,b , Mikhail Borisover c , Robert Armon b , Yael Laor a, * a Agricultural Research Organization, Institute of Soil, Water and Environmental Sciences, Newe Ya’ar Research Center, P.O. Box 1021, Ramat Yishay 30095, Israel b Technion-Israel Institute of Technology, Faculty of Civil and Environmental Engineering, Haifa 32000, Israel c Agricultural Research Organization, Institute of Soil, Water and Environmental Sciences, Volcani Center, Bet Dagan 50250, Israel Received 22 April 2005; received in revised form 20 July 2005; accepted 31 July 2005 Available online 10 October 2005 Abstract The potential of effluent DOM to undergo microbial degradation was assessed in batch experiments. Effluent sam- ples from Haifa wastewater treatment plant and Qishon reservoir (Greater Haifa wastewater reclamation complex, Israel) were incubated either with effluent or soil microorganisms for a period of 2–4 months and were characterized by dissolved organic carbon contents (DOC), UV 254 absorbance and by fluorescence excitation–emission matrices. Three main fluorescence peaks were identified that can be attributed to humic/fulvic components and ‘‘protein-like’’ structures. During biodegradation, specific fluorescences (F/DOC) of the three peaks were increased at various extents, suggesting selective degradation of non-fluorescing constituents. In some cases increase in the effluent fluorescence (F) was observed thus proposing (i) the formation of new fluorescing material associated with DOM biodegradation and/or (ii) degradation of certain organic components capable of quenching DOM fluorescence. Based on the ratio between fluorescence intensity and UV 254 , different biodegradation dynamics for fluorescent DOM constituents as compared with other UV-absorbing molecules was delineated. Overall, about 50% of the total DOM was found to be readily degradable such that residual resistant DOC levels were between 8 and 10 mg l À1 . Enhanced levels of residual DOM in effluent-irrigated soils may contribute to the DOM pool capable of carrying pollutants to groundwater. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Effluents; Dissolved organic matter (DOM); Excitation emission matrix (EEM); Biodegradation; Qishon (Kishon) 1. Introduction The use of treated wastewater effluents to irrigate agricultural land is a common practice in many coun- tries in which the available resources of fresh water are limited. In Israel, a wide national program of waste- water reclamation is being established (Rebhun et al., 1987; Amiel et al., 1990; Fine et al., 2002). As compared with freshwater, effluents used for irrigation contain higher concentrations of organic and inorganic constitu- ents, the concentrations of which depend on the quality and type of sewage and extent of treatment. Dissolved organic matter (DOM) commonly ex- pressed by its C content (DOC) is an important compo- 0045-6535/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2005.07.075 * Corresponding author. Tel.: +972 4 9539539; fax: +972 4 9836936. E-mail address: laor@volcani.agri.gov.il (Y. Laor). Chemosphere 63 (2006) 530–539 www.elsevier.com/locate/chemosphere