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Abstract
Aquatic and terrestrial bioassays were used to assess toxicity at several stages in an industrial wastewater treatment plant that processes 400 L/s from a complex influent formed by wastewater from 135 industries. Daphnia pulex and Lactuca sativa were used to assess and compare toxicity between the influent wastewater and effluent wastewater from an activated sludge process, and compare their relationship with physicochemical parameters of Biological Oxygen Demand (BOD); Chemical Oxygen Demand (COD); Total Suspended Solids (TSS); total Nitrogen (N N-total), and ammonia Nitrogen (N N - NH3). Samples from the primary clarifiers (PC), mix liquor stage (ML) and secondary clarifiers (SC) were processed using physicochemical and bioassay test. Toxicity results with Daphnia pulex showed decreased mean values of acute Toxic Units (a.T.U.) between PC (2.1 a.T.U.) and SC (1,25 a.T.U.). Lactuca sativa showed high values of toxicity between PC and SC (3.37 and 3.32 a.T.U. respectively). Some samples exhibited higher toxicity values at the effluent stage (SC) than the influent stage (PC). The highest correlations of physicochemical properties with toxicity were obtained with COD and nitrogen compounds in effluent samples (SC), but not with influent samples (PC).
Acknowledgments
This work was supported by Autonomus University of State of Mexico through project No. 2051/2005, and RECICLAGUA, S.A. laboratory to conduct the physicochemical analysis required for this study.
Notes
*Represent mean of duplicate test from samples of influent (PC), mix liquor (ML) and effluent (SC); ND = No determined. a.T.U. means acute Toxicity Units.
*Represent mean of duplicate test from samples of influent (PC), and effluent (SC); a.T.U. means acute Toxicity Units.