Investigation of a ponding irrigation system to recycle agricultural wastewater

Cytotoxicity assays to evaluate tannery effluents treated by photoelectrooxidation

The advanced oxidation process (AOP) is used to increase the treatment efficiency of effluents however, it is necessary to compare the toxicity of treated and untreated effluents to evaluate if the decontamination process does not cause any biological harm. Cultured cells have been previously used to assess the genotoxic and cytotoxic potential of various compounds. Hence, the aim of this work was to assess the applicability of cytotoxicity assays to evaluate the toxicity related to the AOP treatment. Samples of an industrial effluent were collected after their treatment by a conventional method. Cytotoxicity of standard and AOP treated effluents was assessed in CRIB and HEp-2 cell line using the MTT and neutral red assays. We observed decrease at cell viability in the both assays (50% MTT and 13% NRU) when cells were exposed to the AOP treatment in the highest concentration. Thus, cytotoxic assays in cultured cells can be explored as an useful method to evaluate toxicity as well as to optimize effluents treatment process.

Uptake of organic emergent contaminants in spath and lettuce: an in vitro experiment

Although a myriad of organic microcontaminants may occur in irrigation waters, little attention has been paid to their incorporation in crops. In this work, a systematic approach to assess the final fate of both ionizable and neutral organic contaminants taken up by plants is described. In vitro uptake of triclosan (TCS), hydrocinnamic acid (HCA), tonalide (TON), ibuprofen (IBF), naproxen (NPX), and clofibric acid (CFA) were studied in lettuce ( Lactuca sativa L) and spath ( Spathiphyllum spp.) as model plants. After 30 days incubation, analyte depletion from the culture medium was 85-99% (lettuce) and 51-81% (spath). HCA, NPX, and CFA exhibited the highest depletion rate in both plant species. Lettuce plant tissue analysis revealed an accumulation of all compounds except for HCA. These compounds reached a peak in tissue concentration followed by a sudden drop, probably due to the plant detoxification system and analyte depletion from the culture medium. Kinetic characterization of the uptake and detoxification processes was fitted to a pseudo-first-order rate. Compounds with a carboxylic group in their structure exhibited higher uptake rates, possibly due to the contribution of an ion trap effect. Molecular weight and log K(ow) played a direct role in uptake in lettuce, as proven by the significant correlation of both properties to depletion and by the correlation of molecular weight to kinetic uptake rates.

Ecotoxicological screening of reclaimed disinfected wastewater by Vibrio fischeri bioassay after a chlorination-dechlorination process

It is well known that different substances can react with chlorine in a water disinfection process to produce disinfection by-products (DBPs). Some of these substances have proven to be carcinogenic in humans and animals. Because it is not possible to detect all DBPs produced in chlorinated wastewater, toxicity tests have been proposed as a useful tool for screening toxic chemicals in treated wastewater. In this study, the Microtox bioassay with Vibrio fischeri was used to evaluate the formation of toxic by-products in wastewater, after a chlorination-dechlorination disinfection treatment. All the variables were found to be normally distributed, so analysis of variance could be directly applied without transformation of variables. Significant correlations were obtained between toxicity values and total carbon, total inorganic carbon, total nitrogen, chlorine, and pH. In contrast, total organic carbon, chemical oxygen demand, electrical conductivity and turbidity had no effect on toxicity formation. Toxicity increased with the Cl2:NH4+ ratio at a higher chlorine concentration released from combined chlorine. Regression models provided a good fit for effective concentration (EC50) as a function of total carbon and total nitrogen, after 5, 10, and 15 min of exposure. These models had greater multiple determination coefficients than previously reported for similar studies, without autocorrelation in the residuals as indicated by the Durbin-Watson statistic test. The measured and predicted ecotoxicity values were strongly correlated.