Phytotoxicity testing of winery wastewater for constructed wetland treatment

Rapid and inexpensive phytotoxicity bioassays for winery wastewater (WW) are important when designing winery wastewater treatment systems involving constructed wetlands. Three macrophyte wetland species (Phragmites australis, Schoenoplectus validus and Juncus ingens) were tested using a pot experiment simulating a wetland microcosm. The winery wastewater concentration was varied (0.5%, 5%, 10%, 25%, 50%, 75% and 100%) and pH was corrected for some concentrations using lime as an amendment. The tolerance of the three aquatic macrophytes species to winery wastewater was studied through biomass production, total chlorophyll and nitrogen, phosphorous and potassium tissue concentrations. The results showed that at greater than 25% wastewater concentration all the macrophytes died and that Phragmites was the least hardy species. At less than 25% wastewater concentration the wetland microcosms were effective in reducing chemical oxygen demand, phenols and total soluble solids. We also evaluated the performance of two laboratory phytotoxicity assays; (1) Garden Cress (Lepidium sativum), and (2) Onion (Allium coepa). The results of these tests revealed that the effluent was highly toxic with effective concentration, EC(50), inhibition values, as low as 0.25%. Liming the WW increased the EC(50) by 10 fold. Comparing the cress and onion bioassays with the wetland microcosm results indicated that the thresholds for toxicity were of the same order of magnitude. As such we suggest that the onion and cress bioassays could be effectively used in the wine industry for rapid wastewater toxicity assessment.