R. Keller, K. Perim, S. Semionato, E. Zandonade, S. Cassini, and R.F. Gonçalves Department of Environmental Engineering (CT-DEA), Universidade Federal do Espirito Santo (UFES), 29060-970 Vitoria ES, Brazil (E-mail:
[email protected]) Abstract The aim of this study was to evaluate the potential cultivation of lettuce (Lactuca sativa) with domestic wastewater effluents with different levels of treatment from a compact WWTP in Brazil. Vegetables were grown in five treatments: nutrient solution (control), secondary effluent diluted 50%, secondary effluent not diluted, tertiary effluent UV irradiated, and UASB effluent. Microbiological analyses from leaves showed low levels of contamination with E. coli, thermotolerant coliforms and total coliforms. Salmonella spp. and helminth eggs were not detected. However, roots showed hardly any concentration of these microorganisms. These results shows that it is possible to cultivate leafy vegetables in a hydroponic system with treated effluents, taking care at the moment of harvesting vegetables. Keywords Hydroponic system; pathogenic microorganisms; reuse; wastewater
Introduction
The scarcity of conventional sources of waters in arid and semi-arid regions in many parts of the world like South Africa, the Middle East, Southern Europe and South America has promoted the search for additional water sources (Asano et al., 1992). Domestic treated wastewater is a stable water source and has been used in agriculture, industry, recreation and gardening (Burau et al., 1987; Oron et al., 1992). Reuse applications of wastewater in hydroponic cultivation represents a choice of production that can be adapted to the demand of high quality, high production and low waste of water and nutrients. The objective of this study was to verify the microbiological quality of lettuce cultivated in a greenhouse with treated effluents from a compact WWTP using a hydroponic system for growing plants.
Water Science and Technology: Water Supply Vol 5 No 1 pp 95–100 © IWA Publishing 2005
Hydroponic cultivation of lettuce (Lactuca sativa) using effluents from primary, secondary and tertiary + UV treatments
Material and methods Description and performance of WWTP
The effluents were obtained from a wastewater treatment plant (WWTP) receiving domestic sewage and planned to cater for 1,000 inhabitants (Gonçalves et al., 1997, 1999). The sewage treatment plant is composed of a UASB reactor (35 m3) and four submerged aerated biofilters (12 m3). The average values obtained from the monitoring of the plant indicated COD = 445 mg/L and TSS = 168 mg/L for raw sewage parameters. The UASB reactor achieved 62% efficiency in the removal of organic matter (COD = 191 mg/L and TSS = 62 mg/L from primary effluent) decreasing the organic matter effluent in the aerobic reactor, minimizing costs due to energy consumption with aeration. The final effluent parameters achieved TSS
