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Using filtered wastewater effluent with SDI

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  032025,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.13995) @2003
Authors:   Juan Enciso, Naomi Assadian, George Di Giovanni, Jaime Iglesias
Keywords:   Drip, Microirrigation, Vegetables, Water Conservation, Effluents, Microbial Contamination, Health Risk

The goal of this project was to promote water conservation in arid and semi-arid communities through the use of SDI systems using wastewater. Since the water is distributed below ground, the risk of disease caused by water-borne bacteria and viruses is greatly reduced. The research focused on the SDI use of wastewater filtered from anaerobically-digested biosolids (FWW, filtered wastewater). This waste stream is not disinfected, and typically recycled within the wastewater treatment plant for de-nitrification. The project objectives were to evaluate and assess soil salinization, survival and potential health risks of coliphages introduced by FWW. A column study was conducted in greenhouse to evaluate SDI with FWW using spinach as a test crop. The drip emitter was installed at a soil depth of 24 cm and the column length was 58 cm. The treatment design was a 2x2x5 factorial with cropping (the presence or absence of spinach plants), soil texture (loamy sand and clay loam), and time (five weekly harvests) as main plots and soil depths as subplots. Treatments were replicated 5 times for a total of 20 columns. Virus movement and persistence in soil was evaluated at 0.10-m depth increments every week for four weeks (28 d) after the last irrigation. Destructive soil sampling each week necessitated the establishment of 20 soil columns for each of the five harvests for a total of 100 columns. SDI water delivery prevented viral contamination on spinach leaf surface but not at the soil surface. Salts accumulated at the soil surface regardless of texture. Conversely, bacteriophage ELP1 showed limited transport and accumulated in the area of water entry in both soil textures or above the emitter in textured soil. Salinity and sodicity increased in both soils after irrigation.

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