As the demand on water supply has increased, irrigation with reclaimed wastewater, replacing potable water, via drip irrigation has become more prevalent. Treated wastewater effluent, which contains both physical and biological contaminants, can lead to clogging of the drippers.
A joint BARD-funded collaboration, led by Dr. Eran Friedler from the Faculty of Civil & Environmental Engineering at the Technion and Dr. Karl Linden from the Environmental Engineering Program at the University of Colorado Boulder, looked into solving this problem with UV-LED irradiation technology. This technology can be used for reducing biological fouling of drip irrigation fed by treated wastewater effluent. They also wished to explore whether locating the UV-LEDs along the irrigation line as an integral part of the system could serve as an advantage and help prevent clogging.
To reach these objectives, the research teams conducted a number of experiments. They used UV-LEDs in a collimated beam to disinfect the treated wastewater. They designed flow-through reactors that were appropriate for the size and geometry of the drip emitters. Finally, biofouling kinetics and characterization were studied in a laboratory-scale pilot pipe-loop system fed by synthetic wastewater effluent.
The biofilm generated on the pipelines was estimated using traditional tools such as Total Suspended Solids (TSS, COD) as well as advanced methods such as Extracellular Polymeric Substances (EPS) analysis (which evaluates fundamental components of the biofilm and determines its physicochemical properties), and Optical Coherence Tomography (OCT) (which provides a visualization of the biofilm structure; see fig 1).
The overall results indicate that UV-LEDs played a critical role in reducing biofouling of drip irrigation fed by treated effluent compared to an untreated control. The UV-LED plus chlorine performed slightly better than the UV-LED alone. Moreover, UV-LED may be located along the irrigation line as an integral part of the system, and does not require added chemicals, and therefore may serve as a sustainable and ecological replacement to chlorine.
The overall results indicate that UV-LEDs played a critical role in reducing biofouling of drip irrigation fed by treated effluent compared to an untreated control. The UV-LED plus chlorine performed slightly better than the UV-LED alone. Moreover, UV-LED may be located along the irrigation line as an integral part of the system, and does not require added chemicals, and therefore may serve as a sustainable and ecological replacement to chlorine.
This study showed that it is possible to minimize effluent-fed emitter biofouling by using UV-LED irradiation. The findings suggest that controlled experimental conditions, the use of such technology enhances irrigation efficiency while potentially reducing environmental hazards.
1 – Figure 2. Drippers fed with synthetic effluent (control & led-UV irradiated effluent) – OCT of the biofouling layer within the dripper Maze
