UV-LED irradiation for biofouling reduction in drip irrigation emitters fed with wastewater effluent†

Crop irrigation with treated wastewater effluent using drip irrigation has become common as the demand for water supply has increased. Because of the quality characteristics of treated wastewater and the narrow and winding geometry of the drip emitter's structure, it is susceptible to clogging. Emitter clogging reduces flow and increases flow variability between emitters that can lead to water stress on crops, thereby reducing crop yield. Several methods to minimize emitter clogging have been suggested and applied; however many drawbacks are associated with them. The use of UV-LEDs (UV light-emitting diodes) is a non-chemical disinfection method that holds great promise for disinfection and biofouling prevention in irrigation systems. In this research, biofouling formation potential was investigated for 12 weeks, in a large pilot-scale irrigation rig consisting of three parallel pipelines, comparing three disinfection treatments: UV-LED, chlorine, and no treatment. The results indicate that the discharges of UV-LED and chlorine-treated lines were similar. However, analyzing the internal fouling material of the opened drippers revealed the significant advantage of the UV-LED treatment, when both OCT (optical coherence tomography) image processing and EPS (extracellular polymeric substance) secretion within the clogging substances indicated significant biofilm inhibition by UV-LED irradiation as compared to the other alternatives. The present study is a proof-of-concept of a new approach of using UV-LED irradiation for minimizing biofouling formation in emitters fed with treated wastewater. UV-LED technology has great potential to become an attractive and feasible alternative for replacing chlorine as a water disinfection technology, specifically for agriculture use.