THE EFFECT OF CHLORINE ON EMITTER CLOGGING INDUCED BY ALGAE AND PROTOZOA AND THE PERFORMANCE OF DRIP IRRIGATION

Abstract

Limited information exists on the use of chlorine in drip irrigation systems (DIS) to prevent or reduce emitterclogging induced by biological clogging agents (BCAs), such as algae and protozoa (AP), and to enhance the performanceof drip irrigation. The objectives of this study were to quantify the impact of AP-induced changes on discharge rate anduniformity from different types of emitters under two management schemes of without (S1) and with (S2) chlorine injectioninto the irrigation water at the Tohaku irrigation project, Japan. In a field experiment, six types of emitters on each of sixlaterals in two similar subunits of DIS, for S1 and S2, were assessed for AP-induced emitter discharge performance. Theassessment also included different orifice area (OA), with or without a pressure compensation (PC) system, and with orwithout built-in filtration area (FA) in the emitters. The discharge from emitters increased with chlorine injection into theirrigation water and with increasing OA and FA, but decreased with increasing algae counts. The values for the meandischarge ratio variation (Dra) indicated that the cumulative impact of manufacturing variations (Vm) and that induced byAP and chlorine on emitter discharge was classified as low during the irrigation season when chlorine was injected into theirrigation water (S2). The values for the statistical uniformity coefficient (Uc) were higher than 93% for both S1 and S2,indicating that the uniformity of emitter discharge along a lateral was high. Due to the reduction in emitter discharge inducedby AP, the clogging was uniform along a lateral. The values for field performance variation (Vf) along a lateral were in theorder S1 > S2 for each emitter. The values were classified low to medium, particularly in PC emitters.