Comparison of Clogging in Drip Emitters During Application of Sewage Effluent and Groundwater

Abstract

Drip irrigation can be an efficient and safe method of applying water from sewage effluent; however, clogging of emitters is one of the most serious problems associated with drip irrigation systems using sewage effluent. The objectives of this study were to investigate the temporal variations of the emitter discharge rate and the distribution of clogged emitters in the system and to quantify the impact of emitter clogging on system performance. In the experiments, six types of emitters with or without a pressure-compensation device and two types of water sources (stored secondary sewage effluent and groundwater) were assessed by measuring the emitter discharge rate of the system at approximately ten-day intervals. The total duration of irrigation was 83 days, with a daily application of 12 h. The water source had a very significant influence on the level of drip emitter clogging. Of all the emitters tested over the entire period of the experiments, the emitters applying sewage effluent were clogged much more severely, producing a 26% lower average mean discharge rate than those applying groundwater. Different types of emitters had different susceptibilities to clogging, but the clogging sensitivity was inversely proportional to the pathway area in the emitter and the emitter's manufacturing coefficient of variability (Mfg CV). The distribution of clogged emitters along the lateral was controlled by the emitter type and the water source. For groundwater application, the clogged emitters tended to be generally located at the terminals of the laterals for emitters without a pressure-compensation device, while randomly distributed clogged emitters were found for pressure-compensating emitters. A more random distribution of clogged emitters was found for the sewage application. Clogging of emitters could seriously degrade system performance. The values of the uniformity coefficient (CU) and the statistical uniformity coefficient (Us) decreased linearly with the mean clogging degree of the emitters. To maintain a high system performance, more frequent chemical treatments should be applied to drip irrigation systems applying the sewage effluent than to systems applying the groundwater.