Assessing Emitter Clogging in Drip Irrigation Systems with Sewage Effluent

Drip irrigation can be an efficient and safe method of applying water from sewage effluent; however, the 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 systems and to quantify the impact of emitter clogging on the system performance. In the experiments, six types of emitters with or without a pressure-compensation device and two types of water sources (secondary sewage effluent and groundwater) were assessed by measuring the emitter discharge rate of the systems at approximately ten-day intervals. The total duration of irrigation was 83 days, with a daily application of 12 h. 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 systems applying sewage effluent were clogged much more severely, producing a 26% lower averaged 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 emitters manufacturing coefficient of variability (Mfg CV). The distribution of the 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 an emitter without a pressure-compensation device, while randomly distributed clogged emitters were found for a pressure-compensating emitter. A more random distribution of the clogged emitters was found for the sewage application. Clogging of emitters could deteriorate system performance seriously. The values of the uniformity coefficient (CU) and the statistical uniformity coefficient (Us) decreased linearly with the mean clogging degree of the emitters. More frequent chlorination should be applied for drip irrigation systems with the sewage effluent than the systems with the groundwater to maintain a high system performance