Predicting emitter sensitivity to clogging: a focus on thebiological component

摘要

A standard test for prediction of emitter sensitivity to clogging has not been developed yet. One conventional test procedure developed by the IRSTEA, France exists but it predicts emitter sensitivity to physical clogging only. This study was carriedout to contribute towards developing a modified clogging test that would consider both physical and biological processes in emitters clogging. In this regard, a microirrigation test rig was constructed containing three types of pressure compensated emitters arranged in four replications inside an environmental chamber. Two tests were conducted, one according to the IRSTEA schedule; and the other according to a modified procedure developed to introduce biological load. The modified test included recycledwater and was formed on the principle that biofilms should be allowed to develop and attain maturity during the test span. The results suggest that clogging due to biofilm growth is always a quicker process than clogging by physical particles alone. Emitters were quick to show signs of clogging in the modified test, while all the emitters managed to pass the IRSTEA test. In case of biofouling, particles were found to be trapped into the slimy bacterial biofilms at the emitter's section of entry. In physical clogging, however, particles were found to be passing through the emitter's section of entry, travelling along the labyrinths and settling at the end basin. In almost all the cases, the IRSTEA recommended filtration requirements were found to be overestimating the appropriate filter sizes.