DRIP IRRIGATION WITH WASTE STABILIZATION POND EFFLUENTS - SOLVING THEPROBLEM OF EMITTER FOULING

A pilot-scale irrigation scheme was set up in South-est Portugal to in vestigate the causes of emitter clogging which has been observed when waste stabilisation pond effluents are used for drip irrigation of cro ps. During field trials over a period of two growing seasons, the oper ating characteristics of five emitter designs were investigated. Susce ptibility of the designs to clogging was compared and the nature of cl ogging particles was analysed. Those emitters that operated most succe ssfully utilised a long water-path labyrinth to reduce flow to the req uired level. The operating characteristics of the most effective emitt er design are presented in detail. Clogging was shown to result from t he deposition and entrapment of sand particles within the emitter laby rinth. Organic material, including pond algae, played a secondary role in the clogging process, Emitter design, rather than water quality, w as shown to be the most important factor determining the degree of clo gging. It was concluded that pond microalgae alone do not constitute a major hazard to the operation of drip irrigation equipment and that w aste stabilisation pond effluents may be safely used for drip irrigati on if safeguards are adopted to prevent the contamination of laterals by sand and soil particles, A number of recommendations are made to pr event emitter clogging in future reuse schemes.