Clogging rate of pressure compensating emitters in irrigation with rainbow trout fish farm effluent

Abstract

One of the most fertilizing effluents for irrigation are those from fish farms. In drip irrigation systems, emitter clogging is the biggest problem of the effluent application. Therefore, the aim of this paper was to assess the clogging rate of a drip irrigation system using the effluent of a rainbow trout farm. A control treatment with the input fish farm freshwater and two more using fish farm effluent, with and without irrigation lateral drainage, were tested. Pressure compensating emitters Microflapper with nominal discharges of 4 and 8 L/h (M4, M8) and Netafim with discharges of 4, 8, and 12 L/h (N4, N8, and N12) were used. For each treatment, 42 irrigations events were carried out with a total of 336 h over a 4-month period. Each irrigation event lasted 8 h every 3 days. Clogging rate, Christiansen uniformity (CU) and emission uniformity (EU) coefficients were utilized for assessing the hydraulic performance of emitters. There was no emitter completely clogged during the experiment. However, as the clogging rate gradually increased, lateral discharges during the irrigation season decreased to a maximum of 57% of the initial value in some laterals. Evolution of the clogging rate was unstable, especially in the control treatment. N4 emitter show the best performance regardless of the quality of irrigation water. The clogging rates of M4 and N8 emitters were significantly (p < 0.05) higher when effluent was used. The N12 and M8 emitters had the highest sensitivity to clogging, without differences between treatments. Results show the dependence of clogging rate on emitter type and its discharge. The CU as well as EU for all emitters and treatments were higher than the allowable minimum. Lateral drainage had the greatest impact on the N12 and M8 emitters, which had the highest discharge. Moreover, some relationships between CU and clogging rate were obtained. It is generally possible to use the rainbow trout effluent in a drip irrigation system with pressure compensating emitters