Partial clogging evaluation of emitters under drip irrigation using aquaculture effluent

Water scarcity is a serious problem for agricultural production in arid and semi-arid. Furthermore, development of new water resources in these areas is too expensive. Now, treated wastewater (TWW) is commonly used as an alternative source for irrigating to alleviate freshwater use. One of the most nutrient-rich wastewaters for plants is aquaculture effluent which contains appropriate nutrients such as nitrogen and phosphorus. The aquaculture effluent which is often drained to rivers causes both an environmental challenge and an agricultural opportunity. The integration of aquaculture with agricultural systems has been identified as a way to increase food production, protect the environment and enhance food security. On the other hand, emitter clogging is the main problem with use of wastewaters in drip irrigation systems which reduces the emitter discharge, emission uniformity, irrigation efficiency and increases maintenance costs. Time and location of partial clogging of emitters, under wastewater using conditions, is an important issue. Thus, in the present study, the mentioned problem was investigated particularly about aquaculture effluents.
For this purpose, three separate drip irrigation systems were established. Netafim and Micro-flopper emitters were used in each treatment, with both 4 and 8 l/h discharges. During a season, 42 irrigation events were done using fresh water (as a control), and aquaculture effluent (with and without ending drainage of pipes). Emitter discharges was measured for each emitter type by volumetric method, through all irrigation events for the all study treatments. Then, clogging percentages were calculated. To perform statistical analysis of data, all the laterals were divided into three hypothetical of elementary, middle and ending one-third parts. Each of these parts included four loops of lateral pipe. The emitter location (on the lateral pipe) factor, along with others (time, type of water, emitter type and emitter discharge) considered in the analysis. Emitter's clogging percentage data were analyzed in the form of combined analysis, based on randomized complete block design with the mentioned factors. MSTAT-C and SAS software was used for statistical analyses.
The results of present study showed that the clogging of Micro flopper 4 l/h emitters has increased sharply over the time in both effluent treatments (with and without ending drainage of pipes), and it has even passed the critical point at the fourth time interval in this study. Therefore, use of these emitters is unsuitable for irrigation with aquaculture effluent. Also, , clogging in Micro flopper 8 l/h emitters has increased passing time in all treatments, and it has even passed the critical point at the fourth time interval; But, in the third and fourth time periods, the role of ending drainage of pipes was obvious and positive. Therefore, using these emitters for irrigation with aquaculture effluent will be more appropriate compared with Micro flopper 4 l/h emitters, if the proper management is applied, such as ending drainage or full washing of lateral pipes. Clogging percentages of Netafim 4 l/h emitters have not any significant differences between three treatments in all of the time intervals. It means that these emitters had the least dependent on water quality and irrigation management compared to the other experienced emitters in this study. Also, the clogging percentages for these emitters never reached the critical levels during the irrigation season, both in the case of fresh water and wastewater usage. Therefore, use of these emitters is very suitable for irrigation with aquaculture effluent. The results showed that for all studied emitters, using aquaculture effluent caused emitter clogging mostly in the ending one-third of lateral pipes. This problem was more acute in the emitters with 8 liters per hour discharges. Therefore, using these emitters with application of aquaculture effluent, ending drainage of lateral pipes or full washing of them is more necessary.
The results of present study showed that the effect of elapsing time on the emitter clogging was in acceptable range in Netafim emitters but not in Micro flopper emitters, when aquaculture effluent was used in drip irrigation. And in both effluent treatments (with and without ending drainage of pipes), Netafim emitter's performance was significantly (P