عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Water scarcity is a serious problem for agricultural production in arid and semi-arid regions of the world. Furthermore, development of new water resources in these areas is too expensive. Now, treated wastewater (TWW) is commonly used as an alternative irrigation water source to alleviate freshwater. One of the most nutrient-rich wastewaters for the trees and plants is aquaculture effluent which contains appropriate nutrients such as nitrogen and phosphorus. Aquaculture effluents are often drained to rivers presenting both an environmental challenge and an agricultural opportunity. The integration of aquaculture with agricultural systems as a way to increase food production, protect the environment and enhance food security has been identified. 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 of irrigation systems. Time and location of partial clogging of emitters, under wastewater using conditions, is an important problem. 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 to 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 other factors (time, type of water, emitter type and emitter discharge) entered in the analysis. Emitter 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 softwares were used to doing 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 fourth time interval in this study. Therefore, the use of these emitters is not suitable for irrigation with aquaculture effluent. Also, In the case of Micro flopper 8 l/h emitters, can be said that the clogging of these emitters has increased over the time in all treatments, and it has even passed the critical point at fourth time interval. But, in the third and fourth time periods, the role of ending drainage of pipes was obvious and positive. Therefore, using of these emitters for irrigation with aquaculture effluent would 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 none of the time intervals. It means that these emitters have had the least dependent on water quality and irrigation management compared to the other emitters which used in this study. Also, the clogging percentages for these emitters never reached critical levels during the irrigation season, both in the case of fresh water and wastewater usage. Therefore, the use of these emitters is very suitable for irrigation with aquaculture effluent. In addition, results showed that for all studied emitters, the use of aquaculture effluent, caused that the largest emitter clogging has occur in the ending one-third of lateral pipes. This problem is more acute in the emitters with 8 liters per hour discharges. On the other hand, efficiency and positive impact of ending drainage of lateral pipes has been higher for these emitters rather than others. Therefore, to using these emitters for drip irrigation with aquaculture effluent, the ending drainage of lateral pipes or full washing of them seems to be more necessary.
Generally, 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 acceptable for Micro flopper emitters, when aquaculture effluent was used to drip irrigation. And in both effluent treatments (with and without ending drainage of pipes), Netafim emitter performance was significantly (P