Irrigation
H. Shirvani Ichi; M. Ghobadinia; negar nourmahnad; Seyed Hassan Tabatabaei
Abstract
Introduction: Nowadays, the use of effluent in irrigation and especially drip irrigation systems has increased. The findings uncovered that drip irrigation is assumed as the only method which is capable of overcoming specific problems caused by wastewater usage. In this study, the efficiency of sand ...
Read More
Introduction: Nowadays, the use of effluent in irrigation and especially drip irrigation systems has increased. The findings uncovered that drip irrigation is assumed as the only method which is capable of overcoming specific problems caused by wastewater usage. In this study, the efficiency of sand and geotextile filters with zeolite on wastewater properties and their application in the filtration of the drip irrigation system was investigated.
Materials and Methods: This study was conducted to investigate the changes in important chemical properties in the municipal wastewater of a university after passing through sand filters, geotextiles, and zeolites in the drip irrigation filtration system. A factorial experiment was performed in a completely randomized design with three replications. Treatments included sand filter (control-CTRL treatment), geotextile filter (G), sand filter with zeolite (SZ), and geotextile filter with zeolite (GZ). The sand used in this study was the usual silica sand which was in three sizes of 3-5, 5-8, and 8-12 mm. In order to remove any contamination and soil particles and increase the accuracy of the measurement of suspended solids in the effluent, the sands were washed several times with water before usage. The geotextiles used in this study had three types with weights of 300, 500, and 1000 grams per cubic meter. The zeolite used in this study was clinoptilolite modified with hydrochloric acid. The wastewater used in this study was obtained from the effluent of Shahrekord University. System flow rate, Pressure, nitrate, suspended solids, sodium, calcium, magnesium, electrical conductivity, effluent pH were measured before and after entering the filters at different hours. Statistical analysis was done by SAS software and the Duncan test was used to compare the means of the data.
Results and Discussion: The results showed that the sand-zeolite treatment had a good performance in terms of pressure and the geotextile-zeolite treatment was able to provide pressure for a short time. The amount of nitrate in the wastewater of the sand filter was not significantly different from the amount of inlet, but in other filters was significantly reduced. The amount of nitrate input of all treatments was 26 mg/l.The average output nitrate in the sand filter was about 25 and in the other filters was less than 20 mg/l. The average amount of suspended solids in the effluent was about 110 mg/l, while the average amount of suspended solids in the wastewater was reduced to less than 72 mg/l. The sand and sand-zeolite treatments increased the total amount of calcium and magnesium in the wastewater more than geotextile and geotextile-zeolite treatments, respectively. The average Ca + Mg of effluent in the total operating hours of the system was higher than the average input in all filters. The percentage of EC changes in total hours increased about 4% in sand and geotextile treatments and 14% in geotextile- zeolite and sand -zeolite filters. The highest percentage of pH changes was related to sand-zeolite filter, which reduced the pH of incoming wastewater by about 4.5%. After that, geotextile- zeolite filter reduced the pH of the incoming wastewater by 4%. The average pH of the effluent of all filters is lower than the average of their inlet.
Conclusion: Sand and geotextile filters alone cause pressure drop and dropper clogging. However, the sand-zeolite treatment has performed well in this regard. The geotextile-zeolite treatment has the potential to be used in terms of supplying the necessary pressure for a short period by applying special treatment measures before this filter. These conclusions are only in terms of pressure drop due to the ability of filters in practical use and do not refer to their ability to filter the parameters and provide the desired flow. All treatments, especially zeolite treatments, significantly reduced nitrate, and these filters can be used to reduce effluent nitrate in cases where the amount of nitrate is more than allowed. However, since the sand filter had no effect on nitrate reduction, the effluent must be treated for nitrate before using sand filters. The geotextile filter had a higher percentage of suspended solids removal at all hours. The addition of zeolites to both geotextile and sand base filters reduced their ability to treat suspended solids. Therefore, geotextile filters can be a good alternative to ordinary sand filters in terms of this parameter. All treatments increased Ca + Mg relative to the input. The sand- zeolite treatment reduced the pH of the incoming wastewater more than other treatments (about 4.5%). Also, desalination of salts from zeolite treatments increased the EC of effluent in the sand-zeolite and Geotextile- zeolite treatments. According to this study, the use of sand-zeolite in terms of reducing nitrate and suspended solid, increasing calcium and magnesium, and reducing pH and no pressure drop is recommended.
shahrzad gharcheh; M. Delbari; F. Ganji
Abstract
Introduction: An appropriate water resources management and planning is necessary due to the scarcity of water resources and rapidly growing world population. In this regard, selecting appropriate methods for irrigation is one of the most important issues. Drip irrigation is a recent advanced irrigation ...
Read More
Introduction: An appropriate water resources management and planning is necessary due to the scarcity of water resources and rapidly growing world population. In this regard, selecting appropriate methods for irrigation is one of the most important issues. Drip irrigation is a recent advanced irrigation method in which fertilizers can be efficiently applied along with irrigation water. Drip fertigation, however, can potentially cause clogging of emitters. Various factors such as clogging increase manufactures’ coefficient of variation and water temperature and pressure changes could alter emitter discharge and water distribution uniformity. The aim of this study is to evaluate the effect of fertigation on clogging of emitters and the performance of drip irrigation systems.
Materials and Methods: This study was performed as a laboratory experiment at the University of Zabol. The experiment was done in the form of factorial in a completely randomized design with three replications in the hydraulics laboratory, the University of Zabol. The first factor was fertilizer type including: F0 (control), F1 (ammonium nitrate) and F2 (urea) and the second factor was the emitter types including one-nozzle on line (A), six-nozzles in line (B) and eight-nozzles on line (C). The tap water was used for irrigation. The system included 9 laterals, 3 m each with 18 emitters on each lateral. Fertilizer solution with known concentrations of 0.08 grams per liter was entered into the system from a plastic tank. Fertilizer tank was covered to avoid water evaporation even in a small amount. The experiment lasted for 60 days with 12 operating hours per day. The emitter discharge was measured every three days at the end of day. In order to evaluate the degree of emitter clogging, the percentages of discharge reduction (Qt), Christiansen’s coefficient of uniformity (CU), distribution uniformity (DU) and discharge coefficient of variations (Vm) were calculated as follows:
(1)
(2)
(3)
(4)
where qa, qm and qt are the average, primary and secondary emitter discharges (L/hrs), respectively, qi is the individual emitter discharge (L/hrs), Sm is the standard deviation of discharge (L/hrs) and n is the number of measurements.
Results and Discussion: The results indicated that both fertilizer and emitter type have significant effect on reduction of emitter discharge and distribution uniformity as well as on increase of emitter coefficient of variation. The Duncan test for comparing means showed that the A type emitters had the highest clogging while the B type emitters had the lowest clogging. The percentages of discharge reduction for emitters A, B and C were about 18, 24 and 22, respectively, for treatment F0 (control); 24, 39 and 30 for treatment F1; and 34, 44 and 32 for treatment F2. The results indicated that the emitter clogging increases with altering fertilizer from F0 to F2. F2 (urea fertilizer) had the worse effect on emitter clogging than F1 (ammonium nitrate fertilizer) which could be due to more nitrate produced by urea fertilizer. Also, the results showed that the emitter clogging and discharge coefficient of variation are increased by increasing the elapsed time. Urea and ammonium nitrate fertilizers are hydrolyzed in water and partly converted to nitrate, which is consumed by algae and other microorganisms causing slime accumulation. Bacterial slimes can be a direct cause of clogging for emitters.
Conclusion: According to the results, both fertilizer and emitter types may significantly change the hydraulic properties of emitters. The smallest clogging belonged to emitter of type A when fertilizer F0 was applied as it results in discharge reduction of 18.44%. The largest clogging belonged to emitter of type B when fertilizer F2 was applied (discharge reduction was about 44%). In general, it could be said that fertigation may influence emitter discharge depending on fertilizer treatments (e.g. fertilizer type and concentration), water properties and emitter type. The clogging problems must be attended more specifically as it may reduce farmers’ willingness for drip irrigation implementation and makes them do surface irrigation which may result in more water losses. This study showed that the quality of water used in drip fertigation increases the clogging made by fertilizer application. So, the quality of irrigation water should be investigated every few days. The use of nitrogen fertilizer may cause biological clogging of emitters, so when such fertilizer are used, the type of emitter should be considered.
