H J; A L; A H
Abstract
Reuse of treated municipal wastewater in agriculture and artificial recharge of aquifers in arid and semi-arid regions are of great interest to water resources specialists. In the use of treated wastewater for artificial recharge operations, the fate of substances added to the soil by wastewater transmission ...
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Reuse of treated municipal wastewater in agriculture and artificial recharge of aquifers in arid and semi-arid regions are of great interest to water resources specialists. In the use of treated wastewater for artificial recharge operations, the fate of substances added to the soil by wastewater transmission of pollutants to the aquifer depth and movement is very important, because they may cause contamination of soil and groundwater resources. In this study, an L-shaped cylindrical column, made of PVC with a diameter of 30 cm was used to simulate the vertical movement of water and its movement in the shallow groundwater layer during artificial recharge operations. Horizontal sections along the vertical length were 300 cm and 250 cm. The column was filled with a sandy loam soil and the treated wastewater of Mahdasht treatment plant located in Alborz Province was used for artificial recharge operations. During the test period, the effect of management strategy of permanent water logging for 40 days and a dry period for the removal of wastewater pollutants in the soil column were examined. Values of BOD5, COD, EC, coliform, fecal coliform, phosphorus and nitrate in water samples collected from the inlet and the path length were measured at one meter intervals. The results indicated the high efficiency of removing pollutants in the soil column, while the nitrate removal efficiency and EC changes were low. The values of BOD5, COD, EC, coliform, fecal coliform, phosphorus and nitrate in the best of cases were 96.4%, 91.8%, 15.4%, 99.3%, 99.4%, 92.4% and 17.2%, respectively. A comparison with National Guides of Iranian Environmental Protection Agency shows that the outflow of artificial recharge system can be used for irrigation of agricultural crops. However, it is to be noted that, generally, use of wastewater for irrigation of food crops is not recommended.
M Z; M GH; A H
Abstract
Recently, use of synthetic materials has increased in irrigation and drainage projects due to their environmental advantages. Also, use of geotextile and PLM has been considered in drainage projects instead of granular envelopes. This study was conducted to evaluate the efficiency of geocomposite envelope-drain ...
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Recently, use of synthetic materials has increased in irrigation and drainage projects due to their environmental advantages. Also, use of geotextile and PLM has been considered in drainage projects instead of granular envelopes. This study was conducted to evaluate the efficiency of geocomposite envelope-drain to reduce water-table levels. To simulate natural conditions of a drained land in the laboratory, a soil and sand tank was used that simulated part of a drainage trench in addition to adjusting the height of water table. Three envelope-drains with different geotextile envelope and drainage pipes with granular and PLM (PP450 type) envelopes were tested. In this study, the perimeter of drainage pipe and envelope-drains was equal. The results of this study showed that the performance of envelope-drain in draining excess soil water and lowering water table was similar to the drainage pipe with granular envelope. Under hydraulic head of 110 cm, in the center of the drain, drop in the water surface profile of geocomposite envelope-drain was 14.3% lower than the drainage pipe with granular envelope. By increasing the horizontal distance to the drains, drop in the water table profile of geocomposite envelope-drain was 9.8% lower than the drainage pipe with granular envelope.
A H; A E; H S
Abstract
In on-farm development projects, implementation of subsurface drainagesystem is one of the most important issues. Considering the high costs ofpreparing mineral envelope for subsurface drain pipes, continued executionof such projects, especially in Khuzestan province, has faced somedifficulties. To overcome ...
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In on-farm development projects, implementation of subsurface drainagesystem is one of the most important issues. Considering the high costs ofpreparing mineral envelope for subsurface drain pipes, continued executionof such projects, especially in Khuzestan province, has faced somedifficulties. To overcome such a problem, use of synthetic envelopes or,where soil characteristics allow, subsurface drainage without using envelopemay also be an option. Thus, in this research, in an experimental field of 20ha under wheat in Shadegan region (Khuzestan province), the performance ofsubsurface drainage without using envelope was compared with theconventional drainage by mineral envelope. Each experimental unit had fivesubsurface drain pipes (laterals) spaced at 50 m and installed at depth of1.7m, with a length of 220 m. To study water table condition, somepiezometers were installed perpendicular to the middle laterals of each unit.Also, the rates of drains discharge and drainage water quality of the middlelaterals in each unit were measured in manholes constructed on them. Themaximum salinity of drainage water from drains with mineral envelope(replicates 1 and 2) and drains without envelope were 36.9, 52.1, and 47dS/m, respectively, and the minimum salinities were 25.7, 23.6 and 12.6dS/m. The maximum drain discharge in the first replication of mineralenvelope was 0.59 lit/sec, and for the second one was 0.28 lit/sec and in thedrains with no envelope was 0.23 lit/sec. Investigation of Salt Exit Index(SEI) of soil showed that salt leaching continued during the wheat growingseason. Results of drains discharge showed the acceptable operation of drainswithout envelope and proper performance of drains with mineral envelopeduring the growing season. No sediment discharge was observed in anytreatment.