IMPACT OF FLUSHING AND FILTRATION SYSTEM ON PERFORMANCE OF MICRO IRRIGATION SYSTEMS - Management, Performance, and Applications of Micro Irrigation Systems - page 76

6.2.2 EXPERIMENTALSET-UP
Drip irrigation system was installed with in-line lateral (J-TurboLine) with emitter
spacing at 40 cm. It was laid on the ground for surface drip and was buried at a 15 cm
depth from ground surface for subsurface drip (SDI). System included: 1. Sand media
filter (F1) with flow rate of 30 m 3 h -1 , 50 mm size, silica sand 1.0 to 2.0 mm, thickness
80 cm, and with backflush mechanism; 2. Disk filter (F2) with flow rate of 30 m 3 h -1,
20 mm size, 130 microns, disc surface of 1.198 cm 2 , screen surface of 815 cm 2 (AZUD
helix system, model 2NR). WW was allowed to pass through filters F1 and F2 alone
as well as in combination of both the filters (F3). Main line (50 mm diameter, PVC
pipe) was connected to submains (35 mm diameter, PVC pipe) for each of the plots
through a gate valve.
6.2.3 OPERATIONALPROCEDURE
WW collected from the drain was stored in a sedimentation tank for a period of 24 h
so that all the suspended foreign particles got settled. Then, the settled WW was fed
to the filtration system and then allowed to pass through emitters. The pump was
turned on, and emitters were allowed to drip for approximately 2 min so that lateral
and pipeline were free from air. The water collection period was set at 5 min. Quantity
of flow of water from drip emitter was collected in containers at 98.06 kPa pressure
and was repeated for three times. The flow rate was estimated by dividing total vol-
ume collected by the time of collection. The measurement was taken from randomly
located sampling emitters for performance evaluation. Discharge from SDI laterals
were measured by excavating the soil around the buried drip laterals so that an emit-
ter is visible with sufficient space below it for placement of the container to collect
discharged water from it, as suggested by Magwenzi [19]. Performance of system was
evaluated at normal operating pressure to discharge sufficient water for infiltration and
to avoid ponding near the emitter. As per manufactures' recommendation, operating
pressure of 98.06 kPa was considered adequate. To achieve accurate pressure, emitter
level measurement was done at the lateral with digital pressure gage having the least
count of 0.01 kPa.
Flushing was carried out with the system main, sub main and then proceeds to the
lateral pipes. It was continued at 2.0 kg cm -2 pressure until clean water runs from the
fl ushed line for at least two minutes. Flushing operation was done at the end of the
crop season. Discharge from emitters under different treatments was measured before
and after fl ushing operation (Fig. 1), and emitter performance evaluation parameters
were estimated.