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Introduction
Emitter clogging can be reduced with an appropriate design and operation of the filters, which are mandatory in any micro-irrigation system. Filtration is especially important when biological effluents are used due to their high clogging risk. The objective of this work was to assess the performance of screen and disc filters, which are widely used in micro-irrigation systems, under different pressures and filtration levels when filtering a reclaimed effluent.
EFFECT OF FILTRATION LEVEL AND PRESSURE ON DISC AND SCREEN FILTER PERFORMANCE IN MICRO IRRIGATION SYSTEMS USING
EFFLUENTS
Conclusions Increasing the working pressure of disc and screen filters from 300 to 400 kPa allowed higher reductions on turbidity. With this pressure increasing, the 130 µm disc filter was able to filter more volume to obtain the same head loss. Filtration levels of 50/55 µm filtered 97 % less volume than 120/130 µm disc and screen filter. On the other hand, turbidity reduction was 5.5 % with 120/130 µm and 10.9 % with 50/55 µm. In order to obtain better turbidity removals 55/50 µm filtration levels and 400 kPa of pressure have to be applied. However, as working at 55/50 µm yields shorter filtration cycles, it would be more practical to work at 120/130 µm filtration levels at 400 kPa for both screen and disc filters.
Figure 2. Disc filter cartridge before and after the backwashing process
Materials and methods
An experimental platform that was placed at the wastewater treatment plant of Celrà (Girona, Spain) was used in the experiments (2200 h) (Fig. 1). A screen filter and a disc filtration system (Fig. 2) were studied at 3 working pressures: 200, 300 and 400 kPa. The filtration levels were 55 and 130 µm for the disc filter, and 50 and 120 µm for the screen one. Filtered flow rate and volume, inlet and outlet pressure, inlet pH, temperature, dissolved oxygen and turbidity and outlet dissolved oxygen and turbidity data were collected every minute with a supervisory control and data acquisition system.
Results and discussion
Screen and disc filters with a filtration level of 50 and 55 µm filtered 97.7 and 96.7 %, respectively, less effluent volume to reach the same pressure loss increasing than the same filters with a filtration level of 120 and 130 µm. Screen filter had the same head loss than disc filter but only filtering the 24 and 33% of the volume filtered by the disc filter, at 120/130 and 50/55 µm, respectively (Fig. 3).
Figure 4. Turbidity reductions obtained with disc and screen filters at 50/55 µm and 120/130 µm filtration levels and 200, 300 and 400
kPa of working pressures.
Figure 3. Volume of effluent needed to increase 10 kPa the filter head loss for a) 120/130 µm filtration level, and b) 50/55 µm filtration
level.
Figure 1. General view of the filtration bank
M. Duran-Ros a, J. Puig-Bargués a, G. Arbat a, J. Barragán b , F. Ramírez de Cartagena a
a Department of Chemical and Agricultural Engineering and Technology - University of Girona. C. de Maria Aurèlia Capmany, 61. 17071 Girona, Spain b Department of Agricultural and Forest Engineering - University of Lleida. Av. Rovira Roure, 191. 25198 Lleida, Spain
The best turbidity removals, which are related to a reduction of the physical clogging risk, were achieved in average for both filtration systems at 50/55 µm (10.9%) than in 120/130 µm (5.5%). Working pressure for both filters is suggested to be 400 kPa as it allowed reducing turbidity (Fig 4).
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