Effect of different filter media on emitter clogging using reclaimed effluents

Abstract

Pressurized media filters are the most effective means of preventing emitter clogging when reclaimed effluents are used in drip irrigation systems. In these filters, water pollutants are retained in a granular bed, which needs to be replaced once its life span has been reached. Silica sand is the most common material used as a filtration bed, but the use of alternative materials which may improve filtration efficiency and reduce environmental impact, should be explored. Thus, the aim of this study was to compare the effect of two different granular media (silica sand and recycled glass) used in three filters with different underdrain designs (collector arms, inserted domes, and porous media) on emitter clogging. Experiments were carried out by filtering a reclaimed effluent for the duration of 1000 h for each filter and material. Four irrigation laterals 90 m in length with a 2.3 l/h pressure-compensating emitter placed every 0.40 m along the dripline were placed after each filter. Filter performances were continuously assessed while emitter discharges at 8 selected locations across the laterals were measured at the beginning, after 500 h, and at the end of the experiment. Filtration cycles lasted longer with recycled glass, but turbidity removal was affected by the combination of bed material and underdrain. Only after 1000 h of irrigation, was the discharge significantly lower for those emitters protected with porous underdrain using glass compared with sand. Emitter discharge was considerably reduced at the end of the lateral due to a higher number of completely clogged emitters at this location, but there were not significant differences between granular materials and filter designs. Overall, the results show that using recycled glass does not significantly increase emitter clogging compared with silica sand