Environmental assessment of underdrain designs for a sand media filter

Increasing energy demand is the main problem linked with the adoption of more efficient irrigation techniques, particularly microirrigation. In microirrigation systems, important pressure losses and therefore energy consumption, occur at the filters, which are a key component in preventing emitter clogging. Previous studies have shown that the main pressure drop across sand media filters, which are widely used in microirrigation, occurs in the underdrain elements. To minimise this problem, new underdrains should be designed but an issue is how their environmental impact can be reduced. Two alternative design strategies were found: firstly, keeping the original filter dimensions and reducing energy consumption during operation by 30%; and, secondly, reducing filter size and reducing construction material by 25% but keeping the original pressure losses. A life cycle assessment transforming environmental effects into monetary values was carried out comparing a commercial sand filter with the two filters designed following the two aforementioned strategies. Results show that both alternatives reduce the environmental impact of the sand commercial filter. Reduction of filter size is the optimum strategy if filtered volumes are below 63,000 m3 along the filter life, while reduction of energy consumption was the best alternative for higher filtered volumes. This work shows the usefulness of life cycle assessment for assessing design strategies that could improve the sustainability of microirrigation equipment.