Assessing the net benefits of using wastewater treated with a membrane bioreactor for irrigating vegetables in Crete

The island of Crete (Greece) suffers from an increasingly severe water shortages, coupled with declining groundwater supplies. We compared the costs and benefits of alternative strategies for treating wastewater for use in irrigating vegetables: (1) using a membrane bioreactor (MBR), (2) connecting new residences to centralized wastewater-treatment plants, (3) building new wastewater-treatment plants, and (4) using natural wastewater-treatment systems in rural areas. We also examined the impact of increasing water scarcity on the net benefits of treating wastewater with an MBR. As expected, the value of treated wastewater increases with increasing water scarcity. The net benefit of treating wastewater with an MBR and using the reclaimed water to irrigate vegetables ranges from about 0.02 [euro]/m3 to 2 [euro]/m3 as water scarcity increases. Our results should be helpful in guiding analysts in Greece and other arid countries wishing to evaluate the financial viability of alternative methods of treating wastewater for use in agriculture.