Development of a membrane disinfection system for closed hydroponics in a greenhouse

A new disinfection membrane system for commercial hydroponics was designed which is capable of minimizing the discharged nutrient solution during the membrane cleaning procedure. Based on a preliminary experiment using Pseudomonas solanasearum as the reference microorganism, a microfiltration (MF) membrane with 0.3 mu m pores was selected to provide complete removal of microorganisms from the nutrient solution which was recycled. The system had a 57.6 m(3)/day filtration capacity and operated in a medium-scale greenhouse for an endurance test. Continuous filtration with automatic reverse flow which aimed at membrane cleaning was applied for more than 2 months. Under 0.2% of the total amount of permeate was discharged outside the greenhouse after the membrane cleaning procedure. In order to establish a completely closed hydroponic system in the near future, further investigations on the possibilities of this membrane disinfection system are needed. (C) 2000 Silsoe Research Institute.