微細藻類の濾過による濃縮・脱水

抄録

Microalgae can produce various materials for food, pharmaceutical, chemical feedstock and fuel by photosynthesis using carbon dioxide and nutrient–containing water. For the construction of material production system, efficient dewatering of microalgae culture is required because suspended solid (SS) concentration of microalgae culture is low (0.02 ～ 0.05 wt%). Filtration is a promising dewatering method because it consumes relatively low energy and is easy to scale up. In this article, dewatering of microalgae culture by filtration is reviewed. Microalgae cultures are generally dewatered by microfiltration and/or ultrafiltration using polyvinylidene or polytetrafluoroethylene membrane. Although almost complete SS rejection is achieved by the membranes, permeate flux and final SS concentration achieved by filtration are affected by filtration process and operation condition. In the most studies on dewatering of microalgae culture, concentration factor of 10 ～ 100 and permeate flux of 10 ～ 100 L/m²/h by cross–flow filtration are reported. For the further dewatering, filter press, belt press and rotary vacuum filter can be used, and over 15 wt% in SS concentration is achieved. We examined submerged siphon–driven membrane concentration system for a primary concentration and single filter cloth type dehydrator for a secondary concentration as a possible energy–saving process. In this dewatering process, the relatively high permeate flux and high SS concentration were achieved.