Carrageenan as a Matrix for Immobilizing Microalgal Cells for Wastewater Nutrients Removal

Microalgae are a group of single celled photoautotrophs and have been suggested as an alternative biological system in treating wastewater to the conventional activated sludge process.1 Soluble contaminants in domestic or municipal wastewater comprise principally organics which are generally referred to as biochemical oxygen demand (BOD) and inorganic nutrients. Domestic wastewater contains basically all the essential elements for algal growth. Growth of the microalgal biomass assimilates inorganic nutrients directly from wastewater while the production of photosynthetic oxygen stabilizes organic matters in the wastewater. This conception has long been conceived in the moats of the medieval castles and realized in waste stabilization ponds.2–5 The full potential in optimizing the photosynthetic oxygen generation for wastewater treatment is credited to William J. Oswald in the conception of the high rate algal pond systems which optimizes algal growth for wastewater treatment.1,6 The algal wastewater treatment system then draws great attention not only as a means of purifying wastewater, but also for generating valuable algal biomass for other usage or extraction of valuable chemicals.7–9 Earlier works were concerned more so with BOD reduction,1,6 whereas attention gradually shifted to nutrients stripping from wastewater as eutrophication of receiving water became more serious