The algal cells can be gathered into a corporation or fixed to the carrier by immobilization technology. Immobilized algae have numerous benefits as follows: high cell density, excellent ability to resist poison, high re­moval efficiency, good stability, easy product separation, etc. At present, immobilization carriers include mainly natural macromolecular materials (such as agar, sodium alginate, etc.) and synthetic polymeric gels (such as polyvinyl alcohol, polyacrylamide, etc.). The natural polymers have no toxicity and good mass transfer property, but their intensity is low. How­ever, the synthetic organic polymer gels have high strength, but poor mass transfer property. Therefore, new immobilization carriers are expected to facilitate the development of algae immobilization technology.

High rate algal pond (HRAP) can achieve efficient removal of organic matter, heavy metals, nitrogen, phosphorus and other nutrients in waste­water by algae-bacteria symbiosis system. In the system, the microalgae provide oxygen and nutrition for bacteria; meanwhile bacteria provide use­ful growth-promoting substances for microalgae. Our team has developed a new type of microalgae immobilization carrier using the fungi [72]. The key of the technology is that fungi mediate pelletization of microalgae. After adding a certain number of fungal spores to the microalgae culture, algae-fungi symbiotic spheres formed accompanied by spore germination. The immobilized microalgae allow efficient recycling of livestock waste­water for algae cultivation and are easy to be harvested. In addition, the fungi can be converted to animal feed.