Study On Purification Of Aquaculture Wastewater Purification By Immobilized Bacteria-algae System

Capacity of ammonia-nitrogen and orthophosphate removal by marine microalgae cells were studied in this paper. Ammonia nitrogen tolerance, immobilization, cell density in airlift bioreactor and starvation on advanced nutrient removal efficiency were studied for aquaculture wastewater treatment. The results showed that three kinds of marine microalgae had a certain tolerance to high concentration of ammonia nitrogen. They had a certain purification ability of removing nitrogen and phosphorus. Marine microalgae cells were immobilized in alginate beads for wastewater treatment. The optimum NH4+-N and PO43--P removal efficiency was obtained when cell density was 2.5 million per bead. Using airlift bioreactor, nitrogen and phosphorus removal efficiency was 100% after 7 days under all bioreactor density. After 48 h starvation, nutrient removal efficiencies were higher than control. Ammonia nitrogen removal efficiency reached 100% after 6days and orthophosphate removal efficiency reached 100% after 4 days.Ammonia-nitrogen, orthophosphate and COD removal efficiency by immobilized photosynthetic bacteria cells were investigated. The inoculation cell density in beads and bioreactor density by different quantity of beads were studied for higher NH4+-N, PO43--P and COD removal. The biomass of bacteria was determined through the treatment process. The results showed that the removal efficiency of COD, NH4+-N and PO43--P reached 91%, 100% and 100% respectively under the condition of 20% inoculation amount, 150 beads per 100 ml wastewater after 4 days. The dry weight of photosynthetic bacteria increased after wastewater treatment, which showed that the cell multiplication was not affected.Photosynthetic bacteria and marine microalgae were co-immobilized in one airlift bioreactor. Ammonia-nitrogen, orthophosphate and COD removal efficiency were determined in this system. The results showed that photosynthetic bacteria 2 and the Chlorella sp 1 combined system had better removal efficiency. COD removal efficiency exceeded 96% after 6 days. Nitrogen and phosphorus removal efficiency were 100% after 2 days. The photosynthetic bacteria 1 and two kinds of microalgae system had inhibitory effect on nutrient removal. In the process of treatment, the dry weight of photosynthetic bacteria and marine microalgae cells were significantly increased.