Study On The Biological Treatment And Aeration Of Recirculating Aquaculture Systems In Industrialized Mariculture

Recirculating aquaculture system is developed for the need of sustainable development in industrialized mariculture, the key of recycled water treatment is to maintain a good quality and high level of dissolved oxygen in the condition of high density breeding. In the previous researches, waste water of aquaculture is almost treated by recycled systems simulated in the laboratory. The effect of simulated waste water treatment of aquaculture is pretty good, but poor in the actual production. The study on optimization of biological treatment unit and aerobic unit in the small scale recycled water system has important significance to practical production.The main research in this paper includes: In the first part, it introduces industrialized mariculture system and the technology of recirculating water treatment, the research status of biological treatment and aerobics unit in recirculating water systems, the contents and significance. In the second part, based on the investigation of typical recirculating water system run in domestic, it describes the basic general situation of recirculating water treatment in detail. In the third part, it introduces concretely cultivate methods of biosystem, which includes the sequence of adding water, aeration time, the amount of nutrients added in. In the fourth part, controlling test conditions through adjusting the system running, firstly it discusses the effect of HRT, water temperature, pH, aeration to remove ammonia in filter. The results show that in a certain temperature (10～17℃) and in a certain HRT (60min, 75min, 90min, 105min), it will lead to the increased ammonia removal in different level,raising the temperature and increasing the HRT. Later, the best operating conditions of the biological treatment unit is established: the circulation flow rate is about 30 m3 / h, the cycle number of one day is 20 to 21, HRT is about 70 min, the water temperature is 15℃, pH is 7.9 to 8.05, aeration is 0.8 m~3/h. In the fifth part, research is begun from the mariculture cycle of water aerobics unit. In the condition of inflatable aerobics, it discusses the effect of sea water aerobics on different end-to-breeding. The results show that, when the ventilation is low, it should choose the smaller mesh airstone; when the ventilation is higher, it should choose the larger mesh airstone. The mesh of airstone should match up to the intensity of air volume in order to obtain the better DO in water body. Oxygenation aerobics, comparing the aerobics effect of oxygen-proliferation devices between oxygenation experiment and dissolved oxygen spreading experiment, the result show that the oxygen utilization rate of nano-airstone is higher than pipeline devices of oxygen dissolved in the range of 2.5% to 7.5%. However, in the actual operation, the oxygen utilization rate of nano-airstone is 73.3%, which is higher than pipeline devices of oxygen dissolved by 16.6%.From the analysis of economic index, the pipeline devices of oxygen dissolved has a high one-time investment and a high oxygen-increasing cost. Nano-airstone is suggested to be putted into the pipeline, water flow and oxygen flow should be controlled in the 30～38m~3 and 1.6～3.2m~3/h.