A Study On The Effect Of Biofloc Technology With Rice Husk As Carbon Resource On Water Purification

As the need for marine product is increasing in recent years, the Litopenaeus vannamei aquaculture has been therefore developed rapidly. The cultivation in large scale and high density has become the trend. As the density of cultivation increases, not only the deterioration of water quality has become severe, but the resource of Litopenaeus vannamei also has been degraded. The bacterial and viral disease becomes intractable challenges for sustainable development of Litopenaeus vannamei aquaculture. Energy was devoted by scholars and technicians towards research on the reason, pathology, transmission route, precautions and treatment of the disease, but limited results have been achieved. For example, there still is no effective treatment to the white spot syndrome virus (WSSV) outbreak in 1990s. Moreover, the backward approaches in most aquaculture regions restrict the orderly development of the area.In soil pond culture of Litopenaeus vannamei, that water is seldom or never changed can result in accumulation of harmful substances, such as ammonia and nitrite nitrogen, which will deteriorate water quality and cause the disease. Recirculating aquaculture system (RAS), however, has the obvious advantages in controlling water quality and effective utilization of resources, which shall create fundamental conditions to scientific management and steady high-production over Litopenaeus vannamei aquaculture, and it is also the current trend in this field. The paper discusses biofloc technology with carbon resource of probiotics and agriculture waste gained from separation technique, and explores its effect on the indexes of ammonia nitrogen and nitrite nitrogen etc. in water and application in aquaculture of Litopenaeus vannamei, aiming to provide theory basis for high-efficiency, energy-saving and environment protecting aquaculture model and develop relevant technologies. The conclusions of the paper are shown as following:(1) The more bacillus (S729) added in water, the degradation to ammonia, nitrite nitrogen and COD is more remarkable. A bacillus density at about 105cfu/mL in water of aquaculture pond has better effect.(2) Effect of molasses reaches the peak when various carbon resource and probiotics are mixed together. Rice hull powder is more applicable when comparing to straw powder by regarding the processing difficulty and effect.(3) Actinomycetes (F28) gained from separation only have obvious degradation effect on ammonia nitrogen no matter whether added alone or mixed with various carbon resources, rather than on nitrite nitrogen.(4) The test of the application of biofloc of rice hull powder and bacillus in aquaculture of Litopenaeus vannamei demonstrated that the biofloc can not only save water resource, but also decrease the cost so that the production can be promoted.