| Biofloc technology which is controlled the C/N(>15) and heterotrophic bacteria assimilate nitrogen to microbial protein. So bioflocs can be taken by filter feeders. Bioflocs can purify the water quality but also can be taken by Aquatic animals. This is similar to the traditional high-yield farming ponds in China which is stared from the feces of herbivorous fish. Therefore study the process of feces to bioflocs in the bioflocs technology. And use of inorganic nitrogen of aquaculture wastewater to aerobic granules sludge in the sequencing batch reactor(SBR)The first part: the change of the shape and nutrients in the process of the tilapia feces decomposedObserving the process of feces of NEW GIFT Oreochromis niloticus became to bioflocs. With the reaction of feces,it became loosely. Finaly feces developed into bioflocs which skeleton were filamentous fungus. With the decomposition of feces,the ammonium began to slowly rise to 7.46 mg/L in the reactor, and the nitrite increased to 7.81 mg/L. But nitrate became rapidly accumulate to 21.6 mg / L. In the 9th day, the content of crude protein reached the peak of 26.37%, and then decreased to 25.45%. In the 7th day, the total amino acids reached to the peak 20.44%, and then decreased to 18.11%. The essential amino acids in the bioflocs were 9.36% lower than the feed which were 13.03%. The loosely bound extracellular polymeric substances(LB-EPS)in the bioflocs mainly substances were polysaccharides, and the tightly bound EPS(TB-EPS)in the bioflocs mainly substances were protein.The second part: the formation of bioflocs in the Oreochromis niloticus with biofloc technologyObserving the formation of bioflocs in the Oreochromis niloticus closed cylinder with carbohydrates. The nitrate was gradual accumulation to 77.09 mg/L in the cylinder. But the ammonium and nitrite were not accumulation, and they were 1.55 mg/L, 2.81 mg/L, respectively. The content of crude protein and total amino acids in bioflocs were gradually increased to 37.55%, 35.79%, respectively. The biomass of bioflocs was gradually increased to 495.02 mg/L. The SVI30 of bioflocs were first increased to 74.97 ml/g and then decreased to 27.66 ml/g. LB-EPS in the bioflocs mainly substances were polysaccharides, and it was not conducive to inter-floc cohesion. Initially, the levels of LB-EPS were high as 37.70 mg/g, and then decreased to 12.05 mg/g. TB-EPS in the bioflocs mainly substances were protein. Initially, the content of TB-EPS were increased to 403.86 mg/g, and then decreased to 116.17 mg/g. At p H=6.0, the nitrification of bioflocs was poor, but the nitrification of bioflocs was well at p H=7.5.The third part: aerobic granules sludge to treat aquaculture wastewaterAerobic granules(AGS)were cultivated with in a sequencing batch reactor fed with aquaculture wastewater. The loosely flocs developed to tight AGS and their mean diameter were 150 μm. When the total suspended solid particles(TSS)at about 17.39 mg / L, The SBR reactor became stability. The removal rates of nitrate, phosphate, dissolved organic carbon(DOC)in the SBR and they were above 96.10%, 91.37%, 92.79%, respectively. But the removal rates of ammonium and were greater volatility. In a typical cycle of SBR reactor, AGS could rapid absorb of nitrate, ammonia, dissolved organic carbon within 30 min. The content of LB-EPS by heating EPS extraction method were higher than use ultrasonic method,But TB-EPS were lower. The content of TB-EPS in the AGS was higher than the bioflocs when used ultrasonic EPS method, but the content of LB-EPS in bioflocs were higher. It suggested that AGS can be used to treat aquaculture water. |
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