The Application And Effects Of Biofloc Reactor On Aquacultural Solid Waste And Aquaculture Wastewater

It may produce a large amount of solid waste and aquacultural wastewater in the aquaculture process, which can easily cause serious problems such as water quality deterioration, disease and even severe environmental pollution. Biolfloc Technology（BFT） can transform suspended solids, dissolved organic matter and inorganic nitrogen into the biofloc that may be ingested by aquaculture animals, realizing the reutilization of aquaculture waste, besides, BFT has good effect on aquaculture wastewater and effluents. Therefore, BFT was paid extensive attention of domestic and foreign researchers in aquaculture. In this current research, a pilot scale bio-floc reactor was employed to study the effects on treatment of aquaculture effluents and the recycling application of flocs. Test contents are divided into the following sections.1. Effects of agitation rate in SBR using biofloc technology to treat aquacultural solid wasteThis study aimed at improve the effects of aquacultural waste treatment by inoculating with activated sludge under three designed agitation rates: 1400 r/min, 1200r/min and 900 r/min, respectively. And aquaculture solid waste was used as nutritional substrate to produce bioflocs using biofloc technology in sequencing batch reactors with an air stirrer to provide dissolved oxygen（DO） and mixing intensity. The results showed that: nitrification occurs in the SBR during the experiment period. The concentration of TAN decreased gradually, and the concentration of TAN in biofloc reactor effluent in1400 r/min group was observed less than 1 mg/L. With no NO₂^--N accumulation in there reactors. The concentration of TP in 1400 r/min group is higher than the other two groups, but and concentration of PO43--P is lower. In a conclusion, The reactor in 1400r/min group has better effect on removal of PO₄^3--P. The protein contents of biofloc are29.60%, 29.70%, 29.73%, respectively, with no significant differences among the three groups（P>0.05）.When agitation rates increase, the crude lipid contents of bioflocincreased, the crude lipid content of biofloc in 1400 r/min is significant higher than the crude lipid content of the other two groups（P<0.05）. Moerover, the sedimentation performance of biofloc in the group of 1400 r/min is superior to those of 1200 r/min and900 r/min groups.2. The effects of biofloc technology in pilot sequencing batchreactor to treat aquaculture wastewaterIn this section, three pilot sequencing batch reactors（SBRs） were employed to treat aquaculture wastewater from a recirculating aquaculture system（RAS） stocking gift tilapia using biofloc technology（BFT） under three designed MLSS（1500 mg/L, 3000mg/L, 5000 mg/L）, with the agitation rate of biofloc reactors 1400 r/min. The results show that SBRs have good effect of nitrogen removal, the effluent concentrations of ammonia（TAN）, nitrate（NO₂^--N） and nitrate（NO₃^--N） were（0.29⁰.39） mg/L,（0.005⁰.006） mg/L,（7.11⁷.60） mg/L, respectively; And those average removal rates were（82.20⁸2.20）%,（98.40）%,（38.40⁴0.00）%, respectively（P>0.05）. The volume removal loads of TAN, NO₂^--N, NO₃^--N were（2.51².64） g/m3 d,（0.56±0.08） g/m3 d,（8.52⁹.78） g/m3 d; The volume removal loads of solubility inorganic nitrogen（DIN）were（10.25¹1.61） g/m3 d, and volume removal loads of DIN in MLSS 1500 mg/L group is the highest. The protein contents of flocs from SBRs were（30.00±1.32）%,（29.87±0.67）%,（31.00±0.75）%, respectively; with no significant differences among the three groups（P>0.05）. The crude lipid contents of biofloc were（ 9.51±0.94） %,（4.37±0.42）%,（3.65±0.22）%, respectively; and the crude lipid content in MLSS1500 mg/L is significantly higher than the crude lipid content of the other two groups（P<0.05）. Compared with traditional nitrification reactor which is only effective to eliminate the TAN, however, the SBRs reactor can effectively remove TAN, NO₂^--N and NO₃^--N simultaneously in aquaculture wastewater from the RAS stocking gift tilapia. It can save lots of equipment investment and aquaculture cost, improve economic efficiency and promote the recycling application of aquaculture wastewater.3. The research on nutrient element release effect of penaeus monodon pond sediment in biofloc reactorAiming at the nutrient element release effect of penaeus monodon pond sediment under the condition of aerobic aeration.The sediment of 0⁵ cm, 5¹0 cm, 10¹5 cm from penaeus monodon pond in Shanghai Fengxian region aquaculture cooperativewere taken for this study. Results indicate that TAN in the surface sediment（5¹0 cm）released quicker, requiring 8 h to release completely; while TAN in sediment of the other two groups release slower, taking 16 h to release completely; and TAN in all groups transform completely in 112 h. In addition, concentrations of NO₃^--N decrease obviously within 8 h, and then slowly rising continuously, which suggest the nitrification occurred in the SBRs. During the experiment, the phenomenon that microbes to utilize phosphate is not obvious, before experiments,the concentrations of PO₄³⁺ decrease in the first 8 h, then continuing to rise. Besides, DOC content in all groups fall rapidly within 16 h, and run out after 64 h, consistently with the change of the DOC/DIN; That shows that the growth of heterotrophic microorganisms need a lot of carbon source, when the carbon source is insufficient, nitrifying bacteria multiply rapidly. The results indicated that the treatment to penaeus monodon pond sediment is better to be taken earlier stage, and treatment in surface sediment（0⁵ cm） is more effective.4. The effect of SRT in SBR using biofloc technology to treat penaeus monodon pond sedimentIn this part, we focus on the effect of sludge retention time on penaeus monodon pond surface sediment（0⁵ cm） in SBRs, and three SRT（3d, 2d, 1d） were investigated.The TAN concentrations in three reactors rise firstly, and then reduce later. The TAN concentration in SRT 3d is significantly higher than the TAN concentrations in other two groups（P<0.05）. There is no obvious production of NO₂^--N or NO₃^--N in the SBRs was observed during this phase, and the concentrations of NO₃^--N in all groups quickly dropped to the lowest in 4 days. The concentrations of PO₄^3--P from 4 days began to decline gradually on the fourth day, while the concentration of PO₄^3--P in SRT 1d decreased faster. In addition, the results indicate that the sediment in shorter SRT of SBRs has better sedimentation performance. The contents of the crude protein, crude lipid in sediments in the SBRs were lower, while the crude ash content are more than90%. However, it is good for the growth of the nutrients with longer SRTs. In a conclusion, the SBRs in this current study are effective to converted TAN, NO₂^--N or NO₃^--N in penaeus monodon pond sediment into heterotrophic bacteria biomass, with a small amount of absorption of PO₄^3--P. That is worthful for the resource reutilization of sediment and reducing the eutrophication of penaeus monodon pond sediment.