| Aquaponic system is based on the ecological principle and the recycling of water,combining aquaculture and hydroponic cultivation techniques to form a highly efficient food production model that can be adapted to urbanization and industrialization and can be precisely controlled.The recycling of nutrients in this system is an important study direction.For aquaculture systems,bait is the source of input.After fish metabolism,part of the assimilation is synthesized into biomass,and the other part is decomposed into dissolved nutrients?urine?and solid particles?feces?.At the same time,the residual bait is partially dissolved and the other part is in the form of solid particles.For the hydroponic system,the dissolved matter produced by fish metabolism and bait residue becomes a nutrient source for direct absorption and utilization of plants,and the solid particles remaining in the feces and baits need to be effectively filtered and transformed to be utilized by plants.Ammonia nitrogen nutrients in water need to be efficiently biotransformed,on the one hand to ensure the quality of aquaculture water,and at the same time form a form of nitrate nitrogen which is more beneficial to plant absorption.This study is aimed at the mechanism of nutrient transformation of farmed animals,aquatic plants and microorganisms in the aquaponic system.The integrated aquaponic system and the separated aquaponic system are adopted.The carp and mint are selected as the breeding objects,respectively.The cycle operation test of 30 days and 60 days was carried out to investigate the cycle characteristics of the two systems.Through the static test of each unit of the aquaponic system,the mechanism of nutrient production in the aquaculture unit,the nutrient absorption mechanism of the hydroponic unit and the nutrient transformation mechanism of the microorganisms in water treatment unit;finally,the biomass filtration system was designed and constructed,and the filter material was formed by the combination of biomass?corn stalk,wheat straw and Chinese fir wood chips?and ceramsite,then,the filtration characteristics of the solid particles and nutritional transformation characteristics in the aquaculture water were investigated.The study indicates:?1?The two systems are stable in operation and have good water quality. The circulating water TAN and NO2--N are kept within the safe concentration range,and the NO3--N concentration has a certain accumulation,but does not affect the normal operation of the system; The growth rates of carp and mint in the integrated aquaponic systemwere 26.6 g/d and 26.07 g/d,respectively.The growth rates of carp and mint in the separated aquaponic system were 20.9 g/d and 33.57 g/d, respectively;?2?The rates of TAN,NO2--N and DTP nutrients produced by the integrated aquaculture unit of the aquaponic system within 24 hours after feeding were:49.8 mg/h,12.2 mg/h,63.2 mg/h;the separated aquaponic system is:76.1 mg/h,14.1 mg/h,93.6 mg/h;?3?The nutrient absorption rate of mint in integrated aquaponic system is 1.04 mg TAN/h,11.03 mgNO3--N/h and 5.88 mg DTP/h,and the nutrient absorption rate of mint in the separated aquaponic system is 2.18 mg TAN/h.21.63 mg NO3--N/h and 23.54 mg DTP/h;?4?The nutrient transformation rate of microorganisms in the water treatment unit in the integrated aquaponic system is 38.18 mgTAN/h,123.12 mgNO2--N/h and 87.48 mg NO3--N/h,and the rate of nutrient conversion of microorganisms in the water treatment unit in the separated aquaponic system was 48.30 mg TAN/h,225.00 mg NO2--N/h and 131 mg NO3--N/h;?5?The three biomass filter materials have a filtering effect on the culture water,and the effluent turbidity is reduced by about 60%.In terms of nutrient conversion,the accumulation time of NO3--N in corn stover,wheat straw and Chinese fir sawdust was 96h,96h and 24h,respectively.Comprehensive filtration effect and nutrient conversion efficiency,Chinese fir sawdust is suitable filter materials for biomass filtration. |
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