Study On The Factors Of Affecting The Startup Of Seawater Biofilter

China is the world's leading aquaculture country with the highest output in the world.However,while the marine aquaculture industry is developing rapidly,the voluntary discharge of aquaculture wastewater has caused great damage to the coastal water environment.The resource dependence and extensive management of traditional marine product farming models are not in line with the requirements of sustainable marine green development.As an emerging industrial aquaculture technology,the recirculating aquaculture system can reduce the amount of water resources and realize wastewater discharge management.It is environmentally sustainable and enables the cultured species to achieve optimal growth throughout the year,which is economically sustainable.Therefore,industrialized recirculating aquaculture is increasingly favored by people.As the water treatment core of the recirculating aquaculture system,the biofilter is still difficult to accurately predict and control.Its stability and work efficiency directly affect the stability and production management of the recirculating aquaculture system.In order to optimize the biofilter start-up conditions and improve its nitrification performance,this paper studied the main factors affecting the membrane start-up,like the effects of temperature,HRT,filter material and other factors on the nitrification ability of the membrane-opening stage,and carried out nitrification kinetics analysis,in order to provide some theoretical guidance of the startup and operation to a biofilter.The conclusions of this study are as follows:1.In the 42-day membrane start-up experiment,the biofilter has the ability to remove TAN,and the removal efficiency is stable at more than 60%.The short hydraulic retention time HRT=1h is suitable for the membrane start-up operation.Appropriate temperature condition?28°C?is suitable for the growth of microorganisms during filming and stable removal of TAN.2.Different film-hanging methods have significant differences in the start-up of the biofilter.The inoculation film can significantly shorten the filming time.The average TAN removal rate can reach 50%in about 15 days,while the natural filming method takes 30 days,and the TAN removal efficiency is finally stable at 80%.3.The effect of different biological filter materials on the start-up effect is obvious.The structure of the sponge-type biological filter material can be suitable for microbial growth,but the accumulation of NO₂^--N also occurs after TAN degradation,and the peak value reaches 1.1 mg/L during the whole operation period.After the system tends to be stable,the concentration of NO₂^--N gradually stabilizes and decreases,and the final effluent NO₂^--N concentration is stable at about0.2 mg/L.Finally,there was no significant difference in the degradation degree of TAN and NO₂^--N between different filter materials.4.The nitrification performance tester combines the degradation kinetics of the matrix.In the42-day rapid membrane start-up experiment,the biofilm has the ability to remove TAN.In the fitting equation after the 80-day mature membrane,the removal effect of TAN is more rapid.The rmax under the four conditions is quite different from the results of other scholars,except for the complex properties of the simulated aquaculture wastewater itself.The analysis of lower mariculture wastewater by Monod may have limitations.5.Calcium carbonate begins to decompose after 530°C,and the hydrochloric acid solubility and alkali solubility of the high temperature treatment group are relatively low.Therefore,a reasonable firing temperature is critical for filler preparation.Appropriate addition of clay,sodium silicate and fly ash materials combined with shell powder,bio-filler has good physicochemical properties.When the shell powder content is 40%,the filler is more stable and strong..