| Biological purification is one of the key water treatment technologies in themariculture recirculating water system, and biological aerated filter (BAF) is thecommon facility of biological purification. This paper mainly researches the biofilmcultivation and water purification effect of six biological stuffings, and investigatesthe factors which are effecting the water purification of the stuffings. Throughoptimizing the method of biofilm cultivation to get the goal of shorten the biofilmmaturity time. Compare the difference of young black sea bream culture efficiency-growth and immune indexes between recirculating aquaculture system and flowingwater culture system. The microbial community structure on the stuffings areanalysed by PCR-DGGE. This paper provides theoretical basis and references for thechoosing of stuffings of fixed-bed biofilters in the mariculture recirculating watersystem. The main contents and conclusions are as follows:1. Flow velocity and stuffings have direct effects on the purifying of biofilter. Inthis chapter, total ammonia nitrogen dynamic adsorption experiments of threebiological filter materials (PE, coralstone and PP) were performed, and thecharacteristics of three stuffings’ biofilm in the treatment of simulated mariculturewastewater were compared. In biofilter for each stuffing, total ammonia nitrogenadsorption and biofilm cultivation experiments under three hydraulic loadings wereimplored. During the biofilm cultivation time under the temperature of22±1℃,several pollutant concentrations were measured, including total ammonia, nitritenitrogen, nitrate nitrogen and total organic carbon. The experimental results showedthat the biofilm cultivation time of coralstone stuffing was obviously shorter than PEand PP. After the biofilm maturation, biofilm thickness was tested by the electronmicroscope and biofilm structure was observed by the scanning electron microscope (SEM). Biofilm thickness and water flow velocity were negatively correlated. Underthe same hydraulic loading, the biofilm thickness of coralstone stuffing was thickerthan PP and PE. The result of SEM showed that biofilm mainly consisted of bacillusand spirillum. Biofilm activity of each stuffing was tested according to the removalrate under five different hydraulic loadings of the simulated mariculture wastewater,and the best hydraulic loading of each stuffing was obtained. When the ripe biofilmformed, biobilm of three stuffings in corresponding biofilter had the different besthydraulic loading to remove ammonia, nitrate nitrogen and total organic carbon,respectively. BAF had good removal effects on total ammonia, nitrite nitrogen, andtotal organic carbon under the hydraulic loading of19m~3/(m/~2·h)–51m~3/(m/~2·h).2. Using microbial ecological agent as strain for three different kinds ofstuffings’(pottery ring, elastic brush and biochemical cotton fiber) biofilmcultivation,after the biofilm maturity, the culture efficiency of young black sea breamare tested. Under the same condition, biofilm maturied time for three stuffings are25d,32d,28d, respectively. Young black sea bream grow well in the simplerecirculating aquacultute system. After the40days’ feeding, compared with controlgroup, the mean body weight and feed conversion rate of black sea bream weresignificantly difference in three experimental groups(P<0.05). The survival rates in allgroups are over95%. The activity of serum LSZ and liver SOD in experimentalgroups are significantly greater than the control group (P<0.05).The quantity anddiversity of digestive tract flora in experimental groups are significantly more thancontrol group. The results show that different filter materials have different biofilmmaturation time under the same operating conditions. Using microbial ecologicalagent as strain can achieve very good effect. Under recirculating aquacultute systemcan not only improve fish’s growth, but also enhance their immune performance.3. Different carbon sources and carbon-nitrogen radios have important effect tothe nitrification and denitrification of biofilter. This chapter chooses the pottery loopas biofilm stuffing, and chooses three organic matters-glucose, peptone and sodiumacetate which are usually used in biofilm cultivation. Use microbial ecological agentas strain for biofilm cultivation at the initial ammonia nitrogen concentration of 10mg/L. The biofilm maturation when the denitrification system is completelyestablished. After the biofilm become matured, three biofilter groups’ nitrification anddenitrification under the condition of three organic matters and four carbon-nitrogenradios are tested. The results show that using glucose, peptone and sodium acetate asorganic carbon sources, the biofilm’ s maturing time are31d,40d and28d,respectively. Changing the initial ammonia nitrogen concentration at5mg/L, threebiofilter groups have the best effect for removing dissolved inorganic nitrogen at4:1carbon-nitrogen radio. At the same time, the total nitrogen removal rates are all getover85%. The biofilter’s nitrification and denitrification can be seriously hinderedwhenever the carbon-nitrogen radio is too high or too low. Adding sodium acetate ascarbon source has the best biological nitrogen removal effect when the otherconditions are same. This paper can provide a theoretical basis and serves as valuablereference of biofilm cultivation and biological nitrogen removal in mariculturerecirculating aquarium system with low ammonia loadings.4. Use the PCR-DGGE technology of molecular biology to research the biofilm’smicrobiological population on the surface of pottery loop stuffing. The microbialcommunity distributes widely in biofilter. The17DGGE bands belonged to theα-Proteobacteria, β-Proteobacteria, Flavobacteria and Bacilli. The anaerobic bacteriasuch as Flavobacteriaceae, Gaetbulibacter.sp and Roseobacter.sp, and the otheraerobic bacteria are coexisting in the microbial community, and keep the balance ofbiofilm’s environment. This indicates that there should have pathways of nitrificationand denitrification in biofilm. |
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