Nitrification in brackish water recirculating aquaculture system integrated with activated packed bed bioreactor

摘要

Recirculation aquaculture systems (RAS) depend on nitrifying biofilters for the maintenance ofnwater quality, increased biosecurity and environmental sustainability. To satisfy thesenrequirements a packed bed bioreactor (PBBR) activated with indigenous nitrifying bacterialnconsortia has been developed and commercialized for operation under different salinities forninstant nitrification in shrimp and prawn hatchery systems. In the present study the nitrificationnefficiency of the bioreactor was tested in a laboratory level recirculating aquaculture system fornthe rearing of Penaeus monodon for a period of two months under higher feeding rates and nonwater exchange. Rapid setting up of nitrification was observed during the operation, as thenvolumetric total ammonia nitrogen removal rates (VTR) increased with total ammonia nitrogenn(TAN) production in the system. The average Volumetric TAN Removal Rates (VTR) at the feedingnrate of 160 g/day from 54–60th days of culture was 0.1533 ^ 0.0045 kg TAN/m3/day.nThe regression between VTR and TAN explained 86% variability in VTR (P , 0.001). The laboratorynlevel RAS demonstrated here showed high performance both in terms of shrimp biomass yieldnand nitrification and environmental quality maintenance. Fluorescent in-situ Hybridization analysisnof the reactor biofilm ensured the presence of autotrophic nitrifier groups such as Nitrosococcusnmobilis lineage, Nitrobacter spp and phylum Nitrospira, the constituent members present in thenoriginal consortia used for activating the reactors. This showed the stability of the consortia onnlong term operation.