Biofiltration for Recirculating Aquaponic Systems: A Review

This article reviews the current literatures published about aquaponics more specifically biofiltration. Aquaponics is seen as a sustainable agricultural technology since it can support high quality production of fishes and vegetables throughout the entire year. Aquaponic systems are sorted according to the type of grow bed for plants employed: floating raft, media filled, and nutrient film technique (NFT). Among the three, NFT and floating raft would require an external biofilter in order to increase plant yield, maintain water quality, and support fish growth. The biofilter provides an area in an aquaponic system where majority of the population of beneficial microbial communities which includes nitrifying bacteria can colonize. This review gathered publications in Scopus and Google Scholar spanning from 2016 to 2020 regarding biofiltration in aquaponic systems. The review found out that the common factors affecting the biofiltration performance are biofilter media, biofilm formation, and water circulation rates. In biofilter media, the current trend based from the number of studies published is going towards synthetic polymer media due to its capability to be formed in many shapes that can provide more surface area for nitrifying bacteria growth. For biofilm formation, shorter biofilter maturation is expected when mature inoculum is used but faster growth of new biofilm is inhibited due to nutrient competition, thus optimum ratio between mature and new inoculum must be determined. Lastly, water flow rate affects the characteristics of the influents and effluents as well as the flux of nutrients. Determination of optimum water flow rate must be established since previous publications showed contradicting results. Aside from the factors affecting biofilter performance, innovative technologies that serve the same purpose as a biofilter were also presented in this review. This includes membrane filtration, down-flow hanging sponge (DHS) reactor, and biofloc technology (BFT). Recommendations for future researches are also presented for each of the biofilter alternatives.