Design, Development, and Performance Evaluation of Plastic-based Radial-flow Settling Unit for NFT Aquaponics

Abstract

Highlights Inclusion of the designed radial flow settler to the aquaponic system helps to remove more than 80% TSS, which is on par with or better in comparison to the TSS removal efficiency of the existing models. Removing excess suspended solids in traditional aquaponic setups could help prevent biofilter choking and hence, water contamination further down the line. The developed radial flow is simple in design, cost-effective, and yet, efficient. Abstract. One cylindrical settler of capacity 200 L (Ø 0.6×0.7 m) with a center-bottom inlet has been designed and developed in High-Density Poly Ethylene (HDPE) under the All-India Co-ordinated Research Project on Plastic Engineering in Agriculture Structures & Environment Management (AICRP on PEASEM) center at ICAR-CIFA, Bhubaneswar for fitting to the developed Nutrient Film Technique (NFT) aquaponics system. The water flow into the settling unit comes from a single-drain fish culture tank with the outlet at the bottom-center with a downward slope of 1:22. The experiment was carried out for the evaluation of the efficiency of Total Suspended Solid (TSS) removal in the developed radial-flow settling unit. The performance is assessed in terms of capturing the suspended solids from the water of aquaculture operation with varying specific gravity (1=SG>2) as well as the skimming of the floating organic surfactants before entering into the biofilter. During the 90 days of study, a total of 60 water samples were collected from the outlet of the fish culture tank and the overflow of the settler, which were filtered through the standard 11 µm pore paper filter for further processing in the laboratory. The average TSS concentration removed was calculated to be 128.55 mg/L on dry weight basis and a mean efficiency of 80.06 ± 9.36% was observed in the experiment with a surface loading rate of 0.00103 m3/min-m2 of the radial flow settler. The right-angle submerged overflow of the settler helped in complete surfactant removal. Keywords: Aquaponics, NFT, Radial-flow, Specific gravity, Suspended solid.