Performance evaluation and mathematical model of pipeline diffused aeration for recirculating aquaculture system

Abstract

High requirement of aerating to increase dissolved oxygen is essential for improving the level of intensive recirculating aquaculture system (RAS). A simple, low-cost and maintainable pipeline diffused aeration (PDA) was proposed and designed for pure oxygen to increase the dissolved oxygen. It mainly consists of a diffused aeration stone, a union tee and an interior plug joint. The aim of this article was to study effects of oxygen flow rate (OFR) or inlet dissolved oxygen (IDO) combined with pipe length (PL) on PDA performance, and to construct a referable mathematical model of outlet dissolved oxygen (ODO) with IDO and gas-liquid contact time (CT) for actual recirculating aquaculture water. Results indicated that the oxygen increment rate and the oxygen utilization rate increased with the increase of PL for tap water, and that increased with the decrease of IDO for actual recirculating aquaculture water. PDA is mainly influenced by PL and thus suitably applied in the treated circulating water back flow to culture ponds, especially for RAS with long pipelines. Under the experimental conditions with OFR of 3 L/min, IDO of 3.92 mg/L, and PL of 10 m, the best oxygen increment rate was 149.02% and the best oxygen utilization rate was 11.60%. The linearly mathematical model of ODO=3.8464+0.6237*IDO+0.2705*CT (R2=0.97) can be referred to develop a controllable PDA system for predicting or regulating the dissolved oxygen of water in culture ponds. In particular, PDA combined with liquid oxygen supply will be further studied to promote its application in RAS.