Effect of Zero Water Exchange Systems for Litopenaeus vannamei Using Sponge Biocarriers to Control Inorganic Nitrogen and Suspended Solids Simultaneously

Abstract

The traditional shrimp farming mode, which mainly uses water exchange to dilute toxic nitrogenous compounds, not only brings risks of disease infections and outbreaks but also results in waste of water resources and has a negative impact on the environment. In this study, zero water exchange systems for Litopenaeus vannamei were constructed by using sponge biocarriers with precultured biofilms (SBBFs), and the effect of SBBFs on controlling inorganic nitrogen, suspended solids and on the performance of L. vannamei was determined. The experiment consisted of four treatments: (1) SBC (control, SB 5% (v/v) + aeration); (2) SBBF2.5a (SBBF 2.5% (v/v) + aeration); (3) SBBF5a (SBBF 5% (v/v) + aeration); and (4) SBBF5 (SBBF 5% (v/v)). The results showed that the concentrations of TAN and NO2−-N in the SBBF treatments were significantly lower than those in the SBC treatments, while the SBBF treatments registered higher NO3−-N concentrations. After the adsorbates were removed by regular cleaning to regenerate the adsorption capacity of the SBs, the turbidity was reduced by 47.8%~71.5%. The shrimp grown in the SBBF treatments exhibited a higher mean final weight, survival and productivity than those grown in the SBC treatments. This work found that the use of SBBFs can maintain the low levels of TAN, NO2−-N and suspended solids while improving the performance of the L. vannamei under the strict requirement of zero water exchange.