An effective biological treatment method for marine aquaculture wastewater: Combined treatment of immobilized degradation bacteria modified by chitosan-based aerogel and macroalgae (Caulerpa lentillifera)

Aquaculture has expanded significantly in recent years, and the effluent it produces has had a significant negative impact on the environment. The survival and growth rates of aquaculture products may impact by the eutrophication of the water body if the effluent from aquaculture is not handled. In this study, chitosan-based aerogel was used as a carrier to immobilize the degrading bacteria, and the adsorption capacity of the carrier material for methyl blue was 1.30 mg·g−1. The Caulerpa lentillifera was added to the shrimp tank at the same time as a biofilter, and a composite in-situ treatment system using microbes and macroalgae was built to handle the effluent from the mariculture industry to test the reduction rates of the nutrients from the wastewater. The outcomes demonstrated that the immobilized bacteria used had reduction rates of COD, NH4+ and NO2− in wastewater that were 48.82%, 9.14% and 40.74% greater than those of the free bacteria, respectively. The reduction effect of macroalgae for nutrients in wastewater is also very ideal, in which the reduction rates of TP and TN reach 32.43% and 74.94% respectively. When the immobilized degrading bacteria and macroalgae are combined, the reduction rates of COD, TN and TP in water reach 68.61%, 59.03% and 34.25%. At the same time, the survival rate of shrimp and the biomass of macroalgae have increased to a positive extent, with increases of 12.5% and 140%, respectively. These results demonstrate that the introduction of immobilized degrading bacteria and macroalgae into the shrimp culture system can effectively reduce the accumulation of nutrients in the shrimp culture system and have a positive impact in a variety of ways. •The aerogel material CCF0.9 can immobilize degradtion bacteria effectively.•The removal effect of immobilized degrading bacteria on nutrients in wastewater is better than that of suspended bacteria.•The macroalgae Caulerpa lentillifera has the effect of removing N and P in the aquaculture wastewater.•The bacteria - algae system can remove the nutrients in the aquaculture wastewater and improve the aquaculture income.