| Recirculating aquaculture system(RAS)is one of the important directions for the transformation and development of traditional aquaculture.As a high density aquaculture system,the accumulation of ammonia and nitrite in circulating water can cause toxic effects on aquatic organisms.Therefore,the efficient treatment of ammonia and nitrite in circulating water is one of the key issues to ensure healthy aquaculture.Seawater has the characteristics of high salinity and low C/N ratio,which makes it difficult for traditional biological methods to meet the needs of efficient treatment of aquaculture recirculating water.Based on the characteristics of high conductivity and high chloride ion concentration of seawater,electrochemical oxidation method can remove ammonia from seawater by active chlorine,which has significant advantages in removal efficiency.At the same time,electro-oxidation in situ produced reactive chlorine can inhibit membrane fouling of membrane bioreactor(MBR),which is helpful to maintain the water treatment efficiency.However,the electrooxidation rate is low in the absence of catalyst,and the performance of electrooxidation in situ control of membrane fouling needs further study.Therefore,in this paper,the electrochemical-membrane bioreactor(EMBR)was constructed to prepare conductive separation membranes with high catalytic activity.Through the anodic membrane catalytic oxidation,the efficiency of aquaculture seawater treatment was improved and the in situ control of membrane pollution was realized.The main research results are as follows:(1)CNx+y%Pt membrane modification additive was loaded onto PVDF membrane to prepare catalyst modified conductive membrane,which was used as anode material to remove ammonia from circulating seawater aquaculture by electro-oxidation method.The catalyst CN1+15%Pt showed the highest electrocatalytic activity of ammonia oxidation.The orthogonal experiment indicated the optimal parameters were Co 100 mg/m L,anodic potential1.7 V vs.SCE,rotational speed 300 r/min,and pH 10.Under these conditions,the ammonia removal rate could reach 3.20 mg/L in 20 min for the simulated aquaculture recirculating water treatment.The quenching experiment proved that the main factor of ammonia removal was active chlorine(by electrochemical indirect oxidation).Treatment of actual aquaculture recirculating water without changing the p H,the ammonia removal rate reached 1.31 mg/L in 40 min.(2)CNTs-x Ti O2-y PEDOT and PVDF were used to prepare the catalyst modified conductive anodic membrane to enhance the chlorine evolution reaction(CIER)and enhance the anti-pollution performance of the membrane.The catalyst CNTs-10%Ti O2-0.25 PEDOT showed the highest electrocatalytic activity of chlorine oxidation.SEM,TEM,EDS and XRD results showed that TiO2 and PEDOT were successfully supported on CNTs with good dispersion.The decrease of membrane flux is mainly due to cake layer pollution,and the antifouling performance is the highest when the applied voltage is 1.2 V vs.SCE.(3)CNTs-10%Ti O2-0.25 PEDOT catalytically modified conductive membrane was used as anode material to construct an EMBR to remove ammonia nitrogen from the circulating water of mariculture and control membrane pollution.The average ammonia removal capacity of EMBR in stage 1 and 2 is 1.72 mg/L and 2.05 mg/L,which is 57.7% and 134.6%higher than that of MBR.The first time of EMBR membrane washing was 40% longer,and the free chlorine formed on the membrane surface could reduce membrane fouling. |
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