| Wastewater from aquaculture has attracted widespread attention as one of the sources of agricultural non-point source pollution,which leads the management of aquatic wastewater to become a current research hotspot.Among many ectopic treatment systems for aquaculture wastewater,a precipitation unit named precipitation treatment unit,has been usually used as the primary unit of such this system.There is no corresponding research on how to improve its purification effect,because the purification efficiency of such this unit is incredible low.The purification materials and exogenous microorganisms has been firstly administrated into the existing precipitation treatment unit.This study attempts to clarify the mechanism of serial catalytic steps,which may contain adsorption and transformation for wastewater pollution.Another aim is to enhance the treatment capacity by adjusting the operating parameters when the unit has been used.The findings of this current study are based on the key technical indicators of purification material such as the type,nature,surface structure,the suitable usage amount,distribution,recycling capacity,as well as functional enzyme activities of microorganisms that distributed over the material,and the details were as follows:1.The purification effects of 7 purification materials(the phosphorus removal type Al-impregnated thermally-treated calcium-rich attapulgite(Al@TCAP-P),the nitrogen removal type(AI@TCAP-N),eramsite sand,bacterial house,volcanic stone,ammonia absorption stone and activated carbon)on total nitrogen(TN),total phosphorus(TP)and permanganate index(CODMn)in aquaculture wastewater were studied.Results showed that Al@TCAP-N had the best removal effect of TN,while volcanic stone had the best removal effect of both TP and CODMn.The optimum addition amount of materials was 6 g/L when the both two were operated independently without the addition of exogenous microorganisms.The most suitable distribution mode of Al@TCAP-N was tiling,while for volcanic stone,it was accumulation.Volcanic stone and Al@TCAP-N were compounded into a composite purification material.with the optimal mix ratio of 1:1,and it had a better purification effect on water than each single-use material.2.The methods of adding exogenous microorganisms and their corresponding operating parameters were also performed,with the application of composite purification material in this primary precipitation unit.Results showed that the purification effect of composite purification material on water quality improved through pre-immobilization treatment or direct addition by exogenous microorganism administration.The most suitable addition method was direct addition.The treatment effect of the primary sedimentation unit on cultured wastewater had been significantly improved,and its removal ratios of TN.TP and CODMn can reach 41.25%,45.31%and 54.97%.respectively,possibly through the combined effect of both composite purification material and exogenous microorganisms.Based on the capacity of reducing addition amount of purification materials and shortening the hydraulic retention time(HRT).the optimal addition amount of composite purification material was set as 1 g/L,and its HRT for wastewater was 48 h.3.The surface characteristics of two purification materials were studied not only by the machine of electron scanning microscope,but through adsorption-desorption analysis.The microbial enzyme activities(AKP,OPH,DHO,NIR,AMO,Nar)and their corresponding water quality indicators(TN,TP,CODMn,PO43-,NH3-N,NO2--N,NO3--N,DO)in the primary precipitation unit were measured,under the combined composite purification material and exogenous microorganisms.Results showed that both Al@TCAP-N and volcanic stone had huge specific surface areas,with BET specific surface areas of 28.58 m2/g and 10.9 m2/g respectively.Al@TCAP-N had a rough and uneven surface,with a large number of gully,protruding granules and pores.The purification effect was mainly purified by adsorption because it was difficult to attach microorganisms.Volcanic stones have granular protrusions,with more pores,and the surface of the protrusions is lumpy and slightly smooth.It is more suitable for microbial attachment.It purified wastewater by the dual effects of adsorption and microorganism attachment.Exogenous microorganisms increased the activity of functional enzymes such as organic degradation enzyme(DHO).key enzymes of the nitrogen cycle(NIR,Nar,AMO),and phosphorus invertase-related enzyme(AKP,OPH),which may result in improvement for both decomposition of organic matter and the conversion efficiency of nitrogen and phosphorus,and finally strengthening the water purification effect.4.The purification effect on water quality showed no significant difference between the composite purification material and the reused one after the recycle procedure of recovery,cleaning and drying,and which supported its certain reusability.The used purification material had a potential utilization value because it contained 201.73 μg nitrogen and 34.98 μg phosphorus per gram.The enhanced treatment efficiency of aquaculture wastewater,with the shortened HRT,obtained with the application of composite purification material and exogenous microorganisms in the primary precipitation unit,and such suggestion hinted a good foundation for its subsequent purification.The advantages containing its clear background,stable property,convenient source,low price,and reusable ability of the combined purification materials and its enhancer,exogenous microorganisms,led their rational co-application to be an economic,effective and practical method for strengthening the purification effect of water quality in such this primary precipitation unit.The current study provided the practical data on the purification ability of composite purification material and exogenous microorganisms,which offered a creative idea of how to manage the wastewater treatment system in aquaculture 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