Studies on water treatment effect of PVA-PVP blends biocarrier for RAS

Polyethylene（ PE） is one kind of conventional material which is generally used for manufacture of biocarriers. However，because of the material’s property，water treatment effect of PE material is difficult to increase. The other problem is that accumulation of nitrate is remarkable because all of TAN has been converted into form of nitrate. In order to solve the problems，one kind of polyvinyl alcohol/ polyvinyl pyrrolidone（ PVA-PVP） blends biocarrier has been developed，of which density is 0.4051 g/cm3，PE，PVA and PVP weight ratio is 90%～91%， 3%～4% and 2%～3% respectively. By using of moving bed biofiltration technology，water treatment of the PVA-PVP blends biocarrier has been evaluated in a recirculating aquaculture system raising russian sturgeon（ Acipenser gueldenstaedtii） as culture specie. Results show that TAN，NO2 - and NO3 removal rate of blends biocarrier is remarkably higher than conventional PE biocarrier. Dissolved oxygen concentration（ DO） has significant effect on water treatment of the blends biocarrier. Under low DO condition，average removal rate on TAN and NO2 - are higher， which is 25.76（±9.26）% and 22.28（±9.25）% respectively. Under high DO condition，average removal rate on NO3 is higher，which is 11.52（±14.23）%. In conclusion，PVA-PVP blends biocarrier can be used in moving bed biofilm reactor very well，which can effectively remove TAN and NO3 from aquaculture water. Using PVA-PVP blends biocarrier to replace conventional PE biocarrier can remarkably increase the stability and performance of recirculating aquaculture system and promote the development of aquaculture industry.