Abstract: A combined system of moving bed biofilm beactor (MBBR) - algae reactor is designed as a biological treatment unit to eliminate inorganic nitrogen in aquaculture water and solve the problem of nitrate accumulation in recirculating aquaculture system(RAS) production, taking the RAS of Litopenaeus vannamei as an example (culture load 5000 kg). According to the principle of material balance, it is determined that the influent flow of the biological treatment unit is 453.3 m3 / h and the MBBR size is 4 m × 4 m × 2.8 m (4), algae reactor size is 6 m × 6 m × 2.8 m (4), the hydraulic retention time of MBBR is 0.3 h, the hydraulic retention time of algae reactor is 0.36 h, the renewal amount of fresh water in the system is 0.97 m3 / h, the number of cycles is 22 times / d, and the nitrate nitrogen in the system can be maintained within the safe concentration range below 70 mg / L. The experimental system was constructed for verification. It was found that compared with MBBR, the removal rate of total nitrogen increased from 3.9% to 42.8%; at the same time, algae can absorb phosphate through photosynthesis. The removal rate of total phosphorus by the combined system is as high as 66.8%, and the SGR of algae is 3.86% - 10.35% / day. The combined system can effectively shorten the hydraulic retention time required to remove the same amount of nitrogen and phosphorus. The research can provide a theoretical reference for nitrate in situ elimination technology and the establishment of a biological treatment unit in RAS, and promote the green development of aquaculture.

Key words: recirculating aquaculture system, moving bed biofilm reactor, algae, nitrate, accumulation of inorganic nitrogen, design

摘要： 为解决循环水养殖生产中硝酸盐积累问题，以凡纳滨对虾(Litopenaeus Vannamei )循环水养殖系统为例（养殖负荷5 000 kg），设计了一种移动床生物膜反应器（MBBR）—藻类反应器联用系统作为生物处理单元用以消除养殖水体中无机氮。根据物质平衡原理确定生物处理单元进水流量为453.3 m3/h，MBBR尺寸为4 m×4 m×2.8 m（4个），藻类反应器尺寸为6 m×6 m×2.8 m（4个），MBBR水力停留时间（HRT）为0.3 h，藻类反应器HRT为0.36 h，系统新水更新量为0.97 m3/h，循环次数为22 次/d，系统硝酸盐氮可维持在70 mg/L以下的安全质量浓度范围内。构建中试系统进行验证，发现MBBR-藻类反应器联用相比MBBR，总氮的去除率由3.9%提高至42.8%；藻类可通过光合作用吸收水体磷酸盐，联用系统对总磷的去除率高达66.8%，藻类特定生长率达到3.86~10.35%/d，联用系统有效缩短了去除同量氮磷所需水力停留时间。本研究可为循环水养殖系统中硝酸盐原位消除技术及生物处理单元的建立提供理论参考，助推水产养殖绿色发展。  

关键词: 循环水养殖系统, MBBR, 藻类, 硝酸盐, 无机氮积累, 设计