碳氮比对生物絮凝反应器处理水质效果的影响

Effect of carbon-nitrogen ratio-nitrogen ratio(C/N) on the water quality in biofloc reactor

为探究不同C/N对以生物絮凝反应器为唯一水处理装置的循环水养殖系统的废水处理的影响,以鳗鱼循环水养殖废水为研究对象,分别设置不同DOC/DIN梯度(Dissolved Organic Carbon,DOC; Dissolved Inorganic Nitrogen,DIN,C/N:0、5、10和15)进行相关研究。实验结果表明:C/N=0时(未添加碳源),反应器没有脱氮除磷的效果,NO_3^--N、PO_4^(3-)出现积累;随着C/N的升高,反应器脱氮除磷的效果也逐渐增加,C/N=15时去除效果显著高于其他处理组(P <0. 05),TN、NO_3^--N和PO_4^(3-)的去除率(RR)分别为46. 60%、43. 49%和24. 40%;在整个实验过程中,反应器的SS、TAN和NO_2^--N在C/N=0和C/N=5的去除效果显著高于C/N=10和C/N=15的去除效果(P <0. 05),并且随着C/N的升高而降低;在C/N逐渐升高的条件下,反应器的稳定性逐渐变差,反应器最高可运行的C/N为15;在低C/N(C/N=0和5)情况下,反应器絮体体积指数(SVI-30)始终小于150 mg/L,未出现絮团膨胀,系统稳定性良好;当10≤C/N≤15时,反应器呈现出絮团微膨胀,反应器的稳定性变得较差,但对反应器脱氮除磷效果没有影响。在BFT(Biofloc Technology)反应器中,反应器的ORP值与反应器的C/N呈负相关关系,可作为BFT反应器反硝化特征和优化的参数。综上可知,BFT反应器在低C/N条件下对SS、TAN、NO_2^--N具有良好的水处理效果,在C/N≥10情况下对TN、NO_3^--N和PO_4^(3-)具有良好的水处理效果,具有同步硝化反硝化(Simultaneous Nitrification and Denitrification,SND)和除磷的作用。研究结果可为其用作RAS核心水处理装置的进一步研究和应用提供参考。

Biofloc reactor was used as a key unit of RAS( Recirculating Aquaculture System). The effects of different C/N on the wastewater treatment of biofloc reactor were investigated,and four different gradients of C/N ratio( DOC,Dissolved Organic Carbon; DIN,Dissolved Inorganic Nitrogen,C/N = 0,5,10 and 15)were set. The experimental results showed that: when C/N = 0( without adding carbon source),the efficiencies of nitrogen and phosphorus removal in the reactor were not obvious,and the accumulation of NO3--N and PO43- appeared. The increase of C/N,the nitrogen and phosphorus removal efficiencies of the reactor were increasing with the rising C/N. The removal efficiency was the best when C/N = 15( P < 0. 05),and the removal rate( RR) of TN,NO3--N and PO43-( RR) were 46. 6%,43. 49% and 24. 4%,respectively. During the whole experiment,when C/N = 0 and C/N = 5,the removal efficiencies of SS,TAN and NO2--N were significantly higher than that of C/N = 10 and C/N = 15( P < 0. 05). The stability of the reactor gradually became poor with the increasing C/N,and the highest C/N of reactor could be 15. When C/N was 5,the volume index of floc reactor( SVI-30) was sostenuto less than 150 mg/L,and floc expansion did not appear. When 10≤C/N≤15,the stability of the reactor became worse,but it had no effect on the efficiency of nitrogen and phosphorus removal in the reactor. The ORP and DO values were negatively related to the C/N of the reactor,and they can be used as the parameters of the BFT reactor to optimize the process.Overall,the BFT reactor had good water treatment efficiencies on SS,TAN and NO2--N under low C/N conditions,when C/N was more than 10,it had a good water treatment performance on TN,NO3--N and PO43-,with simultaneous nitrification and denitrification( SND) and phosphorus removal. For BFT reactor used as a key device of RAS,this study can provide reference for further research and application.