循环流水水产养殖系统接种商品硝化菌的试验研究

Utilization of commercial nitrobacteria additive in the inoculation of a new recirculating aquaculture system

与接种成熟滤料等方法相比,利用商品硝化菌接种生物滤器来源广泛,操作简便。本文使用一种商业上已取得一定成功的商品硝化菌液接种循环流水水产养殖系统试验模型的生物滤器。试验开始时定期接人20mL菌液(细菌含量1.5×10~10CFU·mL^(-1))以处理400g饲料产生的4.27mg·L^(-1)氨氮(TAN),12d后TAN浓度低于0.05mg·L^(-1),20d后NO_2^- -N浓度降至同样水平。在为期30d的检验期中,系统内养殖2.15kg·m^(-3)淡水白鲳,日喂饲率2％。期间养殖池TAN最大值0.465mg-L^(-1),最小值0.393mg·L^(-1),平均值0.427±0.019mg·L^(-1);NO_2^- -N最大值0.062mg·L^(-1),最小值0.038mg·L^(-1),平均值0.052±0.007mg·L^(-1);EC呈线性上升状态,每周增加32.8 μs·cm^(-1);而pH呈线性下降,每周降低0.24。系统结束时生物滤器含细菌8.65×10~6CFU·mL^(-1),水质除TP超标外,其余指标均符合我国淡水水产养殖水质标准,在2.1％～1.4％的日喂饲率下淡水白鲳日增重为1.91g,饲料系数1.164。

In recirculating aquaculture production systems, certain high quality commercial bacterial amendments are easier to be used than getting media from an established biofilter. In this paper, a known commercial bacterial amendment was used to inoculate for a new biofilter of a pilot recirculating aquaculture system. At the beginning, 20 mL amendment in all (300 billion CFU bacteria) was injected into the biofilter basin in four applications during a period of three days. On the first day and the third day of the experiment, 200g of feed containing 32 % protein were dissolved into fish tanks. The peak of total ammonia nitrogen (TAN) concentration was found on the seventh day and that of nitrite nitrogen (NO_2^- - N) was found four days later. It took 12 and 20 days for TAN and NO2_2^- - N, respectively, to achieve a level of 0.05 mg· L^(-1). In the subsequent 30 day investigation, 54 Colossoma brachypomum (mean initial weight 105.7 ± 23.2 g) were stocked in the system at the density of 2.15 kg·m^(-3) and fed a sinking 32% protein diet twice daily. TAN level in two fish tanks was kept between 0.393 and 0.465 with a mean of 0.427 ± 0.019 mg·L^(-1) ; and NO_2^- - N was between 0.038 and 0.062 mg·L^(-1) with a mean of 0.052 ± 0.007 mg· L^(-1) . Diurnal changes of TAN concentration showed two peaks and two troughs, while NO_2^- - N concentration only showed one peak and one trough. Electric conductivity (EC) measurements taken in the fish tanks showed a linear accumulation of 32.8 μs·cm^(-1) weekly while pH descended 0.24 every week. At the end of this experiment, 8.65 million CFU·mL^(-1) of bacteria was found in the biofilter. Except total phosphorus (TP) of 4.81 mg·L^(-1), water quality parameters all conformed to the requirements of Chinese Freshwater Aquaculture Water Quality Standards with TAN of 0.471 mg·L^(-1), NO_2^- - N of 0.05 mg·L^(-1) , nitrate nitrogen (NO_2^- - N) of 7.10 mg· L^(-1), total nitrogen (TN) of 13.16 mg· L^(-1), chemical oxygen demand (COD) of 7.2 mg·L^(-1), and dissolved oxygen (DO) of 8.7 mg·L^(-1). As a result of comfortable environments, the fish grew well under daily feed rates of 2.1% - 1.4% and got a survival rate of 100%, with a daily growth rate of 1.91 g, and a feed conversion ratio (FCR) of 1. 164.