鲍放养密度对循环水养殖水质的影响及生物滤器净化效果

该文以皱纹盘鲍(Haliotis discus hannai Ino)循环水养殖的排放水体为研究对象,以提高水循环系统综合利用率为目标,比较了鲍(壳长为(38.34±1.63)mm,体质量(7.97±0.42)g)在高(500个/m~2)、中(300个/m~2)、低(100个/m~2)密度下养殖水环境的变化特点,并综合评价了移动床曝气生物滤器的水处理效果。研究表明:放养密度对水体中总氨氮(TAN)、亚硝酸盐氮(NO_2~–-N)、总氮(TN)、总磷(TP)、磷酸盐(PO_4~(3–)-P)浓度和可培养异养细菌总数均有显著影响(P0.05),依次表现为高密度组中等密度组低密度组。中、高密度组硝酸盐氮(NO_3~–-N)、化学需氧量(COD)浓度和弧菌总数并没有显著差异(P0.05),但均显著高于低密度组(P0.05)。现行工况下(水循环率、温度、水力负荷等),生物滤器对TAN、NO_2~–-N、NO_3~–-N、TN、PO_4~(3–)-P、TP、COD的平均去除率分别为16.40%、15.81%、2.93%、12.22%、2.91%、6.48%、9.47%。该生物滤器对养殖排放水中能够对鲍产生明显毒害作用的TAN、NO_2~–-N处理效果较好,使其均维持在安全的浓度范围内,满足实际生产需求。但对NO_3~–-N、TN的脱除以及低浓度PO_4~(3–)-P和COD的处理效率相对较低。因此,综合经济和生态效益等多方面因素,在该试验的多层、立体循环水养殖系统内,将皱纹盘鲍的密度设定为500个/m~2时是较为合适的。

Effects of stocking density on water quality of Haliotis discus hannai Ino in recirculating aquaculture and purification effect of biofilter

Abstract: This paper focused on the wastewater discharged from the aquaculture of Haliotis discus hannai Ino (H. d. hannai), targeted at improving the comprehensive utilization rate of water circulation system, compared the changing characteristics of the aquaculture water environment between the high density (HD) group (500 m-2), the medium density (MD) group (300 m-2) and the low density (LD) group (100 m-2), and evaluated the water treatment effect of moving bed aerating biofilter. Results showed that stocking density had a significant effect on the concentration of total ammonia (TAN), nitrite nitrogen (NO2--N), total nitrogen (TN), total phosphorus (TP) and phosphate (PO43--P) (P<0.05), and the degree of effect could be ranked as: HD > MD > LD. The total number of heterotrophic bacteria in each density group increased over time; except the 2nd and 11th sampling, the total number of heterotrophic bacteria in the HD group at other time points was significantly higher than that in the MD and LD group (P<0.05). The MD and HD group showed no significant difference in the concentration of nitrate nitrogen (NO3--N) and chemical oxygen demand (COD) (P>0.05), but were significantly higher than that in LD group (P<0.05). At the 1st, 2nd, 3rd and 5th sampling, no significant difference in respect of the total number of vibrios was identified among the density groups (P>0.05), and from the 6th sampling to the end of the experiment, the total number of vibrios in the MD and HD group was significantly higher than that in the LD group (P<0.05). In current conditions (water circulation rate, temperature, hydraulic loading), the average removal rate of biofilter for TAN, NO2--N, NO3--N, TN, PO43--P, TP, COD was 16.40%, 15.81%, 2.93%, 12.22%, 2.91%, 6.48% and 9.47% respectively. At the point of the last sampling, no significant difference in respect of the removal rate of TAN was identified compared with the 8th and 14th sampling, but it was significantly higher than that in any other time point (P<0.05). At the point of the 14th sampling, no significant difference in respect of the removal rate of NO2--N was identified compared with the 5th and 13th sampling, but it was significantly higher than that in any other time point (P<0.05). The biofilter had a better treatment effect on TAN and NO2--N which produce an obvious toxic effect on abalone in the aquaculture wastewater. However, it had a relatively low treatment efficiency on the removal of NO3--N, TN and the low-concentration PO43--P and COD. Therefore, in view of the multiple factors including economic and ecological benefits, it will be more appropriate to set the density of H. d. hannai as 500 m-2 in the multi-layer, three-dimensional recirculating aquaculture systems.