摘要
养殖水体中固体颗粒物的沉降特性对养殖池和沉淀池的优化设计非常重要。在乌龟温室养殖中期,取距池底10 cm处的养殖水作为沉淀原样进行静态沉淀试验,测得原样的悬浮颗粒物质量浓度为(763±15.3) mg/L,粒径分布范围是1～300μm,其中粒径>100μm的颗粒物体积占20.4%,50～100μm的占39.1%,<50μm的占40.5%。结果表明:在一定的深度范围内颗粒物沉淀速率不受沉淀池深度影响,但若沉淀池太浅且颗粒物浓度较高时会发生拥挤和压缩沉淀;对于乌龟养殖中期的水体,确定了沉淀池的溢流速率和颗粒物去除率之间的关系,当溢流速率为0.0167 cm/s,悬浮颗粒物的去除率为24.9%,且溢流出的水体中总体积90%的颗粒物粒径<98.4μm,50%的颗粒物粒径<41.9μm;在龟鳖温室养殖池中设置平流式沉淀池可有效地进行悬浮颗粒物的管理和去除,且随着养殖水体中细微颗粒物的增加,溢流速率可随之减小。
The settling characteristics and size distribution of solid wastes in aquaculture water play a critical role in designing rearing tank and sedimentation basin.The greenhouse turtle culture is a widely used farming mode,due to its high efficiency and easy to control.The main solid wastes are uneaten feed,faeces and bacterial flocs.Solid wastes can lead to poor water quality and aquacultural benefit if without effectively removed.Research showed that the heterotrophic bacteria can use particulate organic matter for mineralization process.This process not only consumes oxygen,but also produces ammonia.The metabolism of reared organisms also produces ammonia,which lead to a rapid deterioration of water quality.Solids management and removal is the basis for maintaining the aquaculture system operating stably,it is also of great significance for increasing density and ensuring the safety of reared organisms,especially the suspended particles with long contact time and large contact area.Turtle culture is an important economic industry in Yangtze river delta region.In the rearing process,the low removal efficiency of solids,a lot of water exchange and sewage discharge restrict the development of this economic industry.In the middle and later stage of turtle culture,the accumulation of suspended particles caused the water quality to deteriorate and a frequent water exchange,resulting in the increase of rearing cost.The particles under the influence of turtle frequent activities,those large particles are easily broken into suspended particles which is very terrible for the turtle culture.This research took the turtle culture water near the bottom of rearing tank for a simple static sedimentation experiment.The water depth of settling device was 80 cm,the length of two sampling points was 30 cm and the shallow one away from liquid level was also 30 cm.The two sampling points can characterize the difference of suspended particles at different depths in the settling process.The 8 groups of static settling time were 5,10,15,20,30,40,50 and 60 min,respectively.Each group of settling time for static settling experiment was repeated for 3 times.The particle size-volume distribution of water samples was measured by a non-invasive laser scatter instrument.The presentation method of particle size-volume distribution includes interval volume distribution and cumulative volume distribution which can reflect the characteristics of particles size-volume distribution in different aspects and can also be converted to each other.The mass concentration of suspended particles in the original sample was(763±15.3)mg/L and the particles size ranged from 1 to 300μm.The particles size>100μm in total volume accounted for 20.4%,the particles size 50-100μm in total volume accounted for 39.1%,and particles size<50μm in total volume accounted for 40.5%.The results of static sedimentation experiment showed that the depth of the sedimentation will not affect the settling velocity,but it must ensure a certain depth to avoid higher concentration of particles accumulating in the settling zone which will occur hindered and compression settling.For the water in the middle stage of turtle culture,when the overflow rate was 0.0167 cm/s in the sedimentation basin,the removal efficiency of suspended particles was 24.9%.90%in total volume of the particles in the outflow water was less than 98.4μm,and 50%in total volume was less than 41.9μm.For greenhouse turtle culture,the flat flow sedimentation basin can effectively remove suspended particles,and with the increase of fine particles in the aquaculture water,the overflow rate of sedimentation basin can be reduced accordingly.
作者
季明东
李海军
李建平
叶章颖
朱松明
Ji Mingdong;Li Haijun;Li Jianping;Ye Zhangying;Zhu Songming(College of Biosystems Engineering and Food Science,Zhejiang University,Hangzhou 310058,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2018年第21期222-227,共6页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家水体污染控制与治理科技重大专项课题"温室甲鱼清洁生产与废水生态净化处理成套技术研究及示范"(编号:2014ZX07101-012)
杭州市科技计划项目"基于环境友好型池塘内循环流水养殖技术的示范与推广"(编号20172015A05)
关键词
颗粒物
沉淀
去除率
粒径分布
乌龟养殖
particles
sedimentation
removal efficiency
particle size distribution
turtle culture
