沼蛤(Limnoperna fortunei)作为典型入侵性底栖动物,可造成管道严重堵塞,威胁技术供水系统正常运转。前期试验研究了致紊材料对管道水力特性的改变,为验证致紊材料对管道沼蛤幼虫灭杀效果,本研究选用水力学试验推荐的4种致紊材料并采用普通和加密两种方式布置在管道中。分别进行了脉动灭杀试验(试验系统流量=0.018 m^3/s)和死循环(系统补给流量≈0 m^3/s)灭杀试验,采样和显微观测统计不同发育阶段幼虫的密度及死亡率。结果表明试验期间沼蛤幼虫基本处于前期壳顶阶段,经过脉动管后死亡方式主要为组织流出、组织脱落和壳体破碎。脉动试验中6 mm孔板对沼蛤幼虫灭杀效果最好,加密布置可以提升大孔径孔板和筛网的灭杀效果。采用幼虫相对体长d*(幼虫体长与Kolmogorov长度尺度之比)衡量致紊材料的灭杀效果,当下游主流区(d*)max〉0.7时灭杀效果明显。死循环在5 min内可以迅速提高沼蛤幼虫死亡率,之后死亡率基本稳定,所以如能保证幼虫在脉动场中被作用达一定时间,即能对其进行有效灭杀。
Golden mussel(Limnoperna fortunei) is an invading macro-invertebrate species and easily leads to heavy pipe clogging,which casts great threat to the technical water supply system.The previous experimental study explored the influence from turbulence-generating materials(TGMs) on hydraulic characteristics inside a pipeline.To examine the actual efficiency of such TGMs and installation patterns on killing golden mussel larvae,four types of TGMs were installed with intervals of 50 and 25 cm in the same pipeline system of the hydraulic experiment.Direct test(water supply to the pipeline = 0.018 mVs) and circulation test(water supply to the pipeline ≈0 m /s) were conducted to compare the killing efficiency of different materials.Water samples were taken before and after the treatment of pipeline turbulence.The total density and mortality of the larvae in water samples were obtained by counting under a microscope.It was found that most oi the larvae were prediveligers during the entire experiment period.The tissues of the prediveligers were damaged and released out from the shells or the shells of the veligers were broken after they went through the experimental pipeline.The 6 mm pore plate exhibited significant enhancement of larvae mortality among all the tested materials.The dense layout(interval=25 cm) improved the larva killing efficiency of the wire meshes.A relative length scale d~*(the ratio of shell size to the Kolmogorov length)was utilized to evaluate the efficiency of TGMs.The material is supposed to be efficient in improving the mortality of the larvae if the downstream(d^*)max0.7.Larvae mortality was promoted rapidly in 5 min and kept steady afterwards during the circulation experiments,indicating that the larvae were likely to be removed if they were treated in the turbulent field for a certain period of time,e.g.5 min.