[WATER] Cultivation of biological filters for the improvement of reservoir water quality and biodiversity

淡水富营养化在世界许多地方是一个严重的问题，导致生物群发生显著变化。从20世纪40年代以轮藻、大型植物和各种无脊椎动物为主的清水系统，到20世纪80年代以浮游植物和贫穷的无脊椎动物为主的清水系统，诺福克支流的N&P浓缩经历了转变。富营养化导致的生物多样性丧失在许多英国水库是一个令人担忧的问题，这些水库是重要的保护地点(SSSI和SACS)。此外，欧洲水框架指令(WFD)要求在2015年前使所有欧洲地表水保持良好的生态状态。富营养化水库对水的净化、供应和消费也是一个相当大的问题。藻类会阻挡微过滤器和沙子过滤器，减少水的吞吐量，有时还会要求工厂停止运行。最小的藻细胞可以通过过滤器，并在分配管道中分解。一些分解产品，特别是粘多糖，与添加到处理中的铁和铝进行螯合，导致供应中的金属水平增加。真菌和无脊椎动物会以生成的生物膜为食，导致味觉和气味问题。蓝藻水华可产生对人类健康构成威胁的毒素(如微囊藻毒素)。去除营养物质的主要途径包括a)疏浚泥沙并倾倒在陆地上以清除锁住泥沙的磷；b)种植扩大的芦苇床；c)通过微滤直接去除藻类；d)化学投加(例如铁或硫酸铜)，通过混凝去除磷。所有这些技术都很昂贵，其中许多对环境有害，而且大多数技术的性能都不可靠。最近的创新表明，收获滤食性生物，如以浮游植物为食的蓝贻贝(Mytilus Edulis)，可能是一种可持续的方法，可以生产高营养价值的食物，同时将营养物质从海洋循环到陆地。N和P的简单营养收支表明，贻贝养殖可以抵消对一些具有海洋排污口的污水处理厂的需求(Lindahl等人，2005年)。该项目的目的是测试在英国水库大规模种植滤食性生物群是否可以为改善水库水质以提供饮用水供应和增强生物多样性提供同样有效、成本效益高的工具。对英国一些水库的定性观察表明，近年来滤食性鱼类数量的增加推动了水质的改善。该项目将侧重于海绵、苔藓虫和入侵双壳类(斑马贻贝)对水库管理的贡献。通过与Anglian Water(AW)创新团队的合作，该学生将调查自然附着在不同定居钻机上的滤食者的身份、增长率、生物量和营养含量(N&P)。为了解释热层结和紫外线辐射的影响，还将调查深度模式。为了调查粪便和假粪便沉积的影响，将在钻机和对照场地下的配对复制之间比较沉积物和大型无脊椎动物群落。与AW在三个已知含有许多斑马贻贝的水库进行密切合作，将确保钻井平台设计最佳。学生将参观一个海洋贻贝养殖项目，并与饲料和化肥制造商联系，以确定收获材料的可能最终用途。澳大利亚国立卫生研究院还将对学生进行无脊椎动物和藻类收集和鉴定方面的培训。项目最后将进行成本效益分析，考虑收获频率、可能的收入或处置成本、N&P预算与替代品的比较(例如，化学磷肥剥离)、生态效益和设计选择。将对非本土物种的传播进行风险评估。

Eutrophication of freshwaters is a serious problem in many places worldwide, causing marked changes in the biota. N&P enrichment of the Norfolk Broads saw a shift from a clear water system dominated by charophytes, macrophytes and a diverse invertebrate fauna in the 1940s, to one dominated by phytoplankton and an impoverished invertebrate fauna by the 1980s. Eutrophication-driven biodiversity loss is a concern in many UK reservoirs which are important sites for conservation (SSSIs and SACs). Furthermore, the European Water Framework Directive (WFD) demands good ecological status of all European surface waters by 2015. Eutrophic reservoirs also present a considerable problem for water purification, supply and consumption. Algae can block microstrainers and sand filters, reducing throughput of water and sometimes requiring the plant to be taken out of service. The smallest algal cells can pass through the filters, and decompose in the distribution pipes. Some breakdown products, notably mucopolysaccharides, chelate with iron and aluminium that is added to the treatment, leading to increased metal levels passing to the supply. Fungi and invertebrates can feed on the resultant biofilms, leading to taste and odour problems. Cyanobacterial blooms can produce toxins (e.g. microcystin) that pose a risk to human health. The primary routes to nutrient removal include a) dredging of sediment and dumping on land to remove sediment-locked phosphorus; b) planting of enlarged reedbeds; c) direct stripping of algae through microfiltration; d) chemical dosing (e.g. iron or copper sulphate) to strip phosphorus through coagulation. All of these techniques are expensive, many are environmentally harmful, and most are unreliable in their performance. Recent innovations have shown that harvesting filter-feeding organisms such as the blue mussel (Mytilus edulis) that feed on phytoplankton may be a sustainable method for producing food of high nutritional value while simultaneously recycling nutrients from sea to land. Simple nutrient budgets for N and P suggests that mussel farming could offset the need for some sewage treatment plants with marine outfalls (Lindahl et al., 2005). The aim of this project is to test whether the broadscale cultivation of filter-feeding biota in UK reservoirs may offer a similarly efficient, cost-effective tool for improving reservoir water quality for potable supply and to enhance biodiversity. Qualitative observations in a number of UK reservoirs suggest increasing abundance of filter-feeders in recent years has driven improved water quality. The project will focus on the contributions that sponges, bryozoans and invasive bivalves (zebra mussels) can make to reservoir management. By working in collaboration with Anglian Water's (AW) Innovation team, the student will investigate the identity, growth rates, biomass and nutrient content (N&P) of filter-feeders that naturally attach to different settlement rigs. To account for thermal stratification and the effects of UV radiation, depth patterns will also be investigated. To investigate the effects of faecal and pseudofaecal deposition, sediment and macroinvertebrate communities will be compared between paired replicates beneath rigs and control sites. Close collaboration with AW at three reservoirs known to contain many zebra mussels will ensure that rig design is optimal. The student will visit a marine mussel cultivation programme and liaise with feedstuff and fertiliser manufacturers to identify possible end-use of harvested material. AW will also train the student in invertebrate and algal collection and identification. The project will finish with a cost-benefit analysis, considering harvest frequency, possible revenue or disposal costs, N&P budgets compared with alternatives (e.g. chemical phosphate stripping), ecological benefit and design options. A risk assessment will be made relating to the spreading of non-native species.