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

淡水富营养化在世界上许多地方都是一个严重的问题，造成了生物群的显著变化。20世纪40年代，诺福克湖区的水体由以绿叶植物、大型植物和多种无脊椎动物为主的清澈水体系统转变为以浮游植物和贫瘠的无脊椎动物为主的水体系统。富营养化驱动的生物多样性丧失是许多英国水库的一个问题，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）要求到2015年所有欧洲地表水的生态状况良好。富营养化水库在水净化、供水和用水方面也存在相当大的问题。藻类可以阻塞微过滤器和砂过滤器，减少水的吞吐量，有时需要工厂停止使用。最小的藻类细胞可以通过过滤器，并在分配管道中分解。一些分解产物，特别是粘多糖，与添加到处理中的铁和铝螯合，导致进入供应的金属含量增加。真菌和无脊椎动物可以以产生的生物膜为食，导致味觉和气味问题。蓝藻大量繁殖可产生毒素（如微囊藻毒素），对人类健康构成威胁。去除营养物的主要途径包括a)疏浚沉积物和在陆地上倾倒以去除沉积物锁定的磷；B)种植扩大的芦苇床；C)微滤直接脱藻；D)化学剂量（如硫酸铁或硫酸铜）通过混凝去除磷。所有这些技术都很昂贵，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，收获以浮游植物为食的滤食性生物，如蓝贻贝（Mytilus edulis），可能是一种可持续的方法，既能生产高营养价值的食物，又能将营养物质从海洋循环到陆地。简单的氮和磷的营养预算表明，贻贝养殖可以抵消一些有海洋排放物的污水处理厂的需求（Lindahl等人，2005）。这个项目的目的是测试在英国水库大规模培养滤食性生物群是否可以提供一种同样有效的、具有成本效益的工具，以改善水库饮用水的水质，并增强生物多样性。在英国一些水库进行的定性观察表明，近年来滤食性动物数量的增加推动了水质的改善。该项目将重点关注海绵、苔藓虫和入侵双壳类动物（斑马贻贝）对水库管理的贡献。通过与Anglian Water的创新团队合作，学生将研究自然附着在不同沉降平台上的滤食性生物的特性、生长速度、生物量和营养含量（N&P）。为了解释热分层和紫外线辐射的影响，还将研究深度模式。为了调查粪便和假粪便沉积的影响，将比较钻机和对照场地下成对重复的沉积物和大型无脊椎动物群落。在三个已知含有大量斑马贻贝的油藏中，与AW的密切合作将确保钻机设计的最佳化。学生将参观一个贻贝养殖计划，并与饲料和肥料制造商联络，以确定收获材料的最终用途。AW还将培训学生收集和识别无脊椎动物和藻类。项目将以成本效益分析结束，考虑收获频率、可能的收入或处置成本、与替代方案（如化学磷酸盐剥离）相比的N&P预算、生态效益和设计方案。将对非本地物种的扩散进行风险评估。

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.