首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5篇
  免费   0篇
水产渔业   5篇
  2019年   1篇
  2009年   1篇
  2008年   1篇
  2007年   2篇
排序方式: 共有5条查询结果,搜索用时 15 毫秒
1
1.
This study examined the effects of different hydraulic loading rates on the treatment efficiency of subsurface flow (SSF) constructed wetlands treating effluents from trout farming over a period of 6 months. Six identical wetland cells with a pre-sedimentation zone of 9.6 m2 and a root zone of 23.6 m2 were loaded with effluents from intensive trout farming (> 2.1 kg feeding stuff per L/s and day). The total runoff of 13.2 L/s was treated in the wetland cells, where two duplicate cells received equal hydraulic loads of 3.9, 1.8 and 0.9 L/s. All examined wetland cells had significant treatment effects on the nutrient fractions containing particulate matter [total nitrogen (TN), total phosphorous (TP), biological oxygen demand in 5 days (BOD5), chemical oxygen demand (COD), and total suspended solids (TSS)].

Efficiency was between 5.5% for TN and 90.1% for TSS. The SSF wetland also had a high treatment effect on total ammonia nitrogen (TAN), with efficiencies of 61.2 to 87.8%. Nitrate nitrogen (NO3–N) and phosphate phosphorous (PO4–P) showed a significant increase in the wetland effluent by 8.4 to 209%. Nitrite nitrogen (NO2–N), had no significant, or significant effluent increase depending on the inflow rate. Treatment efficiency for particulate nutrients and TAN increased with decreasing hydraulic load, while the differences between 1.8 and 0.9 L/s were not significant. The treatment efficiency for TP was constant for all cells, at around 40%. The wetland receiving 3.9 L/s was over-flooded after 10 to 12 weeks due to colmatation. Nevertheless, the wetland still showed high treatment efficiencies. For commercial trout farms, SSF wetlands are a highly effective method of effluent treatment. A hydraulic load of 1 L/s on 13.3 m2 wetland area (1.8 L/s on the examined wetland) seems most suitable. Higher loads lead to accelerated wetland colmatation, while lower loads waste space.  相似文献   

2.
The present case study, deals with a recently built aquaculture facility using 80–120 L s−1 spring water for trout production. The farm consists of six raceways, discharging in a common outflow channel, leading to a drum filter equipped with 80 μm gauze. About 120 L s−1 of the microscreen effluent is pumped back in the inflow channel of the six raceways. The remaining effluent is oxygenated with pure oxygen in gravity oxygenation units and led to two U-shaped raceways. The farm effluent is finally filtered by a drum filter with 63 μm mesh size. The microscreen backwash sludge is treated in a cone settler, where the sediments are extracted for agricultural manure application. The sedimentation supernatant is further led in a sub surface flow (SSF) constructed wetland prior to discharge.Due to the advanced effluent treatment within the farm, the total farm effect on the receiving effluent is kept to a minimum. The nutrient increase produced by the farm is only 0.03 mg L−1 total phosphorous (TP), 1.09 mg L−1 biological oxygen demand (BOD5) and, 0.57 mg L−1 total suspended solids (TSS) in the brook. Especially the incorporation of an intermediate microscreen prior to water recirculation, prevents leaching of dissolved nutrients from particulate matter, as large particles are effectively and as fast as possible removed from the water flow.At the pumping station, needed for water recirculation, the particle size distribution (PSD) was monitored with the previous microscreen in use and by-passed. When the screen was by-passed a significant crushing effect on PSD through pumping action was found. Through the removal of large particles, the crushing effect of the pumping station on the particles is prevented, as revealed by particle size distribution (PSD) measurement. Thus, leaching of dissolved nutrients is prevented twice.In consequence, the farm configuration can be recommended as an effective possibility for intensive trout production at sites with a small freshwater source and stringent effluent thresholds, even with the unexpected low treatment efficiencies measured for the microscreens. Both drum filters showed relative low treatment efficiencies of 33–53% for total suspended solids, respectively, while an efficiency of 70% should be expected from the measured PSD. With this impact, the farm still emitted a low nutrient amount, especially due to the highly effective offline microscreen backwash sludge treatment, where the SSF wetland efficiently reduced dissolved and particulate nutrients as nitrite (NO2-N), nitrate (NO3-N) and TSS. Thus this SSF wetland application might be suitable as a denitrification step in a closed recirculating trout farm.  相似文献   
3.
In non‐salmonid fish, Aeromonas salmonicidacan cause local infections with severe skin ulcerations, known as atypical furunculosis. In this study, we present a systemic infection by a virulent A. salmonicidain European perch (Perca fluviatilis).This infection was diagnosed in a Swiss warm water recirculation aquaculture system. The isolate of A.  salmonicida encodes a type three secretion system (TTSS) most likely located on a plasmid similar to pAsa5/pASvirA, which is known to specify one of the main virulence attributes of the species A. salmonicida. However, the genes specifying the TTSS of the perch isolate show a higher temperature tolerance than strains isolated from cold‐water fish. The function of the TTSS in virulence was verified in a cytotoxicity test using bluegill fry and epithelioma papulosum cyprinid cells.  相似文献   
4.
5.
A study on effluent treatment with sub-surface flow (SF) constructed wetlands was conducted in a small commercial scale Bavarian (Germany) flow-through trout farm. Under limited spatial and financial conditions a most suitable wetland was constructed. The wetland treatment efficiency at high hydraulic loading rates during raceway runoff and cleaning situation in comparison to sedimentation as initial treatment method was examined.

The constructional solution involved the alteration of six existing sedimentation basins (SB) to SF horizontal flow constructed wetlands with a pre-sedimentation area. As constructional materials only local, cheaply available materials were used in order to reduce the costs. The SF wetland had high treatment efficiencies in the two operational modes examined. During cleaning situation at a hydraulic loading rate (HLR) of 13.6 m/day treatment efficiency for total suspended solids (TSS) was highest and reached 68%. While during raceway runoff situation total ammonia nitrogen (TAN) treatment efficiency of 88% overtopped the efficiency of the other nutrients examined at a HLR of 10.6 m/day. In both treatment situations the SF wetland efficiency was significantly higher than the effect of the SB. SF constructed wetlands treating high hydraulic loading rates accompanied with short retention times were effective on dissolved nutrient treatment only for TAN and nitrite nitrogen (NO2–N), while other dissolved nutrients like nitrate nitrogen (NO3–N) and phosphate phosphorous (PO4–P) showed no or even negative treatment effects through the wetland passage. To reduce these nutrients, other treatment conditions or wetland configurations are needed.  相似文献   

1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号