Marine Outfall Performance. I: Introduction and Flow Restoration

Sewage outfalls are common inclusions in the infrastructure of coastal cities and towns. Near-ocean industries may also make use of such pipes. Keeping such a conduit operating properly is by no means a trivial matter, and this paper is the first of two dealing with this complex topic. Herein, the various failure and impairment mechanisms are summarized, and the need for careful underwater inspection is stressed. Examples are given of inspection, maintenance, and repair operations for various municipal facilities. The paper closes with presentation of two improvement procedures, pigging and sliplining.     

Marine Wastewater Discharges from Multiport Diffusers. IV: Stratified Flowing Water

Experiments on the near-field mixing of wastewater discharged from multiport diffusers into stratified flowing waters are reported for conditions typical of actual ocean sewage outfalls. Dilutions were measured by a newly developed three-dimensional laser-induced fluorescence system combined with refractive-index matching and by a microconductivity probe. The plume dynamics are complex. Depending on port spacing, plumes discharged from the upstream diffuser side may merge first with themselves, and then with the plumes discharged from the downstream side. Or the plumes that are horizontally opposed may first merge, followed by lateral merging. In all cases, however, the wastefield eventually becomes laterally homogeneous. The results are analyzed in terms of line or point-source parameters and it is found that they can be predicted by assuming the discharge to be a line plume when s/lb<1.0 and as point plumes for s/lb ≥ 6.0. Semiempirical equations to predict the near-field dilution, near-field length, and plume rise height are presented.     

Considerations for Storm-Water Outfalls off Exposed Coasts

There is a worldwide movement for coastal municipalities in developed countries to replace whole series of storm drains with far fewer storm-water outfalls that discharge well offshore. Such an extended-length pipe, passing into the surf zone along an exposed coastline, is far from easy to plan, support with data, design, install, and operate. This paper is intended to school drainage engineers in these matters.     

Sedimentation from Buoyant Jets

An integral model is developed to describe sedimentation from a turbulent, buoyant jet injected at an angle into a stationary, uniform ambient fluid. Entrainment is modeled using the standard entrainment assumption and sediment is assumed to fall from the jet where the outward component of the fall velocity normal to the jet boundary exceeds the inward entrainment velocity. When appropriately scaled by source momentum and buoyancy fluxes, turbulent, buoyant jets may be described in terms of a single parameter: the angle θ0 between the flow and the horizontal at the virtual origin (which is close to the actual source for large initial densimetric Froude numbers). Including sedimentation in the model introduces a further parameter ws, which is the ratio of the fall speed of the sedimenting particles to a typical entrainment velocity (and so wS is a nondimensional fall speed). An important result is that this ratio is independent of the source speed, so that the proportion of the sediment load deposited near the source is independent of the flow rate. Sediment remaining in the plume beyond the near-source region is deposited when the plume spreads horizontally once it reaches the free surface. Results for plume shapes, deposition patterns, and the proportion of sediment load deposited in the near-source region (as functions of θ and ws) are given. The results are supported by some preliminary laboratory experiments. The effects of flow in the ambient fluid are discussed briefly and a further parameter uF is introduced, which is the ratio of the ambient flow speed to a typical entrainment velocity (again this ratio is independent of the flow rate).     

Marine Outfall Performance. II: Stabilization and Case Studies

This paper, the second in a series, outlines the various methods that can be used to immobilize and protect an exposed outfall pipe that appears vulnerable to destabilizing agents such as waves, ice, logs, or fishing trawls. Measures covered include the placing of quarry rock or articulated concrete block mats, the driving of piles, and the installation of stapling arrangements. Case studies cover various specific outfalls where particular stabilization measures were employed. Environmental considerations are included.     

淮河入海水道工程规划与移民安置规划的有机结合

为妥善解决移民生产和生活问题,淮河入海水道工程必须与移民安置规划有机结合起来,使入海水道工程的建设促进和改善农田的灌溉、防洪、排涝、降渍条件;结合当地资源优势,广开就业门路;结合航运发展地区经济;同时,即要保障上游安全,也要兼顾下游地区的经济发展,为下游地区的经济发展创造优越的自然环境。     

Deposition from Particle-Laden, Round, Turbulent, Horizontal, Buoyant Jets in Stationary and Coflowing Receiving Fluids

Results are presented from a series of laboratory experiments investigating the characteristic features of particle-laden, round, turbulent, buoyant jets discharged horizontally into stationary and coflowing receiving fluids. For the volumetric source concentrations of particles tested ( ～ 0.1%), the presence of the particle load was found to have no significant influence on mean buoyant jet trajectories. Deposition patterns on the bed of the receiving water container indicated the existence of two separate sedimentation processes for discharges into stationary or coflowing ambients, namely (1) a relatively concentrated, narrow band of particle accumulation associated with near-source fallout from the buoyant jet margins; and (2) a broader and more disperse downstream depositional fan associated with particle fallout from the radially-expanding surface gravity current formed by the impingement of the buoyant jet with the free surface of the receiving fluid. Scaling arguments have been developed and applied successfully to deposition length scales associated with these sedimentation patterns, allowing the quantitative characteristics and parametric dependences of the deposition distributions to be established.     

凌云县污水处理厂入河排污口对澄碧河的影响

分析了凌云县污水处理厂入河排污口有关信息。在满足水功能区保护要求的前提下,论述了入河排污口设置对水功能区、水生态和第三者权益的影响。根据纳污水体的纳污能力、排污总量控制范围、水生态保护等要求提出水资源保护措施。     

Dual Multilevel Urban Drainage Model

In urban areas, when heavy rains occur, the discharge capacity of sewers is usually unable to transport the effective rainfall reaching the streets. When the runoff flow rate exceeds the capacity of the storm sewer system, the excess flow is conveyed through the street network as overland flow. A dual model is proposed for modeling the system as a double network, formed by an upper network of open channels (street gutters) and a lower network of closed conduits (sewer pipes). What is new in this model is its capacity to take into account the hydrodynamic relationship between the flows in the upper and lower networks. The model is applied to computing the response of a real monitored basin; the historical flow rates measured during a first rainfall event are used to calibrate the model, which is then validated using the simulation of two other measured events.     

Marine Wastewater Discharges from Multiport Diffusers. I: Unstratified Stationary Water

Laboratory experiments on the near-field mixing of buoyant plumes discharged from multiport diffusers into unstratified stationary water are reported. Dilution was measured by a newly developed three-dimensional laser-induced fluorescence system and a microconductivity probe. Significant additional mixing (and dilution) occurs beyond the point where the plume impacts the water surface. This mixing ceases when the turbulence generated by the plumes collapses in the surface spreading layer. The port spacing, s, was varied through a range encompassing line to point source conditions. In all cases, the concentration distribution in the surface layer eventually becomes laterally uniform. Measurements of the near-field dilution, length, and layer thickness, and semiempirical equations to predict them are presented. The discharge behaves as a line plume when s/H ? 0.3, and as a point plume when s/H ≥ 1.0. The additional near-field mixing for a point plume is much greater than for a line plume. Basing diffuser design on near-field dilution rather than impact-point dilution allows the use of far fewer ports, or risers, with considerable potential cost savings, particularly for tunneled outfalls.