Authors

D.A. Phipps, R.M.Alkhaddar, E. Loffill, R.Y.G Andoh and M.G. Faram

Abstract

The factors affecting the overall efficiency for the removal of a solid from an influent stream of water by an HDVS (Hydrodynamic Vortex Separator) have been examined using a combination of solids capture/washout experiments and dye tracer studies. The overall solids removal efficiency of the device is a function of loading rate (overall flow). The efficiency can be considered in terms of the balance between initial capture of the sediment and any subsequent re-entrainment. Tracer studies have shown that a well-designed device offers almost complete separation into a mobile and quiescent zone, with slow exchange between the two. This enhances both sediment capture and its subsequent retention.

Authors

K. Osei, R.Y.G. Andoh, J. MacKinnon and M.G.Faram

Abstract

Laboratory testing of stormwater separators can overcome many of the technical challenges associated with field testing. With laboratory testing, sediment characteristics and the flow rates at which a device is tested are known and measurable before, during, and after the test. This controlled environment ensures that test programmes can be set up to meet specific objectives, and data can be obtained in a repeatable and timely fashion. However there are differences in laboratory test protocols that can have a significant bearing on test results which, if overlooked, can result in invalid comparisons being made between different systems. This paper looks at two protocols for testing separators in the laboratory, normally referred to as the Direct Test Method and the Indirect Test Method. The test methodologies are described and the similarities and differences shown. Results from tests on a stormwater treatment separator using the two protocols are presented. The results show that for the same sediment gradation and flow rate, a difference of over 20% in measured removal efficiency is possible. They also show that the Direct Test Method produces outputs that are more consistent, conservative and representative of the removal efficiencies expected for stormwater treatment separators.

Abstract

The paper describes a novel drop shaft system that relies on the use of a selfactivating, non-powered and no moving part air intake control system to prevent instabilities and provide smooth transitions between air-entrained vortex flow modes and pipe full operating modes. This allows more compact drop pipe arrangements to be deployed within a single drop structure, also providing for maintenance access. These systems therefore do not require auxiliary maintenance or air shafts resulting in significant project cost savings. Further optimization of the system has involved the use of compact hydraulic break, rotary flow energy dissipation structures at the base of the vertical drop pipes resulting in a space efficient and effective system for controlling flows into deep tunnels. The operational characteristics of the novel drop shaft system including the basis for more effective flow control and elimination of unstable flow conditions are described in detail in this paper. The paper also includes case studies of its successful application in a number of deep tunnel schemes and at a wastewater treatment plant.

Authors

Robert Y.G. Andoh,Michael G. Faram and Kwabena Osei

Abstract

Globally, the water and wastewater industry faces major challenges, both in developed and developing world regions. The developed world has enjoyed the benefits of the foresight of prior generations, with major strides gained in public health simply from innovations such as the humble sewer which has contributed more to human health than all developments in the medical field. Challenges faced in different regions are diverse in nature, magnitude and scale. Some are local in nature but others such as the impacts of Climate Change are truly global. The paper examines the status and evolution of innovations within urban water management (with particular reference to stormwater management) including impacts of regulation, barriers to innovation, current trends and paradigms. It is argued that there is a need to change the way we approach urban water management challenges, particular if the goal is to achieve more sustainable development in an increasingly urbanizing world.