Justification
The need to have convenient access to water has always been one of the most powerful influences on human life and settlement pattern. Similarly, with the establishment of the first cities, the importance of drainage for the protection against flooding and water disposal and sanitation systems was recognised. Sewer systems serving today’s urban communities range from rudimentary, unlined, open channel drains to highly engineered, expensive, piped systems. In both cases, water is used to transport wastes away from areas of human habitation, where it would otherwise cause illness and disease or disrupt other urban services. In new developments, where such facilities are not available, consideration must be given to the collection, treatment and disposal methods. Systems should be tailor made to fit the local conditions and take into consideration probable future expansion. In the light of sustainable development, most of the current urban water systems, which are similar to those built 50 years ago, are no longer viable for 21st century cities. The provision of safe water and wastewater services; increasing costs of a growing and ageing water infrastructure; increasing water consumption; a reduction in the number and quality of urban and near-urban water environments; and significant disruption to the natural water balance are the key urban water issues that need to be addressed in the context of any strategies for urban sustainability. Though the emergence of these problems is not new, its scale has now reached a level, where solutions require new ways of thinking. Exclusive reliance on gravity sewerage systems cannot solve the current predicament of sustainability related issues. Therefore, technologies that balance cost with respect to different resources (environmental, economic, and socio-political), in such a way that the contribution to local and global problems are minimised or are at least known and accounted for, have to be sought. In the near future, new developments may answer the question of water conservation (by installing new low-water using appliances) or nutrient recycling (by fitting non-mixing toilets). However, these water conservation strategies will cause to reduced flow in sewers and recent research has shown that decreasing WC flush volume may cause problems with the building drainage and local sewers. Therefore, it is timely to research and propose new ideas for small sewer technology based on new low-energy, low-water use toilet equipment, coupled to innovative pipe systems. In this research, alternative sewer technologies, such as settled sewers, vacuum sewers, and low-pressure sewers, will be explored. Their design requirement, performance and relative sustainability will be assessed. The research builds on earlier EPSRC-funded work at Imperial College and WRc under the PTP scheme.
Goals
The aim of the project is to review and develop a new, more sustainable technology wastewater collection. This will be achieved by: - reviewing current and innovative alternative collection technologies
- reviewing and assessing new small-bore systems.
- devising and demonstrating the performance of a new low-water use, small-bore systems
- developing a system model and design rules
- establishing the applicability of the system and interactions with other water systems.
Components of the project The project has four basic components: desk study; laboratory study; visits; and modelling. Desk study: This will consist of a detailed review of collection systems (both conventional and unconventional) and toilet technology. Low-tech and high-tech approaches will be considered. Advantages and disadvantages of each technology will also be discussed and factors that contribute to the sustainability of each system will be quantified. Laboratory Study: An innovative wastewater collection system will be designed based on the desk studies and on previous work of the Urban Water Research Group and WRc. A prototype will be assembled for testing on a rig sited at WRc, in Swindon. The main goal is to develop a system with small-bore, flexible pipe resulting in a system that is cheaper to produce and construct and needs low volume of water to operate. A series of tests will be carried out to assess the performance of the system under normal operating conditions. Particular attention will be paid to assessing the diameter of pipe required and the influence of joints. Also to be examined is the effect of having non-uniform pipe gradient. Modelling: The basic performance of the new system will be modelled. The model will be used in conjunction with laboratory data to develop design guidance for this type of system, including advice on its applicability to the new development scenarios developed in the project as a whole. Visits: Visits which will be made to gather design, operating and cost data. Appropriate fields or industries will be first identified and will be visited when necessary. Related projects The research is part of Water cycle management for new developments (WaND) project funded by EPSRC and industry/regulator. It has interactions with WP1, WP2, WP4, WP5, WP6, and WP7. Collaborators - WRc (Nick Orman): applied R & D company, experts on small sewers
- Phoenix (Garry Moore): innovative toilet manufacturer
- Glynwed (Richard Graty): pipe manufacturer (subject to final confirmation)
- Thames Water (Sian Hills/Rachael Cunningham): water service provider (subject to final conformation)
Timescale: 3 years
Progress To Date:
The WP involves investigation of existing small-bore sewer systems and development of a new system using flexible pipes. So far, a pilot scale test rig based at WRc has been rehabilitated and a range of small-bore pipes tested for low WC flush volumes to investigate their impact on solid movement within pipes laid at different gradients. In total, over 1000 tests have been performed. The WP has also produced a literature review document on wastewater collection systems and is preparing a conference paper.
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