AWWA ACE95228

Severn Trent Water Limited is one of the water utilities created by the privatization of the water industry in England and Wales in 1989. It is one of the largest UK water companies and is based in the heart of the industrial Midlands. Severn Trent serves a population of approximately 8 million, contained within an area of around 8,000 square miles. The Company is responsible for treatment and provision of drinking water, and collection and treatment of sewage. As a result, the size of its asset base is considerable by any standards. This includes--46 impounding reservoirs, 180 groundwater sources, 18 river water intakes, 25 surface water treatment works, 646 water supply booster stations, 615 service reservoirs, 40,380 kms water mains--together with over 1,000 sewage works and in excess of 50,000 kms of sewers. In the 5 1/2 years that have elapsed since privatization, the Company has invested over $5 billion in renewing and extending the capability of its infrastructure. As a result of this investment, drinking water quality has been improved to ensure compliance with the standards of the EU Drinking Water Directive, which is generally more demanding than WHO standards. Additionally, 1994 saw the Companys compliance with bacteriological standards increase to a record 99.8% of the 500,000 plus samples taken annually. Now Severn Trent is faced with the need to develop an asset management plan which would ensure that any desired level of serviceability for assets was maintained. Severn Trent has developed a suite of computer programs which model surface and underground assets. The surface asset modeler (SAM), encapsulates all of Severn Trents design rules for the choice of processes and sizing of units. The Design Manual has been developed to cover logical choices of treatment processes such as selection of appropriate disinfection techniques via a decision tree, or choice of water treatment process according to water source, e.g. wells, upland reservoirs, lowland rivers, etc. All gravity, filtration, and flocculation rules have been encoded into SAM. Around SAM there are four other modules: the asset register, the demand module, compliance module, and the unit cost module. Each of these modules provide a specific service and helps Severn Trent accomplish asset management at a whole new level, allowing them to handle asset serviceability, increased demand, and new regulatory standards. An example is presented of the effectiveness of this program as used in Little Eaton Treatment Works.



Keywords: Utilities; Water Supply; Infrastructure; Operation and Maintenance ; Costs