Advances in Water Treatment and Enviromental Management

94 WATER TREATMENTThe Severn Trent Water business plan clearly identified the framework withinwhich operational needs were to be determined by defining two specificobjectives viz:‘Meet quality and service level specifications at minimum cost’.‘Remove need for further cost increases and, where possible, reduce costsfurther’.Expenditure was to be applied where the greatest step in identified benefitwas possible. The preferred solution was to be appraised by its ability toachieve a given level of service at the lowest operating cost.This implied careful selection of sites and the level of signal and controlprovision for each site. Each District Manager was responsible for providingsuch information from often incomplete and inaccurate records.To assist in the selection and definition of need, the PMCS project team hadconsiderable data available to them covering similar installations throughoutthe UK and some very accurate detail information on some 80 Severn TrentWater sites.This data, held on computer databases, comprised the following typicalfields: site types, levels of signal provision, operational criticality, level ofexisting investments and benefit potential.For PMCS, at the site level, the operational need was classified as:(a)(b)(c)Alarm only—the occurrence of a defined abnormal event.Monitoring—the near constant (hourly) surveillance of process andplant conditions.Remote control—the ability to start/stop operations on site from aremote location.To assist in the evaluation of solutions, two service levels were defined:(i)(ii)Service levels as provided by existing telemetry on some 1900 sites.Service levels achieved on (i) provided for 3450 key sites.In addition to the site related need the analysis determined the operationalfunctionality required from any technology based solution. For example thetype of displays and reports, the archiving of data and the need for operatorassist facilities. Other important issues determined at this stage were theuse of shared facilities, ownership and maintenance, reliability, resilienceand performance requirements.