Full Description

At the end of 1999 United Utilities (formerly North West Water) started up two microfiltrationdrinking water plants in the Lake District region of North West England, at Ennerdale 59 Ml/d (16MGD) and Cornhow 32 Ml/d (8 MGD). This formed part of a strategy to provide protection againstCryptosporidium. The plants are fed from two separate oligotrophic lake sources located within theLake District National Park. Ennerdale is now the longest running microporous membrane plant fordrinking water production in the United Kingdom.There were a number of significant design challenges. No liquid waste discharges are permittedon the sites, so a secondary membrane system is provided as a concentration step. There areseasonal algal blooms in the sources and pronounced temperature variation between summer andwinter (2 - 20 C), which directly affect membrane performance. The paper describes how thesefactors have been reflected in the first 2 to 3 years of operation.Plant operational data tracks the clear seasonal impact on the membranes of temperature andsummer plankton growth over two summers. Changes in backwash and Clean in Place (CIP)efficiencies are analyzed, membrane resistances are related to the fouling characteristics of thesource, and approaches for successfully dealing with problems that arise are described. The effectsof an inadvertent bypass of algae mass from the micro-strainers acting as pre-screens and howthey were overcome are illustrated.The secondary membranes operate in conjunction with a coagulation and sedimentation processusing polyaluminium chloride and receive higher solids loading. This system handles CIP waste aswell as backwash. The plant originally experienced some periods of disturbance related to theintermittent presence of chemicals from cleaning operations. This impacted performance, anddesign adjustments to allow for this are described.Operational data is analyzed and compared. Operational costs are analyzed and opportunity forfuture optimization is identified. Includes 6 references, tables, figures.

Product Details

Edition: Vol. - No. Published: 03/05/2003 Number of Pages: 16File Size: 1 file , 1.3 MB