At the end of 1999 United Utilities (formerly North West Water) started up two microfiltration
drinking water plants in the Lake District region of North West England, at Ennerdale 59 Ml/d (16
MGD) and Cornhow 32 Ml/d (8 MGD). This formed part of a strategy to provide protection against
Cryptosporidium. The plants are fed from two separate oligotrophic lake sources located within the
Lake District National Park. Ennerdale is now the longest running microporous membrane plant for
drinking water production in the United Kingdom.
There were a number of significant design challenges. No liquid waste discharges are permitted
on the sites, so a secondary membrane system is provided as a concentration step. There are
seasonal algal blooms in the sources and pronounced temperature variation between summer and
winter (2 - 20 C), which directly affect membrane performance. The paper describes how these
factors 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 and
summer 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 the
source, and approaches for successfully dealing with problems that arise are described. The effects
of an inadvertent bypass of algae mass from the micro-strainers acting as pre-screens and how
they were overcome are illustrated.
The secondary membranes operate in conjunction with a coagulation and sedimentation process
using polyaluminium chloride and receive higher solids loading. This system handles CIP waste as
well as backwash. The plant originally experienced some periods of disturbance related to the
intermittent presence of chemicals from cleaning operations. This impacted performance, and
design adjustments to allow for this are described.
Operational data is analyzed and compared. Operational costs are analyzed and opportunity for
future optimization is identified. Includes 6 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 1.3 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 16 |
| Published : | 03/05/2003 |
