AWWA MTC69745

In 2005, the City of Minneapolis installed a 70 MGD ultrafiltration (UF) system at Columbia Heights, provided by GEIonics,and based on Norit membranes. The objective of this paper was to demonstrate the development of toolsbased on permeability measurement to assist operational personnel with the monitoring and assessment oftheir plant, and provide guidelines for decision making.At the design conditions used in commercial UF plants, fouling rates increase exponentially with flux.Selection of flux is therefore a finely balanced trade off between capital and operating cost, since anexcessive flux will lead to high operational pressures and high chemical usage. Once a UF plant has beeninstalled, permeability can be monitored to assess operational stability of the plant, and determine theeffectiveness of the chemical wash procedures. However, permeability trends can provide anoverwhelming level of data, especially for a multi-rack system. This paper provides a method of analyzingdata to assist the monitoring process, and proposes the use of two simple indices.The Permeability Recovery Index (PRI) measures the fouling propensity of the feed and the extent ofrecovery of permeability from one Chemically Enhanced Backwash (CEB) to the next. PRI could indicate anineffective CEB procedure, perhaps due to a mechanical failure such as a sticking valve, failed pump, orpoor chemical distribution between racks. The Cleaning Effectiveness Index (CEI) measures theeffectiveness of a series of CEBs, and would demonstrate the suitability of the chosen protocol. Thisindicates whether the CEB strategy has been effective over a period of time, and quantifies long termdownward trends. CEI can be used to both assess the effectiveness of the CEB procedure and predict theneed for a Clean In Place (CIP).The monitoring indices have been used together with absolute levels of permeability, to provideoperational guidance, and ensure stable plant operation. Data is presented for a 2 year period to illustratethe use of the indices at Columbia Heights. The combination CEI and PRI monitoring indices can be usedto define a trigger for action at two different levels. Includes 4 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2009

Number of Pages:

12

File Size:

1 file , 1.5 MB