ALTERNATIVE METHODS FOR THE RECOVERY OF CRYPTOSPORIDIUM FROM WATER
Report No FR0274

T N Whitmore and E G Carrington

March 1992

SUMMARY

I OBJECTIVES

The objective of this study was to evaluate alternative methods for the primary separation ofCryptosporidium oocysts from water and to make recommendations for improving the currently used methodology.

II REASONS

The currently recommended recovery methods for Cryptosporidium oocysts are of low efficiency and time consuming. Hence improved methods to overcome these drawbacks are required.

III CONCLUSIONS

Through the use of spiked waters several methods were evaluated for their potential to recover Cryptosporidium oocysts. Sand column filtration and vortex flow filtration were judged to be too slow for the processing of the large volumes of water required for monitoring. Various cartridge filters were tested as alternatives to the recommended Cuno Microwynd filter, but none was judged as a satisfactory alternative. The continuous flow centrifuges evaluated were not too satisfactory in terms of recovery efficiency. A cross-flow filtration device, however, did show potential since comparatively high recoveries were obtained at realistic flow rates from clean waters.

IV RECOMMENDATIONS

The results of the studies reported here suggest that recovery methods based on cross-flow filtration techniques are adopted.

V RESUME OF CONTENTS

Several methods were evaluated for the primary separation of Cryptosporidium oocysts. Various types of cartridge filter were tested and found to offer no potential advantages over the standard Cuno Microwynd filter. Laboratory scale sand columns were also evaluated. The retention within the column material was satisfactory at low flow rates. However the system was judged inadequate for monitoring because of the poor retention of oocysts within the column matrix at realistic flow rates. The vortex-flow filtration technique using the Anachem Benchmark device gave fairly consistent recoveries of 30-40%. However the comparatively long process times would militate against the use of this device for monitoring purposes. A cross-flow filtration module was evaluated and gave relatively good recoveries (approximately 40-80%) at moderately high flow rates (0.9-1.0 l/min) from clean water samples spiked with Cryptosporidium oocysts (approximately 1x10**7/l). The continuous flow centrifuges tested were shown not to be capable of yielding satisfactory recoveries, although it is considered more refined machines currently available may warrant investigation.

Copies of the Report are available from FWR, price 15.00 less 20% to FWR Members