ASSESSMENT OF THE FEASIBILITY OF DESIGNING A PHYSICAL MODEL OF A
DISTRIBUTION SYSTEM
Report No FR0424

Nov 1993

SUMMARY

I BENEFITS

The outcome of this study will provide the client with more information on the cause of coliform failures in water supplies.

II OBJECTIVE

The objective of this study is to assess the feasibility of designing and building a model distribution system to investigate biofilm growth characteristics and their potential impact on coliform bacteria in distribution.

III REASONS

Compliance failures due to the detection of coliforms occur intermittently in the distribution supply system. However, within the complex microbial environment of a distribution system, little is known about the factors influencing their occurrence. A thorough understanding of the cause of these failures is required before effective strategies can be adopted to prevent their occurrence.

IV CONCLUSIONS

  1. There is a lack of information regarding the impact of the prevailing hydrodynamic conditions on microbial processes.

  2. The selection of appropriate design criteria would be assisted by the availability of such information.

  3. Not all of the hydrodynamic features can be preserved over the entire length of the model if its size is to be reduced.

  4. The configuration of the system can be altered to use a series of tanks of the same volume. Residence time is maintained but the other hydrodynamic conditions are only maintained over the pipework connecting the tanks.

V RECOMMENDATIONS

The preferred design for a model distribution system is the option which incorporates a series of tanks to provide the desired residence time but also provides typical hydrodynamic conditions in the connecting pipework. Ideally, however, it is recommended that before a model distribution system is constructed consideration is first given to the influence of hydrodynamic conditions on microbial processes to confirm that the most appropriate design option has been selected.

VI RESUME OF CONTENTS

This report describes a study undertaken to assess the feasibility of designing and constructing a physical model of a distribution system. As an essential prerequisite, consideration was given to addressing how hydrodynamic conditions could influence microbial processes. On the basis of this information design criteria were established to ensure the model was representative of full scale systems. Other model distribution systems are reviewed to assess their suitability for prospective studies. A series of designs are presented which represent various options for a model distribution system.

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