FINAL REPORT ON THE ASSOCIATION BETWEEN AOC AND BDOC AND AN EVALUATION OF THE LUMAC/KIWA BIOFILM MONITOR
Report No FR0463

MARCH 1994

SUMMARY

I BENEFITS

The customer will benefit from a better understanding of the relationship between assimilable organic carbon (AOC) and biodegradable organic carbon (BDOC) in potable waters and from the influence of biodegradable organic matter (BOM) on the potential for biofilm formation in distribution systems.

II OBJECTIVES

To determine the relationship between AOC and BDOC in potable water. To evaluate the KIWA/Lumac biofilm monitor.

III REASONS

The water industry requires a better understanding of the impact of novel water treatment processes on biodegradable organic matter (BOM), and on the implications of BOM on water quality in distribution. Reliable methods of measurement are therefore required. A review of the literature has been produced, but information on the relationship between AOC and BDOC and their influence on biofilm formation is required.

IV CONCLUSIONS

1. BDOC and AOC are measuring very different parameters, since no relationship can be demonstrated between the two techniques.

2. During this evaluation the Spanish BDOC method did not perform as well as either the Joret BDOC or the WRc AOC methods.

3. The biofilm monitor is able to demonstrate the biofilm formation potential of water.

4. Addition of 20 µg/l AOC to a biostable water produces a hundred fold increase in the amount of biofilm formed.

5. Biofilms appear to influence the accuracy of turbine water meters.

6. The biofilm monitor will contribute to the understanding of the impact of water quality on the distribution system.

V RECOMMENDATIONS

The following recommendations are made for further work:

1. Further studies to determine the reasons why the Spanish BDOC procedure produced anomalous results.

2. Extended survey of AOC and BDOC analyses on distribution systems to provide the necessary data for investigations on association of these parameters with coliform failures.

3. Further evaluation studies on the biofilm monitor, to determine the biofilm formation potential of potable water derived from surface water sources.

4. Studies using the biofilm monitor to determine the effects of changing flow conditions on biofilm stability and its impact on water quality.

5. Studies using the biofilm monitor to determine the effects of disinfectant residuals on biofilm formation and stability.

VI RESUME OF CONTENTS

This report has been produced in connection with the Foundation for Water Research contract on Water Quality in Distribution (F-1702). Presented in Section 2 of this report are details of the operation of the Spanish BDOC methodology and the results of a comparison of the data obtained from this method and those obtained from the WRc AOC and Joret BDOC methods. In Section 3 details are given of an evaluation of the KIWA/Lumac biofilm monitor when applied to the determination of the biofilm formation potential of a high quality groundwater with and without an AOC supplement.

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