A Planning Tool for Optimizing Investment to Reduce Drinking Water Risk to Multiple Water Treatment Plants in Open Catchments

Chris Thompson,Morag Stewart,Nick Marsh,Thomas Lynn,Viet Phung

doi:10.3390/w13040531

Abstract

Supplying safe, secure, and reliable drinking water is a growing challenge particularly in regions where catchments have diverse land uses, rapidly growing populations, and are subject to increasing weather extremes such as in the subtropics. Catchments represent the first barrier in providing ecosystem services for water quality protection and bulkwater suppliers are therefore investing in mitigation measures to reduce risk to drinking water quality for consumers. This paper presents an approach to combine data on erosion processes, pathogenic bacteria and protozoa from several sources, determine the highest risks from these hazards and identify an optimum portfolio of intervention activities that provide maximum risk reduction at water treatment plants (WTP) for a given budget using a simulated annealing optimizer. The approach is demonstrated in a catchment with six WTPs servicing small rural to urban populations. The catchment is predominantly used for agriculture. Results show that drinking water risk from protozoa can be reduced for most WTPs for moderate investment budget, while bacteria risk reduction requires significantly larger budget due to the greater number of significant source sites relative to protozoa. Total suspended sediment loads remain a very high risk to most of the WTPs due to the large extent of channel and gully erosion and landslides. A map of priority areas and associated suite of interventions are produced to guide on groundwork.

Highlights

Bulk water suppliers and water utilities in Australia need to provide safe, secure and reliable water supply for consumers
This represents a multi-barrier approach in which the catchment is the first barrier providing the ecosystem services for water quality [3], bulk water suppliers have a significant role as catchment managers
In southeast Queensland, Australia, where more than 90% of source water supply is from open catchments, the priority contaminants considered risks to water quality that have a direct impact on water treatment plants (WTP) capacity are pathogenic microorganisms [6]

Summary

Introduction

Bulk water suppliers and water utilities in Australia need to provide safe, secure and reliable water supply for consumers. They are regulated to implement the Australian. ADWG Framework) which sets out a comprehensive, integrated approach for managing water contamination risks across all stages of water supply—from catchment to tap [1,2]. This represents a multi-barrier approach in which the catchment is the first barrier providing the ecosystem services for water quality [3], bulk water suppliers have a significant role as catchment managers. Elevated levels of TSS can cause treatability issues at WTPs, through reducing the effectiveness of disinfection, increasing the requirement for chemical dosing [8] and reducing drinking water production rates

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Results

Conclusion