Water Quality Risk

A NEW APPROACH TO ASSESSING WATER QUALITY RISK  
A visual tool combining best practice operations and health based targets
S Westgate, M Robertson
Publication Date (Web): 5 September2018
DOI: https://doi.org/10.21139/wej.2018.028


Water quality risk management has historically been based on a retrospective review of sampling results. Simply monitoring E.coli in the distribution network cannot prevent a water quality event from occurring, and only allows a water utility to respond reactively to events that have already occurred. This paper outlines the development and implementation of a novel visual approach to assess water quality risk in drinking water systems. 

As a legacy of operating as 29 councils and three water utilities, TasWater (Tasmania’s sole water and sewage utility) has an inconsistent application of operational and managerial practices, and targets across the utilities 51 potable systems. Consequently, the risks to customers were not well understood and the potential for water quality breaches was high. Furthermore with a revenue base of approximately 200,000 connections, TasWater faces unique budgetary and cultural challenges compared to its interstate peers. Therefore the business required a robust model to prioritise and focus water quality improvement projects. 

An assessment was developed and implemented by TasWater in an effort to proactively identify water quality risks to prioritise and focus water quality improvement projects. Two Australian, industry recognised methodologies were utilised; the Manual for the Application of Heath-Based Treatment Targets (WSAA) (HBT); and the Good Practice Guide to the Operation of Drinking Water Supply Systems for the Management of Microbial Risk (WRA) (GPG)).

These methodologies were then adapted into an assessment matrix comparing operation practices and health based targets. This combination provided a robust defendable model, capable of assessing risk both theoretically and practically, irrespective of catchment risk profile, treatment type or complexity. 

The HBT manual was adopted as a method to assess the performance, effectiveness and suitability of a water treatment processes against the catchment water quality objectives. The GPG assessment was chosen for the study as it represented an accepted benchmark for management and operational industry best practices. 

Assessments took a weighted score from a pass/fail questionnaire developed from the GPG to provide a percent compliance with industry standard operational practices. This was then compared against the treatment adequacy of each treatment barrier against catchment LRV requirements of the HBT. 

The results of these assessments were plotted onto a single chart which allowed for a utility wide visualisation of water quality risk. This then facilitated the development of operational improvements and capital upgrades to reduce risk to consumers. In particular, the results have been able to demonstrate return on investment for various project options, by allowing a direct CAPEX vs OPEX comparison.

On a system-by-system basis, work plans and improvement projects specific to each system were developed to increase GPG scores and improve HBT compliance. Likewise, themes and trends across multiple systems were observed and large, utility wide programs have been rolled out such as UV disinfections systems and CCP implementation.

In summary, the visualisation of risk has proven to be a powerful tool in TasWater and has illustrated the businesses risk in regard to water quality. To address this, the same system has been used to visualise and justify return on investments for future projects to safeguard our customers, leading to a more proactive approach to water quality security.
 

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