A risk management method for stormwater reuse
An Aquifer Storage Transfer and Recovery (ASTR) project has evolved from earlier ASR projects in Australia (including Andrews Farm and Bolivar, South Australia), the USA and the Netherlands where substantial water quality improvements have been demonstrated during storage of water in aquifers. Assuring the residence time in an aquifer by separating injection and recovery wells, will assist aquifer treatment to be recognized as part of a treatment train for producing a safe water supply. Coupling this subsurface treatment to a reedbed filtration system already in use to treat urban runoff within the City of Salisbury gives the potential to produce drinking quality water. This is the origin of the ASTR stormwater to potable water project.
However, there may be a large difference between what is theoretically possible and the reality of operating an urban catchment for drinking water supply. There is so much potential for incidents such as accidents, spills, fires, floods, construction, changes in land use and so on to impact on the quality of recovered water that it is essential for these hazards to be assessed and multi-barrier management controls identified before proceeding with the project. Hence a preliminary Hazard Analysis and Critical Control Point (HACCP) plan was required to evaluate the viability of the ASTR project.
The intent in preparing this HACCP plan for aquifer storage, transfer and recovery (ASTR) is similar in concept to that for Australian drinking water provision, where water quality and hazards to this are considered from source to supply. For this plan, data was collected on the number and types of industries in the Parafield and Ayfield subcatchments, the likely chemicals used by these industries, stormwater quality, pollutants (and potential pollutants), operational procedures for stormwater management, barriers to hazards entering stormwater and control points for pollutant management. The existing barriers and critical control points at various locations of the wetland and the proposed ASTR well-field are also described. A preliminary risk assessment of some of the identified hazards was made to establish a basis from which a comprehensive HACCP plan could be developed. Some recommendations are made for development of additional barriers to mitigate stormwater contamination, where required to achieve a multiple barrier system. From the review of available data, further technical information considered to be needed for development of a comprehensive HACCP plan was identified and was detailed in the preliminary plan.