A critical control point approach to the removal of chemicals of concern from water for reuse

Abstract

The reuse of water in a range of potable and non-potable applications is an important factor in the augmentation of water supply and in improving water security and productivity worldwide. A key hindrance to the reuse of water is the cost of compliance testing and process validation associated with ensuring that pathogen and chemicals in the feedwater are removed to a level that ensures no acute or chronic health and/or environmental effects. The critical control point (CCP) approach is well established and widely adopted by water utilities to provide an operational and risk management framework for the removal of pathogens in the treatment system. The application of a CCP approach to barriers in a treatment system for the removal of chemicals is presented. The application exemplar is to a small community wastewater treatment system that aims to produce potable quality water from a secondary treated wastewater effluent, however, the concepts presented are generic. The example used seven treatment barriers, five of which were designed and operated as CCP barriers for pathogens. The work demonstrates a method and risk management framework by which three of the seven barriers could also include a CCP approach for the removal of chemicals. Analogous to a CCP approach for pathogens, the potential is to reduce the use of chemical analysis as a routine determinant of performance criteria. The operational deployment of a CCP approach for chemicals was augmented with the development of a decision tree encompassing the classification of chemicals and the total removal credits across the treatment train in terms of the mechanistic removal of chemicals for each barrier. Validation of the approach is shown for an activated sludge, ozone and reverse osmosis barrier.