Managed aquifier recharge - A potential water treatment method in New Zealand

Principle ways of applying Managed Aquifer Recharge (MAR) for water management is presented. Furthermore, the potential pathogen (bacteria/virus) removal capacity of the method is demonstrated by presenting three studies performed in Sweden. The first study was an investigation of a MAR plant for water treatment, utilising basin infiltration of river water. Indicator organisms (bacteria) were measured in the raw water from the river and in the abstracted water from the wells in the plant. Even though the study revealed a MAR plant’s typical good performance regarding bacterial removal, the initial concentrations of indicator organisms in the raw water were relatively low and the viruses/protozoa removal was not measured, therefore it was not possible to draw conclusions on the maximum achievable pathogen removal of the method. A column experiment was performed that displayed a 3-log reduction of virus and a 2.4-log reduction of bacteria. To understand the removal from other sites and with under conditions, a literature survey was performed and results were collected from international studies on pathogen removal (bacteria/virus) that showed that a distance of 40-80 m between the infiltration and the abstraction well should provide a removal of 4-6 log10 removal of viruses, equal to the WHO performance target for a raw water concentration of 1-100 viruses (pfu) per litre.