Do you have data on the aquifer mineralogy or no elemental composition? µg/L* in ambient groundwater? yes expected No arsenic Is As in recovered water from Does reliable existing data no nearby MAR operations or baseline >7 µg/L? no monitoring indicate no As>1 yes yes yes aquifer contain Is As present with aerobic (oxidised) or oxidised anaerobic (reduced) (ie Fe oxides) or minerals? reduced (ie pyrite) minerals? oxidised or aerobic reduced or anaerobic Will source No pyrite No reductive no oxidation water lower the no dissolution of no expected pH of the Fe(III) oxide storage zone? expected yes Pyrite Dissolution of oxidation and Fe(III) oxide no arsenic No arsenic release may expected yes release be slow expected Pyrite oxidation expected Arsenic release expected† Eh = a measure of redox potential the propensity for oxidation and reduction reactions; MAR = managed aquifer — recharge; OC = organic carbon. * Arsenic (As) concentrations should be reported to 1 µg/L. trace metals (see Table A7.1) can be released concurrently. †Other Figure A7.1 Decision tree for identifying arsenic mobilisation in managed aquifer recharge (from Vanderzalm et al, 2009) Arsenic release (Figure A7.1) may also indicate release of other hazards, such as cobalt, chromium, copper, nickel and zinc. It is recommended that groundwater arsenic concentrations, which are used as a surrogate to indicate arsenic in the sediments, be reported to a 1 µg/L detection limit. A concentration reported to a higher detection limit (ie <5 µg/L) does not preclude the potential for sufficient arsenic release to exceed guideline values. The decision tree for iron (Figure A7.2) can be used to consider the potential for iron release and the subsequent recovery of water elevated in iron, or aquifer clogging due to the precipitation of iron oxides in the vicinity of the recharge point. As manganese exhibits
Do you have data on the aquifer mineralogy or no elemental composition? yes Does reliable existing data or baseline no monitoring indicate no As>1 µg/L* in ambient groundwater? Is As in recovered water from nearby MAR operations >7 µg/L? No arsenic no expected yes yes yes Is As present with oxidised (ie Fe oxides) or reduced (ie pyrite) minerals? oxidised or aerobic aquifer contain aerobic (oxidised) or anaerobic (reduced) minerals? reduced or anaerobic No reductive dissolution of no Fe(III) oxide expected Will source water lower the no pH of the storage zone? No pyrite no oxidation expected No arsenic release expected yes Dissolution of Fe(III) oxide expected yes Pyrite oxidation expected Pyrite oxidation and no arsenic release may be slow Arsenic release expected† Eh = a measure of redox potential — the propensity for oxidation and reduction reactions; MAR = managed aquifer recharge; OC = organic carbon. * Arsenic (As) concentrations should be reported to 1 µg/L. †Other trace metals (see Table A7.1) can be released concurrently. Figure A7.1 Decision tree for identifying arsenic mobilisation in managed aquifer recharge (from Vanderzalm et al, 2009) Arsenic release (Figure A7.1) may also indicate release of other hazards, such as cobalt, chromium, copper, nickel and zinc. It is recommended that groundwater arsenic concentrations, which are used as a surrogate to indicate arsenic in the sediments, be reported to a 1 µg/L detection limit. A concentration reported to a higher detection limit (ie <5 µg/L) does not preclude the potential for sufficient arsenic release to exceed guideline values. The decision tree for iron (Figure A7.2) can be used to consider the potential for iron release and the subsequent recovery of water elevated in iron, or aquifer clogging due to the precipitation of iron oxides in the vicinity of the recharge point. As manganese exhibits
water-recycling-guidelines-mar-24.docx