This research has determined the carbon footprint or the carbon dioxide equivalent (CO eq) of potable water production from a groundwater recycling scheme, consisting of the Beenyup wastewater treatment plant, the Beenyup groundwater replenishment trial plant and the Wanneroo groundwater treatment plant in Western Australia, using a life cycle assessment approach. It was found that the scheme produces 1300 tonnes of CO eq per gigalitre (GL) of water produced, which is 933 tonnes of CO eq higher than the desalination plant at Binningup in Western Australia powered by 100% renewable energy generated electricity. A Monte Carlo Simulation uncertainty analysis calculated a Coefficient of Variation value of 5.4%, thus confirming the accuracy of the simulation. Electricity input accounts for 83% of the carbon dioxide equivalent produced during the production of potable water. The chosen mitigation strategy was to consider the use of renewable energy to generate electricity for carbon intensive groundwater replenishment trial plant. Depending on the local situation, a maximum of 93% and a minimum of 21% greenhouse gas saving from electricity use can be attained at groundwater replenishment trial plant by replacing grid electricity with renewable electricity. In addition, the consideration of vibrational separation (V-Sep) that helps reduce wastes generation and chemical use resulted in a 4.03 tonne of CO eq saving per GL of water produced by the plant.

In 2008, the Ontario Geological Survey (OGS) released a map of known and potential karst in southern Ontario. Known karst occurs mostly in areas where glacial overburden is thin (<1m) or absent and in many places the top of bedrock shows evidence of active, ongoing solution-enhancement. Data from deep bedrock boreholes indicate that karst in Ontario's carbonate terrains is much more widespread than can be observed on surface and that it extends into areas covered by thick glacial sediments. Direct evidence for this pre-glacial karst includes: (1) televiewer logs and drill-core showing solution-enhanced bedding planes and sequence boundaries; (2) drill records reporting large cavities in bedrock that are open or filled with glacio-fluvial sediments; (3) epikarst and bedrock conduits in quarries; (4) drift thickness mapping with extensive buried valleys and canyons, some that appear to form natural bridges; and (5) thick glacial sediment-covered areas with extensive interpreted karst rubble at the bedrock surface. Traditional methods for local mapping of subsurface karst and its effects on groundwater cannot be easily adapted for regional-scale studies. Physical techniques include tracer tests and piezometric logging of monitoring wells to detect conduits (by the rapid rise and fall of water levels); chemical techniques include monitoring, at spring vents, of pH, Ca2+, HCO3 - and saturation indices of carbonate minerals to determine the degree of corrosiveness of groundwater. However, these are all proximal techniques that characterize individual, known systems. To date, there are no well-developed regional techniques that can map areas where groundwater is influenced by buried karst over a wide area. Here we describe a methodology that uses dissolved CO2 and O2 in groundwater to map areas in buried karstic carbonates that have a rapid hydraulic connection to surface. O2 originates in the atmosphere and has no geological sources. CO2 in groundwater originates largely in the soil zone and has few other geogenic sources in non-tectonic settings. Because both parameters are attenuated with increasing distance from their sources, a CO2/O2 factor allows for an objective description of how well connected these buried karstic groundwater systems are to meteoric and soil zone recharge sources. An empirically derived lower threshold for the CO2/O2 factor delineates a number of large regions in southern Ontario where groundwater is elevated in either or both gases; all of these are centred on areas of known karst. Groundwater analysis using tritium, nitrate and bacteria (for samples collected from secure-cap water supply wells) show that these areas have younger, more recently recharged groundwater with a relatively rapid connection to the surface environment. Regional CO2/O2 and other chemical, isotopic and bacteriological data were purpose-filtered from the large, publically accessible OGS Ambient Groundwater Geochemistry database. This is an exceptionally well characterized groundwater geochemical dataset for samples collected on a uniform grid from domestic, farm and monitoring wells across southern Ontario. Mapping areas of groundwater vulnerability to surface contamination due to karstic flow systems is another of the many possible uses for this database.

Managed aquifer recharge (MAR) can improve water security by using aquifers to store water when it is abundant until required for future use and can increase the use of urban stormwater and treated wastewater to reduce the demand on traditional surface water and groundwater supplies. Recently, two Australian examples were showcased internationally as sustainable and economic MAR: Perth’s groundwater replenishment scheme (GWRS) with recycled water to increase security of urban water supply and a multi-site urban stormwater MAR scheme for suburban non-potable water supply in Salisbury, Adelaide. This paper provides a synopsis of these Australian exemplars of sustainable and economic MAR.

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The first implementation of the Ambient Groundwater Geochemistry Program (AGGP) in northern Ontario was completed in 2016 in the Sudbury area. The Sudbury program was designed to test if the AGGP could be successful in delineating the effect, on groundwater chemistry, of host rock lithology in northern Precambrian shield aquifers as has been already demonstrated for Paleozoic aquifers of southern Ontario. A second objective of this project was to test the potential for the routine sampling of radiological and radiochemical parameters, including radon and gross alpha-particle and gross beta-particle activity concentrations. Since 2016, the focus of the project has been analyzing the data from the Sudbury area survey and completing a 2017 follow-up project along the north shore of Lake Huron, including Manitoulin Island. In total, 93 overburden and 246 bedrock wells were sampled. This poster illustrates the regional trends and groundwater characteristics observed in the AGGP northern Ontario data thus far. In general, the data indicate fewer water quality related exceedences in the Sudbury area than were observed in southern Ontario. However, a few elements increase in concentration in the Precambrian aquifers of the Sudbury area such as U and Cd. Regional variation in groundwater chemistry was observed and may be controlled by the Precambrian geologic provinces. Bedrock well data from the Grenville Province indicate higher Ca, K and U concentrations than samples north of the Grenville Front. Samples from rocks of the Huronian Supergroup and the Sudbury Basin show relatively high Co, As, Pb and Cu concentrations compared to the Grenville Province. Radioactivity parameters appear to be controlled by the presence of clay rich overburden units rather than bedrock geology. The samples taken from wells that penetrate clay overburden are more alkaline because these older, deeper waters are disconnected from lower pH surface waters. Groundwater samples indicating a road salt NaCl source, as indicated by Cl-Br ratios, have the highest average dissolved oxygen percentage and total coliform relative frequency suggesting interaction with the surface. Some high chloride waters were noted on Manitoulin Island related to connate water in Paleozoic rocks. Future work on Precambrian aquifers will seek to determine if regional geochemical signatures are controlled by lithology, traces of deep formational waters, anthropogenic influences, or smaller scale regional geologic features such as the Sudbury Igneous Complex and associated mineralization.