Groundwater Contamination & Treatment Solutions

Water is a commodity that is in high demand all over the world. Not only do all living organisms require water for their survival, it is also essential for growing food crops, raising livestock, generating electricity, as well as for conducting other commercial and industrial activities and for maintaining recreational facilities such as sports grounds and golf courses. Groundwater provides a valuable source of water needed to meet these demands. But how abundant is it, and what are the associated contamination risks?

How Much Groundwater is There?

A whopping 75% of the Earth is covered with water, yet 97.5% of that is salt water, with freshwater making up only 2.5% of the total. Of this, the majority (1.717%) is frozen in glaciers, with a small percentage (0.025%) frozen elsewhere. Only 0.008% of all water on the planet is available to us as freshwater on the surface. Groundwater stored in underground aquifers makes up 0.750% of the Earth's water, providing a reliable source of freshwater that can be used as a source of drinking water, as well as for agricultural and industrial use.

Australia's Great Artesian Basin, which stretches over 1,700,000 square kilometres and contains enough water to cover the world's surface, is the world's largest and deepest artesian aquifer. The aquifer, which spans across 22% of the Australian continent, provides the sole source of fresh water for many inland communities in Australia. Great Artesian Basin Coordinating Committee

According to the National Water Quality Management Strategy Guidelines for Groundwater Management in Australia, 18% of Australia's water requirements are supplied from groundwater sources. Many of Australia's major cities rely on groundwater to augment their freshwater supply. Perth for example, depends on groundwater to meet two-thirds of its water requirements. Many smaller urban areas as well as rural communities across Australia depend solely on groundwater for their existence. Groundwater has also allowed agricultural enterprises to develop in isolated rural areas, for example pastoral farming in western Queensland and viticulture in southern Australia.

Groundwater Contaminants

Although groundwater is extracted from deep underground, it is still very vulnerable to contamination. Groundwater can become contaminated with a wide range of pollutants arising from human activities, including industrial activities, agriculture and changes in land use practices. It can also be contaminated with naturally occurring substances. Some key threats that can detrimentally affect the quality of groundwater include: acidity, salinity, nutrient runoff (from fertilizers, farm animal manure and septic systems) and toxic contaminants (such as heavy metals, chemicals and pesticides). 

Naturally occurring substances such as arsenic, chlorides, fluoride, iron, manganese, radionuclides and sulfates can leach into groundwater from rocks and soils, while decaying organic particulate matter can be washed into groundwater. Some of these naturally occurring contaminants can potentially pose a health risk when present at high levels or when a person is exposed to them at low levels over a long period of time. Others are harmless, but may make water discoloured and/or give it a foul taste or smell. Groundwater that contains high levels of undesirable pollutants can be treated to meet drinking quality standards.

Contamination from Human Activities

Human activities are the leading cause of groundwater contamination.  Any human activity that releases chemicals or other waste products into the environment (whether intentional or not) can potentially contribute to groundwater contamination. Groundwater is vulnerable to contamination in urban areas with high population densities, where industrial and commercial activities abound. But it is also common in rural areas where land is intensively farmed. Once groundwater has become polluted, it can be difficult and costly to rectify.

Common Groundwater Contaminants

The quality of groundwater stored in underground aquifers varies around the world, and also from region to region within a country. For many countries, such as Bangladesh for example, arsenic contamination is a serious problem. In industrialised countries, such as the United States, contamination from industrial chemicals and pesticides is also an area of grave concern.

In Australia and New Zealand, groundwater is contaminated with a wide mix of pollutants, which vary from region to region. These include, but are not limited to the following contaminants:

Fluoride — (relatively low occurrence compared to other regions of the world) - exposure through drinking water at concentrations exceeding 1.0 mg/l can cause dental and skeletal fluorosis (discolouration of the teeth and weakening of the bones).

Arsenic - for example, groundwater in Gwelup, Perth is becoming increasingly contaminated with naturally occurring arsenic that is released from sediments as a result of chemical reactions caused by a reduction in rainfall and an increase in groundwater extraction for irrigation and water provision. Exposure to high levels of arsenic in drinking water for prolonged periods can cause arsenic poisoning, heart disease and various forms of cancer.

Nitrates - Nitrate contamination of groundwater is widespread in Australia and (although not as widespread) is also present in some groundwater aquifers in New Zealand. When groundwater containing high levels of nitrate is used as a source of drinking water or to water livestock it poses a health risk to both humans and animals. Exposure to high levels of nitrates can cause blue baby syndrome (which can be fatal), and is associated with increased infant mortality, birth defects, hypertension and stomach cancer. Nitrate-rich groundwater can also have serious environmental impacts as the nutrient laden water can fuel algal blooms leading to eutrophication in freshwater and marine waters.

Industrial Chemicals and Pesticides - Given that Australia is an industrialised country that also relies heavily on agriculture, groundwater is vulnerable to contamination by a wide range of potentially harmful industrial and agricultural chemicals, including chlorinated solvents, perfluorinated chemicals (PFAS), pesticides, herbicides (such as glyphosate) and fertilisers. Exposure to these contaminants in drinking water can pose a wide range of health threats. There is also growing concern over the combined cumulative health impact of exposure to a cocktail consisting of a wide range of drinking water contaminants over time.

Iron - One of the most widespread problems associated with groundwater use in Australia and New Zealand is iron fouling. When iron comes into contact with oxygen and water it forms hydrated iron oxide, more commonly known as rust. Iron can discolour water, giving it (and any clothes you wash in it) an unsightly muddy red hue. Iron scale and rust particles can accumulate in pipes and fittings, eventually obstructing water flow. Iron fouling poses a significant problem for farmers as it can affect performance of irrigation equipment, and consequently their maintenance/replacement costs.

Manganese (also in NZ) - Manganese is one of the most abundant metals found in the Earth's crust and is a component of many minerals, including borates, carbonates, oxides, phosphates, silicates and sulfides. Manganese therefore occurs naturally in groundwater, either as dissolved salts or as suspended solid particulates, but manganese from human activities can increase concentrations further still. Human sources of manganese pollution in groundwater include sewage sludge and wastewater effluent discharges, mining activities, emissions from iron, steel and alloy production, and burning of fossil fuels. Manganese contamination of groundwater is widespread across Australia and New Zealand.

Groundwater Quality in Australia & New Zealand

Groundwater quality can be affected by a number of factors. In Australia, where surface water is scarce and groundwater serves as an important primary water source, excessive groundwater extraction can cause several problems, such as lowering the water table, reduced surface water supplies, and land subsidence. In coastal areas, a reduction in groundwater levels can also severely affect the quality of the water by allowing saltwater intrusion into groundwater supplies. According to the Australia Bureau of Meteorology, groundwater salinity provides information on the quality of groundwater. Their salinity map shows that while salinity is widespread in groundwater across Australia, bores with the highest concentrations tend to be located near the coast. In New Zealand, long-term groundwater quality datasets indicate that groundwater salinity is also higher at coastal sites, and is getting worse at the majority of sites measured.

How is Groundwater Recharged?

Water is in a constant state of motion, moving between different reservoirs on land, sea and air in what is known as the water cycle. Water is evaporated into the atmosphere from water surfaces such as rivers, lakes and the sea by heat energy generated by the sun. Following evaporation, water in the atmosphere is in vapor form, but upon cooling it is transformed to liquid form through condensation to produce raindrops, which precipitates to earth to replenish water reservoirs on land. If temperatures drop below freezing, the water droplets are transformed to a solid form to produce sleet, snow, or hail.

The water cycle plays a very important part in maintaining life on earth. As water is cycled through different reservoirs on land, sea and air, minerals essential for plant growth and animal health are transported by the water along its journey; impurities are removed during evaporation to provide a fresh source of purified drinking water in the form of precipitation of rain, snow or sleet; and living organisms and ecosystems are sustained during this process.

After rainfall and other forms of precipitation fall to Earth, water permeates through soil and cracks in rocks to naturally recharge groundwater aquifers. The efficiency of this groundwater infiltration process is significantly affected by soil health. Healthy, humus-rich soils that are teaming with microbes tend to act like a sponge, soaking up and filtering water as it permeates downwards. Unhealthy, nutrient-depleted soils that are lifeless due to intensive farming practices and excessive chemical use do not absorb water, which runs off instead, washing valuable nutrient-rich top-soil and sediments away with it.

However, if carefully managed, this runoff needn't be lost, but rather it can be put to beneficial use instead.  Runoff water can be redirected across the land's surface and temporarily stored in a recharge basin, allowing the stored water to gradually infiltrate the ground. Or it can be mixed with treated wastewater and injected into the ground via injection wells to artificially recharge groundwater aquifers. Other stormwater runoff, for example stormwater runoff from roads and paved surfaces, can also be captured and artificially inject into underground aquifers.

Solutions for Improving Groundwater Quality & Availability

There are several ways that we can improve the quality and sustainability of our groundwater supply:

1. One pro-active approach is to switch from ecologically unsound conventional farming practices to regenerative farming methods where chemical use is reduced and soil health is prioritised. Healthy soils absorb and filter water, allowing it to recharge aquifers naturally.

2. As industrial and municipal wastewater effluent are both important contributors to groundwater contamination, treating wastewater before it is discharged into the environment can help reduce pollutant levels. Recent innovative advances in treatment technology now make it financially viable for companies to implement advanced treatment onsite, thereby enabling them to boost their environmental performance without impacting their economic performance.

3. A third option is to recycle adequately treated sewage wastewater (wastewater that has undergone advanced levels of treatment) and inject it into wells to recharge aquifers.

Poor environmental and groundwater management can seriously affect groundwater quantity and quality, which can ultimately render water unsafe for humans or even animals to drink unless it is appropriately treated. Contaminated groundwater can result in significant environmental, social and economic impacts, disrupting ecological balance in sensitive aquatic ecosystems and contributing to reduced agricultural production, ultimately affecting food production and livelihoods. It can also potentially pose a significant health risk to over 2.5 billion people the world over who depend on groundwater as a source of drinking water. Thankfully, innovative treatment solutions now make it possible to safely discharge treated wastewater directly into freshwater systems and aquifers that provide us with drinking water.

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