Impact of climate change on soil remediation: CDE

Following extreme weather conditions across Australia, Daniel Webber of CDE explains the reality of climate change and how it threatens to unearth the history of Australia’s soil contamination, highlighting remediation solutions that can remove toxins from the environment.

This summer, Australia faced devastation from harsh weather conditions, having experienced some of the worst bushfires on record, extreme dust storms across New South Wales, flash flooding in Queensland and long periods of drought.

Daniel Webber, CDE Business Development Manager, says without stark intervention, the consequences of global warming will be felt for decades to come.

Indeed, the Intergovernmental Panel on Climate Change reported temperatures could rise by 1.7°C by the end of 2100 and sea levels could continue to rise globally.

Daniel explains that there lies a delicate balance between climate and its impact on Australian soils, and the rate of change is having a negative impact on contamination levels.

Contaminated soils are a key contributor to hazardous waste in Australia, yet the full extent of soil contamination is not yet fully known,” he says. 

This is due to variants in reporting between districts, Daniel says, and a lack of historical reporting.

The Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE) reports over 160,000 contaminated sites nationally. Of these, it’s estimated less than 10 per cent have been remediated.

“Australian soil has been contaminated with conventional and emerging contaminants for decades, including heavy metals, hydrocarbons, organic matter and manmade chemicals,” Daniel says. 

He adds that increasing soil temperatures from climate change and recent bushfires has led to increased soil toxicity and greater bioavailability.

“These weather patterns are having devastating effects on our soils and will unearth years of historical contamination,” Daniel explains. 

“In fact, research has shown the long-term effects of climate change, with increasing floods and drought conditions facilitating the movement of soil-based contaminants and soil erosion.”

A study by CRC CARE found soil erosion at a rate of 70-300 tonnes per hectare (tph), compared to what were defined as typical losses in the region of 60-80 tph.

“Our changing weather is causing the level of soil erosion to increase and dust storms will accelerate the spread of toxic pollutants in exposed soil,” Daniel says.

The movement of contaminants in dust storms presents significant health and environmental risks, as pollutants enter the air and water before finally settling into the soil again.

“Exposure to toxic contaminants can have a devastating impact on our health so we must find ways to diminish the risk,” Daniel says.

Many argue contaminated soil sites surrounding our waterways and agriculture lands are those which urgently require remediation.

“Our peers in the waste industry and local government are determined to clean up years of contamination and have already successfully remediated inorganic and organic materials. Yet we cannot do this alone, we need more to join us as we try to make Australia’s soils safe again.”

Successes had been reported. In its 2016 paper, Soil: Formation and Erosion, Australia State of the Environment stated soil ‘erosion rates are equal to soil formation rates.’

However, it remains to be seen how recent and unprecedented bushfires will affect this ratio, or by how much it will set remediation efforts back,” Daniel says. 

Outlining how CDE’s bespoke soil washing solutions can support this effort, Daniel says the company’s technologies utilise a suite of mechanical, chemical and biological processes for recovering washed solids such as sand and aggregates. 

“Contaminants are transferred into the water phase which are effectively treated to produce recycled water for reuse within the process.”

According to Daniel, CDE’s bespoke solutions can be tailored based on tonnage and level of contaminants to ensure maximum efficiency within every project CDE delivers. 

“Our systems provide savings on landfill charges, prevent extra investment in waste storage equipment, and introduce new materials for reuse,” he says. 

“We can no longer ignore soil contamination; we must utilise remediation technology to help us eliminate potential risk to human health and to protect the world around us.”

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Concentrating contaminants: CDE

CDE’s Daniel Webber explains how high-pressure filtration and decontamination can increase the resale potential of construction and demolition waste.

The NSW EPA’s new construction and demolition (C&D) waste guidelines, released April 2019, highlight environmental risk via contamination and poor recycling processes as a core concern.

Daniel Webber, CDE’s Regional Manager for Australasia, says the presence of contaminants in the C&D stream is particularly significant, given one of the material’s major resale markets is road base.

“If the material used in road base contains heavy metals or polycyclic-aromatic hydrocarbons, which are known to be carcinogenic, those materials can leach out and penetrate the water table, and once they enter the water table, they can potentially contaminate drinking water,”
Daniel says.

For CDE, an international materials wet processing design and manufacture company, eliminating contaminants in C&D waste is critical to market viability.

“One of the first things we noticed when we first began working with the C&D waste sector was that there are no completely pure C&D sites.

“They all drag contaminated soil in eventually, and when there are no clean sites, there’s no clean materials. CDE quickly learned that this was something we needed to address with our clients.”

A central challenge to addressing the issue, Daniel says, is the variability of C&D contamination regulations across jurisdictions.    

“Conflicting regulations range from waste levy rates, urban development and state planning zones, to contaminant levels and disposal requirements,” he explains.

“We need to be across all the various legislative requirements and, as such, prioritise working in partnership with our clients to achieve that.”

According to Daniel, leachate is a focal point when dealing with C&D. He adds that because of the location of most C&D plants, large tailing ponds are often unfeasible.

“C&D is not like virgin mining or quarrying, which happens in the outer suburbs or the regions. Most construction sites are in metropolitan areas,” he says.

“To minimise transportation costs and therefore maintain resource recovery practicality, a lot of resource recovery also happens in metropolitan areas, meaning operators have to be much more cognisant of the contaminant problem.”

To remove contaminants, CDE facilitates two separate processing methods, both of which can be customised to suit individual client needs. Daniel adds that contaminants include anything from unwanted material such a plaster board and heavy metals, to dangerous chemicals such as PFAS.

“To wash and process contaminated C&D material, CDE designs plants that push contaminants into a tertiary water body for filtration, or alternatively, into sludge for processing via filter press technology,” Daniel says.

“When a client chooses the filter press option, their material is passed through mesh under extremely high pressure to produce a dry filter cake, which is then discharged into a bay below the filter press enclosure.”

Daniel says the filter press method allows CDE-designed plants to salvage 90 per cent of the original feedstock material.

“If a client is running a 200-tonne-per hour plant, with feeds coming through the front end, CDE equipment can concentrate existing contaminants into 20-tonne-per-hour of feed material.

“That means 180 tonnes of material can be repurposed and put straight back into the market as clean construction material.”

Additionally, Daniel says by concentrating contaminants, operators can save on landfill charges and prevent extra investment in waste storage equipment. Effectively removing contaminants also requires high-energy scrubbing and dewatering cyclone systems.

“By introducing CDE technology, plant operators can eliminate the need for settling ponds, reduce the space required to accommodate a washing plant and maximise water recycling.”

CDE’s minimum target, Daniel says, is an 80 per cent recovery rate, designing plants to increase traditionally unusable recycled sand and aggregates for multiple resale applications.

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