Acid sulfate soils (ASS) present significant environmental challenges. When allowed to oxidise, they can cause soil acidification, water contamination and infrastructure degradation.
Traditional remediation methods are widely understood and have been employed for many years. One such strategy is to use neutralising agents like lime and sulfate-reducing bacteria to increase alkalinity in soil.
However, these approaches can be labour intensive, costly and do not necessarily offer long-term solutions. In response, innovative treatment strategies are emerging to enhance efficiency, sustainability and ecological compatibility.
At West Soil & Water, our team keeps up to date with developments in treatment technology to ensure that our clients receive the best possible solutions.
In this article, we outline some emerging treatment strategies and offer a few thoughts.
If you would prefer to speak directly with an environmental consultant about these, or any other ASS treatments, you can contact WSW at sam@westsoilandwater.com.au or on 0424 021 264.
ASS are naturally occurring soils and sediments that thrive in WA’s low lying coastal regions and wetlands.
These soils are rich in iron sulfides, meaning that if they are disturbed and exposed to air, they will oxidise to produce sulfuric acid. Oxidation is often an unexpected consequence of excavation, demolition and other works.
As mentioned above, soil acidification poses risks to the natural environment and human made structures. There may be lower soil fertility, contamination of drinking water or corrosion of concrete and steel structures.
The most effective way of mitigating these risks is to identify ASS early and implement robust management and treatment plans.
Microbiologically Induced Calcite Precipitation (MICP)
MICP leverages the natural processes of certain bacteria to precipitate calcium carbonate within the soil matrix. This process can improve soil stability and reduce permeability, limiting the mobility of acidic leachates.
The primary groups of microorganisms involved include:
Photosynthetic bacteria
Sulfate-reducing bacteria
Those that participate in the nitrogen cycle
MICP not only neutralises acidity but also enhances structural integrity in the soil, offering a sustainable alternative to conventional chemical treatments.
Phosphate-Solubilising Bacteria (PSB) Applications
PSB solubilise bound phosphates to make them available for plant uptake – crucial in nutrient deficient acidic soils.
Recent studies have explored the use of PSB to remediate ASS. The findings have been promising, including increased seed germination rates and enhanced plant growth.
For instance, treatments with strains like Methylobacterium sp. PS led to significant improvements in vegetation growth in acidic soils.
This suggests a strong potential as biofertilisers in ASS management.
Lime-Assisted Tidal Exchange
A large-scale remediation technique, lime-assisted tidal exchange sees tidal flows reintroduced to ASS affected areas. These flows contain alkaline substances to neutralise acidity.
A notable example is the East Trinity remediation project in Queensland, where a controlled tidal flow combined with lime application successfully restored a degraded wetland ecosystem.
Because it leverages natural tide movements, this method is a cost effective and relatively non-invasive strategy.
Advanced Soil Mixing Technologies
Developments in soil mixing equipment have enhanced the efficiency in ASS treatment. Specialised soil recyclers allow for precise mixing of alkaline reagents into acidic soils.
This technology ensures a thorough treatment, reducing the need for extensive excavation and minimising environmental disturbance.
In Situ Chemical Oxidation (ISCO)
ISCO sees the injection of oxidising agents directly into the soil to transform contaminants into less harmful substances.
Agents like persulfate generate sulfate radicals capable of degrading a wide range of contaminants. This method offers the potential for targeted, in-depth soil remediation although its efficacy in ASS contexts requires further research.
The constant development of new and innovative approaches to ASS treatment represents a shift towards more sustainable and effective practice.
By integrating biological processes, natural patterns and advanced technologies, these methods aim to address the limitations of traditional treatments. They offer a new hope for improved environmental outcomes in ASS-affected regions.
At WSW, we are always looking to improve our understanding of ASS and its treatments. Our team keep their ears to the ground to make sure we are providing the most effective solutions possible.
In addition to treatment services, we also offer:
If you are concerned with a potential ASS presence on your site, please do not hesitate to contact us at sam@westsoilandwater.com.au or on 0424 021 264.
