Open Cut

Treating Acidity in Coal Pit Lakes Using Sewage and Green Waste: Microcosm and Field Scale Trials at Collinsville Coal Project (Queensland)

Open Cut » Environment

Published: March 08Project Number: C14052

Get ReportAuthor: Clint McCullough, Mark Lund, Joel May | Edith Cowan University, Xstrata Coal Qld

This research project involved, collaboration and technology transfer from research in Collie (Western Australia) to Collinsville (Queensland).   Coal mine lakes represent a potentially valuable resource to both the environment and the community in inland Australia, if the water can be remediated to an appropriate standard for its proposed end use. Beneficial end uses include: aquaculture, water for irrigation, recreation, and for nature conservation. Research in Collie coal mine lakes and internationally has found there is considerable potential for utilising biological processes to reverse acidity generating processes. This approach focused primarily on additions of organic material to support sulfate reducing bacteria (SRB) which convert sulfate back to sulfides, removing acidity and metals in the process. The approach also fosters a range of other biological processes which can increase alkalinity and pH.   

Previous ACARP funded research in Collie had tested the use of SRBs for treating acidic mine waters with limited success. Limiting the effectiveness of this approach in Collie are low sulfate concentrations that occur in these pit lakes. Nevertheless, there are a number of highly acidic mine lakes in the Collinsville Coal Project (CCP) with high sulfate levels.   

CCP discharged 4 ML of highly acidic mine water into a 80 ML sewage evaporation pond. CCP and later the authors monitored the effects of this discharge on water quality in the ponds. In approximately 18 months water quality in the evaporation pond had returned to pre-addition conditions. It appeared that a combination of processes, including SRB activity were responsible for the remediation of the mine water. The results of this study suggested that SRB activity might be useful in the treatment of pit lakes on the CCP site.   

This project aimed to establish a full scale demonstration of the application of passive biological remediation in a pit lake on the CCP lease. This pit lake is located near the Bowen Shire's Collinsville Water Treatment Plant (CWTP) and green waste transfer station. Organic substrate in the form of primary treated sludge from the plant were added to the lake. This wastewater provided a ready source of, BOD (Biochemical Oxygen Demand), available carbon, and nutrients. All of these wastewater components have been identified as key factors promoting SRB activity. Monitoring of this experimental lake and control lakes both before and after the addition enabled an assessment to be made of the success of this innovative remediation method.   

The first two experiments using acrylic tubes (microcosms) containing sediment and pit lake water were established firstly in Collinsville and then in Perth. These experiments were used to gain a better understanding of the processes responsible for mine water remediation and to provide estimates of the quantities of organic matter that were likely to be required in a full-scale treatment of a pit lake.   

The microcosm experiment involved testing of greenwaste only, sewage only, and greenwaste and sewage for their effectiveness in remediation of pit lake water, in typical Collinsville conditions.   

This first experiment clearly showed remediation of pit lake water pH from 2.2 to 5.5 in 145 days, with commensurate declines in iron, aluminium and toxic metal concentrations. The presence of greenwaste appeared to be important for the effectiveness of the treatment. This was mainly believed to be due to the bulk of the greenwaste which extended the area of SRB activity up through the water column.   

The second experiment repeated the first experiment in design but added different quantities of organic material and a second sewage type. Another important aim of this experiment was to demonstrate the repeatability of the initial results given the heterogeneous nature of the organic materials being used.   

This second experiment demonstrated that results were generally reproducible from the first experiment. However the performance of greenwaste only was poorer with a pH of >4 reached after 210 days, while the other treatments produced circum-neutral pH (~7) after 120 days with the exception being low levels of sewage only which produced a pH of ~6 after 210 days. Associated with the pH improvements were reductions in electrical conductivity, sulfate and metal concentrations. Key drivers for rapid remediation appeared too be the high tropical temperatures, the combination of greenwaste and sewage, and a 'fresher' type of sewage from Bowen rather than Collinsville. This experiment enabled the team to determine the quantities of organic materials required for a field trial.   

Comprehensive risk assessments and stakeholder consultation identified significant occupational health and safety concern of using sewage and greenwaste at field scale was of high levels of faecal coliforms in the water creating a risk for operators. The second experiment revealed that after 180 days there were no faecal coliforms in the water, although total coliforms were high.   

These latter coliforms were believed to be associated with decomposition process and were not believed to pose a contact risk to operators. Nevertheless, precautions were developed for operators involved in the project.   

In August 2006 to January 2007, the smaller lake (GAEW) was filled with dried sewage sludge (60 t), liquid sewage sludge (3,190 t) and municipal green waste (980 t). Monitoring of this new treatment lake and the remaining control lake and other control lakes then continued for another 6 months at monthly intervals.   

Due to groundwater influx and heavy cyclonic rainfall events, it was often unclear what contribution sulfate reduction process have made to changes seen in water quality. Nevertheless, physico-chemical changes to control lakes during monitoring could generally be explained as a result of these two external influences. However, after four months of filling ceasing, GAEW ORP began to decline from around 600 mV to 200 mV starting from the benthos. Also beginning at the benthos, pH increased soon afterwards reaching a pH of 3.7 across the lowest 3 m of water column by July 2007. The lower 3 m mean pH of the GAEE lake was 2.2 at this time. Similarly, at the end of the experiment electrical conductivity was reduced to 9.0 mS cm-1 compared to 9.4 mS cm-1 in the GAEE lake.   

These field chemistry observations suggest that addition of low-grade organic materials for remediation of acid mine waters at field scale shows promise. However, remediation has only just begun and further monitoring is required to access the degree of treatment that can be achieved and how long this treatment will continue.


Health and safety, productivity and environment initiatives.

Recently Completed Projects

C21013Improving Cavity Prediction On Longwall Faces Through A Combination Of Reliable Convergence, Canopy Attitude And Leg Pressure Monitoring

Most Australian coal mines have shield leg pressure monitoring in real t...

C24014Distributed Acoustic Conveyor Monitoring

CRC Mining have investigated the application of fibre optic Distribu...

C25054Distributed Acoustic Conveyor Monitoring - Phase 2

This project is phase 2 of the distributed acoustic sensing project ...


Open Cut

Safety, productivity and the right to operate are priorities for open cut mine research.

Recently Completed Projects

C23053A Study Of Sustainability And Profitability Of Grazing On Mine Rehabilitated Land In The Upper Hunter NSW

This study was initiated by the Upper Hunter Mining Dialogue (UHMD) ...

C25035Coal Subsurface Mapping For Open Cut Selective Mining

A reliable coal seam sensing system is required to improve the produ...

C23025Coal Pit Lake Closure By River Flow Through: Risks And Opportunities

In 2011, the river diversion channel around Lake Kepwari, a former o...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C26007 Revised Dustiness And DEM Test Method (Update Of AS4156.6) Part 2:Preparation

In 2015 project C23054 investigated and reviewed the Australian Stan...

C22033Advanced Control And Optimisation Of DMC Operation

The objective of this project was to develop, implement and demonstr...

C24045Adaptation Of Coal Grain Analysis To Improve Flotation Yield Estimation

Yield estimation from resource data is notoriously difficult. Facto...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Recently Completed Projects

C25045Stage Two - Assessment Of In Situ High-Temperature Strength Of Cokes

Stage I of this project established a reliable and repeatable proces...

C25044Trace Elements In Coal; Status Of Test Methods In Use And Their Applicability


The key objectives of this stage...

C25042Mechanistic Model Of Coke Development In A Coke Oven Situation

The standard approach to evaluate the potential of coals or blends t...

Technical Market Support

Mine Site Greenhouse Mitigation

Mitigating greenhouse gas emissions from the production of coal.

Recently Completed Projects

C24061Proof-Of-Concept Photocatalytic Destruction Of Methane For Coal Mining Fugitive Emissions Abatement

Australia's fugitive emissions in 2015 were 41 Mt CO2-e (representin...

C23052Novel Stone Dust Looping Process For Ventilation Air Methane Abatement - Phase 3

This multi‐phase project is concerned with the mitigation of m...

C19054VAM Enrichment With A Two-Stage Adsorption Process

Treatment of ventilation air methane (VAM) with cost-effective technolog...

Mine Site Greenhouse Mitigation

Low Emission Coal Use

Step-change technologies aimed at reducing greenhouse gas emissions.

Recently Completed Projects

C17060BGasification Of Australian Coals

Four Australian coals were trialled in the Siemens 5 MWth pilot scale ga...

C17060AOxyfuel Technology For Carbon Capture And Storage Critical Clean Coal Technology - Interim Support

The status of oxy-fuel technology for first-generation plant is indicate...

C18007Review Of Underground Coal Gasification

This report consists of a broad review of underground coal gasification,...

Low Emission Coal Use

Mining And The Community

The relationship between mines and the local community.

Recently Completed Projects

C16027Assessing Housing And Labour Market Impacts Of Mining Developments In Bowen Basin Communities

The focus of this ACARP-funded project has been to identify a number...

C22029Understanding And Managing Cumulative Impacts Of Coal Mining And Other Land Uses In Regions With Diversified Economies

The coal industry operates in the context of competing land-uses that sh...

C23016Approval And Planning Assessment Of Black Coal Mines In NSW And Qld: A Review Of Economic Assessment Techniques

This reports on issues surrounding economic assessment and analysis ...

Mining And The Community


National Energy Research,Development & Demonstration Council (NERDDC) reports - pre 1992.

Recently Completed Projects

1609-C1609Self Heating of Spoil Piles from Open Cut Coal Mines

Self Heating of Spoil Piles from Open Cut Coal Mines

1301-C1301Stress Control Methods for Optimised Development...

Stress Control Methods for Optimised Development and Extraction Operations

0033-C1356Commissioned Report: Australian Thermal Coals...

Commissioned Report: Australian Thermal Coals - An Industry Handbook