An Improved Understanding of The Impacts of Blue-Green Algae Associated with Coal Mining and Identification of the Opportunities to Reduce Impacts at Selected Coal Mines

The objectives for this project were:

• Provide a review of the latest research and water industry findings as to health related issues and water treatment methodologies for the species present in mine waters
• Review current operational techniques and identify successful processes and opportunities for improvement
• Liaise with the mines and use the findings from the literature review and mine data to detail potential impacts of blue-green algae with particular reference to human health issues
• Isolate (and model where possible) the factors triggering toxic algal blooms in mines (including external sourcing of blooms) thus enabling prior warning of their occurrence, a key aspect of successful management
• Investigate the system where contaminated water is sourced from and external supplier and options for the improvement of supply (or warning of water quality problems) not just via supplier but also through catchment management and co-operation with user groups and government agencies
• Identify possible reasons for the absence of problems in some dams while similar water bodies nearby have severe toxic blooms as this may give key insights into control methodologies
• List the opportunities to reduce impacts of blue-green algae with particular emphasis on
• effective algal sampling and identification methods noting the range of toxic species (including unusual toxic forms from the Bowen Basin), variability in their biology and water column positioning (including benthic accumulation)
• enhancement of existing monitoring, counting and treatment procedures
• water quality variables that may be readily modified in order to prevent or control blooms
• early prediction of blooms and component species
• possible alternative biological control methods
• Communicate findings to both the mines associated with this study and the industry as a whole

Main findings and conclusions
Blue-green algae were investigated at 8 sites in Central Queensland as part of this ACARP project and were detected at all mine sites and associated primary water supply dams. The most common toxin producing species was Cylindrospermopsis raciborskii although Aphanizomenon ovalisporum and Microcystis sp. were also detected. Although cylindrospermopsin, the toxin produced by Cylindrospermopsis raciborskii was detected at a number of sites in this study, it was not found to be greater that 1 ?g L-1 nor was it found in water of temperature below 25 oC. This is a particularly important finding for future management as the toxicity of this species is inversely proportional to temperature (Saker and Griffiths 2000).

There was an increased frequency of algal blooms in the spring and summer. The various mine dams that are filled from riverine impoundments, and have an active inflow and outflow, function similarly to riverine impoundments with similar algal populations and dominant species of blue-green algae. The timing of algal blooms in such dams was associated with the pumping of anoxic nutrient rich hypolimnetic water from the stratified primary supply weir on the Mackenzie River, Central Queensland, rather than stratification within the dam itself. Blooms also coincided with increased pH, conductivity and water clarity. Given the design of the pipeline system, the water chemistry and the tropical climate of the region, the most effective means of controlling algal biomass in this system appears to be through the reduction in nutrient loading. One cost effective means of doing this would be through the use of plants. Although the mixing of the primary weir may reduce bioavailable nutrients, the water chemistry of hypolimnetic releases from other weirs and dams in the Mackenzie River system would probably negate any real benefits.

Dams with plastic liners and regular use of copper sulfate or related products recorded lower cell concentrations of blue-green algae and different timing and structures of algal populations. In contrast, the only toxin results from one of these dams show no substantial reduction in toxin concentration throughout the distribution system. This is in stark contrast to the natural dams with or without water treatment facilities where reduction in toxin concentrations was recorded between source and endpoint locations of use. Where cells are lysed by an agent such as copper sulfate, toxin results and cell counts at the primary source weir together with toxin results from the treated dam are of more relevance in assessing human health risk rather than cell counts from the dam where an algicide has been applied.

The most cost effective and reliable method of reducing the human health risk associated with algal blooms in the systems analysed is through water treatment. Critical areas for risk minimization involve overall system assessment, sampling methodologies, enumeration techniques and selection of laboratories, analysis of toxin concentration, compilation of appropriate records for legal purposes, application of protocols for algal management and appropriate treatment of drinking water using sand filtration, activated carbon and disinfection (eg. chlorination) where possible. Activated carbon should be used in the water treatment process and not applied directly to the dam.

Three different guideline systems for management of blue-green algal blooms in mine systems are recommended depending upon the use of the water. They represent a modification of the proposed ARMCANZ national protocols using information derived from this project. They apply to drinking water, contact water and underground water. The most important guideline value is that the toxin concentration in treated or endpoint drinking water should not exceed 1 ?g L-1 or the latest assessment of this maximum permissible exposure by the National Health and medical Research Council or relevant state health department.