Managing the acidity of abandoned water filled coal mining voids in Collie (Western Australia) using organic matter
The effectiveness of using organic matter additions to increase pH in abandoned water filled coal mining voids in Collie was investigated. Previous studies have demonstrated that passing acidic drainage through organic matter increased the waters pH. Laboratory trials using intact sediment cores (collected from Ewington, Collie, Western Australia) were used to assess the effects of additions of hay, manure and mulched vegetation on pH, nutrients an sulphate levels. In a series of experiments the effect of different quantities of organic material, sulphate reducing bacterial inoculations and alkalinity generation were measured. A subsequent field experiment was conducted to examine the impact that manure and mulch had on mine void water in 18 in situ ponds constructed adjacent to Ewington. It was concluded from the laboratory experiments that mulch and manure treatments were significantly better than hay as an organic matter addition for increasing the pH of acidified mine void water at Ewington. The manure produced the greatest increase in pH, although it contributed less to alkalinity than mulch; suggesting mulch bas a greater ability to release carbonates than did manure. The manure and mulch additions increased the pH in the laboratory and field experiment by 0.5-1.5 pH units. This increase was sustained for most of the 21 week field experiment. An increase in pH in the control ponds was recorded over the last 8 weeks of the experiment which was probably due to the inflow of more alkaline groundwater through the substratum as a consequence of the winter rainfall. pH values measured in the experimental ponds 15 months after the commencement of the project indicated that the ponds treated with manure maintained significantly higher pH levels than either the mulch or the control ponds. There was no difference between the pH values for the ponds treated with mulch and the controls suggesting that manure not only provided a greater increase in pH but also over a longer period. The addition of organic mailer also resulted in an increase in gilvin in the laboratory experiments. Low sulphate and sulphide levels were also recorded in all experiments before and after the introduction of organic materials into mine void water and ponds adjacent to Ewington indicating that sulphate reducing bacterial activity was not the cause for the increase in pH as occurred in other situations, but rather the addition of alkaline organic matter caused the increase in pH. The addition of manure organic material was associated with an increase in the ortho-phosphate levels, resulting in an increase in chlorophyll a concentrations. It is believed to be the first stages of succession processes leading to the establishment of a biologically active wetland system. During this process the emerging ecosystem neutralises the acidic content of the water.
Mine water, Purification, Coal mines and mining, Environmental aspects, Western Australia, Collie, Acid mine drainage, Collie., Water Resource Management
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Edith Cowan University, Research Online, Perth, Western Australia