Publications by Year
Potential of sewage and green waste for acidic pit lake bioremediation.
Bacterial sulfate reduction-based bioremediation was trialled in an acidic pit lake, divided into two sections by an earth wall. Sewage and green waste was added to the smallest section, while the other…
Bacterial sulfate reduction-based bioremediation was trialled in an acidic pit lake, divided into two sections by an earth wall. Sewage and green waste was added to the smallest section, while the other was kept untreated as a control. Bioremediation initially increased the pH of the hypolimnion of the treatment lake but after 12 months the pH suddenly returned to pre-treatment levels. This proved to be only temporary and pH bounced quickly back to previous highs. The pH decreases appeared to be associated with heavy rainfall events. These rainfall events affected the bioremediation by mixing the lake and increasing acidity inputs from the catchment.
Biological remediation of low sulphate acidic pit lake waters with limestone pH neutralisation and amended nutrients.
Pit lake water in Collie is typically acidic due to Acid Mine Drainage (AMD) caused by pyrite oxidation and ferrolysis coupled with a low natural buffering capacity in surrounding geologies. These pit…
Pit lake water in Collie is typically acidic due to Acid Mine Drainage (AMD) caused by pyrite oxidation and ferrolysis coupled with a low natural buffering capacity in surrounding geologies. These pit waters have typically low sulphate, Fe and heavy metal concentrations. Nevertheless, Collie pit lakes have low biological productivity probably due to Al toxicity and low nutrient concentrations. Lake Kepwari (24 GL, max depth 65 m) is an acidic former coal open cut mine in Collie (Western Australia) that has been extensively revegetated and contoured for a water-ski park to facilitate its relinquishment back to the State. The main water treatment approach was rapid fill by river diversion but this has failed to prevent ingress of Fe2+ rich groundwater which has reduced pH to 4.8. In a manipulative mesocosm experiment using 1,200 L enclosures containing Lake Kepwari sediment and water, a control and three treatments were replicated three times. Treatment one, acidity was neutralised to pH 7 with powdered limestone, two had P concentrations maintained at eutrophic levels of approximately 20 μg L-1 (using K2HPO4), and three combined these same liming and P additions. Mesocosms were monitored for water quality (physico-chemical, nutrient and metal parameters) at 0, 77, 140, 191 and 255 days after establishment.Rainfall dilution resulted in the pH of the control increasing slowly from 4.8 to 6.5. Neutralised treatments remained circum-neutral, whilst P addition alone produced a higher final pH of >7. Sulphate concentrations fell slightly in all mesocosms by about 10 mg L-1, presumably due to SO42- reduction or secondary mineralisation. In the treatments with P additions, stimulation of NO32- reduction appeared to be the principal mechanism for increasing pH above those of the control. Addition of P had the additional benefit of reducing toxic mono-valent Al concentrations; probably by coprecipitation.This study demonstrated that P additions alone might be a useful remediation approach for the Collie pit lakes, although remediation effectiveness is enhanced with concurrent limestone neutralisation. This combined approach, in addition to ongoing alkalinity production by nitrate reduction and primary production, may facilitate these lakes remaining circumneutral over longer periods of time than single acidity neutralisation treatments alone.
In-situ coal pit lake treatment of acidity when sulfate concentrations are low
Pit lakes (abandoned flooded mine pits) represent a potentially valuable resource to mining companies, the environment and community, if appropriate water quality can be achieved. However, the water is often of low…
Pit lakes (abandoned flooded mine pits) represent a potentially valuable resource to mining companies, the environment and community, if appropriate water quality can be achieved. However, the water is often of low pH with high dissolved metal concentrations. In Western Australia coal pit lakes are acidic (pH 3–5) but with low concentrations of sulfate and metals. Low sulfate concentrations prevent microbial sulfate reduction from reducing acidity in these lakes. However, stimulation of primary production and associated alkalinity generating processes may provide a cost effective and sustainable solution to the acidity problems. A field-scale experiment (with control) involving the treatment of in-situ macrocosms (~600 m3) in a small south-west, Western Australian coal mine lake with municipal mulch and phosphorus additions to enhance primary production was undertaken between June 2003 and June 2004. One macrocosm was treated with P additions, another with mulch, a third with mulch and P, and the untreated lake formed the control. Physico-chemical and algal (chlorophyll a) sampling of the macrocosms and lake occurred at monthly intervals. The decomposition of mulch reduced nitrogen concentrations in the macrocosms to very low levels and necessitated supplementation with urea fertilizer. Phosphorus concentrations dropped rapidly after addition as it became bound to iron, organic matter and sediment. Although there was virtually no difference between treatments and control for most physico-chemical parameters measured (including pH), a PCA of the data showed that the addition of mulch sent the macrocosms on a different trajectory to the control. This difference was reflected in observations of increased abundance and diversity of biofilms and macroinvertebrates within the treated macrocosms. In conclusion, the addition of mulch and phosphorus alone was not sufficient to increase the pH of Collie mine lakes, although it does provide a number of benefits for biota in the water. We therefore recommend that liming be used to increase pH, followed by organic matter and nutrient additions to stimulate primary production.
Microcosm testing of municipal sewage and green waste for full-scale remediation of an acid coal pit lake, in semi-arid tropical Australia.
Pit lakes (abandoned flooded mine pits) represent a potentially valuable water resource to mining companies, the environment and regional communities across arid inland Australia. However, the water is often of low pH…
Pit lakes (abandoned flooded mine pits) represent a potentially valuable water resource to mining companies, the environment and regional communities across arid inland Australia. However, the water is often of low pH with high dissolved metal concentrations. The addition of organic matter to the pit lakes to enhance microbial sulfate reduction is potentially a cost effective and sustainable remediation strategy for these acid waters. However, the cost and availability of sufficient quantities of suitable organic substrates is typically limiting in these remote regions. Nevertheless, small quantities of sewage and green waste (organic garden waste) are often available in these areas from the regional towns which support the mines. This paper reports on preliminary microcosm laboratory experiments in preparation for the treatment of an acid (pH 2.2) coal mine pit lake in semi-arid tropical, inland north Queensland, Australia with municipal treated sewage and green waste. A laboratory experiment using microcosms (acrylic tubes) containing acid pit lake water and sediment were treated as follows; controls (untreated), sewage, green waste and sewage and green waste. The pH increased to a maximum of 5.5 in 145 days in the green waste and sewage treatment, with notable decreases of iron, aluminium and toxic heavy metals. Our results indicated that the green waste was a key component in alkalinity production and heavy metal removal.