MINING & CYANIDE - Environmental Impacts
Mining and Cyanide
The management and treatment of cyanide-containing wastes and wastewaters from gold mining operations continues to be closely scrutinised by regulatory authorities. There have been examples of excursions of wastewaters containing cyanides due to spills and leaks from mills, ponds, leach pads, tailing dams, etc.
Clearly, cyanide containing effluents must be treated prior to disposal to receiving water environments. This also applies to cyanide-containing wastes such as spent heap leach agglomerates.
EnviroGulf Consulting offers the following consulting services to clients:
- Environmental review and, or, audits of cyanide handling and use and potential forenvironmental releases from mining operations.
- Assessment and prediction of the environmental effects of planned releases of cyanide-containing wastewaters.
- Aquatic biological impact and ecotoxicological assessments of cyanide-containing wastes and wastewater effluents discharged to fresh waters and estuarine and marine waters.
- Identification, measurement and characterisation of toxic and non-toxic cyanide species in effluent and receiving waters.
- Monitoring: design, planning, execution of monitoring programs.
- Collation, reduction, analyses and interpretation of monitoring data.
- Advice on implementing toxicity bioassays of liquid effluents and in-plant effluent streams.
- Determination of cause and effect relationships, where possible.
EnviroGulf Consulting subcontracts international test authority-approved or registered laboratories to analyse our clients' samples. The following determinands can be analysed:
- Free cyanide (HCN and/or CN-).
- Total cyanide (TCN).
- Metallocyanide complexes, e.g. Cu(CN)2.
- Thiocyanate (SCN).
- Dissolved metals in hydrometallurgical cyanide solutions and effluents used to predict the most likely metal-cyanide complexes present in discharges.
- Total metals for assessing metal-cyanide precipitates.
EnviroGulf Consulting undertakes water, sediment and aquatic biological monitoring of waters receiving gold mining waste and wastewaters containing residual cyanides Hydrometallurgical process circuits under normal and upset conditions may also be monitored.
This service includes the following:
- Planning, commissioning and execution of monitoring programs designed to measure the significant effects of cyanide-containing wastewater discharges on receiving water ecosystems.
- Critical appraisal of clients existing monitoring databases with data reduction, analysis and interpretation.
- Biological sampling and monitoring of fish, algae and macroinvertebrate populations in receiving waters containing cyanide wastewaters.
- Tailing dam cyanide degradation.
EnviroGulf Consulting can undertake trouble-shooting assignments and field investigations of mining operations having environmental cyanide problems and liaise with government regulatory authorities on behalf of clients. Often there is much debate on the correctness of cyanide analytical methods and the application of water quality criteria for cyanides, especially where ambient standards are applied at the boundary of mixing zones in receiving waters. The Principal of EnviroGulf Consulting has solid experience in this area and has successfully negotiated with regulatory authorities on behalf of clients.
Discussions with mining and process engineers will serve to identify and characterise existing operations, particularly with regard to ore types and blends which may give rise to cyanide problems through excess cyanide demands with resulting spikes of cyanide in process circuits and discharges.
The Principal of EnviroGulf Consulting has conducted cyanide investigations and trouble-shooting at the following mining projects and, or, operating mines:
- Henty Gold Project (Tasmania) - Environmental impact assessment of the effects of construction-derived sediments and residual cyanides on the Henty River and negotiation of discharge and ambient cyanide criteria (with NSR for RGC (Tasmania) Limited).
- Mount Victor Gold Mine (PNG) - Assessment of the impact of residual cyanides on water quality and aquatic life, and giving technical advice on the use of hydrogen peroxide treatment for detoxifying cyanides in tailing supernatant prior to disposal to the receiving river system (with NSR for Niugini Mining Limited).
- Hidden Valley Gold Project Environmental Plan (PNG) - Environmental impact assessment of potential river biological effects arising from the direct discharge of tailing and/or tailing supernatant (with NSR for CRA Gold Pty. Ltd.).
- Beaconsfield Gold Mine (Tasmania) - Environmental assessment of the toxicity of cyanidation tailing and tailing pond cyanogenic supernatant and prediction of potential environmental effects on the Tamar Estuary, Tasmania (with NSR for John Miedecke & Partners Pty. Ltd.).
- Bukit Young Goldmine (Malaysia) - Assessment of water and wastewater management, disposal and detoxification of cyanided gold mill and heap leach effluents from the Bukit Young Gold Mine, Sarawak, Malaysia (with NSR for Middle East Timber Company, Singapore).
- Misima Gold Project Environmental Plan (PNG) - Assessment of the marine biological effects of at-depth marine tailing disposal and near-surface dumping of soft oxidised waste, on the basis of aeration-dilution and bioassay tests, field dump trials and predictions of waste transport and dispersion (with NSR for Placer (PNG) Pty. Limited).
- Ok Tedi Gold Mine (PNG) - Various environmental impact studies on the effects of residual cyanides in mine tailings entering the Ok Tedi and Fly rivers, including fish and macroinvertebrate kills attributed to cyanides (with OTML)
- Various gold mines (Ghana) - Reconnaissance site visits and assessment of cyanide management at gold mines in Ghana (Ashanti Goldfields Corporation, Goldenrae, Canadian Bogosu, and Southern Cross) (with NSR for Ghana Minerals Commission).
Publications / Reports:
- Balloch, D. (1985). Procedures for the toxicity testing and monitoring of mining wastewaters. Ok Tedi Mining Limited, Papua New Guinea. Technical Report No. PA/03/85-6.
- Balloch, D. (1984). The interim tailings system and waste disposal strategies - Environmental impact assessment. Ok Tedi Mining Limited, Papua New Guinea. Technical Report No. PA/03/84-23.
- Balloch, D. (1984). Optimisation of the hydrogen peroxide treatment of mine wastewaters containing residual cyanides. Ok Tedi Mining Limited, Papua New Guinea. Technical Report No. PA/03/84-30.