Treatment of natural Radio-Nuclides and heavy metals in mine wastewater at Mopani Copper Mines in Zambia

katebe, Reuben

Treatment of natural Radio-Nuclides and heavy metals in mine wastewater at Mopani Copper Mines in Zambia

dc.contributor.author	katebe, Reuben
dc.date.accessioned	2011-07-21T14:41:12Z
dc.date.available	2011-07-21T14:41:12Z
dc.date.issued	2011-07-21
dc.description.abstract	The Zambian Copperbelt is one of the great metallogenic provinces in the world and the production of copper and cobalt from sedimentary rocks, locally metamorphosed of the Lower Roan Group of the Supergroup in the Katanga Basin is the main business. It is well known fact that the Katanga Basin is relatively uraniferrous area. The main objective of this post graduate thesis work was to assess the levels of radio nuclides and heavy metals in the mine wastewater at MCM and design a treatment process to reduce these contaminants to levels acceptable by the regulatory authorities before discharged to receiving streams and to the environment.Radionuclides are radioactive decays products of uranium -238 and thorium-232 which if consumed or inhaled can cause lung or bone cancer while heavy metals refers to any metallic chemical element that has a relatively high density and is toxic or poisonous at low concentrations. The mine wastewater from copper and cobalt beneficiation at Mopani Copper Mines Pic is variably discharged to surface watercourses and tailing facilities without proper chemical treatment. This continuous discharge of various kinds of pollutants from mining related activities to the environment has been going on since the late 1920's when mining started in the region. Locally, the Chibuluma, Mindola, Kitwe, Wusakile, Mululu and Uchi streams collect mine wastewater from Mopani Copper Mines (MCM) and discharge to the Kafue River.In the past, there has been no study done to assess and treat radionuclides and heavy metals in mine wastewater emanating from uraniferrous MCM in Kitwe. Previous studies on heavy metals from Kafue River have shown elevated concentrations of copper and cobalt, both in the dissolved and the solid phase. The approach during the study was to identify the main discharge points of mine wastewater to surface watercourses and tailing facilities at MCM. This was followed by 4 sampling trips to MCM in Kitwe between the period of September 2005 and January 2007 where a total of 24 samples were collected for characterization and 30 litres of Tailing Thickener Feed (TTF) for treatment tests. Physical-chemical characterization and subsequent treatment of the sampled mine wastewater was done at the National Institute for Scientific and Industrial Research (NISIR) laboratories. The main aim for physical and chemical characterization of mine wastewater before treatment tests was to establish its physical and chemical properties. The results obtained from the characterization of mine wastewater confirmed the presence of radionuclides (0.123 Bq/m3 in TTF, 0.266 Bq/m3 in TTU and 0.07 Bq/m3 in TTO) and heavy metals (12.87 mg/1 in TTF, 10.70 mg/1 in TTU and 5.25 mg/1 in TTO) in mine wastewater discharged to the receiving streams. In Zambia, under the statutory instrument of 1993 of the Environmental Protection and Pollution Control Act of 1990, no discharge of any radioactive material, is permitted. The overall mean results for dissolved radium-226 discharged to the streams were 0.04 Bq/m3 and less than 0.03 Bq/m3 of radium 228. The radium-226 discharged to the tailing facilities was 0.174 Bq/m3 and 0.07 Bq/m3 of radium-228. For heavy metals in dissolved phase, only manganese (2.16 mg/1) and nickel (0.57 mg/1) were slightly above regulatory limits. This situation can be attributed mainly to poor treatment strategy of lime dosing and sludge settlement currently in place at MCM in Kitwe. It has also been established through laboratory tests that 31 mg/1 of barium chloride (Ba2+) as a precipitating agent and 6 mg/1 of iron (as Fe3+) as a coagulant at a mixing speed of 70 rpm and mixing time of 20 minutes with pH range of 8.5-9 can significantly reduce the concentration levels of radio nuclides by 73.17% and heavy metals by 59.32% in mine wastewater. From the bench treatment results, a treatment process for radionuclides and heavy metals has been designed consisting of two barium chloride (precipitator) reactors in series, a ferric chloride (coagulant) rapid mixing tank, two flocculators and two clarifiers. The radioactive and toxic tailing thickener underflow (TTU) sludge from this treatment process can be disposed off safely by mixing it with cement in the ratio 1:3 to produce concrete matrix sludge that can withstand weathering effects of wind and rains. Environmental monitoring of daily and weekly sampling of wastewater for heavy metals and radionuclides respectively has been proposed. This can be achieved by installing automatic samplers that can record in-situ the pH, temperature, suspended solids and conductivity. The monitoring programme can also be used to assess the performance of the proposed treatment plant and also can facilitate quick intervention in case of pollution. The cost of construction and running of the proposed treatment plant per year at MCM to treat 75,000 m3/day of mine wastewater generated from the beneficiation of copper and cobalt metals was estimated to be ZMK 2,380,000,000.00 (USD 595,000) and ZMK 34,900,000.00 (USD 8,725) for monitoring the effluent from the plant.	en_US
dc.identifier.uri	http://dspace.unza.zm/handle/123456789/609
dc.language.iso	en	en_US
dc.subject	Radioactive decay	en_US
dc.subject	Radioactive substances in rivers, lakes, etc.--Zambia	en_US
dc.title	Treatment of natural Radio-Nuclides and heavy metals in mine wastewater at Mopani Copper Mines in Zambia	en_US
dc.type	Thesis	en_US