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Water Management In Mineral Processing Plants Case Study: Somair Mining Company-niger

Congress: 2015
Author(s): KANO Namata (NIAMEY, Niger), KANO Namata, HAMA Abdou
Ministry of Mines 1, SOMAIR2

Keyword(s): Sub-theme 1: Water supply and demand,
AbstractKANO NAMATA Ministry of Mines and Industrial Development General Directorate of Mines and Geology Environmental Programs Officer Spécialiste en Evaluation Environnementale / QSE Cel : +227- 96 98 51 11 / 90 31 00 90 Email: Kanonamata@ yahoo.fr HAMA Abdou Mining Company of Aïr (SOMAÏR) MCO/DFM/Minage   Introduction The Mining Company of Aïr (SOMAÏR) is a subsidiary of AREVA NC that extracts uranium ore in an open mining pit at a depth of 40-80m. After extraction, the ore, at a grade of 3 in 1000, is admitted to the facility for dynamic processing. The purpose of this treatment is to obtain from the ore a concentrate containing soda uranate, 73.5% of natural uranium. The process requires a large amount of industrial water, estimated at 4808m ³ /j. Given this large quantity of water in the treatment process and in the climatic context of the site, this study has carried out in order to propose collection and treatment system which is an opportunity to SOMAIR for recycling sewage still being evacuated to spreading ponds for evaporation. I. Methodology 1.1 State of wastewater management at SOMAIR To achieve this, the collection and treatment of the industrial waste water from the plant was carried out. This enabled to assess the effectiveness of the system of recycling and reuse of wastewater of the plant. 1.2 Quantitative Study The objective is to identify the different sources of water used in the plant and be able to quantify the incoming water flows in the plant. Hydrogeological datas of the area allowed identifying the sources of water used by the plant. Plant water supply systems study has allowed identifying the locations of the flow meters. Measurements of incoming and outgoing water flows have were made on the site. These measures concerned samples taken continuously during 24 h and during normal plant operation 1.3 Qualitative Study Analyses of samples were conducted by the production laboratory of the SOMAIR. The sampling method is composite with biweekly measurements over a period of a month. Samples been taken at industrial wastewater collectors and Sewage from latrines. Global physicochemical parameters measurements have been made with samples three times per day. Measurements of specific physico-chemical parameters (uranium, sulfate, aluminum, nitrogen, phosphorus, zirconium and molybdenum) were made on daily composite samples. The following parameters were considered: T°, pH, conductivity, and MSE, nitrogen and phosphorus, heavy metals. Due to lack of equipment of the laboratory for biological parameters analysis, the results of analysis carried out in 2012 of Sewage from latrines of the mining city were used for COD and BOD5. II. Résult and Discussion 2.1 water supply balance of the plant dynamic treatment 2.1.1 Drinking and industrial water inflows The waters used for the processing of ore are industrial water. Drinking water is used for human needs and some facilities cleaning. For measuring drinking and industrial water inflows, SOMAIR uses electromagnetic flow meters. For the measurement of the de-mineralized water flow a minimum conductivity of 20μS/cm is used. Most liquids can be measured from a minimum conductivity of 5μS/cm example: acids, bases, drinking water, waste water, etc. As part of this work, drinking water supply flow meters and the one from the industrial water supply of the treatment plant were used. o the flow measurements Conditions - Normal operation of the plant - Posted regime (post 1: 5 am to 1 pm; Position 2:13 h to 21 h and 3:21 h to 5 h post) o Results of the measurements Drinking water inflow is 550 m³ per day. Industrial water inflow is 4808 m³par day. 2.1.2 Outgoing flow of industrial wastewater Industrial wastewater generated is classified into four categories: o Category N ° 1: "cleaned" industrial wastewater: Total flux of this is 1224 m³/day. o Category N ° 2: industrial wastewater generated by washing filtration membranes: This represent 1262 m³par day o Category N ° 3: Effluent from solvent facilities: the flow is 1727 m³ per day o Category N ° 4: filtrates i.e.: filtrates are liquid waste recovered after filtration of the precipitated uranate. The flow of filtrate is 523 m³ per day From the above analysis, the total flow of the wastewater generated by the dynamic processing of Uranium ore is to: 1224 + 1262 + 1727 + 523 = 4736 m³/day for an inflow of industrial wastewater 4808 m³/day. The difference between the incoming and outgoing flow that is equal to: 4808 - 4736 = 72 m³/day represents the amount of water used for dust suppression at the crusher and grinder level, but also the loss of water in the process. 2.2. Outgoing flow of domestic wastewater A recent study on drinking water consumption is about 1000 l per day or 5 m³/day, so in the 550 m3/j of drinking water, the 545 m³/j are transformed into domestic wastewater. 2.3 State of wastewater management at SOMAIR At the processing plant, only industrial wastewater are recycled and/or re-used Drinking water releases are collected in a collection pit and sent directly to an evaporation basin. Recycling/reuse of industrial wastewater is carried at four levels: o First level: reuse of 'cleaned 'industrial waste water: these waters are collected and send to the industrial water basin. At this level, all the waste water generated is reused. o Second level: Recycling/reuse of industrial wastewater generated by washing of filtration membranes: These are collected and send to sand-water separation unit. All the waste water generated is recycled for reuse. o Third level: recycling/reuse of effluents from solvents facilities: They are collected in tank and about 75% of these effluents (1295, 25 m³ per day) are directly reused in the processing. o Fourth level: filtrates recycling/reuse: The filtrates (liquids waste) are still in the process and surplus is discharged through a decanter, by using a portion of approximately 475 M3/j for washing discharge bands and the rest (101 m³ per day) is sent to a collection pit to be evacuated to the spreading basins. 2.4. The State of the plant wastewater treatment The treatment of industrial wastewater and toilet wastewater is done by natural evaporation within the spreading basins 2.5 Optimizing the management of water at the industrial plant The basic principle to consider in an industrial environment is that a proper treatment of industrial waste water must be considered as a result of an intervention at the plant level, by investigating all means for flow reduction. Current recycling/reuse optimization system at the plant consist of resizing of tanks in order to contain any effluent flow. 25. Sewer separation It is sine qua non condition for any further effective treatment. With regard to SOMAIR treatment plant, it is better to separate wastewater generated from plant and residential waste water. By separating these sewages, we diminish releases of flow in spreading basins and suddenly the risk of basins overflowing which can cause dikes rupture. Conclusion The dynamic treatment processing of the ore requires a significant quantity of industrial water (4808 m³/j). Effluents and cleaned wastewater (uncontaminated) generated from treatment are recycled and reused to 75%. With regard to the importance of Wastewater from toilet, a flow reduction study conducted has allowed a reduction of about 10% in water utilization through the implementation of an action plan on water wastage. Physico-chemical, biological and bacteriological analysis allowed to propose sizing of collection and treatment system which is an opportunity to SOMAIR for recycling sewage still being evacuated to spreading ponds for evaporation. REFERENCES  URI: http://id.erudit.org/iderudit/019163ar  KLUTSE A. (1995) : Epuration des eaux usées domestiques par lagunage en zone soudano sahélienne (Ouagadougou, Burkina Faso). Thèse de doctorat, Université Montpellier II, 160p.  Kôkôh Rose EFFEBI (2009). Lagunage anaérobie : Modélisation combinant la décantation primaire et la dégradation anaérobie : Thèse de doctorat, Université de Liège  UNESCO : Traitement des eaux usées par lagunage. Fiche technique/ Août 2008  Dr Joseph WHETHE : Les systèmes d’épuration des eaux usées (atelier de recherche, FIS 2005) CREPA Siège.  A.G.SADOWSKI/Mars 2002 : Méthode de calcul d’une filière de traitement.
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