Table 1 - Characteristics of Caro’s Acid Treatment (2002–2006) Total Cyanide (ppm) Caro’s Acid Molar Ratio (H2SO4 /H2O2) Consumption (Kg Ácido de Caro / Kg CN-) Cost of Caro’s Acid ($/t) Caro’s Acid Destruction Efficiency (%) 15.2 1.35 10.5 0.93 93.7 As observed in Table 1, the characteristics of industrial water offered opportunities for improvement in the following areas: SAFETY AND HEALTH: The use of industrial water in the processing plant presented high levels of total cyanide, posing risks of dissociation of weakly and strongly complexed cyanides into free cyanide and hydrogen cyanide, affecting the safety and health of personnel in direct contact with the industrial water during operations. ENVIRONMENT: These levels of total cyanide in industrial water represented risks to local flora and fauna, migratory birds, and other species in the tailings dam water surface and in the two 600m3 storage tanks supplying the plant, due to potential overflows or contingencies. COMMUNITY RELATIONS: It is important to maintain trust, transparency, and harmony with surrounding communities. Although the tailings dam operates with zero effluent discharge to the environment, it is necessary to provide information to the population regarding responsible water management and compliance with national legislation. In the unlikely event of seepage, contamination of downstream groundwater bodies would be minimal, since the solution complies with permissible cyanide limits. Table 2 - Maximum Permissible Levels for Liquid Effluent Emissions in Mining and Metallurgical Units (Source: MEM) Parameter Value at any time Annual average value pH Greater than 6 and less than 9 Greater than 6 and less than 9 Suspended solids (mg/l) 50 25 Lead (mg/l) 0.4 0.2 Copper (mg/l) 1.0 0.3 Zinc (mg/l) 3.0 1.0 Iron (mg/l) 2.0 1.0 Arsenic (mg/l) 1.0 0.5 Total cyanide (mg/l)* 1.0 1.0 *Total cyanide equivalent to 0.1 mg/L of free cyanide and 0.2 mg/L of weak acid dissociable cyanide.
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