Abstract:

A lot of costs are necessary for mine drainage active treatment at approximately 100 abandoned metal mines in Japan. JOGMEC (Japan Organization for Metals and Energy Security) has been conducting development of passive treatment (PT) system for the cost reduction. Recently, we have been carrying out large-scale PT tests at three abandoned metal mines. At one mine, AMD (pH 3.6, 38 mg/L Fe and 16 mg/L Zn) was treated through Fe oxidation/removal process and a following sulfate-reducing process using agri-waste and limestone with a water flow rate of 100 L/min (total HRT of 25 h), resulting in stable annual treatment efficiency. In another mine (pH 3.7, 6 mg/L Zn, 3 mg/L Cu and 0.8 mg/L Pb), sulfate-reducing reactors with a flow rate capacity of 150 L/min (HRT of 25 h) are being constructed to start PT test in 2024 since SRB process to the AMD was shown to be efficient from bench-scale test results in recent years. A PT test with non-biological system also began in 2023 in other mine (pH 4.1, 20 mg/L Zn, 10 mg/L Cu and 2.1 mg/L Pb). The AMD was first introduced to a limestone reactor for producing bicarbonate and subsequently delivered to a reactor filled with mixture of concrete waste materials and woodchips contributing sustainable treatment and carbon neutrality. Metal ions removals were efficient with a water flow rate of 40 L/min (total HRT of 15 h). Conceptional reactor designs and treatment efficiencies in the three PT test cases are going to be summarized.

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Dr. Takaya Hamai