| 摘要 |
<p>Overburden from surface coal mining in many regions can produce a rain runoff laden with selenium, in the selenate form. This occurs from exposed selenium-containing rocks in the overburden, from which selenate is leached out by the nearly-pure rainwater. The selenium-containing runoff water is caught in ponds. Remediation of the pond water to remove selenate down to permissible levels for discharge to lakes and streams is performed by treatment with sulfur-modified iron (SMI) in a contact bed of an upflow reactor vessel. After a prefiltering step, the pond water is pH-adjusted as needed and pumped through the SMI reactor. The treated water can then be run through an oxidation tank and filtered to remove iron. For extending effectiveness and life of the SMI the contact bed is periodically "fluffed" with a high-velocity upflow of water through the bed, expanding and loosening the contact bed to prevent or break up compacting of the SMI medium.</p> |
