British Columbia Mine Reclamation Symposium

Discussion regulatory compliance strategies to achieve receiving water quality standards using selenium reduction/removal options Adams, D. J.; Clark, J. P.; Opara, A.; Peoples, M. J.


Achieving local regulatory Receiving Water Quality Standards for selenium [Se] (e.g. 2 μg/L in BC, Canada) at some proposed and existing mines requires Selenium Management Plans (SMPs) that demonstrate convincing and effective environmental protection to regulators. This impacts: (a) new mines proceeding through an Environmental Assessment (EA) process with predicted elevated selenium (Se) discharges; and (b) for existing mines with elevated Se discharges, to demonstrate future downstream Se-compliance needed to avoid regulatory permit non-compliance penalties. Unlike traditional heavy metal solubility equilibrium/precipitation, Se is usually controlled by redox conditions, pH, biological activity, and adsorption/desorption reactions. The geochemical characteristics of Se and its relationship with co-contaminants, such as nitrate, should guide approaches for developing effective SMPs. Approaches should consider augmenting mine site active selenium discharge treatments with a combination of: (1) indirect Se treatment strategies that will reduce active water treatment hydraulic retention times by removing co-contaminants; and (2) release prevention, handling seleniferous overburden to reduce weathering and runoff volumes requiring direct Se water treatment. It is expected that these types of mining practices can reduce Se environmental loads, as compared to past, historical mining operations. This analysis should be presented in the EA and permitting processes. Bench- and pilot-scale testing of selenium treatment technologies help put into perspective the importance of site-specific influences on implementation of economical and effective selenium management approaches and treatments, and provides a robust basis for a SMP to be developed for the EA and permitting processes. Preventative or reduction procedures, in situ treatment, semi-passive treatments, and active selenium water treatment technologies to remove selenium to below 5 μg/L (or the local regulatory discharge standard) are discussed in terms of compliance approaches that will maximize the amount of clean water returned to watersheds and reduce or eliminate non-compliance.

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