Meeting Low Level Metals Limits – Challenges and Successes

Regulatory agencies are increasingly lowering metals limitations to part-per-billion and part-per-trillion levels driven by water-quality based standards as well as technology-based standards. Depending on the wastewater characteristics, achieving low levels through treatment can be a challenge. This paper presents several challenges and successes in achieving low levels with a specific focus on coal-fired power plant Flue Gas Desulfurization (FGD) scrubber blowdown treatment and municipal wastewater. Mercury can be limited to part-per-trillion levels, making it especially difficult to treat. The effects of particle size, wastewater residence time in scrubber, and type of coal burned are evaluated for FGD blowdown. In addition, a full-scale evaluation of copper removal through organosulfide addition in a municipal wastewater treatment plant is presented.