Site Characterization and Remediation Demostration Day

Emergencies Engineering Division (Environment Canada)

Session Objectives: After reading this section and attending this demonstration, the attendee will have an increased knowledge of:
		Advanced Oxidation processes and equipment
		Membrane Separation processes and equipment
		Steam Stripping processes and equipment

Section Outline:
The following section presents an overview of the technologies.

Advanced oxidation is a destructive process which takes place at ambient temperatures. It utilizes hydroxyl radicals to oxidize organic compounds into carbon dioxide, water and in the presence of chlorinated organic compounds, salt. A proprietary ultra-violet light source is used to generate these highly reactive hydroxyl radicals from titanium dioxide, ozone, and/or hydrogen peroxide.

Membrane processes involve the use of pressure to drive water through a semi-permeable membrane while leaving the bulk of the contaminant behind. Reverse osmosis involves this process using specialized equipment operating at high pressure levels (700 - 1000 psi). Since the water crosses the membrane more easily than does the contaminant, it is possible through successive passes to concentrate the contaminant in the reject stream. The effectiveness of the process against a particular contaminant is determined by the interaction of the molecule with the membrane surface and substrate. In general, inorganic compounds are easily removed as are organic compounds with molecular weights over 100. This latter number is being reduced as better membranes are being developed.

Steam stripping is a separation process which utilizes the differences in thermodynamic properties of liquids. In this process, organic-contaminated water and steam are fed counter-currently to a packed column, causing the transfer of the contaminant(s) from the water phase to the vapour phase. The driving force for the separation is the concentration differential of the organic components(s) between the liquid and vapour phases. Two streams are generated in this process, namely: the treated effluent (bottoms) and the concentrated contaminant (tops). The bottoms are sent to a holding tank prior to their re-injection so as to ensure that the remediated water discharged is in accordance with regulations. The tops are temporarily stored then either recovered or disposed of in an appropriate manner (e.g. destruction in an advanced oxidation unit).