Jim Dobos, VP of Corporate Learning and Development for Aquatech International in Canonsburg, PA was the featured speaker at the Sept 12, 2013 meeting of the Appalacian Chapter of the American Association of Drilling Engineers (AADE). The 100 luncheon attendees heard an interesting summary of the many options currently available for treating waste water from various gas well activities based on the type of impurities to be removed:
1. Suspended Solids
- Settling ponds
- Clarifier, with optional chemical coagulants
- Filter Screens & Shakers
- Pressure Filter Vessles packed with anthracite, sand, or other filtration media
- Filter Press with batch cleaning and removal of filter cake
- De-watering bags
- Membrane Filters
2. Dissolved Solids
- Chemical reactions (precipitation)
- Lime (or soda ash) softening clarifier
- Ion Exchange Resin to remove calcium, magnesium, and other metal salts (water softener)
- Reverse Osmosis – cartridge of spiral wound membranes
- Evaporation and condense steam
- Thin film evaporator
3. Non-ionic mixtures – organics
- Oil skimmer
- Carbon filter
- Walnut shells
- Air Flotation – fine bubbles injected into bottom of tank
- Bio-degradation is possible but takes time – weeks / months
4. Dissolved Gases
- Vacuum degasser
- Packed column with compressed air injected in bottom
- Packed column with steam or nitrogen injected in bottom
- Always remove coarsest particles first, don’t try to do it all in one stage of filtration
- Some waste streams contain up to 20% solids (200,000 ppm). Sea water is only about 20,000 ppm. A waste stream with 120 ppm contains one lb of solids per 1000 gal. One barrel of 20% waste water contains 51 lbs of solids.
- NORM (Naturally Occurring Radiation Material) salts can sometimes be removed and sold for road salt but there may be permitting issues depending on the level of radiation.
- For drilling waste water, usually need portable treatment facilities, some options offer smaller footprints and are more portable than others.
- Current trend is to move toward zero discharge of water – keep cleaning and reusing it forever
- Removing more impurities to generate cleaner water costs more, generally exponentially more.
- This region (western PA has many plentiful sources of water), problem is much worse in arid regions (TX, etc).
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