inputlloading rates, operating temperatures, waste stream types, fouling potential and scaling potential.
For ozone:
Size: Neutral - 50 t o 200 sf per 1 O00 bblid (1 O00 sf for 5000 bbl/d system).
Weight: Neutral - 5,000 Ib for 1,000 bbl o f water plus 1 O00 Ib for hardware.
Energy: High requirements.
produced water Residence Time: <20 min.
Input/Loading Rates: Limited only b y h o w much oxidant can be supplied.
Operating Temperature: Better efficiency at higher temperature, but ozone is less soluble and decomposes quicker at higher temperatures.
Fouling Potential: Oil may gum up catalyst.
Scaling Potential: Shouldn’t be a problem unless p H adjustment is required. Higher p H may cause precipitation of calcium, etc.
Operation: Should be easy t o operate.
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For peroxide:
Size: Neutral - 50 t o 200 sf per 1000 bbl/d.
Weight: Neutral - 5,000 Ib for 1,000 bbl of wat Energy: Low.
produced water Residence Time: C20 min.
plus hardw re.
Input/Loading Rates: Limited only by how much oxidant can be supplied.
Operating Temperature: Better efficiency a t higher temperature, but is less soluble and decomposes quicker at higher temperatures.
Fouling Potential: Oil may gum up catalyst
Scaling Potential: Shouldn't be a problem unless pH adjustment is required. Higher pH may cause precipitation of calcium, etc.
Operation: Should be easy t o operate.
9. Describe any side effects from use of the technology (e.g., side stream wastes or alteration of ionic composition).
Possible sludge from iron, but it should pass through the system in the treated produced water. System can handle colloidal suspensions.
Oxidation process may form toxic substances, but it hasn't been a problem in commercial applications.
1 O. Consider appropriateness, or necessity, of sequential use of treatment technologies. Note which technologies are compatible/incompatible.
No pretreatment necessary with the exception of oil removal, especially for slugs
Could be coupled with other technologies. For example, oxidation may break down refractory compounds t o biodegradable material for
subsequent biological treatment.
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A P I DRr351 9b W 0332290 0553733 T 9 8 W
11. Evaluate cost as best as possible. Summarize overall costs here.
Capital costs:
e $1 5,000 per 1 O00 bbl/d for peroxide (or other oxidant) system.
$50,000 per 1000 bbl/d for ozone system. Ozonator is at least half of the cost.
Ozone cost does n o t include cost for additional generator if needed.
Operating costs:
Major cost is electrical for ozone generation - $0.05 per kWh.
Peroxide: 30 t o 100 Ibs per 1000 bbl/d at $0.60 per Ib = $18 t o $60 per 1,000 bbl/d. Could be more for delivery t o platform. Could be a potential safety hazard.
12. List any recommendations for research needed t o make the technology more practical for offshore use.
Research effects of produced water components (¡.e., salinity, oil) o n technology performance.
Evaluate need for p H adjustment.
Question: Will it be selective? Need t o target selected compounds.
Otherwise, the system will n o t be efficient if it oxidizes every oxidizable compound.
High temperature may increase oxidation efficiency, but need t o evaluate i t s effect.
Laboratory research should be conducted t o address general upfront issues such as the best type of oxidation process (e.g. ozone vs.
peroxide), type o f catalyst, selectivity in treating toxicants, and the effects of produced water components such as temperature on performance. Later perform demonstration studies on platforms t o address operating issues.
Investigate the feasibility of partial treatment. May n o t be a need t o treat whole produced water waste stream.
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API DR*35L 96 = O732290 0553712 924 =
Filtration Technoloav Workcrroup Participants:
Kris Bancal, Moderator Brad Culkin, Expert Sung-I Johnson Colin Tyrie Dave Mount Philip Dorn Backaround.
The workgroup defined the following feed stream design characteristics:
Flow = 5,000 bbl/d TDS = 100,000 ppm
Oil = will meet guidelines of 2 9 / 4 2 ppm, but can be as high as 1 5 0 ppm with an upset condition of 5 0 0 ppm.
TSS = 1 5 mg/l ( 1 2 t o 20 ppm), composed of silicas, clays, iron.
Temperature = 120°F (80 t o 140OF) pH = 6.5
The following background information o n membrane technology was discussed:
Temperature Effect:
There is a 3% increase in flux per OC. For example, an increase in temperature from 80 t o 140°F will increase flux by 2 times.
Limitations o n Particle Size t o Capture:
Membranes are not a size classifying technology
For size fractionation, must have 100: 1, or at least 1 O: 1 difference, between captured particle size and permeate particle size. Not possible for 5 : l or 2:l ratio.
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API DR*351 96 O732290 0553733 8 b O
There is a limit on size of capture of between 100 t o 200 molecular weight, because of competition with ions in produced water. Affects the reject volume (¡.e., reject volume increases as the capture size decreases).
Membranes won't work for dissolved organic compounds.
Reject Disposal Options:
Concentrate can be routed back t o membrane t o be further concentrated for disposal (reinject or transport onshore).
Concentrate may also be added t o oil, but must be below 1 % solids limit for oil.
Pretreatment Requirements:
Culkin stated that free oil should n o t be a problem, even up t o 150 mg/l.
Tyrie disputed that claim based on his experience in operating such systems.
General group agreement for the need t o remove free oil by
hydrocyclone or dissolved air flotation (DAF) t o prevent possible fouling.
Sulfide is a concern for fouling and may be removed prior t o filtration by air sparging.
Also may remove iron by air sparging pretreatment.
Answers t o Technoloav Checklist Questions.
1. How well do technologies treat (reduce the concentrations of) specific chemical groups (e.g., volatiles, metals, H,S, ammonia and organics)? (Note: salinity is incorporated as a matrix effect).
Dispersed (free) and emulsified oil; however, free oil may foul membrane.
Particulates.
High molecular weight compounds ( > 500 t o 1,000 mw) A-1 9
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Dissolved and volatile compounds will not be removed.
Salinity will not be removed.
Mount stated that salinity shouldn't be a cause of toxicity considering the high dilution provided in the receiving water. Also, ion imbalance should also not be a problem if sufficient dilution is provided.
2. Is additional chemical usage necessary to reduce toxicity?
Sparging air to precipitate out iron. Iron may scavenge toxicants such as metals. Maybe filter produced water, then air sparge to precipitate iron, then filter again to improve overall filtration efficiency.
Sulfides will foul membranes so air sparging may be necessary to remove sulfides.
3. What range of oil and grease and salinity can the technology tolerate?
No limitation of oil and grease ( > 150 ppm); however, pretreatment may reduce potential for fouling.
No problem with salinity (even at saturation limit of 300,000 ppm) as long as crystallization does not occur.
No problem with TSS ( > 1 O0 ppm) 4. What are the equipment specifications?
Choice of membrane.
Membrane area.
Trans membrane pressure (try to run at high pressure using booster pump, 200 psi).
Energy intensity to vibrate membrane for cleaning (design = 10 hp per 300 sf).
Contacting materials - stainless?
Membrane area of 600-1 O00 sf = 3x3 f t footprint, 17 f t tall, 20 hp motor, 2500 Ib operating weight (w1 water).
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A P I DR*35L 96 0732290 0553735 633 =
Flux (gal per sf per day) = 200 gfd low, 500 gfd good, 1000 gfd v.
good.
If 500 gfd, a 1,000 sf machine would process 0.5 mgd or 12,000 bbl/d.
If 200 gfd, a 1,000 sf machine would process 5000 bbl/d.
Explosion-proof motor and pump.
Skid mounted, simple controls (start and stop)
Temperature is important, better performance a t higher temperature.
Currently using membrane filtration in Wyoming on a produced water to meet surface water quality standards.
Radionuclides could be a problem by concentrating on the membrane.
Barium salt t h a t crystallizes in system can may become soluble a t lower pressure and pass through membrane.
Delta p across membrane is about 200 Ib. Discharge to atmosphere.