Environmental Engineering Reference
In-Depth Information
that the nanostructured Osorb matrix can serve as a scaffold where either standard or
novel silica modiication chemistries can be employed to create a range of functionally
similar materials in terms of swelling, but possessing different degrees of selectivity for
organic capture. Large structural changes such as the attachment of bulky ~3000 g/mol
polyethylenimine groups throughout the nanoporous matrix improves absorption of polar
compounds, yet only leads to a ~40% decrease in measured swelling due to pore illing
and potential cross-linking. Regeneration by solvent rinsing and subsequent drying aids
to disrupt noncovalent interactions between the hydrophobic materials and the sorbates.
Such methods are also successful in removing bound species from the hydrophilic poly-
mer functional groups such as organic acids and phenols, allowing Osorb to be regener-
ated for additional use.
8.3 Treatment of Produced Water
Organic components in produced water are either dissolved or dispersed. Although Osorb
has excellent afinity and capacity for dispersed hydrocarbons where the full extent of
swelling can be utilized for capture, other physical processes (e.g., hydrocyclones) may be
more economical for oil-water separation. From a cost-analysis point of view, Osorb might
be useful for free organic capture when polishing or preventing of sheens in hard-to-treat
waters. The distinguishing capability of Osorb is the removal of dissolved organic compo-
nents in produced water. In many respects, Osorb is ideal for removal of dissolved organ-
ics from produced water as (i) most organic solutes are nonpolar hydrocarbons; (ii) the
TDS levels are typically high, leading to improved performance by the salting-out effect;
(iii) the nanoporous matrix has high capacity, allowing for larger volumes of water to be
treated; and (iv) the media can be regenerated for economical reuse of materials. Therefore,
it is hypothesized that Osorb may be best suited to be used as a polishing step in tight
regulatory environments, especially if releases of BTEX is a concern. Evaluation of Osorb
for produced water was conducted on both the bench scale and pilot scale to evaluate per-
formance. Small-scale testing focused on understanding the types of produced water that
could be treated with Osorb, whereas pilot-scale testing was done to determine if the pro-
cesses developed at the bench scale could be incorporated into larger engineered systems.
8.3.1 Bench-Scale Testing
Bench-scale testing was completed using two types of produced water from petroleum
extraction activities. Each contained relatively high (>250 ppm) amounts of dissolved
organics. “Type A” produced water was obtained after signiicant processing to remove
sediment and free oil through physical separation methods. As a result, type A water
had no suspended solids and primarily contained more soluble lower molecular weight
hydrocarbons including signiicant BTEX concentrations. “Type B” produced water was
obtained much closer to the wellhead with only minor pretreatment. Type B water con-
tained a larger fraction of higher molecular weight hydrocarbons (>C
12
) in addition to a
gasoline fraction. Most of the heavy oil components were in ine dispersion or adsorbed to
a small amount of suspended ine particles in type B water. Both waters had nominal TDS
levels around 45,000 ppm. The diversity of water types was investigated to understand the
extraction capabilities of Osorb for two different classes of organic contaminants.
