Titanium (Ti) occurs naturally in soils and as highly purified titanium dioxide (TiO2) in many commercial products that have been used for decades. We report for the first time the occurrence, ...characterization, and removal of nano- and larger-sized Ti at wastewater treatment plants (WWTPs). At one WWTP studied in detail, raw sewage contained 100 to nearly 3000 μg Ti/L. Ti larger than 0.7 μm accounted for the majority of the Ti in raw sewage, and this fraction was well removed by WWTP processes. Ti concentrations in effluents from this and several other WWTPs ranged from <5 to 15 μg/L and were nearly all present in the <0.7 μm size fraction. As Ti was removed, it accumulated in settled solids at concentrations ranging from 1 to 6 μg Ti/mg. Ti-containing solids were imaged in sewage, biosolids, and liquid effluent as well as in commercial products containing engineered TiO2. Single nanoparticles plus spherical aggregates (50 nm to a few hundred nanometer in size) composed of sub-50 nm spheres of Ti and oxygen only (presumably TiO2) were observed in all samples. Significantly larger silicate particles containing a mixture of Ti and other metal atoms were also observed in the samples. To support the field work, laboratory adsorption batch and sequencing batch reactor experiments using TiO2 and activated sludge bacteria verified that adsorption of TiO2 onto activated sludge biomass occurs. Monitoring for TiO2 in the environment where WWTP liquid effluent is discharged (rivers, lakes, oceans) or biomass disposed (landfills, agriculture and soil amendments, incinerator off-gas or residuals) will increase our knowledge on the fate and transport of other nanomaterials in the environment.
Vanadium is listed on the United States Environment Protection Agency (USEPA) candidate contaminant list # 2 (CCL2), and regulatory guidelines for vanadium exist in some US states. The USEPA requires ...treatability studies before making regulatory decisions on CCL2 contaminants. Previous studies have examined vanadium adsorption onto some metal hydroxides but not onto commercially available adsorbents. This paper briefly summarizes known vanadium occurrence in North American groundwater and assesses vanadium removal by three commercially available metal oxide adsorbents with different mineralogies.
GTO (Dow) is TiO2 based and
E-33 (Seven Trents) and
GFH (US Filter) are iron based. Preliminary vanadate adsorption kinetics onto GFH, E-33 and GTO has been studied and the homogenous surface diffusion model (HSDM) is used to describe the adsorption kinetics data. The effects of pH, vanadium concentration, and volume/mass ratio are assessed. Vanadium adsorption decreases with increasing pH, with maximum adsorption capacities achieved in at pH 3–4. Results indicate that all adsorbents remove vanadium; GFH has the highest adsorption capacity, followed by GTO and E-33. Data are best fit with the Langmuir model rather than Freundlich isotherms. Both the sorption maxima (Xm) and binding energy constant (
b) follow the trend GFH>GTO>E-33. Naturally occurring vanadium is also removed from Arizona ground water in rapid small-scale column tests (RSSCTs). Metal oxide adsorption technologies currently used for arsenic removal may also remove vanadium but not always with the same effectiveness.
The use of membrane processes for wastewater treatment and reuse is rapidly expanding. Organic, inorganic, and biological constituents are effectively removed by reverse osmosis (RO) membrane ...processes, but concentrate in membrane retentates Disposal of membrane concentrates is a growing concern. Applying advanced oxidation processes (AOPs) to RO retentate is logical because extensive treatment and energy inputs were expended to concentrate the organics, and it is cheaper to treat smaller flowstreams. AOPs (e.g., UV irradiation in the presence of titanium dioxide; UV/TiO
2) can remove a high percentage of organic matter from RO retentates. The combination of AOPs and a simple biological system (e.g., sand filter) can remove higher levels of organic matter at lower UV dosages because AOPs produce biologically degradable material (e.g., organic acids) that have low hydroxyl radical rate constants, meaning that their oxidation, rather than that of the primary organic matter in the RO retentate, dictates the required UV energy inputs. At the highest applied UV dose (10
kWh m
−3), the dissolved organic carbon (DOC) in the RO retentate decreased from ∼40 to 8
mg L
−1, of which approximately 6
mg L
−1 were readily biologically degradable. Therefore, after combined UV treatment and biodegradation, the final DOC concentration was 2
mg L
−1, representing a 91% removal. These results suggest that UV/TiO
2 plus biodegradation of RO retentates is feasible and would significantly reduce the organic pollutant loading into the environment from wastewater reuse facilities.
This paper investigates the feasibility of arsenate removal by aggregated metal oxide nanoparticle media in packed bed columns. Batch experiments conducted with 16 commercial nanopowders in four ...water matrices were used to select a metal oxide nanoparticle that both amply removes arsenate and can be aggregated using an inert binder. TiO
2, Fe
2O
3, ZrO
2 and NiO nanopowders, which exhibited the highest arsenate removal in all water matrices, were characterized with fitted Freundlich adsorption isotherm (
q
=
K
C
e
1
/
n
) parameters. In 10
mM NaHCO
3 buffered nanopure water and at both pH
≈
6.7 and 8.4,
K ranged from 1.3 to 12.09
(mg As/g(media))
(L/mg As)
1/
n
, and 1/
n ranged from 0.21 to 0.52. Under these conditions, the fitted Freundlich isotherm parameters for TiO
2 nanoparticles aggregated with inorganic and organic binders (
K of 4.75–28.45
(mg As/g(media))
(L/mg As)
1/
n
and 1/
n of 0.37–0.97) suggested favorable arsenate adsorption. To demonstrate that aggregated nanoparticle media would allow rapid mass transport of arsenate in a fixed bed adsorber setting, short bed adsorber (SBA) tests were conducted on TiO
2 nanoparticle aggregates at empty bed contact times (EBCT) of 0.1–0.5
min and
Re
×
Sc
=
1000 and 2000. These SBA tests suggested that the binder has a negligible role in adsorbing arsenic and that mass transport is controlled by rapid intraparticle diffusion rather than external film diffusion.
While both aqueous bromine (HOBr/OBr
−) and chlorine (HOCl/OCl
−) react with natural organic matter (NOM) during water treatment, limited direct parallel comparison of bromine versus chlorine has ...been conducted. Experiments with model compounds and natural waters indicated more efficient substitution reactions with bromine than chlorine. Kinetic experiments with NOM isolates with and without pre-ozonation were conducted to obtain second-order rate constants (
k) with bromine and chlorine. Two-stage reaction kinetics (rapid initial and slower consumption stages) were observed. Bromine reacted about 10 times faster than chlorine with NOM isolates during both stages. The rapid initial stage reactions were too fast to quantify
k values, but qualitative estimates ranged between 500 and 5000
M
−1
s
−1. For the slower second stage
k values for bromine were 15 to 167
M
−1
s
−1 over the pH range of 5–11, and lower for chlorine (
k = 0.7–5
M
−1
s
−1). Values of
k correlated with initial SUVA values of NOM (UVA measured at 254
nm divided by DOC). Based upon UV/VIS and solid-state
13C-NMR spectroscopy, chlorine addition to a NOM isolate resulted in significant oxidation of aromatic and ketone groups while bromine had significantly less change in spectra. Overall, the improved knowledge that bromine reacts faster and substitutes more efficiently than chlorine will be useful in developing strategies to control disinfection by-product formation during water treatment.
Increased contributions from wastewater discharges and algal activity in drinking water supplies can lead to elevated levels of dissolved organic nitrogen (DON), which can increase the likelihood for ...the formation of emerging nitrogenous disinfection by-products (N-DBPs) of health concern. Dissolved organic matter (DOM) isolated from five waters, using a newly developed DOM isolation method specific to DON fractionation, produced thirty-four isolates of suitable mass. Each isolate was treated with free chlorine or chloramines under formation potential conditions. The DBP yields were determined for three halogenated DBPs (trichloromethane, dichloroacetonitrile, and trichloronitromethane) and one non-halogenated DBP (N-nitrosodimethylamine NDMA). Halogenated DBP yields were greater during the application of free chlorine, however chloramination produced significant levels of halogenated N-DBPs for some isolates. NDMA was only observed to form from selected nitrogen-enriched isolates (DOC/DON ratio < 20 mg/mg), especially those isolated from treated wastewater. Other results indicated that nitrogen-enriched DOM resulted in increased yields of the other N-DBPs studied.
Abstract To improve design and preclinical test scenarios of shoulder joint implants as well as computer-based musculoskeletal models, a precise knowledge of realistic loads acting in vivo is ...necessary. Such data are also helpful to optimize physiotherapy after joint replacement and fractures. This is the first study that presents forces and moments measured in vivo in the gleno-humeral joint of 6 patients during forward flexion and abduction of the straight arm. The peak forces and, even more, the maximum moments varied inter-individually to a considerable extent. Forces of up to 238%BW (percent of body weight) and moments up to 1.74%BWm were determined. For elevation angles of less than 90° the forces agreed with many previous model-based calculations. At higher elevation angles, however, the measured loads still rose in contrast to the analytical results. When the exercises were performed at a higher speed, the peak forces decreased. The force directions relative to the humerus remained quite constant throughout the whole motion. Large moments in the joint indicate that friction in shoulder implants is high if the glenoid is not replaced. A friction coefficient of 0.1–0.2 seems to be realistic in these cases.
A series of experiments was performed to measure the retention of a class of functionalized nanoparticles (NPs) on porous (microfiltration and ultrafiltration) membranes. The findings impact ...engineered water and wastewater treatment using membrane technology, characterization and analytical schemes for NP detection, and the use of NPs in waste treatment scenarios. The NPs studied were composed of silver, titanium dioxide, and gold; had organic coatings to yield either positive or negative surface charge; and were between 2 and 10nm in diameter. NP solutions were applied to polymeric membranes composed of different materials and pore sizes (ranging from ∼2nm 3kDa molecular weight cutoff to 0.2μm). Greater than 99% rejection was observed of positively charged NPs by negatively charged membranes even though pore diameters were up to 20 times the NP diameter; thus, sorption caused rejection. Negatively charged NPs were less well rejected, but behavior was dependant not only on surface functionality but on NP core material (Ag, TiO2, or Au). NP rejection depended more upon NP properties than membrane properties; all of the negatively charged polymeric membranes behaved similarly. The NP-membrane interaction behavior fell into four categories, which are defined and described here.
Abstract Until recently the contact loads acting in the glenohumeral joint have been calculated using musculoskeletal models or measured in vitro . Now, contact forces and moments are measured in ...vivo using telemeterized shoulder implants. Mean total contact forces from four patients during eight activities of daily living are reported here. Lifting a coffee pot (1.5 kg) with straight arm caused an average force of 105.0%BW (%body weight) (range: 90–124.6%BW), while setting down the coffee pot in the same position led to higher forces of 122.9%BW on the average (105.3–153.4%BW). The highest joint contact forces were measured when the straight arm was abducted or elevated by 90° or more, with a weight in the hand. Lifting up 2 kg from a board up to head height caused a contact force of 98.3%BW (93–103.6%BW); again, setting it down on the board led to higher forces of 131.5%BW (118.8–144.1%BW). In contrast to previously calculated high loads, the contact force during passive holding of a 10 kg weight laterally was only 12.3%BW (9.2–17.9%BW), but when lifting it up to belt height it increased to 91.5%BW (87–95%BW). The moments transferred inside the joint at our patients varied much more than did the forces both inter and intra-individually. Our data suggest that patients with shoulder problems or during the first post-operative weeks after shoulder fractures or joint replacements should avoid certain activities encountered during daily living e.g. lifting or holding a weight with an outstretched arm. Some energy-related optimization criteria used in the literature for analytical musculoskeletal shoulder models must now be reconsidered.
Abstract Knowledge of forces in the glenohumeral joint is essential for understanding normal and pathologic shoulder function. It forms the basis for performing fracture treatment or joint ...replacement surgery, for optimizing implant design and fixation and for improving and verifying analytical biomechanical models of the shoulder. An instrumented shoulder implant with telemetric data transmission was developed to measure six components of joint contact forces and moments. A patient with humeral head arthrosis achieved good joint function after its implantation. During the first 7 postoperative months, the contact force remained below 100% BW (percent body weight) for most activities of daily living. It ranged up to 130% BW for arm positions close to the limits of motion or when acting against external resistance. When the patient tried to turn a blocked steering wheel with maximum effort, the force rose to about 150% BW, the highest level observed thus far. Of great interest were the force directions relative to the humerus, especially those in the sagittal plane, which were not greatly influenced by the type of exercise, the arm position or the external resistance. The moments due to friction in the joint reached 5.2 N m. The friction-induced shift of contact forces relative to the implant head centre ranged up to 6.3 mm. These first worldwide in vivo measurements of glenohumeral contact forces are being continued in more patients and for longer postoperative times.
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