Removal of antineoplastic drugs cyclophosphamide, ifosfamide, and 5-fluorouracil and a vasodilator drug pentoxifylline from wastewaters by ozonation

We investigated the ozonation of the antineoplastic drugs cyclophosphamide (CP), ifosfamide (IF), and 5-fluorouracil (5-FU) and of the vasodilator pentoxifylline (PEN) in distilled water, in pharmaceutical wastewater, and in hospital effluent at pH 5-11. Under an alkaline pH of 11, all of the target compounds rapidly degraded through the attack of hydroxyl radicals, which resulted in their complete removal within 5 min at an ozone supply rate of 3 g O3/h. Under acidic pH conditions, such as pH 5.6, CP and IF exhibited slower removal rates; however, compounds with unsaturated C-C bonds, such as 5-FU and PEN, were still removed at rapid rates under acidic conditions. Although the parent compounds were removed within minutes, the resulting ozonation byproducts were resistant to further ozonation and possessed increased Microtox acute toxicity. In distilled water, the resulting ozonation products exhibited minimal mineralization but high acute toxicity, whereas in naturally buffered pharmaceutical and hospital effluents, the byproducts were more amenable to removal and detoxification.

Anaerobic digestion of activated sludge after pressure-assisted ozonation

This study was undertaken to examine the benefits of pressure-assisted ozonation (PAO) in enhancing solids reduction and biogas production in anaerobic digestion. The results showed significant improvements in both. With unacclimated inoculum at varied food-to-inoculum (F/I) ratios of 0.5-2, solids and COD reductions were improved by PAO, as well as by increased F/I ratios even without PAO, which would warrant further optimization of the F/I ratio for an unacclimated inoculum. With acclimated inocula at F/I ratio of 0.8, volatile suspended solids reduction and biogas production were improved by up to 60% and 800%, respectively, when the AS had been subjected to 20 cycles of PAO. In extended operation in plants where acclimated anaerobes are encountered, PAO pretreatment offers improved digestion of AS in terms of solids and COD removals and biogas production.

Treatment of oil spill water by ozonation and sand filtration

Increasing volumes of crude oil being produced and transported throughout the world in recent decades have resulted in increased risks of spill and high-profile spill incidents of significant environmental and ecological impacts over extended periods of time. While immediate in situ and ex situ responses have been implemented, none are available for onsite treatment of contaminated water for immediate release of the treated water. We demonstrate here a potential treatment scheme involving ozonation and sand filtration intended for immediate treatment and discharge of the impacted water. Waters of tap, Utah Lake, and Great Salt Lake sources were spiked with crude oil of the Great Natural Butte of Utah at 2.5% and 0.025% oil (v/v) and tested for treatment. The results showed near complete removal (100%) of both Chemical Oxygen Demand (COD) and oil and grease (O&G) from initially 20000 and 11000 mg L(-1), respectively, via flotation pretreatment, ozonation in pressure cycles, and sand filtration. At lower oil level of 0.025%, complete removal of COD and O&G from waters were achieved without floatation. The treated waters showed reduction of turbidity to <1 from 4000 NTU and high Biochemical Oxygen Demand/COD ratio of 0.3-0.5 that reflected highly biodegradable residual organics. The results showed synergistic oil removal when two well practiced methods, namely ozonation and sand filtration that either alone seems ineffective, are combined sequentially. It indicates a potential on-site treatment response for oil spill incidents where the collection and transport of a large amount of contaminated water may be avoided.

Removal of perfluorooctanoic acid and perfluorooctane sulfonate via ozonation under alkaline condition

The elimination of recalcitrant, ubiquitous perfluoroalkyl acids (PFAAs) such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) is desirable for reducing potential human health and environmental risks. We here report the degradation of PFOA and PFOS by 85-100% via ozonation under alkaline condition being studied at environmentally relevant contaminant concentrations of 50 μg L(-1) to 5 mg L(-1), with enhanced removal rates by addition of hydrogen peroxide. Enhanced removal is achieved by ozonation pretreatment for 15 min at the ambient pH (i.e. 4-5), followed by elevation of pH to 11 and continued ozonation treatment for 4h. The ozonation pretreatment resulted in increased degradation of PFOA by 56% and PFOS by 42%. The results indicated hydroxyl radical-driven degradation of PFOA and PFOS in both treatments by ozone and peroxone under alkaline conditions. Wastewaters from electronics and semiconductor fabrication plants in the Science Park of Hsinchu city, Taiwan containing PFOA and PFOS have been readily treated by ozonation under alkaline condition. Treatment of PFAAs by ozone or peroxone proves to be efficient in terms of energy requirement, contact time, and removal rate.

Improved solubilization of activated sludge by ozonation in pressure cycles

The generation of a large volume of activated sludge (AS) from wastewater treatment has increasingly become a great burden on the environment. Anaerobic digestion is routinely practiced for excess waste sludge; however, the process retention time is long because of kinetic limitation in the hydrolysis step. We tested the feasibility of applying ozone in pressure cycles to enhance the disintegration and solubilization of AS with the goal to prepare them for digestion using reduced ozone dose and contact time. The AS was subjected to repetitive pressure cycles in a closed vessel in which an ozone gas mixture was compressed into the slurry to reach 1040 kPa in the headspace to be followed by rapid venting. For a returned AS with total COD (tCOD) of 8200 mg L(-1), a dose of 0.01 gO(3)g(-1) total suspended solids (TSS) delivered via 20 pressure cycles within 16 min resulted in a 37-fold increase of the sCOD/tCOD ratio (due to increased soluble COD, i.e. sCOD) and a 25% reduction of TSS, in comparison to a dose of 0.08 gO(3)g(-1) TSS via bubbling contact over 15 min that resulted in a 15-fold increase of the sCOD/tCOD ratio and a 12% reduction of TSS. Sludge solubilization was evidenced by increased dissolved contents of total phosphorous (from 10 to 64 mg L(-1)), total nitrogen (from 14 to 120 mg L(-1)), and protein (from <15 to 39 mg L(-1)) in the sludge suspension after treatment, indicating significant solubilization of AS.

Capture of metallic copper by high gradient magnetic separation system

Valence copper was recovered from wastewater by chemical reduction and use of a high gradient magnetic separation (HGMS) system. Ammonia (NH3) and sodium dithionate (Na2S2O4) at a molar ratio of [Cu]:[NH3]:[Na2S2O4] = 1:4:3 at pH = 9.5 were used first to chemically reduce copper ion to metallic copper; the resultant metal solids were captured in an upflowing reactor space equipped with a permalloy matrix net under a high gradient magnetic field. The captured solids were predominantly 6-20 microm in diameter, with Cu2O and CuO present among the solids. Four treatment configurations with and without the use of magnetic field and metal alloy as the matrix net were tested and their effects evaluated: (1) no magnetic field or matrix, (2) no magnetic field but with matrix, (3) with magnetic field but no matrix, (4) with both magnetic field and matrix. At flow rates of 40, 60, 80 and 100 cm3/min, capture efficiencies for metallic copper in the absence of magnetic field were 87%, 86%, 63%, and 39%, respectively, and in the presence of magnetic field were 99%, 98%, 95%, and 93%, respectively. The HGMS was critical for a high capture efficiency, whereas a matrix net only marginally enhanced it. Additional tests with a larger reactor confirmed similarly high efficiencies of > 85%. The use of an alloy matrix appeared to be important when high flow rates are most likely to be employed in practical applications.

Effects of operational parameters on decolorisation of C.I. Reactive Black 5 in UV/TiO(2) system

This study utilises a UV/TiO(2) system to decolorise C.I. Reactive Black 5 (RB5). The effects of TiO(2) dosage, pH, RB5 concentration and light power on the decolorisation efficiency using the UV/TiO(2) system were determined. IO(4)(-) was employed as an oxidant to increase the photodegradation efficiency of UV/TiO(2). The decolorisation rate constants (k) of RB5 in the UV/TiO(2) system are consistent with pseudo-first-order kinetics. The k values of 0.1, 0.5, 1.0 and 2.0 g/l TiO(2) were 0.53, 0.52, 0.69 and 0.68 h(-1), respectively. The rate constant increases with decreasing pH from 10 to 4. The decolorisation rate approximates linear relationship with RB5 concentration, as given by k=1.05[1/RB5](0.98); it varies nonlinearly with light power, as given by k=0.178[power](0.63). The experimental results reveal that the rate of decolorisation obtained using UV/TiO(2)/IO(4)(-) exceeds that obtained using UV/TiO(2).

Removal of oil and oil sheen from produced water by pressure-assisted ozonation and sand filtration

Ever increasing energy demand worldwide necessitates energy supply, inevitably leading to an increasing volume of process waters containing hydrocarbon contaminants. Among them, dispersed and dissolved oils in produced water need to be removed adequately in order to reuse or avoid surface sheen from coastal discharge. We have recently developed a new ozonation technique coupled with sand filtration to quickly remove oil from process water and prevent oil sheen. The technique incorporates rapid, successive cycles of compression and decompression during ozonation. Gas bubbles expanding from small to large sizes occur that provide ample reactive zones at the gas-liquid interface, resulting in heightened chemical conversions-notably the conversion of hydrophobic hydrocarbon molecules into hydrophilic ones. This study examined the removal of hydrocarbons and sheen according to treatment parameters and configurations, as assessed by changes in turbidity, COD, BOD, and sheen presence following treatment. When a synthetic produced water containing 120ppm of oil (about 100ppm of dispersed and 20ppm of soluble oil at a total COD of 320mgL(-1)) was subjected to 10 pressure cycles (reaching 1.0MPa; 20s each) of ozonation and sand filtration at 6cmmin(-1) and then repeated by 20 cycles of ozonation and sand filtration, it resulted in removal of oil to 20ppm as water-soluble organic acids, decrease of turbidity from 200 to 2NTU, and complete sequestration of surface sheen. The new technique offers a treatment alternative for produced water and likely other tailings waters, promoting safe discharge to the environment and beneficial uses of the water.

O(3) and O(3)/H(2)O(2) treatment of sulfonamide and macrolide antibiotics in wastewater

The ubiquitous presence of trace pharmaceutical compounds in the environment is a significant concern. While the implications of these compounds on ecosystems and human health are being determined, there has been increasing interest in their treatment such as by tertiary processes at sources and wastewater treatment facilities to arrest further release to the environment. We have examined the degradation of sulfonamide and macrolide antibiotics in a spiked water and a pharmaceutical wastewater by ozonation under varied conditions such as concentration, contact time, pH, and H(2)O(2)/O(3) mole ratio. The results show faster removal kinetics for sulfonamides containing the aromatic ring than for macrolides built of mostly saturated hydrocarbon structure, and that complete removal of all is achieved within 20 min of ozonation at the application rate of 0.17 g O(3)/min. Degradation of contaminants containing unsaturated C-C bonds occurs faster at low pH, consistent with O(3) being the predominant oxidant and its aqueous concentration being higher at low pH. Degradation of erythromycin having a fully saturated structure is slower and more effective at higher pH or with added H(2)O(2), both consistent with the enhanced production of OH radical under such conditions that contributes to removal of the saturated compound. Low pH favors degradation via molecular O(3) while high pH via OH radical; the optimal pH thus depends on target compounds being treated, and buffered pH at 7 facilitates removal of all tested compounds. The addition of H(2)O(2) to ozonation abets contaminant removal, and at mole ratio of H(2)O(2)/O(3)=5 it attains the highest degradation speed for all contaminants. However, a large excess of added H(2)O(2) results in reduced or no benefits relative to O(3) alone. Thus, only a small dose of H(2)O(2) is desirable when widely disparate compounds are treated by ozonation.

Rapid extraction of sediment contaminants by pressure cycles

Sediment contamination is a significant issue. Assessment, management, and monitoring of contaminated sediment require routine analyses of a large volume of sediment samples, which require significant preparation time including extraction of contaminants from samples prior to analysis. This work tested a new method of extracting contaminants from sediment based on the use of rapid, successive pressurization cycles, which involve compression of a gas into the extractive solvent in contact with the sediment immediately followed by decompression via venting. The technique improved extraction amounts and shortened preparation time. Tested were PCB and PAH contaminated sediment samples from various locations of the US, including the Passaic River, St. Louis River, Waukegan Harbor, and Wells National Estuarine Research Reserve. The results were compared to those of Soxhlet extraction. Specifically, the extraction of 15 g of sediment with 50 mL of hexane-acetone (1:1) mixture at room temperature using 10 rapid, successive pressure cycles with N(2) attaining 1.0 MPa during compression was complete within 15 min. Using the new technique, consistently more PAHs and PCBs were extracted from the sediments in comparison to Soxhlet extraction. Extraction was evaluated according to key factors including the number of compression-decompression cycles, compression pressure, sample amount, moisture, and pressurizing gas type. The heightened extraction performance was explained by cyclic changes in gas solubility during repetitive compression and decompression steps, which introduce mechanisms to fragment sediment aggregates resulting in increased contaminant exposure and extraction.

Pressure-assisted ozonation of PCB and PAH contaminated sediments

Sediment contamination by recalcitrant organics such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) is prevalent and of a great concern. Remediation efforts are hampered by the hydrophobic nature of the contaminants that limits their availability as well as by the sediment matrix that limits their exposure to treatment agents. Using contaminated sediment samples from the Passaic River, St. Louis River, Waukegan Harbor, and Wells National Estuarine Research Reserve, this research demonstrated a new ozonation technique that incorporates rapid, successive cycles of pressurization (690 kPa) and depressurization, enabling more effective treatment than conventional ozonation would. Conventional ozonation reached maximum 60% and 40% removal of PAHs from the Passaic River (40 mg kg(-1) initially) and St. Louis River sediment (520 mg kg(-1) initially), respectively, in 1h; however, removals ceased despite prolonged treatment for 2h. The pressure-assisted technique removed 96% of PAHs from both river sediments within 1h; it completely removed both PAHs (16 mg kg(-1) initially) and PCBs (5.1 mg kg(-1) initially) from the Waukegan Harbor sediment in 0.5 h. The heightened treatment is explained by soil aggregate fracturing upon pressure cycles that exposes the contaminants as well as by the confluence of hydrophobic contaminants and O(3) at the gas-liquid interface in the presence of microbubbles. The technique is expected to accelerate O(3) treatment of a wide range of organic contaminants, and it may provide treatment to dredged and stored contaminated sediment.

Pressure-assisted chelation extraction of lead from contaminated soil

Soil contamination by metallic elements including lead occurs frequently. Contaminant metals in soil pose a serious risk to public health and groundwater supplies. Extraction using chelants is seen as a remediation option; however, it is often hampered by access to the contaminants that are shielded by the soil matrix. We have developed a novel extraction technique that utilizes a mildly elevated pressure in consecutive cycles of compression and decompression along with a chelating agent for the soil slurry. Complete extraction of 3300 mg/kg of Pb from soil was achieved by 100 mM of EDTA (ethylenediaminetetraacetic acid) in 10 min using 20 pressure cycles at 150 psi (10 atm). Extraction was studied according to pressure, number of pressure cycles, chelant concentration, solid content, pH, agitation, and use of consecutive washings. Heightened extraction is attributed to fracturing of the soil particles that leads to enhanced contaminant exposure to the chelating agent.