Nilsun H. Ince

The occurrence and fate of anti-inflammatory and analgesic pharmaceuticals in sewage and fresh water: Treatability by conventional and non-conventional processes

The presence of pharmaceutical (PhAC) residues in the environment is an emerging issue due to their continuous and uncontrolled release (via excretion from medical care) to the water environment and detrimental effects on aquatic organisms at low concentrations. A large fraction of PhAC pollution in water is composed of anti-inflammatory (AI) and analgesic (AN) drugs, which are rapidly excreted in urine. The present review is aimed to emphasize the occurrence of AI/AN wastes in sewage and fresh water bodies, their impacts on non-target organisms, and conversion or elimination by chemical, biochemical and physical treatment methods. The first part of the study is devoted to a critical review of most common AI/AN drugs and the relative efficiency of some selected sewage and drinking water treatment operations for their elimination/separation from aqueous systems. The second part focuses on pilot- or lab-scale applications of various advanced oxidation processes that are promising solutions to the ultimate degradation and/or conversion of such medical residues in effluents of drinking water treatment plants (DWTPs) and wastewater treatment plants (WWTPs) to less harmful and non-toxic products.

Critical effect of hydrogen peroxide in photochemical dye degradation

Tertiary or pretreatment of dyeing effluents by advanced oxidation processes (AOP) catalyzed by a source of UV light and a powerful oxidant is a promising alternative for the effective removal of color and refractory organics from the effluent. A crucial feature in designing such systems is the optimization of operating conditions (such as UV and oxidant dosages), which yield maximum removal at acceptable costs. The present study describes a modeling approach to keep the oxidant dosage at the most “effective” level to sustain maximum rate of dye removal at the selected experimental conditions. The method of study involved monitoring the rate of dye degradation in a synthetic azo dye solution of nearly constant concentration during irradiation by a medium pressure light source and varying H2O2 dosages, followed by predicting a mathematical relation between the pseudo-first order rate constant and the “effective H2O2 level” in the photoreactor. It was found that this “effective level” can be set by controlling the initial mass ratio of H2O2 to dye, or the light fraction absorbed by hydrogen peroxide within the UV emission spectra of the light source.

COMBINATION OF ACTIVATED CARBON ADSORPTION WITH LIGHT-ENHANCED CHEMICAL OXIDATION VIA HYDROGEN PEROXIDE

Abstract A tertiary treatment scheme involving simultaneous operation of activated carbon adsorption and advanced oxidation with ultraviolet light and hydrogen peroxide, followed by “destructive regeneration” of the spent adsorbent by advanced oxidation was investigated, using phenol as a model compound. Operational parameters in each step were optimized on the basis of phenol and total organic carbon removal during selected contact times. It was found that in the first stage with adsorption/advanced oxidation, phenol was totally eliminated during the first quarter of the contact time, and 87.5% total organic carbon removal was accomplished at the end. It was further found that advanced oxidation was the dominant pathway in this operation for the disappearance of phenol, while that of total organic carbon was carried out by combined effects of adsorption and oxidative degradation. Optimum regenerating frequency for the spent activated carbon was found to be once every four batches, which was four times slower than the required frequency in the absence of advanced oxidation. In the second part of the operation, where the spent carbon was regenerated destructively via advanced oxidation, 92.5% mineralization was accomplished in the regenerating solution at the end of the optimized contact time. The economic assessment of the system considering the operation of both steps revealed that under the initial and optimized conditions, the operating cost is 2.26 USD per cubic meter of wastewater with 40 ppm phenol.

Sonolytic and sonocatalytic degradation of azo dyes by low and high frequency ultrasound

The study describes degradation of two azo dyes at low and high frequency ultrasound (US) to compare their reactivity and to assess the impacts of frequency, OH, chemical structure and soluble/nonsoluble additives. Low frequency US alone was found totally ineffective for bleaching the dyes even after 2-h irradiation, while high frequency provided significant color decay in 30-min contact. The result was attributed to larger number of oscillations at high frequency that allowed a larger fraction of OH ejection to the bulk liquid. The difference in the rates of dye degradation was due to different substituents around the azo bonds that dictated the reactivities of the dyes with OH and other species. The performance of low frequency US was remarkably improved and exceeded that of high frequency in the presence of CCl(4), nano-sized TiO(2) and zero-valent copper. The effect was attributed to the advantage of low frequency for long bubble-life time, high collapse temperatures, turbulent flow conditions and high sonoluminescence intensity. The efficacies of the additives in terms of the reduction in dye concentration per unit mass of additive were: TiO(2)>CCl(4)>Cu, regardless of the dye structure and the operation frequency. Much better performance of TiO(2) than Cu was attributed to its larger surface area with a slight positive charge on it and to the effect of stable sonoluminescence that may have induced photocatalytic properties on semiconductor surface.

Degradation of Reactive Azo Dyes by UV/H2O2: Impact of Radical Scavengers

Abstract Hydroxyl radical (•OH) scavenging effects of carbonate , bicarbonate and chloride (Cl−) ions on the performance of an ultraviolet light-hydrogen peroxide (UV/H2O2) advanced oxidation process were investigated using a reactive azo dye, C.I. Reactive Red 141 as the model compound. It was found that in the absence of scavengers, complete color removal was possible in 15 min under the experimental conditions employed. The rate of color decay was inhibited remarkably with increasing concentrations of bicarbonate and carbonate species, especially when the distribution of alkalinity favored the dominance of carbonate ions. It was further observed that chloride inhibited the rate only when it was between 100–1250 mM as Cl−, and was ineffective at higher concentrations.

Sonochemical decay of C.I. Acid Orange 8: Effects of CCl4 and t-butyl alcohol

Sonochemical degradation of aryl-azo-naphthol dyes represented by C.I. Acid Orange 8 was investigated at 300 kHz to assess the operational parameters and the impacts of rate enhancers (CCl(4)) and rate inhibitors (t-butyl alcohol). It was found that the degradation of the dye was accelerated with increased concentrations of CCl(4) via the accumulation of reactive chlorine species and the hindrance of OH radical combination reactions with atomic hydrogen. The addition of t-butyl alcohol at all test concentrations inhibited the degradation of the dye regardless of the quantity of OH radicals (or H(2)O(2)) in solution. The inhibition was explained by the competition of the dye and t-butyl alcohol at the gas-liquid interface. Finally, the rate of dye degradation in the presence of both reagents at their effective concentrations was found to be considerably slower than that with CCl(4), showing that the formation of reactive chlorine species was remarkably suppressed by the rapid reaction of t-butyl alcohol at the gas-liquid interface.

Sonochemical destruction of nonylphenol: Effects of pH and hydroxyl radical scavengers

Nonylphenols are water-stable endocrine disrupting compounds that inhibit the growth of sewage bacteria in biological processes. The study describes the decomposition of 4-n-nonylphenol (NP) in water by 20 kHz ultrasound with emphasis on the impacts of pH, concentration and OH scavengers. It was found that the rate of degradation was accelerated by alkalinization, but more so by the addition of hydroxide alkalinity than carbonate. The addition of low doses of CO(3)(2-) and t-butyl alcohol as strong scavengers of OH was also found to accelerate the decomposition of NP. The observation was attributed to the generation of reactive CO(3)(2-) and CH(3) via pyrolysis of the additives in the cavity bubbles. The results also revealed that NP did not compete with OH scavenging agents when their relative concentration was low. In case of high frequency sonication (861 kHz) the competition was slightly effective (slowed down degradation) at an identical dose of t-butyl alcohol. The difference was attributed to shorter bubble life time at high frequencies leading to less violent/less energetic bubble collapse and lower yield of CH(3).

Impact of dilution on the transport of poly(acrylic acid) supported magnetite nanoparticles in porous media

This paper investigates the impact of dilution on the mobility of magnetite nanoparticles surface coated with poly(acrylic acid) (PAA). Transport experiments were conducted in a water-saturated sand-packed column for input nanoparticle solutions with total Fe concentrations ranging from 100 to 600mg/L. Particle size analysis of the synthesized nanoparticle solutions showed that PAA provides good size stability for Fe concentrations as low as about 1mg/L. Time-moment analysis of the nanoparticle breakthrough curves, on the other hand, revealed that nanoparticle mass recovery from the column decreased consistently with dilution, with greater attenuation, sharper fronts and longer tails compared to that of the tracer. Particle size analysis of the eluted solutions shows that the nanoparticle size is negatively correlated with nanoparticle concentration. Modeling results suggest that the decrease in nanoparticle mobility with input concentration can be represented using a kinetic time-dependent deposition term with finite deposition capacity and a kinetic detachment term. For field applications, the increase in particle size and detachment resulting from dilution means reduced transport efficiency of nanoparticles and reaction potential with travel distance.

Volatilization of organic chemicals from water

Liquid-phase transfer coefficients of ten selected organic pollutants were measured simultaneously with the O2 reaeration coefficient in a 2L reactor. The contents of the reactor were stirred in the laboratory by a 0.15 m diameter propeller attached to a constant speed motor. The ratio of the mass transfer coefficient of the chemical to that of O2 is found to vary between 0.43 and 0.60 for eight of the chemicals tested. This result is in good agreement with the literature concerning high volatility chemicals. The value of this ratio for the other two chemicals was found to be 0.10 for nitrobenzene and 0.01 for phenol, confirming the predominance of gas phase resistances in the transport process for these two compounds.

A semi-empirical approach to relate the volatilization rates of organic chemicals to their physical properties

Abstract The experimentally determined volatilization/reaeration ratios for ten organic chemicals of environmental concern are related, to specifically selected physico-chemical properties of the chemical, by the preassumption of a multi-variate linear relation. The selected model is then tested for reliability in a different sample universe whose published values of volatilization/reaeration rate ratios are compared with values calculated by using the estimated coefficient of the model equation.