Copper stabilization via spinel formation during the sintering of simulated copper-laden sludge with aluminum-rich ceramic precursors

The feasibility of incorporating copper-laden sludge into low-cost ceramic products, such as construction ceramics, was investigated by sintering simulated copper-laden sludge with four aluminum-rich ceramic precursors. The results indicated that all of these precursors (γ-Al(2)O(3), corundum, kaolinite, mullite) could crystallochemically stabilize the hazardous copper in the more durable copper aluminate spinel (CuAl(2)O(4)) structure. To simulate the process of copper transformation into a spinel structure, CuO was mixed with the four aluminum-rich precursors, and fired at 650-1150 °C for 3 h. The products were examined using powder X-ray diffraction (XRD) and scanning electron microscopic techniques. The efficiency of copper transformation among crystalline phases was quantitatively determined through Rietveld refinement analysis of the XRD data. The sintering experiment revealed that the optimal sintering temperature for CuAl(2)O(4) formation was around 1000 °C and that the efficiency of copper incorporation into the crystalline CuAl(2)O(4) structure after 3 h of sintering ranged from 40 to 95%, depending on the type of aluminum precursor used. Prolonged leaching tests were carried out by using acetic acid with an initial pH value of 2.9 to leach CuO and CuAl(2)O(4) samples for 22 d. The sample leachability analysis revealed that the CuAl(2)O(4) spinel structure was more superior to stabilize copper, and suggested a promising and reliable technique for incorporating copper-laden sludge or its incineration ash into usable ceramic products. Such results also demonstrated the potential of a waste-to-resource strategy by using waste materials as part of the raw materials with the attainable temperature range used in the production of ceramics.     

Structure characterization and adsorption properties of pyrolyzed sewage sludge

Sewage sludges produced from wastewater treatment plants continue to set environmental problems in terms of volume and way of reuse. Thermal treatment of sewage sludge is considered as an attractive method in reducing sludge volume, and at the same time, it produces reusable byproducts. This paper deals with porous carbonaceous materials production from sewage sludge by pyrolysis (or carbonization) process with a goal of different industrial applications. Carbonization experiments were carried out on two kinds of sludge, namely viscous liquid sludge and limed sludge by varying carbonization temperature between 400 degrees C to 1000 degrees C. The porous structure and surface chemistry of the materials obtained were characterized using nitrogen adsorption, scanning electron microscopy, elemental analysis, Boehm titration, and pH of zero point of charge determination. The results show that basic character of the carbonized residues increases with increasing carbonization temperature. Then, carbonization allows specific surface area and pore volumes to be developed. Carbonized viscous liquid sludge and carbonized limed sludge are mainly mesoporous in nature, with specific surface areas reaching about 100 m2 g(-1) and 60 m2 g(-1), respectively. Finally, adsorption experiments, in aqueous solution, were carried out and show that carbonized viscous liquid sludges and limed sludge remove effectively the metallic ion Cu2+, acid and basic dyes, and phenol. Pyrolyzed sludges properties seem to be encouraging for the preparation of activated carbon by physical activation process.     

Anion leaching from refinery oily sludge and ash from incineration of oily sludge stabilized/solidified with cement. Part II. Modeling

This paper presents the modeling of anion leaching (SO4(2-) and CrO4(2-)) from refinery oily sludge and ash produced by incineration of oily sludge, stabilized/solidified (s/s) with two types of cement, 142.5 and 1142.5. Anion leaching was examined using a sequential toxicity characteristic leaching procedure (TCLP) test. To elucidate the mechanisms of sulfate and chromate leaching, we employed Visual MINTEQ, incorporating a multiple-problem setup. Specifically, 10-14 different problems, depending on the pH range of the leachates, were connected together in the same run. Each problem corresponded to one pH value of the leachate and the model run covered the pH range of the five sequential TCLP extractions. This modeling approach was tested using chemical equilibrium with or without sorption onto ferrihydrite. Good agreement between experimental and modeling results was obtained for sulfate leaching from solidified oily sludge and ash, considering surface complexation onto ferrihydrite on top of chemical equilibrium controlled by gypsum at pH <11 and ettringite at pH >11. Chromate leaching was described by chemical equilibrium, controlled by CaCrO4(s) (at pH <11) and Cr(VI)ettringite (at pH >11).     

Anion leaching from refinery oily sludge and ash from incineration of oily sludge stabilized/solidified with cement. Part I. Experimental results

This paper presents the leaching behavior of anions (SO4(2-) and CrO4(2-)) from refinery oily sludge and ash produced by incineration of oily sludge, stabilized/solidified (s/s) with two types of cement, 142.5 and 1142.5. Anion leaching was examined using a 5-step sequential toxicity characteristic leaching procedure (TCLP) test. A single TCLP extraction resulted in limited sulfate release (<50 mg/L) for s/s ash and significant sulfate release (<850 mg/L) for s/s oily sludge. Chromate release was <1 mg/L for s/s ash and nondetectable for s/s oily sludge. The sequential TCLP tests resulted in increased leaching for both sulfate and chromate. In general,the increase of liquid-to-solid ratio (TCLP leachant-to-waste ratio) resulted in increased leaching of sulfate from solidified samples compared to untreated oily sludge, ash and cement. In contrast, chromate leaching decreased by s/s process. A qualitatively similar leaching behavior for SO4(2-), even for radically different wastes such as oily sludge and ash, solidified with two different types of cement was observed.     

Vitrification of chromium electroplating sludge

This work investigated the vitrification of hazardous electroplating sludge containing 140 mg/g Cr with/without bottom ash or cullet conditioning to lower specimens' basicities to 0.97-1.17 or 0.18-0.23, respectively. The conditioning was found to enhance the smooth/glassy appearance of slags but no ingot was obtained. Cr was >98% retained in the vitrified slags. Cr2O3 dominated in crystalline structure for the slag vitrified from the sludge, but this domination gradually shifted to Fe2SiO4/Fe3O4/SiO2 or SiO2 crystalline with increasing addition of bottom ash or cullet into the sludge, respectively. Compared to the raw sludge, the sludge-vitrified slag displayed lower leaching concentrations for most metals (particularly Cr (2.54 mg/L)), and smaller leaching ratios for Ag, Cr, and Cu (1.35, 0.02, and <0.01%, respectively) but greater ones for Cd, Pb, and Zn (3.83, 2.46, and 0.36%, respectively). The Cr leaching ratios were approximately 0.01% for the slags vitrified from the conditioned sludge. Independent of the slag basicity and crystalline structure, metal leaching quantity increased but leaching ratio decreased with increasing slag metal content. The slag compressive strengths were improved to >14.7 MPa at the mixing ratios > or = 2/1 and 1/1 for bottom ash/sludge and cullet/sludge, respectively. Fulfilling the criteria of Toxicity Characteristic Leaching Procedure (TCLP), all the slags were recyclable.     

Dried sludges and sludge-based chars for H2S removal at low temperature: influence of sewage sludge characteristics

The use of sewage sludge as a precursor of adsorbent/ catalyst materials for environmental applications has been encouraged during the past few years. Due to the heterogeneous nature of sludges, there exists a lack of information regarding the characteristics of these low-cost precursors and how their physicochemical properties affect the final performance of materials prepared from them. In this work, three sewage-sludges collected at WWTPs with assorted sludge/wastewater treatment schemes were used as precursors of adsorbents/catalysts for H2S removal at room temperature. All the solidswere characterized to establish their textural properties and chemical composition, including the speciation of the adsorbents/ catalysts inorganic fraction. Thermal treatment (gasification) of the raw (dried) sludges increased the H2S removal ability in all cases. For these thermally treated materials, catalytic conversion to elemental sulfur and sulfate moieties was found to be the main route of H2S removal. Results indicate that adsorbents based on an iron/calcium-containing sludge were the most reactive and exhibited the highest capacities for H2S retention. Forthis particulartype of sludge, a reasonably good performance was observed even when the dried (raw) sludge was used as adsorbent/ catalyst. Alternatively, the oxidation of H2S by chars obtained from the other two sludges under study was related to their textural properties.     

Behavior of fluoroquinolones and trimethoprim during mechanical, chemical, and active sludge treatment of sewage water and digestion of sludge

The behavior and fate of three fluoroquinolones (norfloxacin, ofloxacin, and ciprofloxacin), one sulfonamide (sulfamethoxazole), and trimethoprim were investigated at a sewage treatment plant in Ume?, Sweden, in 2004. This plant uses conventional mechanical, chemical, and activated sludge methods to treat the sewage water and digest the sludge; the dewatered digested sludge is pelleted (dry weight > 90% of total weight). Raw sewage water and particles as well as effluents and sludge from specific treatment areas within the plant were sampled. In addition to quantifying the antibiotics within the plant, we characterized the sample matrixes to facilitate evaluation of the results. Of the five substances examined, only norfloxacin, ciprofloxacin, and trimethoprim were present in concentrations higher than their limits of quantification. Norfloxacin and ciprofloxacin sorbed to sludge in a manner that was independent of changes in pH during sewage treatment, and more than 70% of the total amount of these compounds passing through the plant was ultimately found in the digested sludge. The results suggest that fluoroquinolones undergo thermal degradation during pelleting, but more studies are needed to confirm this. Trimethoprim was found in the final effluent at approximately the same concentration and mass flow as in the raw sewage, and could not be quantified in any solid sample. Predicted environmental concentrations, based on consumption data for Ume? municipality, correlated well with the results obtained, especially when the predicted concentrations were corrected to account for the amount of each active substance excreted in urine. The results obtained were compared to those of previous studies of these three substances' behavior and fate and were found to be similar, although some of the other plants studied employed the various treatment steps in different orders.     

Effect of microbial activity on trace element release from sewage sludge

The microbial role in mobilization of trace elements from land-applied wastewater sludge is not well-defined. Our study examined the leachability of trace elements (Cd, Cr, Cu, Mo, Ni, P, Pb, S, and Zn) from dewatered sludge as affected by treatments designed to alter microbial activity. Different levels of microbial activity were achieved by incubating sludge columns at 4, 16, 28, and 37 degrees C and by the addition of AgNO3 biocide at each temperature. Columns (with inert glass bead support beds) were subjected to six consecutive incubation-leaching cycles, each consisting of 7.3-d incubation followed by 16-h leaching with synthetic acid rain. Glucose mineralization tests were used to assess overall microbial activity. Significant acidification and trace element leaching occurred when conditions favored microbial activity (16 and 28 degrees C). Extent of mobilization was element-specific with Zn, Ni, and Cu showing the greatest mobilization (99, 67, and 57%, respectively). Mobilization was reduced but still substantial at 4 degrees C. Conditions that best inhibited microbial activity (37 degrees C or biocide at any temperature) resulted in the least mobilization. Characterization of enrichments performed using thiosulfate as the sole energy source revealed the presence of both known and putative S-oxidizing bacteria in the sludge. The results suggest that microbial acidification via S oxidation can mobilize trace elements from sludge. Elemental mobility in field situations would also be governed by other factors, including the capacity of soil to buffer acidification and to adsorb mobilized elements.     

Nickel stabilization efficiency of aluminate and ferrite spinels and their leaching behavior

Stabilization efficiencies of spinel-based construction ceramics incorporating simulated nickel-laden waste sludge were evaluated and the leaching behavior of products investigated. To simulate the process of immobilization, nickel oxide was mixed alternatively with gamma-alumina, kaolinite, and hematite. These tailoring precursors are commonly used to prepare construction ceramics in the building industry. After sintering from 600 to 1480 degrees C at 3 h, the nickel aluminate spinel (NiAl204) and the nickel ferrite spinel (NiFe204) crystallized with the ferrite spinel formation commencing about 200-300 degrees C lower than for the aluminate spinel. All the precursors showed high nickel incorporation efficiencies when sintered at temperatures greater than 1250 degrees C. Prolonged leach tests (up to 26 days) of product phases were carried out using a pH 2.9 acetic acid solution, and the spinel products were invariably superior to nickel oxide for immobilization over longer leaching periods. The leaching behavior of NiAl2O4 was consistent with congruent dissolution without significant reprecipitation, but for NiFe2O4, ferric hydroxide precipitation was evident. The major leaching reaction of sintered kaolinite-based products was the dissolution of cristobalite rather than NiAl2O4. This study demonstrated the feasibility of transforming nickel-laden sludge into spinel phases with the use of readily available and inexpensive ceramic raw materials, and the successful reduction of metal mobility under acidic environments.     

A new process for efficiently producing methane from waste activated sludge: alkaline pretreatment of sludge followed by treatment of fermentation liquid in an EGSB reactor

In the literature the production of methane from waste activated sludge (WAS) was usually conducted in a continuous stirred tank reactor (CSTR) after sludge was pretreated. It was reported in our previous publication that compared with other pretreatment methods the methane production in CSTR could be significantly enhanced when sludge was pretreated by NaOH at pH 10 for 8 days. In order to further improve methane production, this study reported a new process for efficiently producing methane from sludge, that is, sludge was fermented at pH 10 for 8 days, which was adjusted by Ca(OH)(2), and then the fermentation liquid was treated in an expanded granular sludge bed (EGSB) for methane generation. First, for comparing the methane production observed in this study with that reported in the literature, the conventional operational model was applied to produce methane from the pH 10 pretreated sludge, that is, directly using the pH 10 pretreated sludge to produce methane in a CSTR. It was observed that the maximal methane production was only 0.61 m(3)CH(4)/m(3)-reactor/day. Then, the use of fermentation liquid of pH 10 pretreated sludge to produce methane in the reactors of up-flow anaerobic sludge bed (UASB), anaerobic sequencing batch reactor (ASBR) and EGSB was compared. The maximal methane production in UASB, ASBR, and EGSB reached 1.41, 3.01, and 12.43 m(3)CH(4)/m(3)-reactor/day, respectively. Finally, the mechanisms for EGSB exhibiting remarkably higher methane production were investigated by enzyme, adenosine-triphosphate (ATP), scanning electron microscope (SEM) and fluorescence in situ hybridization (FISH) analyses. It was found that the granular sludge in EGSB had the highest conversion efficiency of acetic acid to methane, and the greatest activity of hydrolysis and acidification enzymes and general physiology with much more Methanosarcinaceae.     

Arsenic and lead leaching from the waste derived fertilizer ironite

The toxicity characteristic leaching procedure (TCLP) and the synthetic precipitation leaching procedure (SPLP) were performed on commercially purchased samples of the waste-derived soil amendment marketed as Ironite. Ten samples of the 1-0-0 grade (the most widely available in Florida) were tested. Two samples of the 12-10-10 grade and three samples of the 6-2-1 grade (a liquid version) were tested as well. TCLP leachate concentrations from the 1-0-0 grade samples ranged from 5.0 to 8.0 mg L(-1) for lead and 2.2 to 4.8 mg L(-1) for arsenic. SPLP concentrations from the 1-0-0 samples ranged from 0.62 to 3.1 mg L(-1) for lead and 1.9 to 8.2 mg L(-1) for arsenic. All of the 1-0-0 grade samples exceeded the U.S. hazardous waste toxicity characteristic (TC) limit for lead (5 mg L(-1)), while five of the 10 SPLP samples exceeded the TC limit for arsenic (5 mg L(-1)). The greater arsenic leachability in the SPLP relative to the TCLP was determined to be a result of lower pH conditions in the SPLP. A composite sample of the 1-0-0 grade was found to leach much greater concentrations of both arsenic and lead using California's waste extraction test (WET). Lead leachate concentrations were much lower in the two 12-10-10 samples (0.03 mg L(-1) or less); arsenic concentrations in these leachates (both TCLP and SPLP) exceeded 5 mg L(-1). None of the 6-2-1 samples contained lead or arsenic above TC limits. An experiment performed on the 1-0-0 grade which examined leachability as a function of pH found that at pH values in the range of what is encountered in the human digestive system (pH 4.0 to 1.5) lead leached 2-36% of its initial content, and arsenic leached 1-6% of its initial content. A simple gastric acid leaching experiment found 83 and 37% of the lead and arsenic present to leach, respectively.     

Perrhenate uptake by iron and aluminum oxyhydroxides: an analogue for pertechnetate incorporation in Hanford waste tank sludges

Perrhenate (ReO4-), a nonradioactive surrogate for pertechnetate (99TcO4-), was partitioned during precipitation and aging of iron and aluminum oxyhydroxide solids from aqueous simulants of high-level nuclear waste stored at Hanford, WA. Neutralization of acidic metal nitrate solutions (Al/Fe mole ratio 0.25 and 13.5; 40 ppm Re) to a final pH > 13, followed by aging at 90 degrees C for up to 18 weeks, resulted in substantial amounts of reversibly sorbed Re (approximately 1-10 ppm). Irreversibly sorbed Re increased in the Fe-dominated system with aging, reaching a final value of approximately 83 ppb after 168 h, in a mixture of hematite with minor goethite. Irreversibly sorbed Re in the Al-dominated system generally decreased with time to approximately 30 ppb after 18 weeks in solids dominated by boehmite. Increasing the total amount of Re to 1000 ppm increased the extent of irreversible sorption. The presence of 100 ppm Si prevented transformation of and irreversible Re uptake by ferrihydrite in Fe-dominated systems. In Al-dominated systems, 200 ppm Ni prevented hematite formation but did not affect perrhenate uptake. Results suggest that 5% of the 99Tc inventory in the Hanford waste tanks may be associated with the sludges, and approximately 0.5% incorporated into the solids under oxidizing conditions.     

Enhanced biohydrogen production from sewage sludge with alkaline pretreatment

Batch tests were carried out to analyze influences of the alkaline pretreatment and initial pH value on biohydrogen production from sewage sludge. Experimental results of the impact of different initial pH on biohydrogen production showed that both the maximal hydrogen yield occurred and that no methane was detected in the tests of at the initial pH of 11.0. The final pH decreased at the initial pH of 7.0-12.5 but increased atthe initial pH of 3.0-6.0, probably due to the combination of solubilized protein from sludge and the formation of volatile fatty acids (VFAs) and ammonia during biohydrogen fermentation. The performance of biohydrogen production using the raw sludge and the alkaline pretreated sludge was then compared in batch fermentation tests atthe initial pH of 11.0. The hydrogen yield was increased from 9.1 mL of H2/g of dry solids (DS) of the raw sludge to 16.6 mL of H2/g of DS of the alkaline pretreated sludge. No methane and less carbon dioxide (0.8% of control) were present in the biohydrogen production from the alkaline pretreated sludge. These results clearly showed that biohydrogen production could be enhanced and maintained stable by the combination of the high initial pH and alkaline pretreatment. The mechanism of biohydrogen production from sewage sludge at high initial pH was therefore investigated because the results of this study were differentfrom previous studies of biohydrogen production. Results showed that protein was the major substrate for biohydrogen production from sewage sludge and that Eubacterium multiforme and Paenibacillus polymyxa were the dominant bacteria in biohydrogen production from alkaline pretreated sludge at an initial pH of 11.0. The combination of alkaline pretreatment and high initial pH could not only maintain a suitable pH range for the growth of dominant hydrogen-producing anaerobes but also inhibit the growth of hydrogen-consuming anaerobes. In addition, the changes in pH value, oxidation-reduction potential, VFAs and soluble COD during hydrogen fermentation were also discussed.     

Tobacco waste/industrial sludge based desulfurization adsorbents: effect of phase interactions during pyrolysis on surface activity

Industrial waste derived adsorbents were obtained by pyrolysis of tobacco waste with either metal sludge or waste oil sludge from a shipyard. The materials were used as media to remove hydrogen sulfide at room temperature in the presence of moisture. The initial and exhausted adsorbents after the breakthrough tests were characterized using sorption of nitrogen, thermal analysis, XRD, elemental analysis, and surface pH measurements. It was found that mixing tobacco and industrial sludges results in a strong synergy, enhancing the catalytic properties of adsorbents. This synergy is observed in both surface chemistry and porosity. During pyrolysis, new mineral phases are formed as a result of solid-state reactions between the components of the sludges. They are highly dispersed on the surface of mesopores. A high volume of these pores is a result of activation of the carbon phase in the composite by alkaline earth metals and also by the release of water from the decomposition of an inorganic phase that is in the predominant quantity. A high temperature of pyrolysis is beneficial for the adsorbents due to the enhanced activation of the carbonaceous phase and the chemical stabilization of the inorganic phase. Samples obtained at low temperatures are sensitive to water, which deactivates their catalytic centers.     

Immobilization mechanisms of arsenate in iron hydroxide sludge stabilized with cement

Leaching tests, Fourier transform infrared spectroscopy (FTIR), extended X-ray absorption fine structure (EXAFS) spectroscopy, and thermodynamic modeling were performed to investigate arsenate [As(V)] immobilization mechanisms in iron hydroxide sludge stabilized with cement. The sludge from a groundwater remediation site in Tacoma, WA was mixed and immobilized with premixed cement to reach cement-to-sludge ratios of 2.5, 3.3, 5, 10, and 20 (wt premixed cement/wt dry sludge). The EXAFS analysis determined that As(V) formed bidentate mononuclear complexes on the iron hydroxide surface in the sludge. The adsorbed As(V) had a characteristic FTIR band at 830 cm(-1). Cement treatment converted the adsorbed As(V) to calcium arsenate precipitate with a FTIR peak at 860 cm(-1). The chemical forms of the As(V) were incorporated in an adsorption triple layer model (TLM) to describe the leaching behavior of As(V) in a pH range between 3 and 12. Cement treatment significantly reduced arsenic mobility because of the formation of the sparingly soluble calcium arsenate.     

Residual waste from Hanford tanks 241-C-203 and 241-C-204. 1. Solids characterization

Bulk X-ray diffraction (XRD), synchrotron X-ray microdiffraction (microXRD), and scanning electron microscopy/ energy-dispersive X-ray spectroscopy (SEM/EDS) were used to characterize solids in residual sludge from single-shell underground waste tanks C-203 and C-204 at the U.S. Department of Energy's Hanford Site in southeastern Washington state. Cejkaite [Na4(UO2)(CO3)3] was the dominant crystalline phase in the C-203 and C-204 sludges. This is one of the few occurrences of cejkaite reported in the literature and may be the first documented occurrence of this phase in radioactive wastes from DOE sites. Characterization of residual solids from water leach and selective extraction tests indicates that cejkaite has a high solubility and a rapid rate of dissolution in water at ambient temperature and that these sludges may also contain poorly crystalline Na2U207 [or clarkeite Na[(UO2)O(OH)](H2O)0-1] as well as nitratine (soda niter, NaNO3), goethite [alpha-FeO(OH)], and maghemite (gamma-Fe2O3). Results of the SEM/EDS analyses indicate that the C-204 sludge also contains a solid that lacks crystalline form and is composed of Na, Al, P, O, and possibly C. Other identified solids include Fe oxides that often also contain Cr and Ni and occur as individual particles, coatings on particles, and botryoidal aggregates; a porous-looking material (or an aggregate of submicrometer particles) that typically contain Al, Cr, Fe, Na, Ni, Si, U, P, O, and C; Si oxide (probably quartz); and Na-Al silicate(s). The latter two solids probably represent minerals from the Hanford sediment, which were introduced into the tank during prior sampling campaigns or other tank operation activities. The surfaces of some Fe-oxide particles in residual solids from the water leach and selective extraction tests appear to have preferential dissolution cavities. If these Fe oxides contain contaminants of concern, then the release of these contaminants into infiltrating water would be limited by the dissolution rates of these Fe oxides, which in general have lowto very low solubilities and slow dissolution rates at near neutral to basic pH values under oxic conditions.     

Chemical-equilibrium-based model for describing the strength of sludge: taking hydrogen-producing sludge as an example

A new model, based on chemical equilibrium theory, was established to evaluate the strength of sludges in biological wastewater treatment systems. The effectiveness of this model was demonstrated by the experimental results with an anaerobic hydrogen-producing sludge. The equilibrium dispersed mass concentration of the primary particles in the sludge solution was found to nonlinearly increase with the solid content and shear intensity, and could be well described by the model. The Gibbs free energy of adhesion (deltaG degrees) under shear could also be calculated using this model. The equilibrium constant K degrees and deltaG degrees/ RTat a shear intensity of 800 1/s were estimated to be 6.54 +/- 0.12 and 1.88 +/- 0.02, respectively. The two parameters could be used to evaluate the strength of the hydrogen-producing sludge. In addition, the effectiveness of the established model was also confirmed by the results with activated sludge in the literature.     

Municipal sludge-industrial sludge composite desulfurization adsorbents: synergy enhancing the catalytic properties

Mixtures of sewage sludge, waste oil sludge, and metal oil sludge were prepared and carbonized at 950 degrees C in an inert atmosphere. Dynamic adsorption of H2S was measured on the materials obtained, and the breakthrough capacity was calculated. The initial and exhausted adsorbents after the breakthrough tests were characterized using sorption of nitrogen, thermal analysis, and XRF, XRD, and surface pH measurements. Mixing sludges leads to very high capacity adsorbents on which hydrogen sulfide is oxidized to elemental sulfur. Although the micropore volume of the adsorbents obtained is not high, their high volume of mesopores contributes significantly to reactive adsorption and provides space to store the oxidation products. The H2S breakthrough capacity on the new materials reaches 10 wt %. These adsorbents work until all active pores are filled and the catalytic centers are exhausted. The reason for such high capacity is in the formation of catalytically active mineral like phases during pyrolysis in the presence of nitrogen and carbon. This highly dispersed phase provides basicity and catalytic centers for hydrogen sulfide dissociation and its oxidation to sulfur.     

Elimination of selected acidic pharmaceuticals from municipal wastewater by an activated sludge system and membrane bioreactors

The elimination of six acidic pharmaceuticals (clofibric acid, diclofenac, ibuprofen, ketoprofen, mefenamic acid, and naproxen) in a real wastewater treatment plant (WWTP) using an activated sludge system and membrane bioreactors (MBRs) was investigated by using a gas chromatography/mass spectrometry (GC/MS) system for measurement of the compounds. Limited information is available for some of the tested pharmaceuticals at present. Solid retention times (SRTs) of the WWTP and the two MBRs were 7, 15, and 65 days, respectively. The elimination rates varied from compound to compound. The MBRs exhibited greater elimination rates for the examined pharmaceuticals than did the real plant. Dependency of the elimination rates of the pharmaceuticals on SRTs was obvious; the MBR operated with a longer SRT of 65 days clearly showed better performance than did the MBR with a shorter SRT of 15 days. The difference between the two MBRs was particularly significant in terms of elimination of ketoprofen and diclofenac. Measurements of the amounts of adsorbed pharmaceuticals on the sludge and aerobic batch elimination experiments were carried out to investigate the elimination pathways of the pharmaceuticals. Results of the batch elimination tests revealed that the sludges in the MBRs had large specific sorption capacities mainly due to their large specific surface areas. Despite the sorption capacities of sludges, the main mechanism of elimination of the pharmaceuticals in the investigated processes was found to be biodegradation. Biodegradation of diclofenac, which has been believed to be refractory to biodegradation, seemed to occur very slowly.     

Nutrient and trace-metal removal by Bauxsol pellets in wastewater treatment

In this study, Bauxsol pellets packed in PVC columns were used to remove nutrients and trace-metals from municipal wastewater during a 6 months field trial. Bauxsol pellet columns showed a high phosphate removal rate via precipitation of PO(4)(3-) with Ca(2+) and Mg(2+) ions: at 90% in the 1st month; at 80% from the second to fifth months; and at 60% in the sixth month. Pellet bound total phosphorus and Colwell phosphorus were 7.3 g/kg and 2 g/kg and are about 20 times the concentrations found in most fertile soils. Trace-metals in effluents were bound, probably irreversibly under the columns' environmental conditions, to the Bauxsol minerals that have high surface area to volume ratios and high charge to mass ratios. Experimental results showed a complex nitrogen cycle operating within the Bauxsol pellet columns including anoxic nitrification, denitrification, and anammox processes. Although a transient pH spike, associated with the release of unreacted CaO from the cement binder used in the pellets, was observed, this may be readily corrected through post-treatment pH adjustment. Hence, the geochemistry of Bauxsol pellets can effectively remove and bind nutrients and trace-metals during wastewater treatment, and further research may show that saturated spent pellets can be used as fertilizer.