Pretreatment of Highly Polluted Pharmaceutical Waste Broth by Wet Air Oxidation

The preoxidation of a highly polluted waste pharmaceutical fermentation broth using wet air oxidation (WAO) has been studied as a possible method for the effective removal of organics. The applied (pre)treatment method should enhance the biotreatability of the pharmaceutical fermentation broth in terms of reduced initial toxicity and higher biodegradability. Preliminary experiments in the pilot biological treatment plant were successful only at low organic loads, whereas the system collapses at higher ones. The characterization of the fermentation broth was started by common physicochemical analysis, whereas several bioassays were used to determine its impact on biological treatment plants and the environment. Toxicity prior to and after WAO was determined using the acute Vibrio fischeri test, measurement of inhibition of O2 consumption, and the Daphnia magna acute test. Ready biodegradability of the treated and untreated broth has also been assessed. WAO experiments were accomplished in the 2?L batch reactor at different temperatures (240/280°C) and operating pressures. WAO experiments confirmed reduction of the toxicity toward microorganisms, whereas oxidized wastewater was more toxic to daphnids. Biodegradability of the oxidized broth has also been enhanced. Further work has been focused on designing appropriate combination of WAO and biological processes.     

Effect of Substrate Nitrogen/Chemical Oxygen Demand Ratio on the Formation of Aerobic Granules

The effect of the substrate nitrogen/chemical oxygen demand (N/COD) (mg/mg) ratio on the formation and characteristics of aerobic granules for simultaneous organic removal and nitrification were studied in four sequencing batch reactors operated at different substrate N/COD ratios ranging from 5/100 to 30/100. Results showed that aerobic granules formed at the substrate N/COD ratios studied, and both nitrifying and heterotrophic activities of aerobic granules were governed by the substrate N/COD ratio. The nitrifying activity was significantly enhanced with the increase of the substrate N/COD ratio, while the heterotrophic activity decreased. By determining elemental compositions of aerobic granules cultivated at different substrate N/COD ratios, it was revealed that the cell hydrophobicity was inversely related to the ratio of cell oxygen content to cell carbon content of aerobic granule. The production of extracellular polysaccharides showed a decreasing trend as the substrate N/COD ratio increased. This is probably due to enriched nitrifying population with the high N/COD ratios. This study clearly demonstrated that an aerobic granule-based sequencing batch reactor would have a great potential for simultaneous organic oxidation and nitrification.     

Nitrogen Transformations during Soil–Aquifer Treatment of Wastewater Effluent—Oxygen Effects in Field Studies

Depth-dependent oxygen concentrations and aqueous-phase total ammonia and nitrate/nitrite ion concentrations were measured in the field during the infiltration of wastewater effluent. Measurements illustrated the dependence of nitrogen fate and transport on oxygen availability. Infiltration basins were operated by alternating wet (infiltration) and dry periods. During infiltration periods, ammonia was removed within the top few feet of sediments via adsorption. Biochemical activity rapidly eliminated residual molecular oxygen in the infiltrate, making the soil profile anoxic. During dry periods, oxygen reentered the basin profile and sorbed ammonia was converted to nitrate via nitrification. Oxygen penetrated to a depth of about 0.6?m?(2?ft) within the first few days of dry periods. At greater depths, oxygen levels increased more slowly due to a combination of slow transport kinetics and biochemical (nitrogenous) oxygen demand. During normal wet/dry basin cycles consisting of about 4 wet and 4 dry days, the local vadose zone remained anoxic at depths greater than about 1.5?m?(5?ft) below land surface. As a consequence, conditions for denitrification were satisfied in the deeper sediments. That is, the nitrate nitrogen produced in near surface sediments moved freely downward with infiltrating water where it encountered an extensive anoxic zone before reaching local monitoring or extraction wells. The relative importance of dissolved organics and sorbed ammonia as electron donors for denitrification reactions remains to be established.     

Kinetics of Phosphorus Release and Uptake in a Membrane-Assisted Biological Phosphorus Removal Process

A long-term comparative study on the kinetics of enhanced biological phosphorus removal (EBPR) was carried out in pilot scale membrane-assisted and conventional biological phosphorus removal processes, by monitoring system performance, phosphorus mass balances, and maximum specific rates in off-line batch tests. The two systems exhibited similar performance in the removal of soluble phosphorus (P) from the influent wastewater, in the specific P release observed in the anaerobic zone, and in the maximum specific P release and volatile fatty acid (VFA) uptake rates. However, when the VFA in the influent was limiting, the conventional EBPR (CEBPR) process performed significantly better than the membrane (MEBPR) counterpart, and this behavior was also reflected in the kinetics of P release. Denitrifying dephosphatation was observed to be significant in both processes during periods of satisfactory P removal. When the aerobic recycle ratio was reduced to a minimum level, the anoxic P uptake activity in the CEBPR sludge was lower than that of the MEBPR sludge. Finally, the biomass decay rates of the two sludge types were estimated to be comparable, with significant reduction of the decay under unaerated conditions.     

Characterization of Methane Flux and Oxidation at a Solid Waste Landfill

Methane emissions were measured at several locations at a typical solid waste facility using a static chamber technique. At the entire facility, methane flux varied from ?13.6?to?1,755?g?m?2?day?1. The flux data had an arithmetic mean value of 71.3?g?m?2?day?1 and a geometric mean value of 18.6?g?m?2?day?1. At this site, methane emission was generally lower on the side slopes relative to the flat areas of the landfill. The spatial variability of methane flux was characterized by point kriging and inverse distance weighing (IDW) in an intensive study of a 61×61-m area. The geospatial means in this area obtained by both methods were almost identical (20.9 versus 20.8?g?m?2?day?1). These geospatial means for the area were also similar to the arithmetic mean (24.5?g?m?2?day?1), but 3.4 times the geometric mean (6.5?g?m?2?day?1). Methane oxidation was evaluated at the surface of the landfill and at several depths within the cover soil using stable isotope techniques. The δ?13C of CH4 averaged ?55.4% in the anoxic zone. Methane collected in chambers and in surficial soil probes exhibited more 13C enriched values, ranging from ?55.4 to ?34.5%, due to the preferential uptake of 12CH4 by methanotrophic bacteria. Methane oxidation at the landfill averaged 22% and occurred in the upper 70?cm of the landfill cover soil. Oxidation occurred in all tested locations of the landfill and for all ages of buried waste.     

Simultaneous Nitrogen and Phosphorus Removal from High-Strength Industrial Wastewater Using Aerobic Granular Sludge

Aerobic granular sludge technology was applied to the simultaneous nitrogen and phosphorus removal from livestock wastewater that contains high concentrations of nitrogen and phosphorus (TN: 650?mg/L; TP: 125?mg/L). A lab-scale sequencing batch reactor was operated in an alternating anaerobic/oxic/anoxic denitrification mode. Granular sludge was first formed using synthetic wastewater. When livestock wastewater was diluted with tap water, the shape and settleability of aerobic granular sludge were maintained even though livestock wastewater contained suspended solids. Simultaneous nitrification, denitrification, and phosphate uptake were observed under an aerobic condition. However, when nondiluted livestock wastewater was used, the diameter of granular sludge and the denitrification efficiency under an oxic condition decreased. When the concentrations of nitrogen and phosphorus in wastewater increased, hydraulic retention time (HRT) increased resulting in a decrease in selection pressure for granular sludge. Therefore, the sustainment of granular sludge was difficult in livestock wastewater treatment. However, by applying a new excess sludge discharge method based on Stokes’ law, the shape of granular sludge was maintained in spite of the long HRT (7.5?days). To select large granular sludge particles, excess sludge was discharged from the upper part of settled sludge because small particles localized there after settling. Finally, excellent nitrogen and phosphorus removal was accomplished in practical livestock wastewater treatment. The effluent concentrations of NH4–N, NOx–N, and PO4–P were <0.1, 1.4, and 1.2?mg/L, respectively.     

Fenton and Electro-Fenton Methods for Oxidation of H-Acid and Reactive Black 5

Oxidative treatment of H-acid (HA) and Reactive Black 5 (RB5) using Fenton reagent (Fe2+/H2O2) and the electro-Fenton (EF) method is reported. Optimization of doses of ferrous iron and hydrogen peroxide was carried out in each case using HA; and the oxidation of RB5 was also carried out under the optimized conditions. Approximately 71% chemical oxygen demand (COD) was removed in 2 h using the conventional Fenton method at optimized doses: Fe2+ = 0.3?g/L (5.37 mM), H2O2 = 6?mL/L (53.0 mM), H2O2/Fe2+ = 10. In contrast, more than 92% COD was removed in 15 min using the EF method with an optimized Fe2+ dose of 0.130?g/L (2.34 mM) and 8?ml/L (70.6 mM) of H2O2. The pseudo-first-order rate constants (k) for the Fenton reagent and EF method were 0.054 and 0.38?min?1. The COD removal through the EF method was seven times faster. The calculated energy requirement of the EF method was 0.82?kg?COD/kW?h at the minimum applied current (0.25 A) when approximately 92.5% COD was removed. In the case of RB5, about 67 and 87% COD was removed under optimized Fenton and electro-Fenton conditions, respectively. The higher efficiency of the EF method was attributed to incremental addition of Fe2+ and accompanying higher H2O2/Fe2+ molar ratio. The results are discussed in the light of the mechanism for Fenton’s oxidation.     

Kinetics of Arsenite Oxidation by Chemoautotrophic Thiomonas arsenivorans Strain b6 in a Continuous Stirred Tank Reactor

As(III) oxidation by a chemoautotrophic bacterium, Thiomonas arsenivorans strain b6, was evaluated in a continuous stirred tank reactor (CSTR) under a range of influent As(III) concentrations (2,000–4,000 mg/L) and hydraulic retention times (HRTs) (21.7–74.9 h). Five steady states were obtained after the CSTR was continuously operated for 115 days with over 99% As(III) oxidized under the optimal growth conditions for strain b6 at pH 6 and 30°C. The culture exhibited strong resilience by recovering from an As(III) overloading of 4,847.4±290.9?mg/day/L operated at a HRT of 21.7 h. Arsenic mass balance analysis revealed that As(III) was mainly oxidized to As(V), with unaccounted arsenic well within the analytical error of measurement. The best estimates of biokinetic parameters for As(III) oxidation were obtained using the steady-state data and the Monod expression based model [k = 5?mg As(III)/mg dry cell weight/h; Ks = 20.1?mg/L; kd = 0.008?h?1; and Y = 0.011?mg cell dry weight/mg As(III)]. The Monod model and the reactor mass balance successfully simulated both the steady-state and transient phases of CSTR operation. Sensitivity analyses defined Y and k to be the most sensitive to model predictions, whereas kd and Ks were least sensitive to model simulations of As(III) oxidation under steady-state conditions.     

Effects of Iron on Chemical Sulfide Oxidation in Wastewater from Sewer Networks

Effects of iron on the kinetics and stoichiometry of aerobic chemical sulfide oxidation in wastewater from two different sites were studied at pH 8 and 20°C. Iron(III) chloride was added to the wastewater in concentrations of up to 20?g?Fe?m?3. The rate of aerobic chemical sulfide oxidation increased linearly with the iron(III) additions resulting in equal effects with wastewater from the two sites. Despite the significant effect of the iron(III) additions, the background concentrations of iron cannot explain the significant temporal and spatial variability of aerobic chemical sulfide oxidation kinetics reported in this study and in the literature. In this respect, other metals are probably also important. In addition to the impacts on the oxidation kinetics, the iron(III) additions resulted in a change of the oxidation stoichiometry. With increasing amounts of iron(III) added to the wastewater, less dissolved oxygen was required for the sulfide oxidation.     

Effect of Dissolved Oxygen on Oxic/Anoxic Diauxic Lag of P.?denitrificans

Nitrogen is removed in suspended growth wastewater treatment systems by passing mixed liquor from an aerobic zone in which nitrification takes place to an anoxic zone in which denitrification takes place. Following the switch from oxygen to nitrate as terminal electron acceptor, a diauxic lag may occur. The present study tested the hypothesis that lower dissolved oxygen concentrations in the aerobic phase lead to shorter diauxic lags. Bacterial cultures exposed to low dissolved oxygen concentrations (<0.70 mg/L) during the aerobic growth phase had significantly shorter diauxic lags than cultures grown at air saturation. Furthermore, these cultures generally grew faster during the anoxic phase. These results indicate that the effect of dissolved oxygen concentration in aerobic reactors on diauxic lags and anoxic growth rates in anoxic reactors should be considered in the design and operation of nitrogen-removing, suspended growth biological treatment processes.     

Electrochemical Oxidation and Ozonation for Textile Wastewater Reuse

Ozone and electrochemical oxidation treatment technologies were evaluated for wastewater recycling in the textile industry. Textile wastewater was collected from eight textile mills that use different dying processes. Both ozone and electrochemical oxidation removed the color from wastewater containing acid, reactive, and natural dyes, while mixed results were achieved with pigment and disperse dyes. The variability in color removal for the pigment and disperse dyes may be related to the concentration and type of auxiliary chemicals used. Color criteria for reusing wastewater for reactive dye was determined to be ΔE ? 2. This level of treatment provided an acceptable level of residual color for reuse in dark color dyeing operations and for rinse water. Some reformulation of the dye concentration and auxiliary chemicals is necessary for wastewater reuse in light color dyeing operations. Also, multiple reuse of the treated wastewater, as would occur in a completely closed system, would require changes in salt and other auxiliary chemicals to achieve the same fabric color as clean process water.     

Biocover Performance of Landfill Methane Oxidation: Experimental Results

An experimental passive methane oxidation biocover (PMOB) was constructed within the existing final cover of the St-Nicéphore landfill. Its substrate consisted of a 0.80-m-thick mixture of sand and compost. The goal of this experiment was to evaluate the performance of the PMOB in reducing CH4 emissions when submitted to an increasing methane load. The CH4 load applied started with 9.3?g?CH4?m?2?d?1. When the site had to be closed for the winter, the CH4 input was 820?g?CH4?m?2?d?1. Throughout the study, practically all the CH4 input was oxidized; absolute removal rates were linearly correlated to methane loading; and the oxidation zone was established between 0.6–0.8 m. These results seem to indicate that the upper limit potential of this PMOB to oxidize CH4 was not necessarily reached during the study period. Surface CH4 concentration scans showed no signs of leaks. The substrate offered excellent conditions for the growth of methanotrophs, whose count averaged 3.91×108?CFU?g?dw?1 soil.     

晶格氧部分氧化甲烷制合成气及其氧扩散行为研究

介绍了一种在熔融盐中利用金属氧化物的晶格氧部分氧化甲烷制合成气的新方法。以NiO为氧载体对其部分氧化甲烷的氧扩散行为进行了初步研究。利用XRD和GC等分析手段,在自行设计的氧扩散行为研究反应器中对熔融盐体系和产物气进行了分析研究。结果表明,在800℃的碳酸熔融盐中,CH4通过不含NiO氧载体的熔融盐层时H2、CO浓度仅为13.67%和20%,而通过含NiO氧载体的熔融盐层时H2、CO浓度明显增至45.9%和24.5%;实验表明NiO能够提供出自身晶格氧把CH4部分氧化成n(H2)/n(CO)接近理论值2的合成气;NiO在熔融碳酸盐体系中虽有少量溶解,但主要不以离子化形式扩散氧,而是CH4与NiO分子间发生气固反应占主导,在这一过程中NiO分子中晶格氧是甲烷部分氧化的活性氧物种。     

Pretreatment by Fenton Oxidation of an Amoxillin Wastewater

Relatively few reported works have dealt with wastewaters arising from amoxillin manufacture. To develop a treatment process for one such wastewater, several physicochemical methods such as coagulation, ultrafiltration, and Fenton oxidation (FO), have been investigated. Among these methods, FO proved effective. Consequently the method was further investigated to identify the appropriate H2O2/FeSO4 ratio, FeSO4 and H2O2 concentrations, and reaction pH and temperature. In relation to the wastewater, a suitable H2O2/FeSO4 weight ratio was 5:1 (molar ratio: 22.4:1) with H2O2 and FeSO4 concentrations at 20?g/L, 4?g/L, respectively. The corresponding pH range was 2.0–4.0 while the reaction temperature was 60°C. Given these conditions, wastewater total organic carbon was reduced by 48.8–49.4%. After FO treatment, reverse osmosis (RO) effectively reduced the dissolved salt content. The contribution of FO and RO pretreatment improved the wastewater’s biodegradability thus making a downstream biotreatment polishing process viable.     

Treatment of High Nitrate-Containing Wastewaters by Sequential Heterotrophic and Autotrophic Denitrification

The treatment performance of sequential heterotrophic and autotrophic denitrification process was evaluated using synthetic wastewaters containing high nitrate concentrations. The effluents from two sequentially connected reactors, for heterotrophic denitrification and sulfur-based autotrophic denitrification, were analyzed for more than 200 days. Experimental results indicated that higher than 95% of the nitrate removal could be achieved with volumetric nitrate loading rates of 2.16, 3.24, and 4.32 kg/m3?d. The maximum denitrification rates, with 1,000 mgN/l influent nitrate concentrations, for the heterotrophic and sulfur-packed autotrophic reactors, were found to be 2.47 and 3.61 kg/m3?d, respectively. A sequential heterotrophic and autotrophic denitrification process is considered a good alternative for the sole autotrophic denitrification process, providing excellent nitrate removal, especially for nitrate-rich wastewaters with very low organic contents.     

Metal Recovery and Catalyst Reuse from the Photocatalytic Oxidation of Copper-Ethylenediaminetetraacetic Acid

Photocatalytic oxidation (PCO) is an advanced oxidation process that has recently been shown to be effective in the treatment of recalcitrant metal complexes, such as Cu(II)-ethylenediaminetetraacetic acid (EDTA). The PCO of Cu(II)-EDTA was studied to determine copper recovery and the reusability of the titanium dioxide (TiO2) photocatalyst. Aqueous solutions of Cu(II)-EDTA (10?4?M) were treated using illuminated TiO2. After PCO treatment, TiO2 was filtered and extracted with H2SO4 (0.1, 0.5, 1 N) to remove adsorbed copper. The recovered TiO2 catalyst was then reused in subsequent experiments. The recovered copper was concentrated in the extraction solution by a factor of 14.7 over that of the initial copper concentration. An additional experiment was performed using the same TiO2 without copper removal for eight consecutive PCO treatments. In both experiments, the initial rate of photocatalysis did not change significantly with reuse and was similar to that obtained from virgin TiO2 (5.6 μM/min). It is suggested that Cu(II)-EDTA could be effectively treated using an integrated cyclic procedure of PCO, catalyst recovery, and acid extraction for Cu recovery.     

Combined Anaerobic/Aerobic Secondary Municipal Wastewater Treatment: Pilot-Plant Demonstration of the UASB/Aerobic Solids Contact System

Anaerobic pretreatment followed by aerobic posttreatment of municipal wastewater is being used more frequently. Recent investigations in this field using an anaerobic fluidized bed reactor/aerobic solids contact combination demonstrated the technical feasibility of this process. The investigation presented herein describes the use of a combined upflow anaerobic sludge bed (UASB)/aerobic solids contact system for the treatment of municipal wastewater and attempts to demonstrate the technical feasibility of using the UASB process as both a pretreatment unit and a waste activated sludge digestion system. The results indicate that the UASB reactor has a total chemical oxygen demand removal efficiency of 34%, and a total suspended solids removal efficiency of about 36%. Of the solids removed by the unit, 33% were degraded by the action of microorganisms, and 4.6% accumulated in the reactor. This low solids accumulation rate allowed operating the UASB reactor for three months without sludge wasting. The long solids retention time in this unit is comparable to the one normally used in conventional sludge digestion units, thus allowing the stabilization of the waste activated sludge returned to the UASB reactor. Particle flocculation was very poor in the UASB reactor, and therefore, it required postaeration periods of at least 100?min to proceed successfully in the aerobic unit. Polymer generation, which is necessary for efficient biological flocculation, was practically nonexistent in the anaerobic unit; therefore, it was necessary to maintain dissolved oxygen levels greater than 1.5?mg/L in the aerobic solids contact chamber for polymer generation to proceed at optimum levels. Once these conditions were attained, the quality of the settled solids contact chamber effluent always met the 30?mg BOD/L, 30?mg SS/L secondary effluent guidelines.     

Engineering Aspects of the Integration of Chemical and Biological Oxidation: Simple Mechanistic Models for the Oxidation Treatment

Oxidation processes can oxidize biorecalcitrant compounds into biodegradable intermediates, which in turn can be treated less expensively by a subsequent biological process. To design such a two-step (chemical+biological) process to treat poorly characterized wastewaters, it is useful to model the time evolution of characteristic global variables, chemical oxygen demand (COD) and biochemical oxygen demand (BOD), in order to develop a useful treatment strategy based upon these classical variables. We consider two simple model reaction networks, requiring three- and five-rate constants, respectively. The first model, proposed recently, involves conversion of a nonbiodegradable species, C, into a single biodegradable intermediate S. Here, biodegradable compounds are immediate kinetic products of oxidation. In general, it is not probable that a single recalcitrant compound undergoes a single-step reaction to CO2. However, when working with complex undefined wastewaters streams, single-step reactions may be used to simplify. The second new model corresponds to a lag time in BOD formation due to the necessity of multiple partial oxidations to reach a first biodegradable intermediate. The second network includes two intermediates, I and S, which are, respectively, nonbiodegradable and biodegradable. We then compare model behavior with an unfortunately sparse literature on BOD and COD values versus time in chemical reactors, and demonstrate the convenience of the first model, and the occasional necessity of the second, which reflects the presence of early intermediates which are nonbiodegradable.     

Kinetics of SO2 Absorption with Fly Ash Slurry with Concomitant Production of a Useful Wastewater Coagulant

This research was aimed at recovering Fe and Al compounds to produce a useful complex coagulant from fly ash using H2SO4 and SO2 from flue gas oxidized to SO3 by NaClO3. The reaction kinetics of wet SO2 scrubbing from simulated flue gas with fly ash slurry was studied. The SO2 scrubbing experiments were carried out in a jacketed glass reactor system with a simulated flue gas containing SO2 and N2 in the gas phase and fly ash slurry in the liquid phase. Sodium chlorate was added to oxidize SO2 to SO3, adding H2SO4 in the slurry. The reaction orders of both Fe2O3 and Al2O3 extraction from fly ash slurry were shown to be 1.5. The empirical Arrhenius expressions were also derived from the reaction rate constants obtained at each reaction temperature. The mass transfer process of SO2 with ClO3? was evaluated using a two-film theory model.     

Catalytic Wet Oxidation of Ammonia Solution: Activity of the Copper–Lanthanum–Cerium Composite Catalyst

Aqueous solutions that contained 400–1,000 mg/L of ammonia were oxidized in a trickle-bed reactor in this study of copper–lanthanum–cerium composite catalysts, which were prepared by the co-precipitation of copper nitrate, lanthanum nitrate and cerium nitrate at various molar concentrations. Results revealed that the conversion of ammonia by wet oxidation in the presence of copper–lanthanum–cerium composite catalysts was a function of the molar ratio of the copper–lanthanum–cerium catalyst. The ammonia solutions were barely removed by wet oxidation in the absence of any catalyst, while around 95% of the ammonia was reduced during the wet oxidation over the copper–lanthanum–cerium (7:2:1, molar/molar/molar) catalyst at 503 K and an oxygen partial pressure of 4.0 MPa. The kinetics of ammonia oxidation over a catalyst could be explained by a zero-order rate expression. Furthermore, the effect of the initial concentration and reaction temperature on the removal of ammonia from the effluent streams was also investigated at a liquid hourly space velocity of under 9?h?1 in wet catalytic processes.