Laboratory-scale Batch Experiments Research Articles

Post-Removal of Phosphorus from Biologically Treated Wastewater and Recovering It as Fertilizer: Pilot-Scale Attempt—Project PhoReSe

The major issue of raw materials’ depletion, and more specifically, of phosphorous (an important fertilizer) has currently become an emergent aspect due to expected depletion problems needing immediate handling. This was the reason for the implementation of the PhoReSe project that aimed to remove and recover phosphorus from the secondary (biologically treated) effluent of a municipal wastewater (biological) treatment plant (WWTP “AINEIA”, located near Thessaloniki, N. Greece), treating the wastewaters of the nearby touristic area. Regarding the phosphorous supplementary removal and recovery treatment options, two methods were examined, initially at the laboratory scale (batch experiments), i.e., (1) the adsorption of phosphorous, and (2) the chemical precipitation of phosphorus. Both methods were further applied at the pilot scale by initially performing the adsorption of phosphorous onto the AquAsZero commercial sorbent, which is a mixed manganese iron oxy-hydroxide, followed by the chemical precipitation of phosphorous implemented after the desorption process of the previously saturated adsorbent. The final precipitate of this procedure was examined as an alternative/supplementary fertilizer, this way returning phosphorus into the natural cycle. These experiments, as applied successfully in at the pilot scale, set the basis for larger-scale relevant applications for similar WWTP facilities.

Optimization of Calcium Fluoride Crystallization Process for Treatment of High-Concentration Fluoride-Containing Semiconductor Industry Wastewater.

This study utilized a fluidized bed reactor (FBR) for fluoride removal from high-concentration fluoride-ion-containing simulated semiconductor industry wastewater and recovered high-purity CaF2 crystals. The effects of hydraulic retention time (HRT), pH, Ca2+ to F- ratio, upflow velocity, seed size and seed bed height were investigated by performing lab-scale batch experiments. Considering fluoride removal and CaF2 crystallization efficiency, 5 h HRT, pH 6, seed height of 50 cm and [Ca2+]/[F-] ratio of 0.55 (mol/mol) were found to be optimum. The effect of the interaction between the important process parameters on fluoride removal was further analyzed using response surface methodology (RSM) experimental design. The results showed that all the individual parameters have a significant impact (p = 0.0001) on fluoride removal. SEM-EDX and FTIR analysis showed the composition of the crystals formed inside FBR. HR-XRD analysis confirmed that the crystalline structure of samples was mainly CaF2. The results clearly demonstrated the feasibility of silica seed material containing FBR for efficient removal and recovery of fluoride as high-purity calcium fluoride crystals.

Continuous Hydrothermal Carbonization of Olive Pomace and Orange Peels for the Production of Pellets as an Intermediate Energy Carrier

The ever-increasing volumes of food waste generated and the associated environmental issues require the development of new processing methods for these difficult waste streams. One of the technologies that can treat these waste streams directly is hydrothermal carbonization. In this work, olive pomace and orange peels were treated via a mild hydrothermal carbonization process (TORWASH®) in a continuous-flow pilot plant. For olive pomace, a solid yield of 46 wt% and a dry matter content of 58% for the solid press cakes were obtained during continuous operation for 18 days. For orange peels, the values were lower with 31 wt% solid yield and a 42% dry matter content during 28 days of continuous operation. These values corresponded fully with initial laboratory-scale batch experiments, showing the successful transformation from batch to continuous processing. The obtained hydrochar from both feedstocks showed an increase in higher heating value (HHV) and a significant reduction in ash content. Pellets produced from the solids met the requirements for industrial use, demonstrating a large increase in the deformation temperature and a significant reduction in the potassium and chlorine content compared to the original feedstock. These results indicate the excellent potential of these pellets for combustion applications.

Electrolyte migration through electrochemical membranes: Potential source of error in batch electrochemical cells

AbstractElectrochemical membranes (ECMs) and porous electrodes have gained much attention in a broad range of applications including water and wastewater treatment, energy production and storage, and carbon dioxide capture. Lab scale batch experiments (electrochemical stirred cells) are the baseline for developing ECMs and porous electrodes. We observed electrochemical dissolution of metal fasteners (alligator clips), used to hold porous conductive and non‐conductive membranes in batch electrochemical cells, despite being kept outside the electrolyte. The electrolyte migrated through the porous membranes by the action of capillary forces, forming a closed electrochemical circuit with the metal fasteners. This unexpected leaching can lead to misleading results for electrochemical experiments on porous electrodes and ECMs. In this study, we compared (1) porous membranes versus non‐porous electrodes, (2) hydrophilic versus hydrophobic membranes, and (3) conductive versus non‐conductive membranes in their ability to cause capillary wetting‐induced corrosion of metal fasteners. We proposed a simple solution for the problem: separating the metal fasteners from the porous membrane electrode with a non‐porous conductive graphite foil, which keeps the electrochemical circuit open. We have validated this solution and propose it as a standard method for experiments using porous electrodes and electrically conductive membranes.

Estimation of optimal conditions for crystallization of calcium fluoride for treatment of high-concentration fluorine-containing industrial wastewater

This study attempted to utilize fluidized bed reactor for fluoride removal and CaF<sub>2</sub> purity from the industrial wastewater including high concentration of fluoride ion. Effects of HRT, pH, Ca<sub>2</sub><sup>+</sup> amount and seed height were investigated through lab-scale batch and continuous experiments. Considering fluoride removal efficiently and CaF<sub>2</sub> purity that HRT 5hr, pH6, seed height of 50 cm, [Ca<sub>2</sub><sup>+</sup>]/[F<sup>-</sup>](mol/mol) ratio of 0.55 were found to be optimum. Correspondingly, removal fluoride was 82.5%, with a CaF<sub>2</sub> the crystallization rate of 95.1%, respectively. The results of continuous experiment showed that with pellet as CaF<sub>2</sub> , fluoride concentration can be stably reduced to less than 45mg/L in effluent from the influent 300mg/L on average. HR-XRD analysis showed that the crystalline structure of crystals was mainly CaF<sub>2</sub> .

Wastewater from textile digital printing as a substrate for microalgal growth and valorization

This study aims at evaluating an innovative biotechnological process for the concomitant bioremediation and valorization of wastewater from textile digital printing technology based on a microalgae/bacteria consortium. Nutrient and colour removal were assessed in lab-scale batch and continuous experiments and the produced algae/bacteria biomass was characterized for pigment content and biomethane potential. Microbial community analysis provided insight of the complex community structure responsible for the bioremediation action. Specifically, a community dominated by Scenedesmus spp. and xenobiotic and dye degrading bacteria was naturally selected in continuous photobioreactors. Data confirm the ability of the microalgae/bacteria consortium to grow in textile wastewater while reducing the nutrient content and colour. Improvement strategies were eventually identified to foster biomass growth and process performances. The experimental findings pose the basis of the integration of a microalgal-based process into the textile sector in a circular economy perspective.

Part I: Predicting performance of Purolite A532E resins for remediation of comingled contaminants in groundwater

Ion exchange (IX) resins are used in pump-and-treat (P&T) facilities to remove soluble groundwater contaminants. However, natural anions present at concentrations orders of magnitude higher than contaminants can compete for IX sites and impact resin lifecycles. Here, the Hanford Site’s 200 West Area P&T facility (Washington State, USA) was selected as a case study because it currently uses two IX resins: Purolite® A532E (A532E) to remove pertechnetate (TcO4-) and DOWEX 21K (DOWEX) to remove uranium from groundwater. Nitrate (NO3-), sulfate (SO42-), chloride (Cl-), and carbonate (CO32-) anions have been identified to potentially compete for A532E and DOWEX IX sites. Hanford-relevant anion groundwater concentrations were used to design a series of laboratory-scale batch experiments to evaluate the impact of competing anions on resin performance and potential kinetic effects. These data are then modeled to obtain Cl--normalized equilibrium exchange coefficients (K) needed to predict IX resin performance. The work is presented in two parts, with IX performance evaluated for A532E in Part I and DOWEX in Part II. Part I results demonstrate that TcO4- uptake is not impacted by NO3-, SO42-, Cl-, CO32- (as HCO3-) and U(VI) carbonate anions, with KTcO4-/Cl- > 4,000, likely due to the high selectivity of A532E trihexylammonium sites for the large, weakly hydrated TcO4- anion. Other anion K values were KNO3-/Cl- = 20, KSO4--/Cl- = 0.2, KHCO3-/Cl- = 0.09, KU/Cl- = 370–1000. These K values provide conservative parameters for predicting A532E performance, and demonstrate that, under these test conditions, A532E will remove TcO4- from current and future influent streams to meet groundwater treatment objectives.

Cascade utilization of rice straw for biogas production.

To improve the biogas yield of rice straw, an innovative cascade utilization process for biogas production was proposed using a method referred to as "the first digestion + NaOH treatment + the second digestion" (labeled FSD). Both the first digestion and the second digestion of all treatments were conducted at the initial total solid (TS) loading of straw of 6%. A series of lab-scale batch experiments were conducted to investigate the effect of first digestion time (5, 10, and 15days) on biogas production and lignocellulose structure destruction of rice straw. The results showed that the cumulative biogas yield of rice straw using the FSD process was increased by 13.63-36.14% compared with the control (CK), and the highest biogas yield of 233.57mLg-1 TSadded was obtained when the first digestion time was 15days (FSD-15). The removal rates of TS, volatile solids, and organic matter were increased by 12.21-18.09%, 10.62-14.38%, and 13.44-16.88%, respectively, compared with those of CK. The results of Fourier transform infrared spectroscopy analysis revealed that the skeletal structure of rice straw was not significantly destroyed after the FSD process, but the relative contents of functional groups in rice straw were changed. The FSD process accelerated the destruction of crystallinity of rice straw, and the lowest crystallinity index of 10.19% was obtained at FSD-15. The abovementioned results indicated that the FSD-15 process is recommended for cascade utilization of rice straw in biogas production.

Nontarget screening based on molecular networking strategy to identify transformation products of citalopram and sertraline in wastewater

Citalopram (CIT) and sertraline (SER) are highly consumed antidepressants worldwide and have been extensively detected in wastewater. Due to the incomplete mineralization, transformation products (TPs) of them can be detected in wastewater. Comparing with parent compounds, knowledge on TPs are limited. To fill these research gaps, lab-scale batch experiments, WWTPs sampling and in silico toxicity prediction were implemented to investigate the structure, occurrence and toxicity of TPs. Based on molecular networking nontarget strategy, 13 TPs of CIT and 12 TPs of SER were tentatively identified. Among them, 4 TPs from CIT and 5 TPs from SER were newly found in present study. TPs identification results compared with results obtained from previous nontarget strategies demonstrated that the excellent performances for molecular networking strategy on candidate TPs prioritizing and new TPs finding, especially for low abundance TPs. Further, transformation pathways for CIT and SER in wastewater were proposed. Newly identified TPs provided insights on defluorination, formylation and methylation for CIT and dehydrogenation, N-malonylation and N-acetoxylation for SER transformed in wastewater. Nitrile hydrolysis and N-succinylation were found to be the dominant transformation pathways for CIT and SER in wastewater, respectively. WWTPs sampling results shown the concentrations of SER and CIT ranged from 0.46 to 28.66 ng/L and 17.16 to 58.36 ng/L. In addition, 7 TPs of CIT and 2 TPs of SER found in lab-scale wastewater samples were found in WWTPs. In silico results suggested 2 TPs of CIT may be more toxic than CIT toward all three trophic levels organisms. Present study provides new insights into the transformation processes of CIT and SER in wastewater. In addition, the necessity of paying more attention on TPs was further highlighted from the aspects of toxicity for TPs of CIT and SER in effluent of WWTPs.

Torrefaction at low temperature as a promising pretreatment of lignocellulosic biomass in anaerobic digestion

The lignocellulosic structure of agricultural biomass, which makes it resistant to microbial attack, is the main obstacle in its anaerobic digestion. However, not all biomasses behave the same in the face of anaerobic digestion. Instead, depending on their composition in terms of lignin, cellulose and hemicellulose content, the anaerobic digestion process may be more or less favoured, although a pretreatment stage is usually necessary. This paper presents the results of a laboratory scale batch experiment to study the effect of thermal pretreatment (torrefaction) on the anaerobic digestion of two biomass materials: barley straw and vine shoot. For this, thermal pretreatment temperatures of 100, 130, 180 and 210 °C, with a residence time of 24 h, were studied for both biomasses and the results were compared with the material without pretreatment. Significant differences in biogas production were observed for both biomasses depending on the pretreatment temperature. The highest biogas yields of 458 and 213 mL/gVS for straw and vine shoot, respectively, were observed from biomass pretreated at 100 °C. Barley straw pretreated at 100 °C showed 275% higher methane yield compared to untreated straw. In the case of the vine shoot, the increase was 210%. Furthermore, FTIR-ATR analysis and thermogravimetric analysis coupled with a pseudocomponent kinetic model revealed changes in the lignocellulosic composition of both biomasses while SEM analysis revealed also structural changes. The modified Gompertz model fitted the production data well and predicted shorter lag time and higher biogas production at pretreatment temperatures from 100 to 180 °C compared with the untreated materials. From there, a reduction in methanogenic activity is observed when the pretreatment temperature increases. In general, the change in the lignocellulosic structure and the decrease in the hemicellulose content could be considered as the main reasons to improve the biogas production.

Assessment of energy recovery potential and analysis of environmental impacts of waste to energy options using life cycle assessment

Effective waste management such as energy recovery from waste is not very successful in many cities of India. The present study is carried out in the Dhanbad city, India where all the generated wastes are managed unscientifically through open dumping. Most of the reported life cycle assessment-based studies for Indian cities have focussed on the common waste management options such as composting and recycling. This study aimed to evaluate the energy recovery potential and environmental impacts of mainly waste to energy options namely; anaerobic digestion, landfill gas to energy, mass incineration and refuse derived fuel incineration based on the characteristics and composition of wastes of the study area. The selection of waste to energy options is done based on the composition of waste suitable for the respective options, thus making it helpful in reproducing the present work in other cities as well. Anaerobic digestion technology is evaluated based on the biogas generation potential of total food waste generated in the study area using laboratory-scale batch experiments. Similarly, landfill gas to energy is evaluated based on the estimated landfill gas generation (using LandGEM model) from the existing landfill of the study area. While incineration (mass and refuse derived fuel) is evaluated based on the heating value of combustible waste fractions. For the comparison of energy recovery potential and environmental impacts, six scenarios are developed. The maximum energy recovery potential of 602 kWh/tonne of dry waste is found for the scenario mass incineration of combustible waste fractions (72%) and landfilling of remaining wastes (28%). This scenario also showed the maximum net environmental savings due to avoided electricity production. The sensitivity analysis revealed that the collection efficiency of generated landfill gas for electricity conversion significantly impacts the change in global warming and photochemical ozone creation potential. The outcomes of this study will help the concerned authorities in developing the efficient waste to energy system.

Disinfection efficiency prediction under dynamic conditions: Application to peracetic acid disinfection of wastewater

In this work, a mechanistic dynamic model of continuous flow peracetic acid (PAA) disinfection was developed, calibrated and validated, assuming E. coli as indicator microorganism. The model was conceived as a 1-dimensional dispersion model integrating PAA first order decay and E. coli inactivation rate. Lab-scale batch experiments of PAA decay and E. coli inactivation experiments were performed to calibrate corresponding kinetic models. In each sample, conventional wastewater quality parameters were monitored. A PAA pilot reactor was set up to perform both tracer studies, for dispersion model calibration, and continuous flow disinfection experiments, to validate the integration of hydraulics and kinetics models, under both stationary and dynamic conditions. Linear regression models were calibrated to predict hydrodynamic dispersion, given the flow rate, and PAA decay parameters, given effluent quality and PAA dosage. Successful validation of the PAA disinfection model proved the importance of (i) considering the disinfection process as a dynamic system and (ii) integrating real-time estimation of process disturbances, being the initial E. coli concentration and the impact of effluent quality and PAA dosage on PAA decay kinetics. Importantly, novel inactivation models were proposed, as two different modifications of a literature model for thermal inactivation. These models are suitable for dynamic simulation of Eulerian models and can describe the typical triphasic behavior of inactivation kinetics.

Factors controlling the effectiveness of rechlor(am)ination to recover chloramine from nitrification

The two most commonly adopted strategies, rechlorination (addition of chlorine) and rechloramination (addition of chlorine and ammonia), to recover and stabilise chloramine from nitrification were comprehensively evaluated in laboratory- and full-scale systems. Laboratory-scale batch experiments were conducted in a nitrifying sample (~0.05 mg-N/L). In the full-scale service reservoir, repeated rechlorination was ineffective in suppressing nitrification and microbial chloramine decay during warmer months (>20 °C), even when rechlorination was started at nitrite <0.005 mg-N/L. Measurement of decay rates through microbial chloramine decay factor method provides a deeper understanding of a water sample than traditional nitrification indicators. The method has the ability to provide an early warning (one month in advance), show the presence of microbial chloramine decay in non-nitrified water and that of chloramine decaying proteins in any samples. In the batch sample, nitrification and the production of chloramine-decaying proteins and bacterial regrowth had to be suppressed to recover chloramine. Rechloramination (~2.5 mg/L) outperformed rechlorination, as it maintained a relatively higher chloramine concentration. Microbes were killed within 30 min of dosing chlor(am)ine, likely due to shock or compounds formed during chloramine formation reactions; however, microbes regrew (or survive) to a different degree in all samples despite the prolonged presence of chloramine (large CxT), defying the CxT concept. The key to the recovery of chloramine appears to be consistently maintaining chloramine >1.7 mg/L and shocking with a high chloramine dose. The findings will assist water utilities in designing and assessing the effectiveness of nitrification remediation strategies in chloraminated water supply systems.

English

In areas where conventional sewer systems are not possible, innovative and low-cost methods are needed to get rid of pathogens in human urine. Treatment through acidification is a reliable method. In this study, the effect of fresh cabbage waste, potato peel, and teff flour water as substrate for lactic acid treatment of source-separated urine was investigated. Laboratory scale batch experiments were conducted to compare the substrates for pH 4 and high distribution of lactic acid bacteria (LAB), important for urine hygienization and urea stabilization. It was found that with the addition of 10% molasses as a sugar supplement, fermentation of fresh cabbage waste could establish the desired effect for lactic acid treatment of source-separated urine. The final pH in the urine mixed with lactic acid in the ratio of 1:1 and 1:2 (lactic acid: urine) was 4.12 and 4.26, respectively. While the final pH in the 1:4 and control reactors was 8.3 and 9.2, respectively. Escherichia coli count was below the detection limit in both 1:1 and 1:2 reactors after 5 days, whereas the number of E. coli in the samples collected from 1:4 and control reactors showed only slight reduction until the final day of the treatment process. Urea decomposition improved in 1:1 and 1:2 reactors, while it kept increasing in 1:4 and control reactors. The results revealed that food waste produced lactic acid enhances pathogen inactivation, urea stabilization and reduce odors in human urine. Key words: Lactic acid, odor control, pathogen inactivation, urea stabilization

Effect of Organic Substances on Nutrients Recovery by Struvite Electrochemical Precipitation from Synthetic Anaerobically Treated Swine Wastewater.

Anaerobically treated swine wastewater contains large amounts of orthophosphate phosphorus, ammonium nitrogen and organic substances with potential nutrients recovery via struvite electrochemical precipitation post-treatment. Lab-scale batch experiments were systematically conducted in this study to investigate the effects of initial pH, current density, organic substances upon nutrients removal, and precipitates quality (characterized by X-ray diffraction, scanning electron microscopy and element analysis via acid dissolution method) during the struvite electrochemical precipitation process. The optimal conditions for the initial pH of 7.0 and current density of 4 mA/cm2 favoured nutrients removal and precipitates quality (struvite purity of up to 94.2%) in the absence of organic substances. By contrast, a more adverse effect on nutrients removal, morphology and purity of precipitates was found by humic acid than by sodium alginate and bovine albumin in the individual presence of organic substances. Low concentration combination of bovine albumin, sodium alginate, and humic acid showed antagonistic inhibition effects, whereas a high concentration combination showed the accelerating inhibition effects. Initial pH adjustment from 7 to 8 could effectively mitigate the adverse effects on struvite electrochemical precipitation under high concentration combined with organic substances (500 mg/L bovine albumin, 500 mg/L sodium alginate, and 1500 mg/L humic acid); this may help improve struvite electrochemical precipitation technology in practical application for nutrients recovery from anaerobically treated swine wastewater.

Micropollutant transformation and taxonomic composition in hybrid MBBR – A comparison of carrier-attached biofilm and suspended sludge

The suspended sludge and carrier-attached biofilms of three different hybrid moving bed biofilm reactor (MBBR) systems were investigated with respect to their transformation potential for a broad range of micropollutants (MPs) as well as their microbial community composition. For this purpose, laboratory-scale batch experiments were conducted with the separated suspended sludge and the carrier-attached biofilm of every system in triplicate. For all batches the removal of 31 MPs as well as the composition of the microbial community were analyzed. The carrier-attached biofilms from two hybrid MBBR systems showed a significant higher overall transformation potential in comparison to the respective suspended sludge. Especially for the MPs trimethoprim, diclofenac, mecoprop, climbazole and the human metabolite 10,11-dihydro-10-hydroxycarbamazepine consistently higher pseudo-first-order transformation rates could be observed in all three systems. The analysis of the taxonomic composition revealed taxa showing higher relative abundances in the carrier-attached biofilms (e. g. Nitrospirae and Chloroflexi) and in the suspended biomasses (e. g. Bacteroidetes and Betaproteobacteria). Correlations of the biodiversity indices and the MP biotransformation rates resulted in significant positive associations for 11 compounds in suspended sludge, but mostly negative associations for the carrier-attached biofilms. The distinct differences in MP removal between suspended sludge and carrier-attached biofilm of the three different MBBR systems were also reflected by a statistically significant link between the occurrence of specific bacterial taxa (Acidibacter, Nitrospira and Rhizomicrobium) and MP transformation rates of certain MPs. Even though the identified correlations might not necessarily be of causal nature, some of the identified taxa might serve as suitable indicators for the transformation potential of suspended sludge or carrier-attached biofilms.

Modeling the anaerobic digestion of wastewater sludge under sulfate-rich conditions.

Anaerobic digestion (AD) is a biological treatment process to stabilize organic solids and produce biogas. If present, sulfate is reduced to sulfide by anaerobic sulfate-reducing bacteria and the sulfide can be toxic to anaerobic microorganisms. Here, the effect of high initial sulfate concentration on AD of wastewater sludge was investigated using lab-scale batch experiments. Additionally, a systematic mathematical modeling approach was applied for insight into the experimental results. Cumulative biogas and methane production decreased with increasing initial sulfate doses (0-3.300mgSL-1 ). The correlation between the sulfate dose and methane production was consistent with theoretical predictions and model results, indicating no toxic effect of sulfide on methane production. The carbon dioxide content in the biogas decreased linearly with the increasing sulfate dose, which is consistent with the model-predicted behavior of the bicarbonate and hydrogen sulfide buffering system. The examined high sulfate concentrations resulted in no clear negative effects on the COD removal or VSS destruction of the wastewater sludge, indicating negligible inhibition by sulfide toxicity. Even considering the possibility of ferrous sulfide precipitation and the low model estimates of residual sulfide concentration the residual sulfide concentration was higher than reported concentrations that trigger process inhibition. PRACTITIONER POINTS: The effect of sulfate loading on anaerobic digestion of waste activated sludge was characterized. The stoichiometry of sulfate reduction allows accurate prediction of CH4 loss. High sulfate levels (up to 3300mg/L as S) did not affect COD/VSS removal. Sulfide formation increases effluent COD; often misinterpreted as sulfide toxicity. Correcting COD for sulfide's contributions is crucial for results interpretation.

Removal of iron, aluminium, manganese and copper from leach solutions of lithium-ion battery waste using ion exchange

The shift to electric mobility necessitates recycling the metals from lithium ion battery waste. Ion exchange was studied for use in the removal of impurities from synthetic lithium ion battery waste leachate in laboratory-scale batch and column experiments. Aminomethylphosphonic acid functional chelating resin (Lewatit TP260) was capable of removing Fe, Al, Mn, and Cu from the leachate, while leaving valuable Co, Ni, and Li as a pure mixture in the raffinate. Increasing the pH up to 3 and the temperature to 60 °C improved the purity and productivity. Iron and aluminium could not be eluted efficiently by mineral acids, but an oxalate solution was found feasible. A two-step elution procedure, in which Cu and Mn are first removed with sulfuric acid, followed by Fe and Al removal with potassium oxalate, was successfully demonstrated. The suggested process produced a > 99.6% pure Li + Co + Ni solution (battery grade), along with a Mn and Cu rich sulfuric acid solution with Co as an impurity and an oxalate solution of Fe + Al as by-products. The productivities for these solutions were 0.39, 0.16, and 0.38 BV/h, respectively. The Co loss was very low (1.1%) as compared to previously suggested impurity removal processes using precipitation and solvent extraction. Moreover, Co can be easily recycled back to the ion exchange column feed after Mn and Cu are recovered as pure by-products.

Ozonation products of zidovudine and thymidine in oxidative water treatment

Ozonation is an advanced treatment technology that is increasingly used for the removal of organic micropollutants from wastewater and drinking water. However, reaction of organic compounds with ozone can also result in the formation of toxic transformation products. In the present study, the degradation of the antiviral drug zidovudine during ozonation was investigated. To obtain further insights into the reaction mechanisms and pathways, results of zidovudine were compared with the transformation of the naturally occurring derivative thymidine.Kinetic experiments were accompanied by elucidation of formed transformation products using lab-scale batch experiments and subsequent liquid chromatography – high resolution mass spectrometry (LC-HRMS) analysis. Degradation rate constants for zidovudine with ozone in the presence of t-BuOH as radical scavenger varied between 2.8 ∙ 104 M−1 s−1 (pH 7) and 3.2 ∙ 104 M−1 s−1 (pH 3).The structural difference of zidovudine to thymidine is the exchange of the OH-moiety by the azide function at position 3’. In contrast to inorganic azide, no reaction with ozone was observed for the organic bound azide. In total, nine transformation products (TPs) were identified for both zidovudine and thymidine. Their formation can be attributed to the attack of ozone at the C–C-double bond of the pyrimidine-base.As a result of rearrangements, the primary ozonide decomposed in three pathways forming two different TPs, including hydroperoxide TPs. Rearrangement reactions followed by hydrolysis and subsequent release of H2O2 further revealed a cascade of TPs containing amide moieties. In addition, a formyl amide riboside and a urea riboside were identified as TPs indicating that oxidations of amide groups occur during ozonation processes.

VERMICOMPOST AS A POTENTIAL ADSORBENT FOR THE ADSORPTION OF METHYLENE BLUE DYE FROM AQUEOUS SOLUTIONS

Abstract: Vermicompost (VC) as a low cost and waste-derived material was used as an adsorbent to remove textile dye effluents from the wastewater. Methylene blue (MB) was selected as a representative of dye effluents and its adsorption to VC was investigated. The effect of parameters such as pH, adsorption time, and the initial concentration of MB were determined via lab-scale batch experiments. The highest adsorption capacity of VC was reached when the pH of the solution was 4. The equilibrium was maintained after 90 minutes of operation since the removal percentage of MB was stabilized at 99%. The pseudo-second-order kinetic model described the most appropriate adsorption kinetic behavior. BothLangmuir (R 2 =0.9891) and Freundlich isotherms (R 2 =0.9895) fitted very well to the experimental data. Based on these results, vermicompost can be evaluated as an alternative adsorbent for the removal of dye effluents.