Simultaneous biofiltration of BTEX and Hg� from a petrochemical waste stream

A biofiltration system was developed to treat benzene, toluene, ethylbenzene, and xylene (BTEX) and Hg� vapour from a petrochemical waste stream during overhaul maintenance. The biofilter compost bed was inoculated with a microbial consortium provided by a petrochemical wastewater treatment plant. The effect of the a BTEX concentration (192.6e973.8 g/m3h) and empty bed residence time (EBRT) of 20 e100 s were studied under the conditions of steady state, transient, shock BTEX-loading, and off-restart. The findings revealed that during a biofilter start-up, an increase in the influent BTEX concentration to around 334.3 g/m3h did not notably affect the biofiltration function at an EBRT of 100 s, and the removal efficiency was higher than 98%. Further, the low EBRT of 60 s did not have adverse effects on the BTEX and Hg� biofiltration (the removal efficiency in both was >93%). For the biofiltration system, the BTEX and Hg� critical attenuation capacity were obtained as 663 gBTEX/m3h and 12.6 gHg�/m3h respectively. A maximum attenuation capacity of 774.5 gBTEX/m3h was achieved in the biofilter when the BTEX loading rate was 973.8 gBTEX/m3h. The parameters of km and rmax of the MichaeliseMenten kinetic model were obtained as 0.099 g/m3 and 0.578 g/m3min respectively. Both BTEX and mercury vapours were completely mass balanced during a continuous biofiltration test. In general, the developed treatment system exhibited a good performance in the treatment of the BTEX stream containing Hg� vapour in the off-gas of a petrochemical compan

Role of Fungal Biomass in N-Hexane Biofiltration

The biofiltration of n-hexane is studied to optimize determinants factors of hydrophobic VOC filtration efficiency. Four trickle-bed air biofilters (TBABs) were employed; two of which were supplied with nutrients buffered at a neutral pH, while another two at an acidic pH of 4 to induce and enhance fungal growth. The loading rate of n-hexane was kept constant in all TBABs at 13 g/m3/h. At each pH levels studied, the biomass of the TBABs was pre-acclimated using different ratios of n-hexane and methanol. The fungal biomass responsible for the degradation of n-hexane was then examined and quantified. Dichloran Rose Bengal Chloramphenicol agar was used for fungi quantification, and optical microscopy for classification. Effluent biomass was validated by measuring volatile suspended solids. Fungal counts resulting from n-hexane biodegradation were related to nitrate and carbon consumption. It was found that n-hexane elimination capacity closely followed biomass growth, and reached a steady-state at an optimum biomass density of roughly 3000 cfu/ml. Major shifts in fungal species were observed in all TBABs. Dominant fungal species grew slowly to become the most numerous, and were found to provide maximum elimination capacity, although TBABs pre-acclimated to higher methanol concentrations took less time to reach this steady-state. It was concluded, therefore, that steady and monitored growth of TBAB biomass is an essential factor in maximizing fungi’s ability to metabolize VOCs and that a new ecological biofiltration model may be the most effective at VOC purification

Effects of source and seasonal variations of natural organic matters on the fate and transport of CeO2 nanoparticles in the environment

Natural organic matter (NOM) affects the stability and transport of nanoparticles (NPs) in natural waters by modifying their physiochemical properties. Source location, and seasonal variations, influence their molecular, physical and electrical charge properties. To understand the variations of NOM on the mobilization of NPs, large volumes of water were collected fromthe Ohio River (OR) over winter and summer seasons and dissolved NOMs were concentrated. The chemical and structural differences of these NOMs were compared with the Suwannee River humic acid (SRHA) SRHA using 1H and 13C nuclear magnetic resonance spectroscopy, and Fourier transforms infrared (FTIR) spectroscopy. Thermal analysis and FTIR confirmed that differences in composition, structure, and functional groups are a result of SRHA fractionation compared to wholemolecule OR-NOM. The influence of OR-NOMs on the surface charge of CeO2NPs and the effects on the transport and retention in a three-phase (deposition-rinse-re-entrainment) sand-packed columns were investigated at CeO2 NPs initial concertation of 10 ppm, pH 6.8, increasing ionic strength (3, 5, and 10 mM), retention time of 1 min, and increasing NOM concentration (1, 5, and 10 ppm). The summer OR-NOM showed higher stabilization and mobilization effect on the CeO2 than the winter NOM; while their effect was very different form the SRHA. The stabilization of NPs is attributed to both electrostatic and steric effects. The differences in the chemical structure of the complex and heterogeneous NOMs showed disparate reactivity and direct impact on CeO2-NPs stability. Using SRHA to study the effect of NOMfor drinkingwater related assessment does not sufficiently represent the natural conditions of the environment

Comparative Study on the Performance of Anaerobic and Aerobic Biotrickling Filter for Removal of Chloroform

Use of biotrickling filter (BTF) for gas phase treatment of volatile trihalomethanes (THMs) stripped from water treatment plants could be an attractive treatment option. The aim of this study is to use laboratory-scale anaerobic BTF to treat gaseous chloroform (recalcitrant to biological transformation) as a model THM and compare results with aerobic BTF. Additional investigations were conducted to determine the microbial diversity present within the BTFs. Chloroform is a hydrophobic volatile THM known to be difficult to biodegrade. To improve the degradation process, ethanol was used as a cometabolite at a different ratio to chloroform. The experimental plan was designed to operate one BTF under anaerobic condition and the other one under aerobic acidic condition. Higher elimination capacity (EC) of 0.23 ± 0.01 g/[m3·h] was observed with a removal efficiency of 80.9% ± 4% for the aerobic BTF operating at pH 4 for the concentration ratio of 1:40 chloroform to ethanol. For similar ratio, the anaerobic BTF supported lower removal efficiency of 59% ± 10% with corresponding lower EC of 0.16 ± 0.01 g/[m3·h]. Carbon recovery acquired for anaerobic and aerobic BTFs was 59% and 63%, respectively. The loading rate for chloroform on both BTFs was 0.27 g/[m3·h] (per m3 of filter bed volume). Variations of the microbial community were attributed to degradation of chloroform in each BTF. Azospira oryzae and Azospira restrica were the dominant bacteria and potential candidates for chloroform degradation for the anaerobic BTF, whereas Fusarium sp. and Fusarium solani were the dominant fungi and potential candidates for chloroform degradation in the aerobic BTF

Effects of source and seasonal variations of natural organic matters on the fate and transport of CeO2 nanoparticles in the environment

Natural organic matter (NOM) affects the stability and transport of nanoparticles (NPs) in natural waters by modifying their physiochemical properties. Source location, and seasonal variations, influence their molecular, physical and electrical charge properties. To understand the variations of NOM on the mobilization of NPs, large volumes of water were collected fromthe Ohio River (OR) over winter and summer seasons and dissolved NOMs were concentrated. The chemical and structural differences of these NOMs were compared with the Suwannee River humic acid (SRHA) SRHA using 1H and 13C nuclear magnetic resonance spectroscopy, and Fourier transforms infrared (FTIR) spectroscopy. Thermal analysis and FTIR confirmed that differences in composition, structure, and functional groups are a result of SRHA fractionation compared to wholemolecule OR-NOM. The influence of OR-NOMs on the surface charge of CeO2NPs and the effects on the transport and retention in a three-phase (deposition-rinse-re-entrainment) sand-packed columns were investigated at CeO2 NPs initial concertation of 10 ppm, pH 6.8, increasing ionic strength (3, 5, and 10 mM), retention time of 1 min, and increasing NOM concentration (1, 5, and 10 ppm). The summer OR-NOM showed higher stabilization and mobilization effect on the CeO2 than the winter NOM; while their effect was very different form the SRHA. The stabilization of NPs is attributed to both electrostatic and steric effects. The differences in the chemical structure of the complex and heterogeneous NOMs showed disparate reactivity and direct impact on CeO2-NPs stability. Using SRHA to study the effect of NOMfor drinkingwater related assessment does not sufficiently represent the natural conditions of the environment

Treatment of Dynamic Mixture of -Hexane, Benzene, and Methanol and Fungi Community Characterization in an Integrated Scheme of Cyclic Adsorption/Desorption Beds and Trickle Bed Air Biofilter

This study investigates the effect of volatile organic compound (VOC) feed fluctuations on trickle bed air biofilters (TBABs) and the ability of a two-bed adsorption/desorption unit in dampening fluctuations. A mixture of n -hexane, benzene, and methanol with concentration ratios of 1:3:6.6 was fed to two parallel TBABs. To simulate feed fluctuations, four different square waves were applied. The total VOC loading rates (LRs) varied from 28.4 to 107.3 g/m 3 h. The average concentration of VOCs applied to both TBABs was within allowable limits as determined in an earlier study. One TBAB was preceded by a two-bed cyclic adsorption/desorption unit (integrated unit), while the other TBAB (control unit) was directly subjected to the high and low peaks. n -Hexane elimination in the integrated unit was steady, and stable performance was obtained (75%-89%) based on the LRs, whereas the control unit showed erratic performance. The other two VOCs were mostly removed

Sponge City — An emerging concept in sustainable water resource management: A scientometric analysis

‘Sponge City’ is managing stormwater through increased infiltration, detention, storage, treatment, and drainage. By implementing this concept, the impact of urban development on water-related problems and natural ecosystems is diminished. This scientometric study analyze the global articles on ‘Sponge City’ which have been indexed in the Clarivate Analytics. A total of 199 articles were analyzed for visualization of the sponge city researches. China, as the stabilizer of the issue, has the highest betweenness centrality (1.37). The analysis of keyword co-occurrence and Clarivate Analytics category showed that the trend of the field is gradually shifting to managerial and practical phases. Based on co-citation and bibliographic coupling, the principal authors and resources have not been recognized yet. More research should be done to form the main paths of bibliographic entities. Generally, this scientometric analysis may help practitioners, policymakers, funders, editors, and researchers to understand the current state of the field and serve as a turning point for future progress in the studies

Comparative Study on the Performance of Anaerobic and Aerobic Biotrickling Filter for Removal of Chloroform

Use of biotrickling filter (BTF) for gas phase treatment of volatile trihalomethanes (THMs) stripped from water treatment plants could be an attractive treatment option. The aim of this study is to use laboratory-scale anaerobic BTF to treat gaseous chloroform (recalcitrant to biological transformation) as a model THM and compare results with aerobic BTF. Additional investigations were conducted to determine the microbial diversity present within the BTFs. Chloroform is a hydrophobic volatile THM known to be difficult to biodegrade. To improve the degradation process, ethanol was used as a cometabolite at a different ratio to chloroform. The experimental plan was designed to operate one BTF under anaerobic condition and the other one under aerobic acidic condition. Higher elimination capacity (EC) of 0.23 ± 0.01 g/[m3·h] was observed with a removal efficiency of 80.9% ± 4% for the aerobic BTF operating at pH 4 for the concentration ratio of 1:40 chloroform to ethanol. For similar ratio, the anaerobic BTF supported lower removal efficiency of 59% ± 10% with corresponding lower EC of 0.16 ± 0.01 g/[m3·h]. Carbon recovery acquired for anaerobic and aerobic BTFs was 59% and 63%, respectively. The loading rate for chloroform on both BTFs was 0.27 g/[m3·h] (per m3 of filter bed volume). Variations of the microbial community were attributed to degradation of chloroform in each BTF. Azospira oryzae and Azospira restrica were the dominant bacteria and potential candidates for chloroform degradation for the anaerobic BTF, whereas Fusarium sp. and Fusarium solani were the dominant fungi and potential candidates for chloroform degradation in the aerobic BTF

Dispersant Effectiveness on Oil Spills: Impact of Environmental Factors

Abstract: When a dispersant is applied to an oil slick, its effectiveness in dispersing the spilled oil depends on various factors such as oil properties, wave mixing energy, temperature of both oil and water, and salinity of the water. Estuaries represent water with varying salinities. In this study three salinity values in the range of 10-34 ppt (parts per thousand) were investigated, representing potential salinity concentrations found in typical estuaries. Three oils were chosen to represent light refined oil, light crude oil and medium crude oil. Each oil was tested at three weathering levels to represent maximum, medium and zero weathering. Two dispersants were chosen for evaluation. A modified trypsinizing flask termed the 'Baffled Flask' was used for conducting the experimental runs. A full factorial experiment was conducted for each oil to investigate the effect of salinity on three environmental factors: temperature (4 levels), oil weathering (3 levels) and mixing energy (150,200 and 250 rpm). Each experiment was replicated four times in order to evaluate the accuracy of the test. Statistical analyses of the experimental data were performed separately for each of the three oils three times (with or without dispersant). A linear regression model representing the main factors (salinity, temperature, oil weathering and flask speed) and second order interactions among the factors were accurately fit to the experimental data. Salinity was found to play an important role in determining the significance of temperature and mixing energy on dispersant effectiveness for almost all the oil dispersant combinations

Physicochemical Behavior of Penaeuse semisulcatuse Chitin for Pb and Cd Removal from Aqueous Environment

A beta type-chitin was produced from the shell of Penaeuse semisulcatuse shrimp for removal of lead and cadmium from the aqueous environment. Full physicochemical properties of the chitin (FTIR, SEM, mapping, XRD, EDX, AFM, and TGA-DTG) were obtained. Effects of solution pH, chitin dose, metals concentration, and contact time on the lead and cadmium adsorption were assessed. The solution pH had a great influence on the metal removal. Pseudo-first and pseudo-second order models were used to evaluate the kinetic behavior of metals adsorption by P. semisulcatuse chitin. Freundlich isotherm model was slightly better than the Langmuir model to describe the adsorption data. The R L value (obtained from the Langmuir model) for the adsorption of lead and cadmium was calculated to be 0.027 and 0.133, respectively, which showed the metals adsorption process by the chitin is desirable. The maximum adsorption capacity of lead and cadmium by P. semisulcatuse chitin was determined 13.14 mg/g and 19.15 mg/g, respectively. To desorb the adsorbed-metal from the chitin, the 1M HNO 3 solution was applied and the heavy metals desorption was suitable (90%). The half life (t 1/2 ) factor in the adsorption of Pb and Cd onto chitin was calculated 2.817 min and 3.876 min, respectively