Removal Efficiency Rate Research Articles

Enhanced oxidation potential of Ti/SnO2-Cu electrode for electrochemical degradation of low-concentration ceftazidime in aqueous solution: Performance and degradation pathway

In order to develop an efficient electrode to remove pharmaceutical and personal care products from wastewater, copper and antimony doped Ti/SnO2 electrode were prepared by thermal decomposition. Electrochemical characterization was undertaken on Ti/SnO2-Cu using cyclic voltammetry and linear sweep voltammetry, indicating an ultra-high 2.1 V of oxygen evolution potential, better stability, and superior corrosion resistance rather than traditional Ti/SnO2-Sb electrode. Competitive degradation experiments showed more efficient removal rate was achieved on Ti/SnO2-Cu electrode, which could remove more than 90% ceftazidime within 60 min. The microstructure and crystal orientation of the modified electrodes were investigated by scanning electron microscopy, which indicated that the crystal of the Ti/SnO2-Cu electrode grew in more porous and uniform condition, covered with closely arranged layers of the coating. X-ray photoelectron spectroscopy and X-ray diffractions suggested that Cu2O was successfully coated on the Ti/SnO2-Cu electrode surface. The operating parameters of electrochemical degradation process were also investigated, including current density, initial concentration, electrode distance, stirring rate and supporting electrolyte. Consequently, the intermediate products of electrochemical degradation were monitored by liquid chromatography-mass spectrometry and a major degradation pathway was proposed.

Surface conversion reaction and high efficient grinding of CVD diamond films by chemically mechanical polishing

The competitive growth of crystals results in a rough diamond film, which prevents CVD diamond films from reaching their full potential in devices requiring a smooth film. To address the issue, a high-efficiency grinding wheel is developed by adding titanium into the vitrified bond wheel. The polished films have been characterized by stylus profilometer, Scanning Electron Microscopy, X-ray diffraction and nanoindentation. The results indicate that the hardness of the polished diamond film with adhesion layer has been reduced to 1.85 GPa, which enables highly efficient removal rate using Al2O3 abrasive. The material removal rate could reach 120.2 µm h−1 due to the formation of graphite and carbides (TiC) during the polishing process.

The process intensification of CO2 absorption in honeycomb fractal reactor fabricated by 3D printer

The present study investigates CO2-monoethanolamine (MEA) absorption reaction in a novel honeycomb fractal reactor under the laminar flow, with particular reference to the conventional serpentine tubular reactor. The results show the CO2 removal efficiency and absorption rate increase with the increasing liquid flow rate, as well as the increasing MEA when the other conditions remain unchanged. In general, the CO2 removal efficiency and absorption rate in honeycomb fractal reactor are higher than those in serpentine tubular reactor. The honeycomb-shaped configuration provides reaction space with larger surface-to-volume ratio. The fluid from the upper level channel split at the bifurcation when flowing towards the next level of hexagonal unit, leading to a declined reactant velocity in the latter branches and hence increasing the residence time. Besides, in the honeycomb fractal reactor, the flow pattern is maintained as slug flow in which the contact time and area are intensified, leading to the strengthened interface mass transfer. The maximum CO2 removal efficiency of 168% was obtained in honeycomb fractal reactor.

Studies on removal of arsenic using cellulose acetate\u2013zinc oxide nanoparticle mixed matrix membrane

Mixed matrix membranes prepared by varying compositions of Cellulose acetate, acetone and formamide for the synthesis of ultrafiltration/nanofiltration membranes with and without nanoparticles for the removal of arsenic from synthetic solution. Zinc oxide nanoparticles were synthesized by an in situ ultrasonic technique and characterization done using XRD and SEM. In the current study, batch experiments were conducted to characterize the maximum removal efficiency of arsenic by cellulose acetate–ZnO mixed matrix membrane. It was found that 58.77% of arsenic removal was obtained for the feed concentration of 1000 mg/L and pH range 6.8 ± 0.6. The nanoparticle-embedded membranes show higher removal efficiency, high flux and permeation rate than cellulose acetate membranes without embedded nanoparticles.

Bioaugmentation of membrane bioreactor with Achromobacter denitrificans strain PR1 for enhanced sulfamethoxazole removal in wastewater

Achromobacter denitrificans strain PR1, previously found to harbour specific degradation pathways with high sulfamethoxazole (SMX) degradation rates, was bioaugmented into laboratory-scale membrane bioreactors (MBRs) operated under aerobic conditions to treat SMX-containing real domestic wastewater. Different hydraulic retention times (HRTs), which is related to reaction time and loading rates, were considered and found to affect the SMX removal efficiency. The availability of primary substrates was important in both bioaugmented and non-bioaugmented activated sludge (AS) for cometabolism of SMX. High HRT (24 h) resulted in low food to microorganism ratio (F/M) and low SMX removal, due to substrate limitation. Decrease in HRT from 24 h to 12 h, 6 h and finally 4 h led to gradual increases in primary substrates availability, e.g. organic compounds and ammonia, resulted in increased SMX removal efficiency and degradation rate, and is more favorable for high-rate wastewater treatment processes. After inoculation into the MBRs, the bioaugmentation strain was sustained in the reactor for a maximum of 31 days even though a significant decrease in abundance was observed. The bioaugmented MBRs showed enhanced SMX removal, especially under SMX shock loads compared to the control MBRs. The results of this study indicate that re-inoculation is required regularly after a period of time to maintain the removal efficiency of the target compound.

Evaluating organics removal performance from lagoon-pretreated swine wastewater in pilot-scale three-stage surface flow constructed wetlands

Pilot-scale three-stage surface flow constructed wetlands (SFCWs) planted with Myriophyllum aquaticum were constructed to study the organics removal performance from lagoon-pretreated swine wastewater. The removal performance of organics in the SFCWs was evaluated using deterministic and probabilistic methods and the results were consistent. The SFCWs achieved a relatively high removal efficiency (79.0–82.7%) for a wide influent COD concentration range (456–1010 mg L−1). No significant difference (p > 0.05) of COD removal efficiency and first-order removal rate constant among the various strengths of influent suggested that the present loading rates (2.74–6.06 g m−2 d−1) have not yet reached the maximum removal capacity of the SFCWs. The mean emission fluxes of methane from the SFCW units fed with different strengths of wastewater were 25–1210 mg m−2 d−1. A significantly positive correlation (p < 0.01) between methane emission fluxes and COD loading rates indicated that the anaerobic digestion of organics was an important process for organics removal in the SFCWs. No significant organics accumulation in the sediment over time suggested that plant harvest could be in favor of reducing the organics accumulation in the substrate and should be considered important during management of constructed wetlands.

Experimental studies on graphite powder-mixed electro-discharge machining of Inconel 718 super alloys: Comparison with conventional electro-discharge machining

Inconel 718 is a nickel-based super alloy widely applied in aerospace, automotive, and defense industries. Low thermal conductivity, extreme high temperature strength, strong work-hardening tendency make the alloy difficult-to-cut. In contrast to traditional machining, nonconventional route like electro-discharge machining is relatively more advantageous to machine this alloy. However, low thermal conductivity of Inconel 718 restricts electro-discharge machining from performing well. In order to improve the electro-discharge machining performance of Inconel 718, powder-mixed electro-discharge machining was reported in this paper. It was carried out by adding graphite powder to the dielectric media in consideration with varied peak discharge current. The morphology and topographical features of the machined surface including surface roughness, crack density, white layer thickness, metallurgical aspects (phase transformation, crystallite size, microstrain, and dislocation density), material migration, residual stress, microindentation hardness, etc. were studied and compared with that of the conventional electro-discharge machining. Additionally, effects of peak discharge current were discussed on influencing different performance measures of powder-mixed electro-discharge machining. Material removal efficiency and tool wear rate were also examined. Use of graphite powder-mixed electro-discharge machining was found to be better in performance for improved material removal rate, superior surface finish, reduced tool wear rate, and reduced intensity as well as severity of surface cracking. Lesser extent of carbon migration onto the machined surface as observed in powder-mixed electro-discharge machining in turn reduced the formation of hard carbide layers. As compared to the conventional electro-discharge machining, graphite powder-mixed electro-discharge machining exhibited relatively less microhardness and residual stress at the machined surface.

Start-up and Process Characteristics of Simultaneous ANAMMOX and Denitrification (SAD) in a Pilot-scale Anaerobic Sequencing Batch Reactor (ASBR)

A pilot scale anaerobic sequencing batch reactor (ASBR, working volume 530 L), inoculated by anaerobic sludge from an A2O process, was developed to investigate the start-up of anaerobic ammonia oxidation (ANAMMOX) and its combination with denitrification for deep-level nitrogen removal from saline wastewater. Simultaneously, the flora structure was analyzed. Results showed that under the conditions of temperature 35℃±1℃ and reaction time 14 h, ANAMMOX was successfully started-up after 160 days of operation. During the stabilized operation stage, ANAMMOX coupled with denitrification (SAD) led to a total nitrogen (TN) removal efficiency and removal rate of 91.1% and 0.45 kg·(m3·d)-1, respectively. The successful cultivated sludge formed granules and presented as a light red color, with the main bacteria genus being Candidatus Brocadia (10.6%). Additionally, high efficiency nitrogen and organic carbon removal (COD and TN removal efficiency of 93.2% and 90.0%, respectively) from wastewater simulating desulfurization and denitrification tailings with high salinity (Cl- concentration of 8000 mg·L-1) was achieved in the SAD system by gradually increasing the salinity gradient. Moreover, the denitrification in SAD was mostly NO3--N→N2, with partial denitrification (NO3--N→NO2--N) accounting for only 30.3%.

Temporal and longitudinal biofilm matrix analysis of a biofilter treating ethyl acetate during ozonation.

The present paper focuses on the biofilm composition and pattern of biomass in gas biofiltration of ethyl acetate working under continuous addition of ozone (O3). Two biofilters were operated for 230days, one under continuous addition of O3 (90ppbv) and another one without. Throughout the operation time, the extracellular polymeric substances (EPS), the main components in the extracellular matrix (ECM), were extracted from the biofilm and characterized qualitatively using Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and quantitatively by analyzing its main constituents: carbohydrates, proteins, and glucuronic acid. To date, EPS characterization has been attempted mainly with biofilm aggregates related to water treatment, not air biofiltration. The results of this study may be helpful and provide more information about EPS structure when O3 was added. O3 addition only affected the amount of EPS and not its composition. The greater effect was observed on carbohydrate content since it is the main component in EPS. The EPS/biomass ratio measured was twice lower with O3 addition. Higher removal efficiency (RE) and mineralization rates were obtained with the biofilter subjected to O3 addition, and a smaller volume of a reactor would be necessary to treat all contaminant under this condition. EPS content is only quantitatively reduced by O3 addition, and at the low O3 concentration applied, no structural alteration is noted regarding the composition of the EPS.

The impact of hydraulic retention time and operating temperature on biofuel production and process wastewater treatment

Breweries wastewater containing high concentration of organic and inorganic compounds ranks them among the top pollution generating industries. Anaerobic wastewater treatment with high organic loading rates can be achieved with lower COD strength at higher flowrates using a two–stage expanded granular sludge bed reactor. Hydraulic retention time (HRT), pH, temperature, and COD strength were varied for process optimization. Brewery wastewater with 20, 30, and 40 g COD/L as a substrate for two temperature ranges were evaluated. Under mesophilic conditions (36 °C), results show COD removal efficiency (R%) and biogas production rate increased by 6% and 40% respectively as HRTs increased, maintaining a constant OLR. Results imply for equivalent OLRs, better reactor performance is achieved when running high concentration COD at slower rate compared with a lower concentration at higher rate. This implies diffusion limitation where complex proteins and fats are passed through the reactor faster than their metabolism rate in the digester. Under thermophilic conditions (50 °C), results show COD removal efficiency (R%) and biogas production rate increased by 4% and 40% respectively as the HRTs increased, while maintaining a constant OLR. This implies the higher and stronger population of anaerobes are present under thermophilic condition rather than mesophilic condition.

New insights into enhanced anaerobic degradation of coal gasification wastewater (CGW) with the assistance of graphene

The up-flow anaerobic sludge blanket (UASB) system with graphene assisted was developed for coal gasification wastewater (CGW) treatment. Short-term results showed that optimal graphene addition (0.5 g/L) resulted in a more significant enhancement of methane production and chemical oxygen demand (COD) removal compared with that of the optimal activated carbon addition (10.0 g/L). Long-term results demonstrated that COD removal efficiency and methane production rate with graphene assisted achieved 64.7% and 180.5 mL/d, respectively. In addition, graphene could promote microbes accumulation and enzymes activity, resulting in higher extracellular polymeric substances (EPS) and coenzyme F420 concentrations. X-ray Diffraction (XRD) analysis indicated that chemical of graphene changed insignificantly during the experiment. Meanwhile, with graphene assisted, cells were attached together to form microbial aggregates to facilitate sludge granulation process. Furthermore, the enriched Geobacter and Pseudomonas might perform direct interspecies electron transfer (DIET) with Methanosaeta via biological electrical connection, enhancing the anaerobic degradation of CGW.

Effect of Cu, Ni and Zn on Fe(II)-driven autotrophic denitrification

Fe(II)-mediated autotrophic denitrification in the presence of copper (Cu), nickel (Ni) and zinc (Zn) with four different microbial cultures was investigated in batch bioassays. In the absence of metals, complete nitrate removal and Fe(II) oxidation were achieved with a Thiobacillus-dominated mixed culture and Pseudogulbenkiania sp. 2002 after 7 d. A nitrate removal of 96 and 91% was observed with a pure culture of T. denitrificans and an activated sludge enrichment, respectively, after 10 d of incubation. Cu, Ni and Zn were then supplemented at an initial concentration of 5, 10, 20 and 40 mg Me/L. A decrease of approximately 50% of the soluble metal concentrations occurred in the first 4 d of denitrification, due to metal precipitation, co-precipitation, sorption onto iron (hydr)oxides, and probably sorption onto biomass. A higher sensitivity to metal toxicity was observed for the microbial pure cultures. Pseudogulbenkiania sp. 2002 was the least tolerant among the biomasses tested, resulting in only 6, 8 and 6% nitrate removal for the highest Cu, Ni and Zn concentrations, respectively. In contrast, the highest nitrate removal efficiency and specific rates were achieved with the Thiobacillus-dominated mixed culture, which better tolerated the presence of metals. Averagely, Cu resulted in the highest inhibition of nitrate removal, followed by Zn and Ni.

Performance of an under-loaded denitrifying bioreactor with biochar amendment

Denitrifying bioreactors are recently-established agricultural best management practices with growing acceptance in the US Midwest but less studied in other agriculturally significant regions, such as the US Mid-Atlantic. A bioreactor was installed in the Virginia Coastal Plain to evaluate performance in this geographically novel region facing challenges managing nutrient pollution. The 25.3 m3 woodchip bed amended with 10% biochar (v/v) intercepted subsurface drainage from 6.5 ha cultivated in soy. Influent and effluent nitrate-nitrogen (NO3–N) and total phosphorus (TP) concentrations and flowrate were monitored intensively during the second year of operation. Bed surface fluxes of greenhouse gases (GHGs) nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) were measured periodically with the closed dynamic chamber technique. The bioreactor did not have a statistically or environmentally significant effect on TP export. Cumulative NO3–N removal efficiency (9.5%) and average removal rate (0.56 ± 0.25 g m−3 d−1) were low relative to Midwest tile bioreactors, but comparable to installations in the Maryland Coastal Plain. Underperformance was attributed mainly to low NO3–N loading (mean 9.4 ± 4.4 kg ha−1 yr−1), although intermittent flow, periods of low HRT, and low pH (mean 5.3) also likely contributed. N removal rates were correlated with influent NO3–N concentration and temperature, but decreased with hydraulic residence time, indicating that removal was often N-limited. GHG emissions were similar to other bioreactors and constructed wetlands and not considered environmentally concerning. This study suggests that expectations of NO3–N removal efficiency developed from bioreactors receiving moderate to high NO3–N loading with influent concentrations exceeding 10–20 mg L−1 are unlikely to be met by systems where N-limitation becomes significant.

A feasibility Study on the Movement Control of Particulate Enforced by Electrodynamic Force

Fine dusts, solid form of IAQ pollutants, can cause severe influences on human health due to the small size, huge surface area and the adsorptive characteristics for various harmful substances within the human respiratory organs. In this study, we tried to develop a technique and prototype to prevent indoor air pollution by removing fine particles from the surface using electrodynamic force. For this purpose, a 3-phased AC power generator with controlled voltage and frequency was applied to 3-electrode substrate for particle control tests, in which an activated carbon powders were used to simulate dust particles. As a results, first, the pitch pattern of the electrode substrate for the efficient generation of the electrodynamic force was found to be higher in the 3-electrode substrate than in the single electrode substrate and in the substrate having the narrow pitch in electrode. Second, the minimum voltage for the carbon powders to move from the surface of 3-electrode substrate were found 0.20 kV and the most efficient removal rate from the electrode substrate was 84.7%, as estimated through the image analysis when 0.50 kV and 0.96 kHz were supplied. As a result of analyzing the particle behaviors through the geometry selection of the electrode substrate using the EDEM, the results were similar to those of the lab experiments. Through these results and analysis, it is possible to reduce the pollution of indoor air quality by moving to a specific position where pollutants can be easily removed if operated with electrical force that matches the physical characteristics of particulate pollutants falling down to the indoor surface by the development system. Key words: Indoor Particular Contaminants, Electrodynamic Force, 3-phased AC Generator, 3-electrode Substrate, Discrete Element Method

Refitted inclined plate for improving suspended solids removal in standard storm-water sumps.

Suspended solids (SS) in the storm-water makes up a significant source of total suspended solids in wet weather flow. With appropriate modification and maintenance, the standard sumps in the drainage system can remove SS from storm-water runoff as a best management practice device. To increase the removal efficiency, especially in the condition of high flow rate, inclined plates, based on the shallow pool sedimentation theory, have been designed and refitted to the sump. Its performance under the different surface load and flow rate were evaluated through scale models. The results show that the preliminary design, Model A, had limited removal efficiency, and even played a negative role sometimes due to the concentrated flow in the axis. The optimizations through installing a non-uniform porous baffle (Model B) and adopting inverted V-shaped plates (Model C) were improved, and results show that removal efficiency rate can be increased by around 15-20%, even at high flow rates. Moreover, too many plates cannot improve the removal rate further, because they make the cross-section decline and lead to higher velocity between plates.

Ranking media for multi-pollutant removal efficiency in bioretention.

Bioretention is an effective best management practice for urban stormwater. This study aims to provide guidance for selecting the best bioretention medium in terms of pollutant removal capacity. Fuzzy set theory was applied with the improved analytic hierarchy process (IAHP) for weight determination, thus forming the fuzzy synthetic evaluation model, to assess the comprehensive efficiencies of certain sand media. This work is the first to use this method to study bioretention. Results demonstrated that the fuzzy synthetic evaluation model was a rational choice for the selection of bioretention media. The studied media were ranked by pollutant removal capacity as follows: Media III > Media V > Media I > Media VI > Media II > Media VII > Media IV. Media I had the best comprehensive removal efficiency and infiltration rate in bioretention. Moreover, the removal rates for Cd2+, Zn2+ and Pb2+ were excellent (>80%), those for Cu2+ and NH+4-N fluctuated from 58.1% to 92.7% and 64.7% to 95.9%, respectively, and those for NO-3-N and TP of the seven media did not show distinct differences.

Preparation, Characterization of Coal Ash Adsorbent and Orthogonal Experimental Rsearch on Treating Printing and Dyeing Wastewater

Using high temperature activated sodium flying ash and carboxymethyl chitosan as raw material to prepare carboxymethylchitosan wrapping fly-ash adsorbent (CWF), combined with iron-carbon micro-electrolysis treatment of simulated and actual printing and dyeing wastewater. The conditions for obtaining are from the literature: the best condition for CWF to treat simulated printing and dyeing wastewater pretreated with iron-carbon micro-electrolysis is that the mixing time is 10min, the resting time is 30 min, pH=6, and the adsorbent dosage is 0.75 g/L. The results showed that COD removal efficiency and decoloration rate were above 97 %, and turbidity removal rate was over 90 %. The optimum dyeing conditions were used to treat the dyeing wastewater. The decolorization rate was 97.30 %, the removal efficiency of COD was 92.44 %, and the turbidity removal rate was 90.37 %.

Research on dispose of wastewater from printing and dyeing by CWF combined with Iron-carbon Microelectrolysis

The carboxymethylchitosan cladding coal ash (CWF) was oxidized by the high temperature using coal ash and sodium carboxymethyl chitosan as raw and processed material for treatment of simulated and actual printing and dyeing wastewater over iron-carbon micro-electrolysis. The results on pH and CWF dosage for effluent dispose were evaluated by the decolorization rate, COD removal efficiency and turbidity removal rate. The experimental results indicated that the decolorization rate was first augmented and then declined with the increase of pH, and attained a peak value when pH was at 5-6. The COD removal efficiency augmented with the augmented of pH, and attained a peak value when pH was 6-7. The turbidity removal rate was first increases and afterwards decreases with the augment of pH, and attained a peak value when pH was at 5-6. Furthermore, the optimum pH for the treatment of simulated dyeing wastewater was 6 over iron-carbon micro-electrolysis, which indicated that the appropriate pH can promote the degradation of wastewater.

Central Composite Design Optimization of Zinc Removal from Contaminated Soil, Using Citric Acid as Biodegradable Chelant

Citric acid (CA) was evaluated in terms of its efficiency as a biodegradable chelating agent, in removing zinc (Zn) from heavily contaminated soil, using a soil washing process. To determine preliminary ranges of variables in the washing process, single factor experiments were carried out with different CA concentrations, pH levels and washing times. Optimization of batch washing conditions followed using a response surface methodology (RSM) based central composite design (CCD) approach. CCD predicted values and experimental results showed strong agreement, with an R2 value of 0.966. Maximum removal of 92.8% occurred with a CA concentration of 167.6 mM, pH of 4.43, and washing time of 30 min as optimal variable values. A leaching column experiment followed, to examine the efficiency of the optimum conditions established by the CCD model. A comparison of two soil washing techniques indicated that the removal efficiency rate of the column experiment (85.8%) closely matching that of the batch experiment (92.8%). The methodology supporting the research experimentation for optimizing Zn removal may be useful in the design of protocols for practical engineering soil decontamination applications

Effectiveness of Biochar from Hydrothermal Carbonization of Wetland Biomass for Sorption of Ammonia

AbstractThe aim of this study is twofold: firstly, to characterize the biochars resulting from the hydrothermal carbonization (HTC) of different types of wetland biomass and, secondly, to assess their potential for ammonia removal in aqueous solutions. The chars produced were carbon rich. The adsorption experiments indicated that hydrothermal treatment improved the ammonia removal efficiency rate, and loaded adsorbents were regenerable. Using an HTC char of reed as adsorbent has several advantages: it has the highest adsorption performance, the highest char yield, and the greatest affinity for regeneration.