Investigation of a sewage-integrated technology combining an expanded granular sludge bed (EGSB) and an electrochemical reactor in a pilot-scale plant

A sewage-integrated treatment system (SITS) for the treatment of municipal wastewater, consisting of an expanded granular sludge bed (EGSB) reactor to remove soluble organic matter and an electrochemical (EC) reactor to oxidize the NH₃-N, was evaluated. The performance of the EGSB reactor was monitored for 12 months in a pilot-scale plant. Iron shavings were added to the EGSB reactor on the sixtieth day to improve the removal efficiency of the chemical oxygen demand (COD), suspended solids (SS) and total phosphorus (TP). After the iron shavings were added, the effluent COD, SS and TP decreased from 104 to 46 mg L⁻¹, 21 to 8.6 mg L⁻¹ and 3.62 to 1.36 mg L⁻¹, respectively. Moreover, in the EC reactor, which was equipped with IrO₂/Ti anodes, the NH₃-N and total nitrogen (TN) concentrations decreased from 25 to 12 mg L⁻¹ and 29 to 15 mg L⁻¹, respectively. The NH₃-N was directly oxidized to N₂, resulting in no secondary pollution. The results demonstrated the possibility of removing carbon and nutrients in a SITS with high efficiency. The system runs efficiently and with a flexible operation, making it suitable for low-strength wastewater. The results and parameters presented here can provide references for the practical project.     

Treatment of Terasil Red R Dye Wastewater using H2O2/pyridine/Cu(II) System

The H₂O₂/pyridine/Cu(II) advanced oxidation system was used to assess the efficiency of the treatment of a 1 g L⁻¹ Terasil Red R dye solution. This system was found to be capable in reducing the concentration of chemical oxygen demand (COD) of the dye solution up to 90%, and achieving 99% in decolorization at the optimal concentration of 5.5 mM H₂O₂, 38 mM pyridine and 1.68 mM Cu(II). The final concentration of COD was recorded at 117 mg L⁻¹ and color point at 320 PtCo. Full 2⁴ factorial design and the response surface methodology using central composite design (CCD) were utilized in the screening and optimization of this study. Treatment efficiency was found to be pH independent. The amount of sludge generation was in the range of 100–175 mg L⁻¹ and the sludge produced at the optimal concentration was 170 mg L⁻¹.     

Utilization of landfill leachate parameters for pretreatment by Fenton reaction and struvite precipitation—A comparative study

This paper reports results of laboratory studies on two pretreatment methods, struvite precipitation using aeration with H₃PO₄ and Fenton oxidation. These methods utilized specific properties of the leachate: high magnesium content (172 mg L⁻¹) for struvite precipitation and a high iron concentration (56 mg L⁻¹) for Fenton treatment. Struvite precipitation (H₃PO₄, 700 mg L⁻¹) removed 36% of NH₃-N and 24% of SCOD. Fenton treatment (at pH 3.5) required 650 mg L⁻¹ of H₂O₂ and removed 66% of SCOD. The effect of each pretreatment on the returned activated sludge (RAS) was evaluated using respirometry. Both methods reduced the inhibitory effect of the leachate and substantially increased biokinetic parameters. The BOD₅/SCOD ratio increased from 0.63 for raw leachate to 0.82 (struvite) and 0.88 (Fenton). Estimation of capital and operational costs of the total leachate treatment indicated that aeration with struvite precipitation, followed by biological treatment, would be the preferred option.     

Sulfamethoxazole abatement by photo-Fenton: Toxicity,inhibition and biodegradability assessment of intermediates

The objective of this work was to study the abatement of 200 mg L⁻¹ sulfamethoxazole (SMX) solution by means of photo-Fenton process. Biodegradability of the treated solutions was followed by the ratio biochemical oxygen demand at five days/chemical oxygen demand (BOD₅/COD) and toxicity by Microtox^® and inhibition tests. Experiments with different initial concentration of H₂O₂ were carried out. The initial amount of Fe²⁺ and pH of the solution were set at 10 mg L⁻¹ and 2.8 respectively. The temperature of the reactor was kept constant in all the experiments (25 ± 0.8 °C). Photo-Fenton process is thought to be a successful treatment step to improve the biodegradability of wastewater containing SMX. The complete antibiotic removal was achieved for a H₂O₂ dose over 300 mg L⁻¹. Biodegradability (BOD₅/COD) rose from zero (SMX solution) to values higher than 0.3 (treated solutions). Toxicity and inhibition tests pointed out in the same direction: oxidized intermediates for initial H₂O₂ dose over 300 mg L⁻¹ showed no toxicity effects on pure bacteria and no inhibition on activated sludge activity.     

Liquid–liquid extraction/separation of platinum(IV) and rhodium(III) from acidic chloride solutions using tri-iso-octylamine

Liquid–liquid extraction/separation of platinum(IV) and rhodium(III) from acidic chloride solutions was carried out using tri-iso-octylamine (Alamine 308) as an extractant diluted in kerosene. The percentage extraction of platinum(IV) and rhodium(III) increased with increase in acid concentration up to 8 mol L⁻¹. However, at 10 mol L⁻¹ HCl concentration, the extraction behavior was reversed, indicating the solvation type mechanism during extraction. The quantitative extraction of ∼98% platinum(IV) and 36% rhodium(III) was achieved with 0.01 mol L⁻¹ Alamine 308. The highest separation factor (S.F. = 184.7) of platinum(IV) and rhodium(III) was achieved with 0.01 mol L⁻¹ Alamine 308 at 1.0 mol L⁻¹ of hydrochloric acid concentration. Alkaline metal salts like sodium chloride, sodium nitrate, sodium thiocyanate, lithium chloride, lithium nitrate, potassium chloride and potassium thiocyanate used for the salting-out effect. LiCl proved as best salt for the extraction of platinum(IV). Temperature effect demonstrates that the extraction process is exothermic. Hydrochloric acid and thiourea mixture proved to be better stripping reagents when compared with other mineral acids and bases.     

Preparation of a modified flue gas desulphurization residue and its effect on pot sorghum growth and acidic soil amelioration

A modified flue gas desulphurization residue (MFGDR) was prepared and its effects on sorghum growth and acidic soil amelioration were evaluated in this paper. The MFGDR was prepared by calcining a mixture of dry/semi-dry flue gas desulphurization (FGD) residue from a coal-fired power plant, sorted potash feldspar and/or limestone powder. The available nutrients from the MFGDR were determined with 4.91 wt% K⁺, 1.15 wt% Mg²⁺, 22.4 wt% Ca²⁺, 7.01 wt% Si⁴⁺ and 2.07 wt% SO₄²⁻-S in 0.1 mol L⁻¹ citric acid solution. Its pH value was held at 9.60 displaying slightly alkaline. The results of sorghum pot growth in both red and crimson acidic soil for 30 days indicated that adding the MFGDR at a dosage of 2 g kg⁻¹ in total soil weight would increase the growth rate of biomass by 24.3-149% (wet weight basis) and 47.3-157% (dry weight), the stem length and thickness increase by 5.75-22.1% and 4.76-30.9% in contrast with CK treatment for two test cuttings, respectively. The effect on sorghum growth was attributed to the increase of available nutrients, the enhancement of soil pH value and the reduction of aluminum toxicity in acidic soil due to the addition of the MFGDR. The experimental results also suggested that the MFGDR could be effectively used to ameliorate the acidic soil which is widely distributed throughout the southern China.     

Novel modeling concept for evaluating the effects of cadmium and copper on heterotrophic growth and lysis rates in activated sludge process

A new modeling concept to evaluate the effects of cadmium and copper on heterotrophic growth rate constant (μ_H) and lysis rate constant (b_H) in activated sludge was introduced. The oxygen uptake rate (OUR) was employed to measure the constants. The results indicated that the μ_H value decreased from 4.52 to 3.26 d⁻¹ or by 28% when 0.7 mg L⁻¹ of cadmium was added. Contrarily the b_H value increased from 0.31 to 0.35 d⁻¹ or by 11%. When adding 0.7 mg L⁻¹ of copper, the μ_H value decreased to 2.80 d⁻¹ or by 38%. The b_H value increased to 0.42 d⁻¹ or by 35%. After regression, the inhibitory effect was in a good agreement with non-competitive inhibition kinetic. The inhibition coefficient values for cadmium and copper were 1.82 and 1.21 mg L⁻¹, respectively. The relation between the b_H values and heavy metal concentrations agreed with exponential type well. The heavy metal would enhance b_H value. Using these data, a new kinetic model was established and used to simulate the degree of inhibition. It was evident that not only the inhibitory effect on μ_H but also that the enhancement effect on b_H should be considered when heavy metal presented.     

The effect of pure iron in a nanocrystalline grain size on the corrosion inhibitor behavior of sodium benzoate in near-neutral aqueous solution

The effect of grain size reduction on the electrochemical and corrosion behavior of iron with different grain sizes (32–750 nm) produced by direct and pulsed current electrodeposition were characterized using Tafel polarization curves and electrochemical impedance spectroscopy. The grain size of deposits was determined by X-ray diffraction analysis and scanning electron microscopy. The tests were carried out in an aqueous electrolyte containing 30 mg L⁻¹ NaCl + 70 mg L⁻¹ Na₂SO₄. Results obtained suggested that the inhibition effect and corrosion protection of sodium benzoate inhibitor in near-neutral aqueous solutions increased as the grain size decreased from microcrystalline to nanocrystalline. The improvement on the inhibition effect is attributed to the increase of the surface energy.     

Microwave enhanced Fenton-like process for the treatment of high concentration pharmaceutical wastewater

This paper explored a novel process for wastewater treatment, i.e. microwave enhanced Fenton-like process. This novel process was introduced to treat high concentration pharmaceutical wastewater with initial COD loading of 49,912.5 mg L⁻¹. Operating parameters were investigated and the optimal condition included as follows: microwave power was 300 W, radiation time was 6 min, initial pH was 4.42, H₂O₂ dosage was 1300 mg L⁻¹ and Fe₂(SO₄)₃ dosage was 4900 mg L⁻¹, respectively. Within the present experimental condition used, the COD removal and UV₂₅₄ removal reached to 57.53% and 55.06%, respectively, and BOD₅/COD was enhanced from 0.165 to 0.470. The variation of molecular weight distribution indicated that both macromolecular substances and micromolecular substances were eliminated quite well. The structure of flocs revealed that one ferric hydrated ion seemed to connect with another ferric hydrated ion and/or organic compound molecule to form large-scale particles by means of van der waals force and/or hydrogen bond. Subsequently, these particles aggregated to form flocs and settled down. Comparing with traditional Fenton-like reaction and conventional heating assisted Fenton-like reaction, microwave enhanced Fenton-like process displayed superior treatment efficiency. Microwave was in favor of improving the degradation efficiency, the settling quality of sludge, as well as reducing the yield of sludge and enhancing the biodegradability of effluent. Microwave enhanced Fenton-like process is believed to be a promising treatment technology for high concentration and biorefractory wastewater.     

Fluoride removal performance of glass derived hydroxyapatite

A novel sodium calcium borate glass derived hydroxyapatite (G-HAP) with different ranges of particle size was prepared by immersion sodium calcium borate glass in 0.1 M K₂HPO₄ solution by the ratio of 50 g L⁻¹ for 7 days. The unique advantage of G-HAP for the adsorption of fluoride ions in solutions was studied. The effects of size and quantity of particles, pH value and adsorption time on adsorption performance were investigated. The maximum adsorption capacity was 17.34 mg g⁻¹ if 5 g L⁻¹, <100 μm G-HAP was added to a solution with an initial pH value of 6.72 and the adsorption time was 12 h. The results showed that the micro-G-HAP could immobilize F⁻ in solution more effectively than commercial nano-HAP, which makes potential application of the G-HAP in removing the fluoride ions from wastewater. The adsorption kinetics and isotherms for F⁻ could be well fitted by a second order kinetic model and Freundlich isotherm model respectively, which could be used to describe the adsorption behavior. The mechanism of G-HAP in immobilizing F⁻ from aqueous solutions was investigated by the X-ray diffraction (XRD), infrared spectra (IR) and scanning electron microscopy (SEM).     

Long-acting antibacterial activity of quaternary phosphonium salts functionalized few-layered graphite

Tetradecyl triphenyl phosphonium bromide (TTP) functionalized few-layered graphite (FG) was prepared to investigate the effects of phosphonium salts usage on the characteristics, morphology, thermal stability and long-acting antibacterial property of TTP functionalized FG (TTP-FG) by introducing different content of TTP into FG. The results showed that the phosphonium salt was intercalated into FG, and the basal spacing of TTP-FG was enlarged with the increasing of phosphonium salt content. TTP-FG-3 with 33.7% (mass fraction) of TTP, displayed excellent thermal stability and long-acting antibacterial activity with the minimal inhibitory concentrations against E. coli and S. aureus of 580 mg L⁻¹ and 285 mg L⁻¹ after 72 h soaking, respectively.     

Treatment of anaerobic sludge digester effluents by the CANON process in an air pulsing SBR

The CANON (Completely Autotrophic Nitrogen removal Over Nitrite) process was successfully developed in an air pulsing reactor type SBR fed with the supernatant from an anaerobic sludge digester and operated at moderately low temperatures (18–24 °C). The SBR was started up as a nitrifying reactor, lowering progressively the dissolved oxygen concentration until reaching partial nitrification. Afterwards, an inoculation with sludge containing Anammox biomass was carried out. Nitrogen volumetric removal rates of 0.25 g N L⁻¹ d⁻¹ due to Anammox activity were measured 35 d after inoculation even though the inoculum constituted only 8% (w/w) of the biomass present in the reactor and it was poorly enriched in Anammox bacteria. The maximal nitrogen removal rate was of 0.45 g N L⁻¹ d⁻¹. By working at a dissolved oxygen concentration of 0.5 mg L⁻¹ in the bulk liquid, nitrogen removal percentages up to 85% were achieved.     

Tl-208, Pb-212, Bi-212, Ra-226 and Ac-228 adsorption onto polyhydroxyethylmethacrylate-bentonite composite

The adsorption of naturally occurring radionuclides (²⁰⁸Tl⁺, ²¹²Pb²⁺, ²²⁶Ra²⁺, ²¹²Bi³⁺ and ²²⁸Ac³⁺) onto Polyhydroxyethylmethacrylate-bentonite (PHEMA-B) composite was investigated. Experimentally obtained isotherms were evaluated with reference to Langmuir, Freundlich and Dubinin-Radushkevich (DR) models. The adsorption isotherms were L type of Giles classification proving that PHEMA-B had a high affinity adsorbent for the studied radionuclides. The Langmuir adsorption capacities (X_L) were in the order of ²²⁶Ra (2.8 MBq kg⁻¹)>²¹²Bi (0.4 MBq kg⁻¹)>²¹²Pb (0.3 MBq kg⁻¹)>²²⁸Ac and ²⁰⁸Tl (0.2 MBq kg⁻¹). The adsorption process was physical via complex formation after proton exchanger for which the adsorption energies obtained from DR model was evidence. The enthalpy and entropy changes were positive and the negative free enthalpy change was proof for the spontaneity of adsorption. The reusability tests for PHEMA-B for five uses demonstrated that the adsorbent could be reused after complete recovery of the loaded radionuclide ions by 1 M HCl. The chemical structure of the composite did not change after the reuses and storage foregoing.     

Reactive radio frequency sputtering deposition and characterization of zinc nitride and oxynitride thin films

Zinc nitride films were deposited on glass or silicon substrates by reactive magnetron radio frequency sputtering of zinc in either N₂-Ar or N₂-Ar-O₂ ambient. The effects of varying the nitrogen contents and the substrate temperature were investigated. X-ray diffraction data showed that the as-deposited films contain the zinc nitride cubic crystalline phase with a preferred orientation, and Raman scattering measurements revealed ZnN related modes. According to energy-dispersive X-ray spectroscopy analysis, the as-deposited films were nitrogen-rich and contained only a small fraction of oxygen. Hall-effect measurements showed that p-type zinc nitride with carrier concentration of ~ 10¹⁹ cm⁻³, mobility of ~ 10¹ cm²/Vs, resistivity of ~ 10⁻² Ω ∗ cm, was obtained. The photon energy dependence of optical transmittance suggested that the material has an indirect bandgap.     

Adsorptive separation and photocatalytic degradation of methylene blue dye on titanate nanotube powders prepared by hydrothermal process using metal Ti particles as a precursor

Titanate nanotube powders (TNTPs) with the twofold removal ability, i.e. adsorptive separation and photocatalytic degradation, are synthesized under hydrothermal conditions using metal Ti particles as a precursor in the concentrated alkaline solution, and their morphology, structure, adsorptive and photocatalytic properties are investigated. Under hydrothermal conditions, the titanate nanotubes (TNTs) with pore diameter of 3-4 nm are produced on the surface of metal Ti particles, and stacked together to form three-dimensional (3D) network with porous structure. The TNTPs synthesized in the autoclave at 130 °C for 24 h exhibits a maximum adsorption capability of about 197 mg g⁻¹ in the neutral methylene blue (MB) solution (40 mg L⁻¹) within 90 min, the adsorption process can be described by pseudo second-order kinetics model. Especially, in comparison with the adsorptive and the photocatalytic processes are performed in turn, about 50 min can be saved through synchronously utilizing the double removal ability of TNTPs when the removal ratio of MB approaches 95% in MB solution (40 mg L⁻¹) at a solid-liquid (S/L) ratio of 1:8 under ultraviolet (UV) light irradiation. These 3D TNTPs with the twofold removal properties and easier separation ability for recycling use show promising prospect for the treatment of dye pollutants from wastewaters in future industrial application.     

Non-aqueous solution processed ZnO thin film transistors

Zinc oxide based thin film transistors (TFT) fabricated by a non-aqueous sol-gel solution process with a zinc neodecanoate precursor are demonstrated. X-ray diffraction measurement reveals that the ZnO films adopt a hexagonal structure with a random crystal orientation. Atomic force microscope and scanning electron microscope characterizations show that the films are closely packed and consisted of particles with an average size of 45 nm. The devices exhibit an n-channel enhancement mode behavior, with saturation mobility in the range of 0.95-1.29 cm² V⁻¹ s⁻¹, drain current on-to-off ratios higher than 10⁷ and threshold voltages between 5.3 and 16.8 V in an ambient environment. The results imply that high-performance ZnO TFTs produced by a simple and low-cost technique could be applicable to electronic devices.     

The biochemical response to different Cr and Cd concentrations in soils amended with organic wastes

The effects of adding municipal solid waste (MSW) or poultry manure (PM) on the biochemical properties of a soil polluted with Cr and Cd were studied. Soil was mixed with Cr(NO₃)₃ and Cd(NO₃)₂ to give three concentrations (0, 100, and 250 mg Cr kg⁻¹ and 0, 100, and 250 mg Cd kg⁻¹) in the soil, which was then treated with MSW at a rate of 10% or PM at a rate of 7.6%. The pH and biochemical parameters were measured at 0 and 120 days. An unamended and no-polluted soil was used as control. Compared with the non-polluted soil, for the 250 mg Cd kg⁻¹ treatment the microbial biomass-C, dehydrogenase, urease, β-glucosidase, phosphatase, and arylsulphatase activities decreases 23%, 26.2%, 36%, 34.8%, 18.4%, and 15.8%, respectively, whereas for 250 mg Cr kg⁻¹ treatment the biochemical parameters were slightly lowest than for 250 mg Cd kg⁻¹ treatment. For 250 mg Cr kg⁻¹ soil + 250 mg Cd kg⁻¹ soil treatment, the inhibition percentages of the biochemical parameters increased. After the application of organic wastes in Cr + Cd polluted soil, the inhibition of biochemical properties was greater with the MSW amendment than with PM, possibly due to its higher humic acid concentration.     

Zincon-modified activated carbon for solid-phase extraction and preconcentration of trace lead and chromium from environmental samples

A new method that utilizes zincon-modified activated carbon (AC-ZCN) as a solid-phase extractant has been developed for simultaneous preconcentration of trace Cr(III) and Pb(II) prior to the measurement by inductively coupled plasma optical emission spectrometry (ICP-OES). The separation/preconcentration conditions of analytes were investigated, including effects of pH, the shaking time, the sample flow rate and volume, the elution condition and the interfering ions. At pH 4, the maximum adsorption capacity of Cr(III) and Pb(II) onto the AC-ZCN were 17.9 and 26.7 mg g⁻¹, respectively. The adsorbed metal ions were quantitatively eluted by 1 mL of 0.1 mol L⁻¹ HCl. Common coexisting ions did not interfere with the separation. According to the definition of IUPAC, the detection limits (3σ) of this method for Cr(III) and Pb(II) were 0.91 and 0.65 ng mL⁻¹, respectively. The relative standard deviation under optimum condition is less than 3.5% (n = 8). The method has been applied for the determination of Cr(III) and Pb(II) in biological materials and water samples with satisfactory results.     

Optimizing preparation of the TiO2 thin film reactor using the Taguchi method

In this study, titanium dioxide thin film was prepared using the modified chemical vapor deposition. The parameters employed to control the preparation of the catalyst include the temperature of water bath, the Ti(OC₃H₇)₄/H₂O ratio, the flow rate of carrier gas, the oxidation temperature, the oxidation time, the calcination temperature, the rotating speed of furnace, and the speed of geared motor. The orthogonal arrays in the design of experimental method proposed by Taguchi were adopted to conduct the multiple-factor experiment. The conversion rate of salicylic acid in the aqueous or heterogeneous phase photocatalysis experiment was employed to identify the optimal conditions for assembly. The results indicated that a higher conversion ratio of the organic substance could be achieved under catalytic oxidation temperature of 400 °C, calcination temperature of 550 °C, and spraying speed of 30 rpm and the optimal experimental conditions obtained in this study were irradiation with intensity of 2.9 mW cm⁻² on salicylic acid at concentration of 250 mg L⁻¹ by both agitation and aeration processes (dissolved oxygen level = 8.2 mg O₂ L⁻¹) at pH 5, which could achieve optimal hydroxyl radical yield of 5.1 × 10⁻¹⁷ M.