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Dried sludge as additive for making ceramsite is a new effective approach for disposal of sludge. In this study sewage sludge, water glass and clay were chosen as the components, the optimal ratio of the components and the most appropriate conditions were obtained. The functions of primary components in the sintering process, porosity formation mechanism and solid phase reaction also have been discussed. The optimized process parameters were shown as follows: the ratio of dried sludge/clay (wt%) was 33%, ratio of adherent /clay (wt%) was 15%, sintering temperature was 1000 degrees C, sintering time was 10 min. Bulk density was 582 kg m(-3), particle density was 1,033 kg m(-3), water absorption was 9.5%, porosity was 43.7%. SEM, EDS, XRD and XRF analyses were also carried out. The results indicate that dried sludge as raw material is a good way for making ceramsite. Biological Aerated Filters (BAFs) with filter media of Guangzhou ceramsite, Jiangxi ceramsite, activated carbon and ceramsite (obtained in test) were selected to treat municipal wastewater. The average removal efficiencies of ceramsite (obtained in test) for turbidity, COD, SCOD and NH3-N were about 96.4%, 76.2%, 59.6% and 82.3% respectively and were higher than those of other ceramsites.
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PMID:Utilization of dried sludge for making ceramsite. 1716 44

In order to develop a catalyst with high activity for catalytic wet oxidation (CWO) process at room temperature and atmospheric pressure, Fe2O3-CeO2-TiO2/gamma-Al2O3 catalyst was prepared by consecutive impregnation method and the prepared parameters were optimized. The structure of the catalyst was characterized by BET, XRF, SEM and XPS technologies, and the actual wastewater was used to investigate the catalytic activity of Fe2O3-CeO2-TiO2/gamma-Al2O3 in CWO process. The experimental results showed that the prepared catalyst exhibited good catalytic activity when the doping amount of Ti was 1.0 wt%/o (the weight ratio of Ti to carriers), and the middle product, CeO2-TiO2/gamma-Al2O3, was calcined in 450'C for 2 h. The CWO experiment for treating actual dye wastewater indicated that the COD, color and TOC of actual wastewater were decreased by 62.23%, 50.12% and 41.26% in 3 h, respectively, and the ratio of BODs/COD was increased from 0.19 to 0.30.
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PMID:Preparation and characterization of Fe2O3-CeO2-TiO2/gamma-Al2O3 catalyst for degradation dye wastewater. 1729 63

Characteristics of anaerobic granules before and after acclimation, removal efficiencies of 3-nitrophenol (3-NP) and performance of 3-NP wastewater treatment were investigated in a lab-scale upflow anaerobic sludge bed (UASB). The results showed that granular sludge acclimatized to 3-NP rapidly during acclimation. Using SEM, the filamentous bacteria was the predominant bacteria on the surface of granules. Throughout the study of 3-NP wastewater anaerobic degradation, hydraulic retention time (HRT) and input COD concentration were kept constant as 26 h and 2 500 mg/L, respectively. While 3-NP concentrations increasing from 20 mg/L to 250 mg/L gradually, COD removal decreased from 95.2% to 85.1% and 3-NP removal efficiencies were always more than 99%. 3-AP was found to be the major intermediate during the degradation of 3-NP. Out of the total input of 3-NP concentration, on molar basis, about 58.7% - 111.9% of 3-NP was recovered in the form of 3-AP. With increasing 3-NP concentration, the variations of gas production were minimal. The minimum methane percentage was 65% and the maximum was 74%.
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PMID:[Study on 3-nitrophenol wastewater treatment in UASB]. 1732 27

The high concentration of trivalent chromium along with organic/inorganic compounds in chrome buffing dust (CBD), the solid waste discharged from leather industries, causes severe groundwater contamination on land co-disposal and chronic air pollution during thermal incineration. In the present investigation, CBD was subjected to starved air incineration (SAI) at 800 degrees C in a thermal incinerator under different flow rates of oxygen to optimize the oxygen required to incinerate the organic compounds and simultaneously preventing the conversion of Cr(3+) to Cr(6+). The energy audit of SAI of buffing dust under the external supply of oxygen was carried out under different incineration conditions. The bottom ash from SAI was effectively solidified/stabilized using Portland cement and fine aggregate. The solidified blocks were tested for unconfined compressive strength and heavy metal leaching. Unconfined compressive strength of the blocks was in the range of 120-180 kg/cm(2). The stabilization of chromium(III) in the cement gel matrix was confirmed using Scanning Electron Microscopy SEM, Electron Paramagnetic Resonance spectroscopy (EPR) and X-ray diffraction spectroscopy (XRD). Leachability studies through TCLP on solidified blocks were carried out to determine the degree of leaching of chromium and organic compounds (expressed as COD) under standard conditions.
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PMID:Safe disposal of toxic chrome buffing dust generated from leather industries. 1756 Jul 15

Sewage sludge thermal hydrolysis experiments with 2,450 MHz microwave energy were carried out under 80-170 degrees C with 1-30 min. Max. microwave output power was 1 kW. Volatile suspended solid (VSS) dissolving ratio, COD dissolving ratio, liquor COD and TOC, sludge particle size distribution, micro-structure, and elements (C, H and N) hydrolysis were measured. Also, sludge dewaterability improvement was inspected. Results show that microwave heating leads fast sludge hydrolysis reaction. Temperature was the controlling process factor. Under 150 degrees C and 170 degrees C with 5 min, 15.8% and 29.4% VSS dissolved respectively. While, with 10 min 19.07% and 25.75% COD moved to liquor. Release of organic materials increased liquid sludge COD and TOC concentration. Under 170 degrees C with 10 min, COD and TOC concentration were 9,860.0 mg/L and 2,949.70 mg/L respectively. More than 5 to 10 min, VSS and COD dissolving trend turned slow down. SEM test showed cell disruption of hydrolyzed sludge. N could dissolve more easily than C and H. 67% N hydrolysiszed under 170 degrees C with 5 min. Bacterial cell disruption and organic solid hydrolysis improved sludge dewaterability. Sludge cake moisture content decreased from 82% to 73.1% and 65.5% under 150 degrees C, 170 degrees C with 10 min microwave hydrolysis. Accordingly, sludge amount reduction ratios were 33.9% and 51.7% respectively.
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PMID:[Sewage sludge microwave thermal hydrolysis process]. 1844 33

Bioalkylation and colloid formation of selenium during selenate removal in upflow anaerobic sludge bed (UASB) bioreactors was investigated. The mesophilic (30 degrees C) UASB reactor (pH = 7.0) was operated for 175 d with lactate as electron donor at an organic loading rate of 2 g COD L(-1) d(-1) and a selenium loading rate of 3.16 mg Se L(-1) d(-1). Combining sequential filtration with ion chromatographic analysis for selenium oxyanions and solid phase micro extraction gas chromatography mass spectrometry (SPME-GC-MS) for alkylated selenium compounds allowed to entirely close the selenium mass balance in the liquid phase for most of the UASB operational runtime. Although selenate was removed to more than 98.6% from the liquid phase, a less efficient removal of dissolved selenium was observed due to the presence of dissolved alkylated selenium species (dimethylselenide and dimethyldiselenide) and colloidal selenium particles in the effluent. The alkylated and the colloidal fractions contributed up to 15 and 31%, respectively, to the dissolved selenium concentration. The size fractions of the colloidal dispersion were: 4 to 0.45 mum: up to 21%, 0.45 to 0.2 mum: up to 11%, and particles smaller than 0.2 mum: up to 8%. Particles of 4 to 0.45 mum were formed in the external settler, but did not settle. SEM-EDX analysis showed that microorganisms form these selenium containing colloidal particles extracellularly on their surface. Lowering the temperature by 10 degrees C for 6 h resulted in drastically reduced selenate removal efficiencies (after a delay of 1.5 d), accompanied by the temporary formation of an unknown, soluble, organic selenium species. This study shows that a careful process control is a prerequisite for selenium treatment in UASB bioreactors, as disturbances in the operational conditions induce elevated selenium effluent concentrations by alkylation and colloid formation.
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PMID:Biological alkylation and colloid formation of selenium in methanogenic UASB reactors. 1868 30

As lack of electron donor (carbon source) is a key problem of in-situ denitrification in groundwater, slow-release organic carbon-source (SOC) materials were produced as appropriate electron donor in denitrification PRB. GPVAS and GEPVAS series were manufactured by blending starch and PVA together, with alpha-amylase as the additive, and their performance was detected through SEM and static batch experiments. The results showed that PVA formed the framework filling with starch molecule, and the carbon releasing process followed the law of second order kinetics. Equilibrium concentration of COD (c(m)) and release rate coefficient (k) were key factors of kinetics evaluation. Both c(m) and k of GPVAS-40 were the lowest. The influence of alpha-amylase to the performance of SOC materials was remarkable. The c(m) values would ascend rapidly with augmenting of alpha-amylase content, while the releasing speed rose when amylase activity was lower than 0.03 U/g and then decreased. Consequently, the releasing process was controllable through changing the content of starch and activity of alpha-amylase to meet needs of different situations and pollution of groundwater and improve the effect of in-situ nitrate removal.
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PMID:[Performance of slow-release organic carbon-source (SOC) materials for in-situ biological denitrification in groundwater]. 1883 70

Nanosized multi-walled carbon nanotubes (MWCNTs)/TiO2 composite and neat TiO2 photocatalysts were synthesized by sol-gel technique using tetrabutyl titanate as a precursor. The as prepared photocatalysts were characterized using XRD, SEM, FTIR and UV-vis spectra. The samples were evaluated for their photocatalytic activity towards the degradation of 2,4-dinitrophenol (DNP) under solar irradiation. The results indicated that the addition of an appropriate amount of MWCNTs could remarkably improve the photocatalytic activity of TiO2. An optimal MWCNTs:TiO2 ratio of 0.05% (w/w) was found to achieve the maximum rate of DNP degradation. The effects of pH, irradiation time, catalyst concentration, DNP concentration, etc. on the photocatalytic activity were studied and the results obtained were fitted to the Langmuir-Hinshelwood model to study the degradation kinetics. The optimal conditions were an initial DNP concentration of 38.8 mg/L at pH 6.0 with catalyst concentration of 8 g/L under solar irradiation for 150 min with good recyclisation of catalyst. The degree of photocatalytic degradation of DNP increased with an increase in temperature. The MWCNTs/TiO2 composite was found to be very effective in the decolorization and COD reduction of real wastewater from DNP manufacturing. Thus, this study showed the feasible and potential use of MWCNTs/TiO2 composite in degradation of various toxic organic contaminants and industrial effluents.
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PMID:Photocatalytic degradation of 2,4-dinitrophenol (DNP) by multi-walled carbon nanotubes (MWCNTs)/TiO2 composite in aqueous solution under solar irradiation. 1897 88

Multi-walled carbon nanotubes (MWNTs) without any metal ions were used as the catalyst, and investigated in the CWAO of phenol and aniline in a batch reactor. The structures of the MWNTs were characterized by means of SEM and TEM. It showed that the MWNTs, treated with the mixed acid (HNO3-H2SO4), displayed excellent activity and stability in the CWAO. Under the reaction temperature of 160 degrees C, the total pressure of 2.5 MPa, the initial concentration of 1000 mg/L and loading the catalyst of 1.6 g/L, 100% phenol and 86% COD were removed after 120 min reaction in CWAO of phenol. At the same operating conditions, 83% aniline and 68% COD removals were obtained in the CWAO of aniline solution when the initial concentration of aniline was 2 000 mg/L. The surface functional groups played the important role for the high activity of the MWNTs in CWAO of organic compounds.
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PMID:[Catalytic wet air oxidation of phenol and aniline over multi-walled carbon nanotubes]. 1906 37

The present study explores the degradation of azo dye (Congo red) by catalytic wet peroxide oxidation using Fe exchanged commercial Y zeolite as a catalyst. The effects of various operating parameters like temperature, initial pH, hydrogen peroxide concentration and catalyst loading on the removal of dye, color and COD from an aqueous solution were studied at atmospheric pressure. The percent removals of dye, color and COD at optimum pH(0) 7, 90 degrees C using 0.6 ml H(2)O(2)/350 ml solution and 1g/l catalyst was 97% (in 4h), 100% (in 45 min) and 58% (in 4h), respectively. The % dye removal has been found to be less in comparison to % color removal at all conditions, e.g. dye removal in 45 min and at above conditions was 82%, whereas the color removal was 100%. The results indicate that the Fe exchanged Y zeolite is a promising catalyst for dye removal. Fe exchanged catalyst is characterized using XRD, SEM/EDAX, surface area analyzer and FTIR. Though the dye, color and COD removals were maximum at pH(0) 2 but as the leaching of Fe from the catalyst was more in acidic pH range, pH(0) 7 was taken as operating pH due to almost comparable removals as of pH(0) 2 and no leaching of Fe ions.
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PMID:Catalytic wet peroxide oxidation of azo dye (Congo red) using modified Y zeolite as catalyst. 1913 90


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