"The Effects of Temperature and PH on Settlability of Activated Sludge Flocs"

The effluent quality of a sewage treatment plant using activated sludge process and finally secondary treatment depends on the flocculation efficiency and settling of the flocs. The survey of various treatment processes in water and wastewater treatment shows that temperature and pH are the important factors affecting efficiency of flocculation and settling properties. This study was performed to determine the effects of pH and temperature on settling of the flocs in activated sludge process. It was carried out for three months in two phases, using mixed liquor suspended solids (MLSS), obtained from aeration tank from one of wastewater treatment plants in Tehran. In the primary phase, the temperature of samples was increased from 15°C to 35°C. As a result, the sludge volume index (SVI) and effluent suspended solids increased and consequently, COD removal percent decreased. In the second phase, the pH was increased from 5.7 to 9. As a result, SVI and effluent suspended solids decreased and COD removal percent increased

Removal of Methylene Blue Dye from Synthetic Wastewater with Bone Char

"n "n "nBackgrounds and Objectives: Dyes  are  organic  materials  with  complex structures, toxic,  carcinogenic, teratogenic,nonbiodegredable properties and!the most!important pollutants of textile industrial wastewaters. The goal of this study was to survey the feasibility application of bone char (BC) as a sorbent for the  of methylene blue (MB) from synthetic wastewater.The sub goals of the research!were to determine!the adsorption isotherm, !effects of primary concentration of dye, adsorbent!dose, contact!time, and pH for the adsorption of MB with BC."nMaterials and Methods: BC was prepared under laboratory conditions by using of electrical furnace at 400°C for 2h. The prepared BC was crushed and pulverized by standard ASTM sieves with range of 10-16mesh(1.18-2mm).The  chemical composition  and  solid  structure  of BC was  analyzed using X-ray diffraction(XRD) and  scanning  electronic  microscopy (SEM). Measurement  of  the surface area was carried out by N2 gas via BET isotherm and Belsorb software. The concentration of dye was measured by photometric!method (663nm)."nResults: Predominant!compositionof BC is calcium hydroxyl apatite (Ca5 (PO4)3OH with 14m2/g surface area. The results of this study showed that increasing of primary concentration of dye, adsorbent dose and pH (5 to12) would lead to increasing of adsorption/removal of MB dye.Equilibration of dye adsorption was reached at lapse of 2h andoptimum pH for adsorption of MB with BC found in the rage of 8.5-12.Adsorption of MB witht BC complies witht freundlich isotherm(R2:0.99)."nConclusion: Bone char is a cheap component that can be used as an adsorbent in water and wastewater treatment. Based on optimum pH of 8.5-12 found for the removal of MB and the fact that many of textile!industrial wastewaters have an alkaline pH, this adsorbent can be!used for the removal of dyes from these wastewaters

Application of Enzymatic Polymerization Process for the Removal of Phenol from Synthetic Wastewater

"n "nBackground and Objectives: Phenolic compounds are presence in many industrial wastewaters, and have been classified as priority pollutants. Application of several conventional processes due to high cost and low efficiency has been limited. Thus, new methods such as enzymatic polymerization seem to be preferable and effective processes with high potential to substitute the conventional processes. This study was carried out to evaluate Raphanus sativus extract as a peroxides enzyme source for polymerization and removal of phenol from synthetic wastewater in the presence of hydrogen peroxide."nMaterials and Methods: The study was performed in batch reactor at room temperature. Peroxidase enzyme was extracted from Raphanus sativus plant roots . Primary concentration of phenol in wastewater was 100 mgl-1. The concentration of phenol and enzymatic activity was been measuredby photometric assay."nResults: The results show that Raphanus sativus extract is a suitable source of peroxidase enzyme. Mean enzymatic activities in this extract was 3.107 Uml-1. Also, our results showed that elevation of extract volume lead to high efficiency of phenol removal, in which the increase in the extract volume from 5 to 50 ml, resulted in the efficiency of processes increased from 7.6 to 98.2 %. Also, sequencing addition of H2O2 and extract has improved the effects. The phenol removal efficiency of the reaction time after 3 h with single and three stages adding of reactants was 84.2 and 93.1% , respectively."nConclusion:Enzymatic polymerization can be used as an appropriate process for the removal of phenolic compounds from wastewaters. To meet the optimized condition in process, the ratios of phenol/ enzyme and H2O2/ phenol and sequences of the adding of reactants should be considered

Application of iron impregnated activated carbon for removal of arsenic from water

The presence of arsenic in drinking water is one of the greatest threats to public health. The aim of this experimental investigation was to study the removal efficiency ofAs(v) from water by application of iron-impregnated activated carbon(Fe-AC). Coating of activated carbon with iron salt was carried out by impregnation method and thermo-chemical reactions with using of 100 mM FeCl 3 solution. The Fe-AC was pulverized using ASTM standard sieves with the range of 16-20 mesh. The solid structure and surface characteristics of Fe-AC were determined using conventional techniques. Batch adsorption experiments were carried out with 300 and 600μg/L arsenate. Langmuir, Freundlich and Dubinin-Radushkevich models were used to describe the isotherm and energy of adsorption. The results of this study showed that 2.5 h contact time was enough to achieve the equilibrium. The adsorption of As(v) had a good compliance with Langmuir model (R 2 = 0.995 ) and the maximum adsorption capacity was obtained as 0.024 mg/g. The results of kinetic studies showed that As(v) adsorption on Fe-AC may be limited by film diffusion step (m=0.26). The mean free energy of adsorption (E) calculated from Dubinin-Radushkevich isotherm was found to be 1.52 kj/mol which implies that the adsorption of As(v) on Fe-AC is a physical adsorption. The results indicated that Fe-AC is one of the suitable adsorbents which can be used for the treatment of arsenic contaminated waters

Equilibrium And Kinetics Study Of Reactive Red 123 Dye Removal From Aqueous Solution By Adsorption On Eggshell

The aim of this study was to determine the equilibrium and kinetics adsorption of reactive red 123 dye (RR 123) from aqueous solution with chicken’s eggshell as an adsorbent. The initial concentrations of reactive red 123 dye were selected in the range of 25 and 50 mg/L. The target adsorbent was prepared in laboratory conditions and pulverized by ASTM standard sieves. Measurement of the adsorbent surface area was carried out via Brunauer-Emmett-Teller isotherm. The experimental data were analyzed with Langmuir, Freundlich and Temkin isotherm models. The results showed that the calcium components were the main constituents of eggshell (around 95% Ca). The experimental adsorption isotherm was in good concordance with Langmuir and Freundlich models (R2>0.90) and based on the Langmuir isotherm the maximum amount of adsorption (qmax) was 1.26 mg/g. Increase of the eggshell dose and the solution temperature beyond 45ºC led to decrease of the adsorbed dye per mass unit of the adsorbent, but increase of the solution pH up to 9 led to the improvement of dye adsorption. The kinetic studies revealed that the adsorption of reactive red 123 was rapid and complied with pseudo-second order kinetic (R2= 0.99), with the kinetic constant of 0.02 g/mg.min

Application of Solar Irradiation / K2S2O8 Photochemical Oxidation Process for the Removal of Reactive Blue 19 Dye fromAqueous Solutions

"n "n "nBackgroundandObjectives: Dyes are organic compoundswith complex structures,which due to toxicity, carcinogenicity and nonbiodegredabity, this type of pollutants is one of the most important pollutants of the environment. The goal of this researchwas to study the feasibility of the application of solar irradiation in presence of potassium persulfate (K2S2O8) for the removal of Reactive blue19 (RB19) from synthetic wastewater."nMaterials andMethods: This researchwas carried out in laboratory scalewith using of 200ml volume of batchphotoreactor.The effectsofoperatingparameters suchas concentrationofK2S2O8,pH,photoexposure time and preliminary concentrations of dye on decolorization have been evaluated.Different concentrations of pollutant inwastewaterwere prepared by solution of variousmasses of RB19 on tapwater. The reactors were exposedwith natural solar irradiation as aUVAsource from11 amto 14 pm.Themaximumabsorbtion wave length of this dye (!max) was determined by spectrophotometer (Unico, 2100). The measurement of dye concentrations was determined with using of standard curve and its best line equation"nResults:Analysis of absorbtion spectra showed that the !max of RB19 is 592 nm. The average intensity of the UVA irradiated from solar system was 54.6 µW/Cm2. The results of decolorization process showed that 38.2%of this dye can be removed within 3 hr in the presence of potassium persulfate and decreasing of pH leads to the elevation of dye removal efficiency. Based on these findings, the efficiency of dye removal with 3h photoexposure time and pH ranges of 4,6 and 8 were found to be 98.2 88.5 and 78.5%, respectively.Also, the results showed that increasing of K2S2O8 dosage leads to elevation of dye removal efficiency in 3h photoexposure time and K2S2O8 dosages within 1-5mmol/L, with the removal efficiency of 75,86,92,95 and 98.5%, respectively.Analysis of data indicates that the kinetic of the removal of RB19 with this process is a first order reaction which its rate constant is 0.01min-1."nConclusion: Due to the operation problems presented in heterogeneous photocatalitical processes such as catalysts separation and high costs of operation and maintenance of these processes caused by manmade sources of irradiations; homogeneous photocatalitical process with using of potassium persulfate associated with natural solar irradiation can be used as a suitable process for the removal of dyes from textile industries wastewaters