Iranian Journal of Environmental Health Science and Engineering
Volume:7 Issue: 5, 2010

Biodegradation and decolorization of Drimarene blue K2-RL (anthraquinone) dye by a fungal isolate Aspergillus niger SA1 was studied in self designed lab scale bioreactor system with different solid supports. Aspergillus niger SA1, was efficiently immobilized on sand and sodium alginate beads. The immobilized cells were used in the form of fluidized bed reactor for textile dye (Drimarene blue) removal. Both the reactors were operated at room temperature and pH=5.0 in continuous flow mode with increasing concentrations of dye in simulated textile effluent. The reactors were run on fill and draw mode, with hydraulic retention times of 24-72 h. The fluidized bed bioreactor with sand as immobilizing support (FBR1) showed overall better performance as compared to fluidized bed bioreactor with sodium alginate as immobilizing support (FBR2). The average overall color, BOD and COD removal in the FBR1 system were up to 78.29, 70.81 and 83.07% respectively, with 50 ppm initial dye concentration and HRT of 24 h. While 72.19%, 86.63% and 74.74% removal of color, BOD and COD were observed, respectively, in FBR2 with the same conditions. Reductions in BOD and COD levels along with color removal proved that decolorization and biodegradation occurred simultaneously.

Presence of heavy metals is considered to be a major challenge in wastewater treatment. In this research the effect of heavy metals such as nickel (Ni), chromium (Cr), and manganese (Mn) on fouling in membrane bioreactors was investigated. Fouling tendency of a cellulose acetate membrane was evaluated in MBRs with different concentrations of the mentioned elements. The concentrations of extractable extracellular polymeric substances in the mixed liquor at the steady-state condition and different concentrations of heavy metals were compared. Also the effects of concentration of heavy metals on mean floc diameter, hydrophobicity, and hence the fouling propensity of membrane was investigated. The Analysis of variance (ANOVA) method has been used to illustrate the important factors for the prediction of the fouling behavior. Results showed that different salts of the same heavy metal ion and various concentrations of heavy metals in wastewater had different effects on sludge properties and hence induced different fouling tendency of sludge.

Application of a fluidized bed bioreactor working for treatment of colored wastewaters has been studied using Phanerochaete chrysosporium fungus immobilized in calcium alginate biogel beads. The working volume of the bioreactor was 1 L; experiments were performed at room temperature and pH of culture medium was initially adjusted to 4. Manganese Peroxidase activity, glucose and ammonium concentrations have been assayed daily along the 7 operating days. Azo dye Reactive Orange 16 was added to the bioreactor after 7 days of incubation and decolorization was assayed by spectrophotometer for 1 h intervals. Maximum Manganese peroxidase activity of 96±8 U/L was obtained on day 7, and 70±3 % decolorization was achieved after 6 h of dye addition. The results were compared to free cell cultures from previous studies and the role of agitation and immobilization of cells in increasing of the efficiency of decolorization was discussed. The mechanism and morphology of the immobilization of cells in ca-alginate beads were studied and the relationship between glucose and ammonium consumption and ligninolytic activity of fungi were discussed.

This investigation was performed on the biological removal of nitrogen from refinery's wastewater by the nitrification and denitrification process. In a petroleum refinery, removing of hydrocarbons is the main concern and nitrogen content is supposed to be negligible. The aim of this work was to search for nitrogen in Tehran Refinery wastewater and employing a biological technology to reduce this pollutant. Samplings were done in different points of wastewater treatment plant; influent to aeration unit, effluent of aeration unit and effluent of clarifiers. The results showed that despite of a high average removal efficiency of COD > 93%, the nitrogen removal during conventional activated sludge process was not efficient and sludge rising due to denitrification was observed within the clarifier. The analysis conducted in laboratory scale showed that a simultaneous nitrification and denitrification (SND) process could easily be realized in the same activated sludge plant by using the flocculating sludge and control of dissolved oxygen concentration. It was found that the higher MLSS value (10.0 g/L) and mixing rate (300 rpm) is effective in improving total nitrogen removal and overall SND performance. Our experimental results indicated that the SND process is very efficient for nitrogen removal from industrial wastewater.

Dewatering of waste activated sludge is a complex process because of the influences of different factors. Previous studies have shown that extracellular polymeric substances (EPS) are the major constituents of waste activated sludge. Results of previous works on determining the role of EPS on dewaterability of WAS are limited, different and sometimes seem controversial. In this study, protein and carbohydrate parts of EPS were measured in untreated, sonicated and digested waste activated sludge and the relationship between these parameters to dewaterability of sludge was found. In untreated sludge samples, a decrease of dewaterability (increase of specific capillary suction time) was observed with the decrease of protein and carbohydrate parts of EPS. On the other hand, sonication and digestion caused an increase in the amounts of protein and carbohydrate parts of EPS, but a decrease in dewaterability of sludge samples. It is also shown that sonication, in general, made the dewatering of sludge more difficult even after biological digestion. Sonication, however, caused 26.5%, 18.6% and 3.8% dewaterability improvement at sonication intensities of 18.4, 73.6 and 165.6 W/cm2, respectively.

Heavy metals accumulation in soils under the application of sewage sludge and effluent from wastewater treatment plants is a major environmental concern. Transport of heavy metals through the soils may eventually lead to the groundwater contamination and their accumulation in soils and crops. Silt loam soils covered by sludge and effluent of Tehran wastewater treatment plant were used in this study. The vertical and horizontal distributions of sludge-borne Cd, Cr, Zn, Pb, Fe, Cu and Ni were studied within four plots. Measured loadings of heavy metals to the plots from the sludge application were Fe, 284.75, Pb, 90.28, Zn, 109.5, Ni, 60.28,Cu, 27.76 Cr, 28.58 and Cd, 4.5 mg/kg. Two hundred and forty soil samples were taken from areas within the plots and up to 100 cm depth on each side of the plots. Leachate water from the plots which contaminates groundwater was collected and the concentrations of heavy metals were measured. The determined concentration of sludge-borne in leachate Cr, Ni, Zn, Fe, Pb, Cu and Cd were 0.803, 0.785, 0.532, 0.439, 0.110, 0.180 and 0.019 mg/l respectively. The results of this study can be used for the management of effluent and sewage application in agricultural lands and crop production. The groundwater quality can be monitored and improved as well.

Polysulfone nanofiltration (NF) membranes with higher pore size and higher charge density are capable of removing metal ions from water. In the present study the graft-modification of ultrafiltration (UF) membranes by UV irradiation was considered. UF membranes were prepared via phase inversion method using polysulfone (17% wt) as polymer and N-methyl-2-pyrrolidone (75% wt) as solvent in which polyethylene glycol with molecular weight of 3000 g/mol (8% wt) was used comparatively as big sized pore former. Prepared UF membrane was modified by polymerization of acrylic acid as monomer in the presence of UV irradiation on the membrane surface. Effect of grafting conditions including acrylic acid concentration and irradiation time on membrane performance properties as pure water flux and sulphate rejection were studied. FTIR-ATR and AFM were employed to characterize the chemical and structural changes on the modified membrane surface. The results showed pure water flux significantly declined and sulphate rejection improved with increase in both graft irradiation time and monomer concentration. At 25 °C, pure water flux of this prepared NF membrane was 13.26 L/m2.h at 300 kPa. The rejection of 96.3% and 58.8 % to Na2SO4 and MgSO4 solutions were obtained respectively. The RMS roughness of this membrane was 1.65 nm which is in the range of NF membrane properties.

Laboratory-scale reverse osmosis (RO) studies were carried out to determine feasibility of the process for treatment of Tehran refinery oily wastewater. The effects of transmembrane pressure (TMP), cross flow velocity (CFV), temperature and pH on permeation flux and separation performance of the thin film composite (TFC) polyamide (PA, type UTC-70UB) RO membrane were investigated. At original effluent composition, high rejection of TDS (87.0%), COD (95.0%), BOD5 (95.3%), TOC (90.0%), turbidity (81.8%) and oil and grease content (86.1%) along with complete rejection of color, free oil and TSS were achieved with a reasonably high flux of 50 L/m2h. Permeation flux was found to improve with increasing TMP, CFV and temperature at constant feed concentration but rejection decreased slightly. The pH effects were found to be complex; by increasing acidic and basic nature of the feed, permeation flux was found to increase and rejection to reduce. The results showed that, RO is very suitable for treating and recycling refinery oily wastewater effluents. Also, fouling of the membrane completely followed Hermia's model (cake filtration mechanism).

Uranium is a toxic and radioactive heavy metal found in nuclear effluents and should be treated by considering economic and environmental aspects. In this study, uranium separation from synthetic effluents by electrodialysis was investigated. Taguchi method was used to plan a minimum number of experiments. An orthogonal L9 array (three factors in three levels) was employed to evaluate the effects of flow rate (5, 15 and 30 mL/min), voltage (10, 20 and 30 V) and feed concentration (200, 500 and 1000 mg/L) on performance of uranium separation. ANOVA method was applied to evaluate the relative effect of each factor. Results showed that increasing voltage and decreasing flow rate improves performance, and initial concentration does not affect it considerably. The effect of flow rate was more significant. Electrodeionization was applied for final treatment of dilute solutions. The effect of magnesium ions in the feed solution caused a decrease in uranium removal. The relation between current and voltage was linear. A comparison between actual and theory energy consumption showed a considerable difference due to concentration polarization. Based on the results, electrodialysis was found to be very effective for uranium removal from wastewaters.

Dye removal from wastewater has received considerable attention with several classes of dye being investigated. Methylene blue has wide applications and can cause some harmful effects in humans. The use of clean technology of low-priced and biodegradable absorbents could be a good tool to minimize the environmental impact caused by dye manufacturing and textile effluents.The present study deals with the preparation of a novel sIPN (semi interpenetrating) hydrogel composed of copolymer of acrylamide and acrylicacid with poly vinyl alcohol as linear polymer there in. The adsorption abilities of hydrogels with different molar ratios for removal of methylene blue from aqueous solutions were investigated. A weighed quantity of dry hybrid hydrogel was immersed in 50 ppm MB solution and kept at 37 oC. The amount of MB adsorbed was measured spectrophotometrically (λ= 661.6 nm) in periodically taken solution samples. The maximum dye adsorption concentration for hydrogel composites was 95% and no dye desorption of MB/polymer solutions was observed. Hence, the composites can be used as good membranes for removal of cationic dyes from aqueous solutions while they do not release harmful materials into water.

In this research, sludge of Jalaliyeh water treatment plant in Tehran was used as an alternative coagulant for the removal of a specific type of acid dye (acid red 119 (AR119)). For this purpose, the effect of initial pH, coagulant dose and initial dye concentration on dye removal efficiency were investigated. Results showed that the dye removal rates were largely dependent on pH. When the solution pH was increased from 3 to 8, the dye removal rates decreased from 96.3% to 2.3%. The removal efficiencies of the dye using 130-350 mg dried sludge/L were more than 90% at initial pH =3. With the increase of initial dye concentration in the range of 10-200 mg/L, the removal efficiency increased at first (from 10-40 mg/L) and then declined. So, sludge of Jalaliyeh water treatment plant may be considered as an appropriate coagulant for the removal of AR119 dye.