WATER AND WASTEWATER
Year:2007 | Volume:18 | Issue:1 (61)|Papers Count:9

Traditional lumped and conceptual hydrological models are appropriate for dealing with certain aspects of a major portion of current water resources management. However, more advanced tools are required for integrated water resources management. In this research, an integrated model to account for qualitative and quantitative stream-groundwater interactions is developed for application in large-scale, integrated, water resources management. One of the challenges in understanding the interactions between stream and groundwater systems lies in their different time scales. In this paper, the stream quantity model is developed and is embedded into groundwater quantity model using the couple method. Then the stream quality model and the groundwater quality model are integrated using an uncouple approach, with mesh generation to ensure stability of the numerical method. Confirmation of the coupled-uncoupled model was examined using analytical solution from previous studies.

The aim of present work was to investigate effects of the water pressure and ion compound present in water to be treated on nitrate removal efficiency of a nanofiltration membrane. Experiments were performed using sodium salts (NaNO3, NaZSO4, NaF), KNO3, Ca(NO3)2, and Mg(NO3)2 added to tap water. The effects of operating pressures were investigated for a pressure range of 4-10 bars for a nitrate concentration of 150 mg.L-1(NO3-). The effects of concentration levels were studied for the levels 50, 100, 150, 200, 250 and 300 mg.L-1(NO3-). Finally, the effects of anions were investigated for concentration levels of 50, 100, 150, 200 and 250 mg.L-1 of F- and  SO42-. The results showed that nitrate removal increased with increasing pressure by up to 8 bars beyond which removal goes steady. Increased nitrate salt concentrations in monovalent salts led to reduced nitrate removal but in divalent salts led to increased nitrate removal. The effect of associated cation on nitrate removal was observed to be higher in the case of NaNO3 compared to KNO3. It was further observed that increasing sulfate ion concentrations reduced nitrate removal while increasing fluoride levels increased nitrate removal.

Coagulation and flocculation are essential processes in water treatment plants. Metal salts such as aluminum sulphate and ferric chloride are commonly used in the coagulation process in Iran. Poly-aluminum chloride (PAC) has been used recently in Baba-Sheykhali Water Treatment Plant in Isfahan. Synthetic coagulants have health problems associated with them and are additionally uneconomical for use in developing countries. In this study, PAC and Moringa oleifera seed extract were compared for their efficiency as coagulants. Moringa oleifera, locally called "oil gaz" in Iran, grows in southern parts of Iran. One variety of this tree, Moringa progeria, is indigenous to Iran. For the purposes of this study, lab experiments were performed using distilled water containing synthetic caoline. Four turbidity levels of 10, 50, 500, and 1000 (NTU) and four pH levels of 5, 6, 7, and 8 were used for the jar test. It was found that oleifera seed extract was capable of removing 98, 97, 89, and 55% of the turbidity in the four experiments at optimum concentration levels of 10-30 (mg/I) for all four pH levels of 6 to 8, respectively. PAC, in contrast, removed 99, 98, 95, and 89% of the turbidity at optimum concentrations of 20-30 (mg/I) for a pH level of 8. The results indicate that Moringa oleifera seed extract has little effect on pH level and enjoys higher removal efficiency for higher turbidity levels. Reducing pH level decreased PAC turbidity removal efficiency.

UV/H2O2, UV/H2O2/Fe (II) and UV/H2O2/Fe (III) processes are very effective in removing pollutants from wastewater and can be used for treatment of dyestuff units wastewaters. In this study, Rhodamine B was used as a typical organic dye. Rhodamine B has found wide applications in wax, leather, and paper industries. The results from this study showed that this dye was degradable in the presence of hydrogen peroxide under UV-C irradiation (30W mercury light) and Photo-Fenton process. The dye was resistant to UV irradiation. In the absence of UV irradiation, the decolorization efficiency was very negligible in the presence of hydrogen. The effects of different system variables such as initial dye concentration, duration of UV irradiation, and initial hydrogen peroxide concentration were investigated in the UV/H2O2 process. Investigation of the kinetics of the UV/H2O2 process showed that the semi-log plot of the dye concentration versus time was linear, suggesting a first order reaction. It was found that Rhodamine B decolorization efficiencies in the UV/H2O2/Fe (II) and UV/H2O2/Fe (III) processes were higher than that in the UV/H2O2 process. Furthermore, a solution containing 20 ppm of Rhodamine B was decolorized in the presence 18mM of H2O2 under UV irradiation for 15 minutes. It was also found that addition of 0.1 mM Fe(II) or Fe(III) to the solution containing 20 ppm of the dye and 5mM H2O2under UV light illumination decreased removal time to 10 min.

In this study, the nitrification process using enriched ammonia oxidizing bacteria was used for ammonium removal from coke wastewater of Isfahan Steel Company (ISCO). Influent and effluent samples containing ~600 mg 1-1 ammonium and 2530-550 mg 1-1 phenol were collected. For comparative assessment, ammonia removal was performed on artificial media in which removal of ammonium took a shorter time (8 days) than in the real wastewater. Ammonium removal efficiency from the effluent was higher than that from the influent due to the reduced phenol content in the former. The best result occurred in the treatment composed of effluent, enriched nitrifies, and bicarbonate for which a record ammonium removal of 14 days was observed. MPN method was used to count and compare colonies of nitrifying bacteria in the samples. The enriched nitrifier sample containing 4.6x103 cell ml-1 was the best. The results show that phenol has inhibitory effects on nitrification. Carbonate ions and enriched nitrifying bacteria have positive effects on ammonium removal in all samples.

In this research, heavy metal resistant microorganisms were isolated from several industrial wastewater samples in order to determine their adaptability to metal concentrations higher than MIC.Investigation of these isolates may be used in future wastewater biological treatment processes. For this purpose, two industrial wastewaters were selected and their heavy metal contents, percentage of resistant bacteria, and adaptability of bacteria isolated from each metal to concentrations higher than MIC were determined through cultures on the same metal in each case over long periods of incubation.Our findings indicated that the highest resistance belonged to the Zinc-resistant microorganisms while the lowest belonged to cupper-resistant ones. Also, the zinc-resistant bacteria showed the highest adaptability at zinc concentrations of 16 and 24 mM/L (80%) followed by cupper-resistant bacteria at metal concentrations of 4 mM/L (40%), Cd-resistant bacteria at 12 and 16 mM/L (30%), and finally Pb-resistant ones (around 0%). Compared to results from previous studies, the resistant isolates in the present study showed higher resistance and adaptability.

Application of electron beam as a strong oxidation method for disinfection of drinking water and wastewater has been investigated. Drinking water samples were prepared from wells in rock zones in Yazd Province. Wastewater samples were collected from Yazd Wastewater Treatment Plant. Samples were irradiated by 10 MeV electron beam accelerator at Yazd Radiation Processing Center. The irradiation dose range varied from 0.5-5 kGy. Biological parameters and microbial agents such as aerobic mesophiles and coliforms including E. coli count before and after irradiation versus irradiation dose were obtained using MPN method. The data obtained from irradiated water and wastewater was compared with un-irradiated (control) samples. The results showed a removal of 90% of all microorganisms at irradiation doses below 5 kGy, suggesting electron beam irradiation as an effective method for disinfection of waste water.

Zebra mussel (Dreissenidae polymorpha) is capable of filtering Great volumes of water due to its high population density. In this study, Nitrate and Phosphate removal capability of 3 shell masses (20, 40, and 60 gr) in urban wastewater was investigated based on filtering rate measurements (using simultaneous phytoplankton, chlorella, and Scenedesmus cultures) and indirect absorption of nitrate and phosphate in open and closed systems with 3 to 10 replications. Open and closed systems showed a positive correlation between shell weights and Nitrate and Phosphate filtration rates (R2=0.99) but a negative correlation between influent Nitrate and Phosphate concentrations and their filtration rates (R2=0.97). Increasing of shell weights in the open system resulted in absorption rates of 0.08-0.2mg.1-1 of the shell dry weight for Nitrate and 0.02-0.04 mg.1-1 for Phosphate. In the closed system, these rates were 0.03-0.11 mg.1-1 of the shell dry weight for Nitrate absorption and 0.01-0.02 mg.1-1 for Phosphate.These results show that shell masses have a low nitrate and phosphate removal efficiency, especially in the case of phosphate, and they can not be, therefore, recommended for urban wastewater treatment.

The anaerobic baffled reactor (ABR) includes a mixed anaerobic culture separated into compartments and a novel process with a series of vertical baffles at each compartment. It dose not require granulation for its operation, resulting in shorter start-up time. In this study, the feasibility of the ABR process was investigated for the treatment of wheat flour starch wastewater. Simple gravity settling was used to remove suspended solids from the starch wastewater and used as feed. Start-up of a reactor (13.5L with five compartments) using a diluted feed of approximately 4500 mg/L chemical oxygen demand (COD) was accomplished in about 9 weeks using seed sludge from the anaerobic digester of a municipal wastewater treatment plant. The reactor with a hydraulic retention time (HRT) of 72 h at 35°C and an initial organic loading rate (OLR) of 1.2 kgCOD/m3.d showed a removal efficiency of 61% COD. The best reactor performance was observed with an organic loading rate of 2.5 kgCOD/m3.d (or hydraulic retention time of 2.45 d) when a COD conversion of 67% was achieved. The main advantage of using an ABR comes from its compartmentalized structure. The first compartment of an ABR may act as a buffer zone to all toxic and inhibitory materials in the feed and, thus, allows the later compartments to be loaded with a relatively harmless, more uniform, and mostly acidified influent. In this respect, the later compartments would be more likely to support active populations of the relatively sensitive methanogenic bacteria.