Water and Wastewater
Year:2009 | Volume:20 | Issue:3 (71)|Papers Count:13

A main challenge in the Iranian water management system concerns the discrepancy between the needs and the potential for ensuring funds needed for projects. The growing financial load of large projects, particularly water resources development projects, on the government has made the public budget practically inadequate to meet the financial needs of significant infrastructural plans. The lack of transparency in the process of decision making in water management and especially a disregard for priorities in the selection of plans and projects for study or implementation have caused the number of ongoing plans to increase and the allocated funds to be inadequate for their timely implementation. This state of affairs no doubt means projects of too long durations, execution and management problems, and cost overruns of the plans. Prioritization of water resources development plans has been considered since 1984 as an important measure to facilitate the process of decision making in the national water management system. This article reviews the previous methods of water plan prioritization, highlights the weaknesses and strengths of each method, and introduces the most appropriate one for practice today. The proposed method consists of four subsystems: 1) Projects evaluation; 2) Computation of economic, financial, social, and environmental measures; 3) Multi-criteria prioritization; and 4) Coordination. Once the model is developed, one can expect to find uncertainties in the system and to use fuzzy logic to prioritize water resources development plans.

Groundwater contamination with arsenic (As) has been recognized as a serious problem and there are various reports from different regions, especially from Kurdistan Providence, indicating the presence of As in the from of arsenate and arsenite in water recourses. Removal of these compounds can be accomplished by various methods but they are all expensive. In this study, three concentrations (0.5, 1, and 1 mg/L) of iron filings (0.25, 0.5, 1 and 1.5 grams) were used as a cheap and available material for adsorption of As and the effects of contact time and pH as well as chloride and sulfate ion concentrations on removal efficiency were determined. Description of adsorption isotherms (Ferundlich and Langmuir) was accomplished. Finally, the data obtained were analyzed using the Excel softwere. The results indicate that iron filings show a high capability in adsorbing both arsenate and arsenic compounds from polluted water samples at pH 7 over a short contact time of 30 minutes. In fact, this cheap adsorbent shows good treatment when used at doses as low as 1g/L with no considerable interference by interfering anions (SO42- and Cl-). It appears that the absorbability of both arsenate and arsenite by iron filings can be expressed by Ferundlich isotherm with R2>0.96, whereas arsenate adsorption (with a R2 value of more than 0.96) can be better described by Langmuir isotherm than arsenite (with R2 value of more than 0.91). Results also indicate that the amount of iron added to water is much more than the standard value of 0.3 mg/L set for dinking water. Nevertheless, this method has far greater advantages in terms of costs and availability than similar methods. Besides, as removal by this method is efficient without pH modification, iron filing treatment of drinking water may, therefore, be recomnended as a convenient solution to the problem of water resources polluted with As in Iran.

Experiments were carried out to study the effects of high-energy electron beam irradiation on reactive azo dyes (Remazol blue 133%, and Remazol red) which are widely used in Yazd textile plants. Laboratory scale experiments were carried out using advanced 10 MeV electron beam accelerator service in Yazd Radiation Processing Center (YRPC). The irradiation dose was varied over 1, 3, 5, 8, and11 kGy. Dicoloration of the prepared dye solution was monitored by comparing the absorption spectra of the samples before and after irradiation. Mineralization of the dye solutions were estimated by measuring COD and PH of the irradiated samples. Our results show a color removal efficeincy of 83% in from different samples by applying 1 kGy irradiation dose. This value increases by up to 96% under 3kGy irradiation. pH and COD values decrease with increasing absorbed doses. COD removals for Remazol blue 133% and Remazol red samples were calculated as 20% and 18% for an absorbed dose of 1 kGy and 60% and 72% for an absorbed dose of 11 kGy, respectively.

Sludge volume index (SVI) and zone settling velocity (ZSV) are parameters to quantify the settleability of activated sludge. Natural wastes commonly enter the environment as useless material. The assessment of the influence these materials have on activated sludge settleability was the principal objective of this research. Natural wastes used included: maize stalk, almond shell, coconut shell, walnut shell, hazelnut shell, egg shell, peanut hull, and pine bark. The experiments were conducted in five stages and three iterations, based on the standard methods. Average values of SVI for the control (blank) sample was 823 mL/g. The optimum dosage of different natural wastes reduced SVI value to 100 mL/g (88 percent decrease). The average value of ZSV for the control (blank) sample was 1.222 m/h and different natural wastes increased ZSV of the control samples by up to 2 to 3 times. With this increase in ZSV, Surface Overflow Rate (SOR) could also be increased without losing its efficiency. Activated sludge return with natural additives caused an improvement in sludge settleability. Jar tests revealed that natural wastes typically act mainly as ballasting agents and to some extent as coagulator which causes a reduction in SVI.

A combination of ozonation and an aerobic biological process such as the activated sludge has been recently developed as an alternative solution for sludge reduction with the objective of minimizing the excess biological sludge production. In this study, two SBR reactors each with a capacity of 20 liters and controlled by an on-line system are used. Once the steady state conditions were set in the reactors, sampling and testing of such parameters as COD, MLSS, MLVSS, DO, SOUR, SVI, residual ozone, and Y coefficient were performed over the 8 months of research. Results showed that during the solid retention time of 10 days, the kinetic coefficients of Y and Kd were 0.58 mg biomass/mg COD and 0.058 1/day, respectively. In the next stage of the study, different concentrations of ozone in the reactor were intermittently used to reduce the excess biological sludge production. The results showed that 22 mg of ozone per 1 gram of MLSS in the reactor was able to reduce the yield coefficient Y from 0.58 to 0.23 mg Biomass/mg COD. In other words, the excess biological sludge reduced by 60% but the soluble COD increased slightly in the effluent and the removal percentage decreased from 92 in the blank reactor to 76 in the test reactor. While the amount of SVI and SOUR for this level of ozone concentration reached 6 mgO2/h.gVSS and 27 ml/g, respectively. No excess sludge was observed in the reactor for an ozone concentration of 27 mg per 1 gram of MLSS.

In this study, four aerobic sequencing batch reactors (SBRs) were operated under the same conditions for the treatment of milk wastewater at different organic loading rates (OLRs). Cylindrical Plexiglas reactors were run for 56 days (including 21 days of acclimatization and 35 days of data gathering). Effective volume, influent wastewater flowrate, and sludge retention time (SRT) of reactors were 5.5 L, 3.5 L/d, and 10 d, respectively. The average COD removal efficiency for the reactors R1, R2, R3, and R4 with influent OLRave values of 633, 929, 1915, and 3261 gCOD/m3d were 95, 96, 95, and 82 percent, respectively. The average effluent suspended solid (SS) for all reactors was lower than 44 mg/L. Also, except for R4 with an average effluent turbidity of 270 NTU, other reactors met the Iranian wastewater emission standard (50 NTU). In addition, the average sludge volume index of reactors R1 to R3 was found to be lower than 67 mL/g. According to the results, the overall variation of COD removal efficiency versus influent OLR shows a decreasing rate with a correlation factor of 0.8 (R2).

In this study, biodegradation of floating diesel fuel was investigated by using two gram negative strains designated as A1 and A2 which were isolated from a reservoir tank of a gas station in Isfahan. One of them was identified as pseudomonas aeruginosa. The percent removal of diesel fuel was evaluated for pure and mixture cultivations. The highest removal percent belomged to A1, which was able to remove 88% of the floating diesel fuel. Also the evaluation of emulsification index (E24) of the cultivation mixture indicates that the microorganisms can produce a significant amount of biosurfactant. The emulsification index values for A1 and A2 were 23% and 21%, respectively. pH, nitrogen source concentration, fuel concentration, and salinity at three levels were investigated and the optimum values of these parameters were determined at 8, 0.55 g/lit, 2%, and 8%, respectively.

Soil is a suitable medium for the growth and transport of different microorganisms. Recently, an increasing interest has been shown in the transport and fate of microorganisms in porous media due to the concern for potential outbreaks of diseases caused by surface and groundwater contamination. Soils in arid and semi-arid regions as in Iran contain considerable amounts of sulfates and carbonates which may influence the adsorption and filtration of bacteria. This research was carried out to determine the adsorption and filtration of Pseudomonas fluorescens through sand columns mixed with different amounts of calcium carbonate and calcium sulfate under unsaturated flow conditions. Four levels of calcium carbonate: 0, 5, 10, and 20 %w/w and three levels of gypsum: 0, 5, and 10 %w/w were mixed with sand and the treatments were arranged in a (completely randomized) factorial design with three replicates. The prepared mixtures were poured homogenously into Pyrex pyrex cylinders with height of 20 cm and internal diameter of 7 cm. A constant concentration (106 CFU m-1) of cylinders 20 cm high and 7 cm in internal diameter. A constant concentration (106 CFU m-1) of bacteria suspensions was supplied at the upper boundary limit of the columns in a steady state flow and was followed for five pore volumes (PV). The bacteria concentration was measured at 0-5, 5-10, 10-15, and 15-20 cm sections of the columns immediately after leaching. The results showed that calcium sulfate and calcium carbonate were able to significantly influence the filtration of bacteria in all measured sections. The combination of carbonate sulfate and calcium carbonate treatments also significantly increased the physical filtration of bacteria along the columns. The retained bacterial profiles and the filtration coefficient obviously showed that the bacteria were held mostly in the upper layers of the columns. Enhanced physical filteration, tortuosity, and reduced apparent pore water velocity are known to be important in bacterial filtration under unsaturated conditions along the column layers. Therefore, these results imply that soils with calcium carbonate and calcium sulfate may play an important role in bacterial filtration and, thereby, in reducing the pollution of water resources.

The purpose of this study was to develop a model of the Karkheh Dam Reservoir that can (1) simulate temperature and water quality in the reservoir, (2) aid in developing a more in-depth understanding of reservoir circulation and quality as well as the processes affecting these, and (3) carry out a sensitivity analysis to examine the response of the model to specific parameters and coefficients and tributaries concentration. The two-dimensional model CE-QUAL-W2 was used to simulate the hydrodynamics, temperature, and water quality in the Karkheh Reservoir over the years 2005 through 2006. Input data included Lake Bathymetry, meteorological conditions, inflow rates, inflow temperature, water quality, and lake outflows. The parameters and coefficients affecting model calibration included PO4, NH4, NO3, DO, and Chlr a concentration. Other simulated constituents included dissolved and particulate organic matter, total suspended and dissolved solids, CBOD, and pH. Calibration and validation of water temperature and water quality relied upon vertical profile data taken in the four parts of the lake. Model calibration was accomplished during May to December 2005 and later evaluated during the period from December 22, 2005 to July 22, 2006. The model results show approximately proper convergence to observed data. After considering the eutrophication process in the Karkhe Reservoir, sensitivity analysis was performed on important parameters affecting temperature and water quality simulation. Also, sensitivity analysis was performed on tributaries concentration to predict system reactions. The results show that phosphorus concentration is a limiting factor in the eutrophication process in the Karkhe Reservoir.

River sediments are a mixture of eroded soils washed in from the upstream areas that can be put to reuse. Depending on the particle size, heavy metals concentration, and the physical and chemical characteristics of the dredged sediments, they can be used for a variety of applications such as wild habitant development, agricultural soil enrichment, or for manufacturing constructional materials. The objective of this study was to determine the physico-chemical characteristics of the Karoon River sediments at different depths and in different seasons at 4 gauging stations along the river in the city of Ahvaz. Samples were collected from 4 depths (0-25, 25-50, 50-75, and 75-100 cm) by a pistonic sampler in the spring and summer seasons (Feb. 2008 and Sep. 2008). The sediment samples were analyzed to determine concentration of heavy metals (Cr, Co, Cu, Zn, Pb, Cd, and Ni), OM%, CEC, TN, P, and soluble cation and anion concentrations .The results showed that the concentration of heavy metals, EC, pH, OM%, TN, and P in the shallower sediments were higher than those of the deeper samples. The results also showed that copper concentration was at its upper limit but TN%, P, and OM% in the sediments were low. However, EC, pH, and potassium concentration in sediments were at their normal levels. It was concluded that the sediments could be recommended for reuse in farms where farm products are not used as food or for direct human use.

Water losses are inevitable in urban water distribution systems. The two approaches adopted nowadays to combat this problem include management of hydraulic parameters such as pressure and leakage detection in the network. Intellitgent pressure management is a suitable technique for controlling leakage and reducing damages due to high operating pressures in a network. This paper aims to investigate the effects of pressure reduction on leakage. The EPANET 2.10 software is used to simulate the water distribution network in the Sarafrazan District, Mashhad, assuming leakage from network nodes. The results are then used to develop a pressure variation program based on the patterns obtained from the simulation, which is applied to the pressure reducing valve. The results show that pressure management can reduce nightly leakage by up to 35% while maintaining a more uniform pressure distribution. Implementation of the time-dependent pressure pattern by applying programmable pressure reducing valves in a real urban water distribution network is feasible and plays a key role in reducing water losses to leakage.