مجله آب و فاضلاب
پیاپی 96 (خرداد و تیر 1394)

Removing pollutants from aquatic ecosystems, especially from drinking water, has always been a major concern for scientists. Recent decades have witnessed the widespread application of natural compounds used as adsorbents to remove various pollutants. On the other hand, studies have proved nanotechnology to be an effective way of removing pollutants. A new type of sponge belonging to the family Demospongiae that has nano holes and is native to the Persian Gulf was investigated for the first time in the present study for use as an adsorbent to remove calcium, magnesium, cobalt, cadmium, and lead ions from water. For this purpose, adbsorption in sponges of different aggregate sizes, contact time, particle size, and ambient pH were measured. The results showed that the proposed sponge is capable of adsorbing the above-mentioned metal ions to various degrees. While small amounts of calcium, magnesium, and cobalt were adsorbed by this sponge, cadmium recorded a higher adsorption of 2.37 mg/g at pH=5. The highest adsorption level of 79.19 mg per gram of adsorbent was recorded for lead at a pH range of 4.5-5 with a mesh size of 230. This is the highest adsorption ever recorded for lead in the literature on selective separation of lead from the other ions.

In this research, ozonation was used for treating wastewater containing acid orange 7 in a batch reactor. The independent parameters were initial dye concentration, pH, and ozone mass and volumetric flow rates. The experiments were conducted with initial concentration in the range of 5-250 mg/L, pH levels of 4-12, ozone mass flow rates of 12 and 20 mg/min, and volumetric flow rates of 0.5 and 1 L/min. Based on the results, the optimum conditions were achieved at a dye concentration of 100 mg/L, a pH level of 11, an ozone mass flow rate of 20 mg/min, and an ozone volumetric flow rate of 1 L/min. Dye and COD removal efficiencies in these conditions were 100% and 30%, respectively, after 150 minutes. According to the absorbance curves, light absorbance of wastewater increased by 100% in the range of 450-500 nm by ozonation under the optimum conditions after dye removal. Based on the GC-Mass test and the values of LD50, acid orange 7 was converted to toxic compounds of aniline, 1-naphthylamine, 2-naphthol, and 1, 4-naphthalenediol indicating that ozonation had to be continued until complete COD removal. Based on the Taguchi experimental design data for real textile wastewater, the optimum conditions were obtained for a pH level of 11, a gas flow rate of 1 L/min, and an ozonation injection rate of 20 mg/min.

Water scarcity is now one of the most vital challenges in most countries around the world.Tehran, as the most populated city and the capital of Iran, has also been recently experiencing a shortage of water, which may turn into a threatening crisis for the region if a proper water management system is not put in place. Employing dynamic modeling and the dynamic system analysis method, the present study was conducted to address the integrated water resources management in Tehran region taking advantage of a comprehensive outlook of the water resources system in the region and implementing a behavioral simulation in the Vensim software. Once pattern validation was accomplished, the policies developed to decrease the gap between water demand and supply regarded as the main variable and the reference behavior of the system were examined. The simulation results showed that, compared to other policies, population control and technological development polices seemed to have more significant effects on improving the water situation in the region. However, it is also observed that if combined with such other polices as taxation and pricing, the above-mentioned policies will work more effectively.

Clean water is vital to both human life and preservation of ecosystems. The goal of this study was to investigate the antibacterial effects of ZnO nanoparticles and filters coated with different sizes of ZnO nanoparticles on Escherichia coli (ATCC: 25922) and Enterococcus faecalis (ATCC: 11700) as the predominant bacteria in contaminated water. The antibacterial effects of ZnO nanoparticles (5 and 100 nm in size) at concentrations of 12.5, 25.0, 50.0, and 100.0 mg/ml were determined using the well diffusion method in vitro. Minimum inhibitory concentrations and minimal bactericidal concentrations of ZnO nanoparticles were determined by the broth micro-dilution method. In another part of the study, ZnO nanoparticles were coated on polypropylene filters using the precipitation method to investigate their removal efficiency. Filtration of contaminated water was performed using a standard number of the bacteria being tested. ZnO nanoparticles (5 nm) at a concentration of 100.0 mg/ml showed maximum sensitivity against E.coli and Enterococcus faecalis by inhibition zones of 14.00±1.73 and 11.67±1.52 mm, respectively. Maximum inhibitory concentration of ZnO nanoparticles was determined as 25mg/ml. A significant relationship was found between antibacterial activity and ZnO nanoparticles concentration (P. value <0.001). It may be claimed that treatment with polypropylene filters coated with ZnO nanoparticles (5nm) is an effective process for controlling bacterial growth and eliminating E.coli.

Performance of wastewater treatment plants (WWTPs) in Urmia, Khoy, Miandoab, Salmas, and Bookan were evaluated during the years 2008 to 2011 based on the reliability approach. The approach predicts the overall performance of WWTPs and their processes and, thereby, makes the screening of treatment technologies possible. The required BOD5, COD, and TSS data were collected using the records available at West Azerbayejan Water and Wastewater Company, local surveys, and interviews with operators. Statistical analysis was performed by SPSS. The valid Niku modeling was employed to calculate the Rmeasured, Revaluated, COR, and expected percentages of compliance with discharge standards and a significant relationship was found among these parameters. The results also showed the log normal distribution of effluent characteristics. Furthermore,SBR and biolac processes exhibited higher values of Rmeasured (90-100%), Revaluated (93-100%), and expected percentages of compliance with the discharge standards (95-99.97%) in all the WWTPs studied but lower values of COR (0.41-0.64) than those in aerated lagoons. The coefficients obtained in this study can, therefore, be used for the development and construction designs of similar systems.

Biosorption is a most effective technology for the removal of such toxic substances as heavy metals. The objective of this study was four-fold: 1) to isolate lead resistant Pseudomonas strains, 2) to determine the optimal conditions of their growth, 3) to obtain the minimum inhibitory concentration of lead, and 4) to evaluate the bioremoval of lead from culture solutions. For the purposes of this study, oil-contaminated wastewater samples were collected from Khuzestan region and transferred to laboratory where they were homogenized and serially diluted up to 10-10 with sterile saline before they were cultured in Luria Bertani agar medium containing 5ppm of lead nitrate. Resistant strains were then isolated at 37°C for 24h. The samples were subsequently cultured in Macconkey agar for isolation of appropriate gram negative strains. Biochemical tests were used to identify the bacteria, 10 strains of which were screened as lead resistant ones from all the 24 isolates. The bacterial colonies were selected and tested with different concentrations (100- 2100 ppm) of lead for their resistance. The plates were then incubated at 37ºC for 24h and Mso1 was chosen from among the lead resistant colonies for further experiments. This strain showed resistance to chloramphenicol (30µg) and erythromycin (15µg) when subjected to the antimicrobial susceptibility test. Optimal growth conditions included a temperature of 40°C at 100 rpm and a pH level of 6 in the presence of lead by spectrophotometry at 600nm. Absorption tests showed that the Mso1 strain had a metal removal efficiency of 38.45% from an aqueous solution containing 100 ppm of lead over 24h. The results confirmed the capability of Pseudomonassp in the bioremediation of Pb-contaminated wastewaters.

Extraction of sugar from sugarcane produces a high volume of effluent carrying large amounts of organics and BOD5. Discharging the effluent into rivers and into the environment endangers the aquatic life and increases the risks of environmental pollution. This study was conducted in 2012 to determine the kinetic coefficients of the anaerobic treatment systems (UASB) at the wastewater treatment plant of Imam Khomeini Sugarcane Agro-industrial Plant in Shushtar. The parameters of BOD5, COD, and TSS were measured at the inlet and outlet of the WWTP. Subsequently, the operation and design parameters of the system were determined. Using the modified Monod Equations, the kinetic coefficients Ks, Y, Kd, μ max, and K max for employing the UASB process at the WWPT in question were calculated as 506.4mg/l, 0.11 g VSS/g COD, 0.0045 d-1, 0.0069 d-1, and 0.055 d-1, respectively. The kinetic coefficients obtained in this study can be used in the steering and operation as well as fundamental design of similar plants, especially in hot areas.

The assessment of environmental flows in a river ecosystem is a new practice in Iran. The main aim of the present study was to use different Eco-hydraulic-hydrologic methods to determine the environmental flow requirements in a typical perennial river. The ecological needs of the transboundary Zab River (located in the northwest of Iran) were investigated in three different reaches along the 160 km length of the river course using the hydraulic-wetted perimeter method (and taking advantage of the two different algorithms of slope method and maximum curvature), the synthetic habitat simulation method, and the water quality control method. The results were compared with those obtained from different echo-hydrologic methods. It was found that the FDC Shifting method (considering Class B: ecologically important rivers despite water resources development) is well adapted to the conditions in the upper reaches of the river (Derabkay Khaneh). The synthetic Eco-hydraulic method is to be recommended for the middle and downstream reaches (Grezhal and Pol–Sardasht) providing the ecological requirements of the Barbus Capito fish (as the bio– indicator species) are met. The mean annual flows in the three river reaches are determined as 2.3, 7.6, and 7.9 m3/s, respectively. The potential monthly flow rates are also proposed for preserving the riverine life.

Deliberate chemical contaminant injection is one of the most important dangers which threatens urban water distribution networks. Decisions made following the detection of such contaminant attacks are affected by complicated conditions. A variety of optimal operational measures and strategies must be adopted to safeguard the public health which may include isolation of the contaminated area through valve operations for pollution containment, public alarms, and flushing of the polluted water out of the system through hydrants or pumps. In this study, consequence management of chemical intrusions using the above strategies is investigated with two main minimizing the number of polluted nodes and minimizing the operational activities while minimizing "the recovery time of the network to normal conditions" is also considered as a novel objective. The problem is treated as both a single- and a multi-objective optimization problem in which the Ant Colony Optimization Algorithm is used for the first time. One of the most important achievements of this study is the substantial role of pumps in consequence management of such attacks.

The aim of this study was to investigate the application of micro-filtration and ultra-filtration membrane systems in order to improve the physical and microbial quality and the reuse of backwash water from the sand filter units in water treatment plants. The backwash water from filters makes up for 3 to 5 percent of the total water treated, which is disposed in most WTPs. However, the treatment and reuse of the backwash water is more admissible from technical and economic viewpoints, especially in view of the present water scarcity. For the purposes of this study, use was made of membrane modules of micro- and ultra-filters on a pilot scale. The micro-filter employed consisted of a polypropylene membrane module with a porosity of 1 micron in size and a fiberglass module with a porosity of 5 microns. The ultra-filter was made of PVC hollow fiber with a molecular weight of 100,000 Dalton. In order to feed the two pilots, backwash water from a sand filter was collected from one of the WTPs in Tehran. After samples were taken from the backwash water, the physical and microbial removal efficiency was periodically evaluated based on the standard method and the micro-filtration, ultra-filtration, and combined MF/UF processes were compared with respect to their performance. The results indicate that the combined MF/UF process is able to decrease turbidity, MPN, COD, TSS, and Fe with efficiency values of 99.9, 100, 61.5, 99.9 and 98.8 percent, respectively. Overall, the findings confirmed the technical capabilities of this method for the recovery and reuse of the effluent produced in the backwashing mechanism of sand filters in WTPs.

Polyethylene Terephthalate (PET) is the most common material used in manufacturing mineral water bottles. Antimony trioxide (Sb2O3) used to form the PET containers may pollute water with their ingredients. In this research, graphite furnance atomic absorption spectrometry was used to investigate the effects of storage time (1 to 8 weeks), storage temperature (-20 to 80 °C), pH (6.3 to 8.3), exposure to sunlight, and UV radiation on leaching antimony from PET bottles into the mineral water of 15 bottled water brands available in Fars Province. Concentrations of antimony in the first and second weeks were lower than the maximum standard limit (5 ppb) recommended by Iranian regulations. Antimony concentration in one sample (brand A) rose above the standard limit after four weeks and in 3 samples (brands A, F, and J with antimony concentrations of 5.48, 5.08, and 5.06 µg/L, respectively) exceeded the standard limit after 8 weeks. Sunlight, UV radiation, changes in pH, and storage at temperatures of -20 ℃, 60 ℃, and 80℃ were also found to increase antimony concentrations to levels above the maximum standard limit. Clearly, storing bottled mineral water in ambient conditions may lead to the release of antimony into bottled water, which is a serious threat to public health.

Rice is an important staple food in most parts of the world. The water resources in Guilan Province are receiving large quantities of herbicides (butachlor) due to the vast rice fields in the province and the indiscriminate use of chemical fertilizers for increased harvest. The present study investigates the effects of ozone used for removing the remaining butachlor from groundwater. Samples were collected from 20 wells during four seasons and their physicochemical parameters were analyzed using gas chromatography and liquid extraction after their fixation. Quantitative measurements were performed using the standard enhancement method and removal methods were evaluated using an ozone generator. The results were subjected to statistical analysis using the SPSS software. The results showed that the residual concentration of butachlor in the samples was not above the recommended international limits. The effects of temperature, hardness, and pH were investigated to determine the efficiency of the removal method used and it was found that the butachlor removal efficiency of ozonation was higher in waters with an alkaline pH and high temperatures, while it decreased with increasing hardness. The pseudo-first order kinetic model was used to investigate the rate of ozone to butachlor contact to find that the product of ozone concentration by contact time had a linear and indirect relationship with the logarithm of the butachlor content.

The presence of nondegradable toxic compounds such as phenol in the environment has nowadays led to many health and environmental problems. The present empirical study was conducted on the lab scale to evaluate the efficiency of Acacia tortillis pod shell as a new alternative and low cost adsorbent for removing phenol from aqueous solutions. The experiment was performed in a batch system and the effects of important operation variables including initial phenol concentrations of 0.5, 1, 2, 4, 8, 16, 32, and 64 mg/l, absorbent doses of 0.1, 0.2, 0.4, 0.8, and 1.6g/l in predetermined mesh sizes (ranging over 30-60 and 60-100), pH levels of 2, 4, 6, 8, 10, and 12, and contact times of 10, 20, 30, 40, 50, and 60 min were evaluated. Finally, the Freundlich and Langmuir adsorption isotherms were determined in order to describe the relationship between the colored solution and the absorbent. Results showed that the highest phenol absorption efficiency achieved was above 95% which was obtained with an optimum pH level of 2, an optimum absorbent dose of 0.2 g/l, and a mesh size of 60-100 for a contact time of 10 minutes and at a low pollutant concentration. Increasing phenol concentration increased its removal efficiency but this removal rate was lower at extreme concentrations. Also, the adsorption process was found to be more compatible with the Freundlich model. Based on the results obtained, the pod shells of Acacia tortillis pod shell may be claimed to be an effective, efficient, and cheap absorbent for the removal of phenol from aqueous solutions.