WATER AND WASTEWATER
Year:2017 | Volume:28 | Issue:6 |Papers Count:11

Halophytes are plants able to tolerate high salt concentrations. Among the many applications they have found، one is the phytoremediation of pollutants from the environment. Salt phytoremediation by halophytes is a field of research that has recently attracted the attention of researchers in the field. The present study is devoted to the phytoremediation of salt using the halophytic plant Salicornia europaea. The hydroponic system was employed at three salinity levels (EC~ 2، 000، 6، 000، and 10، 000 µ s/cm) with a retention time of 7 days. Electrical Conductivity (EC) and concentrations of calcium، magnesium، sodium، and chloride ions were measured before and after treatment with S. europaea. Finally، reductions in the parameter were calculated and reported as percents. The plant was found capable of reducing EC by 16. 75، 17. 05، and 18. 11% for calcium ion concentrations of 28. 71، 27. 18، and 40. 43%، magnesium ion concentrations of 31. 64، 25. 35، and 17. 46%، sodium ion concentrations of 20. 41، 17. 29، and 23. 89%، and chloride ion concentrations of 23. 24، 18. 84، and 22. 16% at EC~2، 000، 6، 000، and 10، 000 µ s/cm، respectively. S. europaea is a crop that can be irrigated with saline water. Based on the results of this study، it may be recommended as a potential candidate for salt phytoremediation.

2، 4-Dichlorophenol is one of the most common and abundant pollutants widely found in various industrial effluent. The obvious effect of this organic compound on health and environment depends on enhancing the degradation efficiency of this aqueous pollutant before wastewater being discharged into the receiving water. Therefore، in this study، removal of 2، 4-dichlorophenol from aqueous solution was investigated through using UV-LED/TiO2 process. In this experimental study، removal of 2، 4-DCP in the presence of TiO2 by using UV-LED in a bench scale reactor was examined. The effects of operational parameters such as pH (3-11)، initial concentration of 2، 4-DCP (50-200mg/L)، TiO2 concentration (0. 003-0. 025mol/L) and ionic strength were evaluated. The results indicated that removal of 2، 4-DCP was influenced by different operational parameters. The highest 2، 4-DCP removal rate were obtained at pH=3 by adding 0. 012 mol/L of TiO2 to solution with an initial concentration of 50mg/L of 2، 4-DCP which more than 95. 82% of 2، 4-DCP was removed. While UV-LED and TiO2 were used separately، the 2، 4-DCP removal efficiency was 32. 11% and 36. 56%، respectively. Also، the results indicated that maximum COD removal rate was 71. 5% in optimum condition and also indicated lack of impact on ionic strength changes for removal of organic material. The results indicated that combined TiO2/UV-LED process in optimal conditions can be used as a new technology for treatment of various industrial wastewater containing 2، 4-DCP.

Lead is a heavy metal which has many applications in different industries. Due to toxicity of lead، discharging industrial effluents which contain these ions will bring irreversible risks to the environment and living ecosystems. The objective of this study is to analyse the use of Eucalyptus sawdust as a cheap adsorbent for lead removal from effluent. The experiments were conducted in batch system and the effect of pH، the amount of adsorbent، contact time and the initial concentration of lead were examined. Noticing the results، the maximum efficiency of lead adsorption is 96. 25% which was obtained in pH of 7 and contact time of 30 minutes and 10 g/L of adsorbent. By increasing the initial concentration of lead، the adsorbed metal and removal percentage also increased. Achieved data from this study indicated a good compatibility with Langmuir adsorption isotherm. Kinetic analysis indicated that lead adsorption matches with the second-order kinetic adsorption model (R2=0. 998). Noticing the high efficiency of lead removal by Eucalyptus sawdust، this method could be used as an effective and cheap adsorbent for lead removal.

Noticing drought crisis in Iran and importance of water conservation and recognizing its determinants، this research attempted to study the applicability of the theory of planned behavior variables in predicting water conservation behaviors among college students. Survey method was used for this research and questionnaires were distributed among 122 female college students resided in dormitories of Yazd University. Finally، collected data were analysed by SSPS statistical method. The results indicated that behavioral intention and perceived behavioral control variables were able to predict 44% of variance in water conservation practices among participants. Also، two structures of subjective norms and perceived behavioral control explained 34% of variance in behavioral intention for water conservation among participants. College students who had more intention for water conservation and believed to have more control over their behavior for water conservation، behaved better in conserving water accordingly

Arsenic is one of the most hazardous pollutants of water resources which threaten human health as well as animals. Therefore arsenic removal from water resources is the priority of health programs. There are several ways to remove arsenic. In this study، reverse osmosis and zero-valent iron nanoparticles methods have been used in a laboratory scale. To perform the test، the variables of temperature، arsenic concentration، pH، iron nanoparticle concentration and mixing time were considered. The results indicated that in both methods of reverse osmosis and iron nanoparticle، through increasing arsenic concentration، arsenic removal efficiency has been also increased. At concentration of 1. 5 mg per litre in reverse osmosis method، the maximum efficiency was achieved by 98% and 95. 2% removal of arsenic respectively. The effect of temperature and pH were similar in reverse osmosis; by increasing these two variables، arsenic removal percentage also increased. The highest removal rates of 95. 98% and 95. 56% were observed at pH 9 and Temperature 30oC respectively. The results indicated that in iron nanoparticles method the arsenic removal efficiency increases by increasing mixing time and temperature، while it decreases with increasing pH.

Biological processes of wastewater treatmnent have found wide applications due to their lower costs and higher efficiency. Membrane bioreactors (MBR’ s) form one group of such processes in which membrane fouling is of great importance. Efficiency of critical flux (CF) has been proved to be a parameter effective in fouling control (CF). CF is itself influenced by three main groups of variables that include sludge parameters، operating conditions، and membrane types. In this stidy، the effects of such factors as trans-membrane pressure، protein and carbohydrate concentrations in extracellular polymeric substances (EPS)، and soluble microbial products (SMP) on CF were investigated in a submerged MBR. Moreover، the effects of such operating conditions as periodic and continuous suctions at two sludge concentrations were studied. It was found that increasing flux led to enhanced membrane fouling rates. Extracellular polymeric substances (EPS) were found to have no relations with critical flux (CF)، probably because EPS are mostly found as bigger flocks. Finally، a reverse relationship was established between CF and carbohydrate concentration of the SMP. Membrane fouling control was observed to be positively affected by the rest modes during periodic suctions.

One of the reasons for poor performance of filters is their being backwashed. The purpose of this study is to evaluate filtration process and sand filters operation after being backwashed through examining turbidity and zooplanktons in Esfahan water treatment plant. This study was conducted during 4 months in the sand filters (phase 1 & 2) of the treatment plant. Turbidity and microscopic counting were studied to assess the performance after filtration. The average for turbidity variations and nematodes & rotifers counting were evaluated in different times after backwash. Turbidity break point and zooplanktons reduction occurred after 15-20 minutes of backwash. The number of nematodes and rotifers in phase 1 after 10 minutes increased respectively by 13 and 12 numbers per liter and within 20 minutes، it reduced to 7 and 9 numbers، respectively. Also after 20 minutes in phase 2، the number of nematodes and rotifers decreased respectively by 8 and 6 per liter. This changes were significant based on t-test (p <0. 001). Also after 15-20 minutes، filters effluent turbidity reduced to less than 0. 2 NTU. It is better to put filters in the circuit 20 minutes after being backwashed in order to restrict the number of suspended particles and organisms inside the effluent.

The growing population and enhanced industrial activities coupled with limitations on freshwater availability have led to efforts to desalinate salt water from the seas. Membrane and thermal technologies are the two commonly used for this purpose. In this study، the direct freezing and hydrate formation techniques were used for salt water desalination. Materials and Methods: Distilled water، sodium chloride، and sodium bromide were used as raw materials in the experiments. The experimental setup included a stationary reactor with two coaxial cylinders، in which ice crystals were deposited outside the cool inner cylinder to increase the salt concentration in the residual brine. An electrical conductivity instrument was used to measure sal removal. Results: Salt removal was shown to decrease with increasing salt concentration in the direct freeze method. A different trend was، however، observed in the hydrate formation method; salt removal was negligible at low concentrations in this method but increased at high concentrations before a constant value was reached. Overall، the hydrate formation recorded a higher salt removal efficiency than the other method. To investigate the effect of anion size on salt removal efficiency، experiments were carried out using NaCl and NaBr، which have the same cation but different anion sizes. Result showed that removal efficiency increased with increasing anion size. Conclusion: It was found that increasing ion radius leads to the lower likelihood of ion presence in the crystal lattice، thereby reducing salt removal efficiency. On the other hand، low concentrations of salt serve as site for the generation of cores، which naturally serve as removal accelerators.

Hydrocyclones are used for removing suspended solids such as silt and sand from water. In this study، all the factors involved in the performance of hydrocyclones were initially identified and listed before they were optimized using the Taguchi experiment design method. It was the objective of the present study to optimize the efficiency of hydrocyclones in removing sand from water. For this purpose، 18 hydrocyclones were designed and constructed to test all the variables affecting their performance including hydrocyclone inlet، overflow، apex، and body diameters as well as cylindrical، total، and vortex finder heights. Minimum (20 mg/l) and maximum (100 mg/l) concentrations of total suspended solids (sand) in the samples from the water wells in Mashhad city along with the observed particle distribution were used in the optimization. Statistical analysis of the results showed that the ratio of the inlet and overflow diameters to that of the hydrocyclone was 0. 225 and that the ratio of the apex diameter to that of the hydrocyclone was 0. 15. Also، the ratios of the cylindrical and vortex finder heights to the total height of the hydrocyclone were 0. 12 and 0. 08، respectively. Under optimum conditions، sand removal efficiency varied from 95. 9% to 98. 4% in different experiments. This is while a value of 97. 2± 1. 1% was obtained as the result of three tests in the hydrocyclone optimized in this experiment. Comparison of the mass removal efficiencies predicted by the Taguchi method and the values measured in the optimal hydrocyclone tests showed that both sets of data were very close and substantially high. Moreover، it was found that the geometric elements obtained in this study were generally in the range of minimum and maximum ratios proposed for hydrocyclones used in mining. These ratios may، therefore، be recommended for use in the construction of real-scale hydrocyclones for sand removal from water.

Determination of the extent and growth rate of contamination zones in water resources is a crucial stage in remediation studies. The process is especially complicated due to the multiplicity of the variables involved and the limited access to groundwater aquifers. The present study uses the image processing technique to define the contaminant plume and to analyze diffusivity coefficients for seepage flows in porous media. The image processing algorithm was developed in MATLAB software and the least squares method was used to solve the diffusion equation. Thus، the hydrodynamic dispersion coefficients in porous media were calculated without any turbulence over wide ranges of time and place with an acceptable accuracy. Analysis and verification of the data thus obtained confirmed the accuracy of the proposed model and revealed a limited error range of less than 11%. It may، therefore، be claimed that the proposed method is an effective means for studying diffusivity. The equations for estimating diffusivity coefficients were developed as a function of both the porous media characteristics and the Pé clet number. Using the equations، diffusivity coefficients in the range of 0. 002 to 0. 0028 m were obtained for a porous medium with a grain size varying from 0. 5 to 3 mm.