مجله آب و فاضلاب
پیاپی 111 (آذر و دی 1396)

Nitrate pollution is at the forefront of groundwater contamination which poses serious environmental and public health hazards. Nitrate is usually released in solution from agricultural activities and finds its way into groundwater resources. The objective of the present study was to determine, accurately concentrations of nitrate ions in water samples from the environment using sensitive electrochemical methods. For this purpose, a modified glassy carbon electrode modified with a nanocomposite consisting of silver nanoparticles, nanocellulose, and graphene oxide (Ag/NC/GO-GCE) was used. The characterization of the nanocomposite was investigated using scanning electron microscope (SEM), X-Ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). The modified Ag/NC/GO-GCE electrode was used as nanosensor for the electrocatalytic determination of nitrate using the voltammetric method. The effects of the parameters of scan rate, pH, and different nitrate concentrations were studied and the optimum conditions were obtained. A limit of detection of 0.016 µM (S/N=3) was found in the linear range of 0.005 to 10 mM nitrate. The Ag/NC/GO-GCE electrode exhibited a synergistic effect toward voltammetric determination of nitrate in the presence of graphene oxide, nanocellulose, and silver nanocatalyst. The nanosensor developed here showed excellent sensitivity, selectivity, and stability toward nitrate determination in aqueous solutions without any significant interference.

Dyes are a main source of pollutants in textile plant effluents. Due to their molecular structure, they are usually toxic, carcinogenous, and persistent in the environment. The aim of the present work was to explore the removal of basic blue159 (BB159) using magnetic sodium alginate hydrogel beads. Magnetic sodium alginate hydrogel beads were initially synthesized accoriodng to Rocher method using CaCl2 as a crosslink agent. Fourier transform infrared spectroscopy (FTIR) was then employed to examine the functional groups on the surface of the magnetic sodium alginate hydrogel beads. In a third stage, the magnetic properties of the beads were measured using a vibrating sample magnetometer (VSM) and the magnetic parameters were calculated. Subsequently, the effects of such parameters as adsorbent dosage, pH, initial concentration of dye, and contact time were evaluated on the BB159 removal efficiency of the adsorbent used. Finally, the Langmuir, Freundlich, Temkin, and B.E.T models were exploited to study the adsorption isotherm of BB159 onto the magnetic sodium alginate hydrogel beads. It was found that the magnetic sodium alginate beads possess both –COO and –OH groups that play important roles in the adsorption of the positively charged BB159 dye. A saturation magnetization equal to 21/8(emu/g) was obtained for the sodium alginate beads/nano Fe3O4. Results also revealed that the highest dye removal from aqueous solutions was achieved at pH=11 in 120 minutes for 9 grams of the adsorbent. The study indicated that BB159 removal using the magnetic sodium alginate hydrogel beads as the adsorbent obeys the Langmuir model. Moreover, it was shown that the efficiency of the process for BB159 removal from aqueous solutions was satisfactory (85%).

Long-term drinking of nitrate-contaminated water poses a serious risk to human health. The present study explores the possibility of enhancing the adsorption capacity of graphene oxide via activation with hydrochloric acid for nitrate removal from aqueous solutions. Experiments were performed in a batch reactor in which such major factors as pH, reaction time, and concentrations of both graphene oxide (GO) and activated graphene oxide (AGO) were used as variables. Nitrate removal efficiency was investigated using the One-Way ANOVA statistical test and SPSS-16 software. The chemical composition and solid structure of the synthesized AGO were analyzed using FE-SEM coupled with energy dispersive spectrometry (EDS). The micropore volumes of the samples were determined using the BET and BJH. The predominant composition (52%) of the synthesized AGO was C and its mean pore diameter was 26.896 nm. The maximum adsorption capacity of AGO was estimated at 3333.33 mg/g. Based on the results, the AGO nano-structure may be recomended as a new means for nitrate removal from aqueous solutions.

A major concern about pharmaceutical pollution is the presence of antibiotics in water resources through their release into sewers where they cause bacterial resistance and enhanced drug-resistance in human-borne pathogens and growing microbial populations in the environment. The objective of this study was to investigate the efficiency of the advanced H2O2/ZnO oxidation process in removing ceftriaxone from aqueous solutions. For this purpose, an experimental study was conducted in which the SEM, XRD, and TEM techniques were employed to determine the size of Zinc oxide nano-particles. Additionally, the oxidation process parameters of pH (3-11), molar ratio of H2O2/ZnO (1.5-3), initial concentration of ceftriaxone (5–15 mg/L), and contact time (30-90 min) were investigated. Teh data thus obntained were subjected top statistical analysis using the SPSS (ANOVA test). XRD results revealeda hexagonal crystal structure for the nano-ZnO. TEM images confirmed the spherical shape of the nanoparticles. Finally, SEM images revealed that the Zn nanoparticles used in this study were less than 30 nanometers in diameter. Based on the results, an optimum pH of 11, a contact time of 90 minutes, and a H2O2/ZnO molar ratio equal to 1.5 were the optimum conditions to achieve a ceftriaxone removal efficiency of 92%. The advance H2O2/ZnO oxidation process may thus be claimed to be highly capable of removing ceftriaxone from aqueous solutions.

Water plays a vital role in mineral processing as evidenced by the approximately 2 to 3 tons of water used for the treatment of one ton of ore. A major portion of this water may be recovered in thickeners. This study aimed to control the wet tailings output of the Hematite Gol-e-Gohar plant by changing flocculant dosage and type and solid percentage in the feed in order to enhance effluent clarity and reduce water consumption. Materials and A series of settling experiments were performed using different combinations of the flocculants (A25, A26 Yazd, A26 Esfahan, A27, and A28), flocculant doses (20, 25, 30, 35, and 40 gr/ton), and solid loads in the feed (5, 7, 9, 10, and 11%) to the thickener. The L25 Taguchi design method was chosen to handle the five different levels of the three factors. Adopting a 95% confidence interval, the results of analysis of variance (ANOVA) revealed that flocculant consumption rate had a high effect on settling velocity (p = 0.006) while flocculant type and solid percentage in the feed had no significant effects. Moreover, it was found that A26 (Akhtar-chemistry Company, Yazd) used at a rate of 40 g/ton improved the settling performance to yield an optimal water clarity. Using the findings of this study in process planning at the plant led to a considerable reduction (from the original 0.86 to 0.49 m3) in average water consumption per ton of input material so that the solid content of the thickener underflow rose from 7 to 45%.

Cutting and drilling mud contains significant amounts of petroleum hydrocarbons that are detrimental to both the environment and public health. The objective of this study was to remove the hazardous components of drill cutting mud using the two biological processes of sewage sludge vermicomposting and biocomposting. In an experimental laboratory research, two pilot composting and vermicomposting processes, each over a period of two months with 2 repetitions, were conducted using the the same biological sludge mixed with drill cuttings contaminated with total petroleum hydrocarbon (TPH) along with sawdust and yard waste. The GC-FID unit was used to determine the residual total petroleum hydrocarbon concentrations. Results showed that the vermicomposting pilot had a higher TPH removal efficiency than did the composting one so that TPH concentration in the mixed waste mass declined after 60 days from its original value of 42.004 g/kg to 11.316 g/kg. In other words, TPH removal in the pilots A (vermicomposting) and B (biocomposting) were 73/06% and 55/3%, respectively. Moreover, the TPH levels in the two composting and vermicomposting pilots on the 45th and 60th days showed significant differences (p

High groundwater levels in urban areas pose major problems in construction and mining projects. A typical and effective solution in these situations is to dig drainage wells to lower the water table to the desired level through an appropriate pumping strategy. Although the method is efficient, the operating costs are relatively high and it is, therefore, of great importance to optimize the groundwater pumping system to save costs. In this paper, a simulation-based optimization approach is exploited to minimize the total costs through optimizing the layout and capacity of pumping wells. For this purpose, MODFLOW, the groundwater simulation software, is used to investigate aquifer behavior under pumping wells and the well-known Firefly Optimization Algorithm is exploited to find the optimal well layout and capacity. The proposed FOA-MODFLOW model is tested on the small urban ancient Grand Mosque region in Kerman City, southeast of Iran, to minimize the cost of the draining project. Experimental results indicate that the proposed cost-effective design noticeably outperforms the one proposed by the consulting engineers in terms of both the number of drilled wells and the associated pumping costs. The optimal strategy observes the constraints and demands by constructing only two wells with a total pumping rate of 5503 m3/day and a water table drawdown of more than 1.5 m provided the ground subsidence is within the allowable limit of less than 80 mm. Additionally, examination of the values obtained for the various design parameters shows that the proposed strategy is the best and its sensitivity to maximum permissible water level and pumping rates is highest as compared with other similar designs.

Investigation of channel capability for sediment transport is an important factor in sanitary sewer and urban runoff drainage system design. This is because of the undesirable effects arising from the reduced channel hydraulic capacity due to the deposition of sediment particles. Self-cleansing channel designs minimize sediment deposition and, thereby, prevent reduced channel hydraulic capacity. Our literature review revealed no previous report on self-cleansing models yet proposed for channels with trapezoidal sections. An experimental study was conducted using a trapezoidal channel and a non-deposited bed to investigate the self-cleansing process with four different sediment particle sizes under various slopes and discharge rates. The experimental data were exploited to develop a bed load self-cleansing model for the trapezoidal channel considering the specific flow, fluid, sediment, channel, and sediment characteristics. The proposed model was then compared with those reported in the literature for circular and rectangular channels. It was found that channel section geometry is a decisive factor in channel self-cleansing rate. Comparisons revealed that circular and rectangular self-cleansing models produce an error of approximately 15% when employed for designing channels with trapezoidal sections. Hence, the model developed in this study is recommended for designing channels with trapezoidal sections

Water quality management in groundwater aquifers requires accurate water quality monitoring to ensure they meet a variety of relevant standards. Given the rather few reported studies in the field, the present study was designed and implemented to investigate the groundwater quality of Shahr-e-Babak aquifer that is exploited for agricultural, mining, drinking, and industrial consumptions. The kriging and IDW (power:1-3) techniques with spherical, exponential, and Gaussian variogramsare were compared using R2, RMSE, MAE, and RSS indices to find the optimum model for determining the spatial variability of sixteen groundwater quality parameters. Multi-purpose zoning of groundwater quality was accomplished in the ArcGIS environment in terms of the Wilcox, Schuler, drip and sprinkle irrigation as delineated by Iran Power Ministry, corrosiveness, and sedimentation standards as well as the WHO and IRISI indices before spatial correlations were determined accordingly. Based on the water quality zoning maps thus derived, Langelier, Corrosiveness, and Ryznar indices were several times larger than the threshold levels across the whole aquifer plain, indicating the wide corrosiveness of the water in industrial applications. The results also revelaed that 93% of the groundwater in the plain area was classified as C4-S1 and C4-S2, which are unsuitable for irrigation, while only 1.3% of the groundwater was acceptable for drinking uses. Drip irrigation zoning revealed that 64% of the plain area had the lowest water quality.The undesirable quality zones in a vast area of the aquifer investigated calls for accurate quality monitoring and management to meet the development objectives in the region.

Nowadays most organizations have found that improving the quality of goods and services is the necessary condition to attend and survive in the market and in universal competition. ISO quality management system encompasses requirements for creating, deploying, implementing and maintaining quality management system. The purpose of this research is to investigate the effectiveness of implementing quality management system in some ministry of energy’s subsidiaries in Isfahan province to whom the ISO certificate is given. In order to do that, the research questionnaire was made and data was collected from statistical society containing managers of subsidiaries. The results show that in the above mentioned subsidiaries, after receiving ISO certificate, the desired goals of the quality management system has not been fulfilled generally. The results indicate that lack of knowledge about the capabilities of human resources in implementing the quality management system and lack of efficient staff, lack of continuous control and supervision, exclusiveness of the services and lack of competing conditions, lack of trust among senior managers about the usefulness of quality management system and also lack of sufficient support and relying on dissatisfactory old processes has paved the way for inefficiency of quality management system.

In recent years, low-impact development (LID) has been well established as a method to provide the best and most affordable solutions for managing and alleviating the negative impacts of urban floods. Application of this practical method is regarded as a major step toward sustainable development as it employs eco-friendly storage instruments, reduces the effects of urbanization on impervious surfaces, and helps water infiltration to recharge groundwater resuorces. Although low-impact development tools have proved effective in the management of surface water resources and conservation of water quality, finding proper locations for the deployment of the equipment and the optimal use of each tool are still questions of much controversy and no definitive solutions are provided yet as environmental conditions keep changing. The present study exploits bio-retention cells, rain barrels, green roofs, and vegetable swales as storage instruments under different rainfall scenarios with return periods from 2 to 100 years extracted from the statistical data of Sanadaj City to determine the flood volumes and hydrographs for each sub-basin before and after the low-impact development tools are employed. Moreover, SWMM 5.1 software developed by the American Environmental Protection Agency is used to develop hydraulic and hydrologic models of the basin and the changes are monitored with each development tool selected. The most outstanding results obtained from this study include the change observed in thet form of hydrograph, a reduction of 50% in time of concentration, and reductions of 35 to 50% in peak flow in the city of Sanadaj as a result of employing the low-impact development method. Classification of the equipment into infiltration and storage tools used for urban runoff control allows the best runoff control model to be developed such that the grounds are prepared not only for the return to the conditions before a certain development took place but even for flood management in challenging and riskful urban areas.