WATER AND WASTEWATER
Year:2019 | Volume:30 | Issue:5 (123) |Papers Count:10

The application of residues of agricultural products as low-cost biosorbents for removing heavy metal from water, is particularly appropriate for developing countries. This study was conducted to compare the removal efficiency of lead (Pb (II)) from aqueous solutions with initial concentration of lead (0-100 mg/L) by some raw (unmodified) biosorbents (sunflower stalks, wheat straw and corn stalks) and chemically modified forms of these biosorbents with NaHCO3 0. 5 mol/L and NaOH 0. 5 mol L. Also in this study, lead adsorption isotherms and lead removal efficiency by these biosorbents were investigated. Biochemical composition analysis of the studied biosorbents showed that sunflower stalks had the highest cellulose, lignin and ash content. Hemicellulose was highest in wheat straw but lowest in sunflower stalks. Langmuir and Freundlich models had better fitness than the Temkin model for removal of lead by unmodified and modified biosorbents. The removal efficiency (RE) for unmodified sunflower stalks, wheat straw and corn stalks was obtained 94-99%, 85-97% and 55-95%, respectively. Also, by modification of biosorbents with NaHCO3, the removal efficiency (RE) of sunflower stalks, wheat straw and corn stalks was 94-99%, 85-97% and 55-95%, respectively. Maximum mono layer adsorption (qmax) of modified sunflower stalks, wheat straw and corn stalks increased 293, 305, 394 and 226, 265 and 363 percent compared to unmodified biosorbents, respectively. Separation factor of Langmuir (RL) increased from 0. 014-0. 73 (for unmodified biosorbents) to 0. 065-0. 93 (for modified biosorbents by NaHCO3) and 0. 023-0. 56 (for modified biosorbents by NaOH), which indicated that the sorption reaction of lead by studied biosorbents is favorable. Chemical modification of the biosorbents with NaHCO3 could significantly increase the efficiency and removal capacity of lead from aqueous solutions. The ease of preparation of these chemically modified low-cost biosorbents and the high removal capacity for lead makes these biosorbents a good practical candidate for removal of lead from aqueous solutions.

Toxic waste water and infected water are considerable sources of environmental contaminations. Dyes as the source of toxicity of waste water are used in various industries like dyestuff, textile, paper, plastics and pharmaceutical. Recently, reactive dyes have become more commonly used because of their advantages such as better dyeing processing conditions and bright colors. So, removal of dyes from effluents is very important. Among the materials used as the common adsorbents, chitosan and polyacrylamide are relatively cheap and the promising materials that can be used as adsorbents. In the present study, TiO2 nanoparticles dispersed in chitosan grafted polyacrylamide matrix were synthesized by in situ method and used for the removal of Sirius yellow K-CF dye from aqueous solution. The synthesized nano-composite was characterized by FE-SEM, TEM, XRD and FT-IR. The effect of pH, adsorbent dosage, time and temperature were investigated. The results showed that the highest dye removal efficiency happended in the acidic pH of 2 with 0. 05 g of TiO2-PAA-Ch adsorbent. The equilibrium data were well compatible with the Langmuir isotherm (qm=1000 mg/g, 96. 81% of dye removal). The Dubinin-Radushkevich isotherm and thermodynamic studies proved that the adsorption process is physical, endothermic and spontaneous. Kinetic study verifies that pseudo second order kinetic model is the predominant model. In this study, TiO2 nanoparticles dispersed in polymer matrix were synthesized and employed for the removal of Sirius yellow KCF from aqueous media. Electrostatic attraction between positive charges of adsorbent surface (NH3 +) and molecules of anionic dye together with formation of hydrogen bond (Dye-NH3 +), cause the adsorption of dye on PAA-Ch. On the other hand, Ti+4 in PAA-Ch structure can interact with the anionic molecules through the electrostatic adsorption. The results of this study show that the new synthesized TiO2-PAA-Ch composite with high amount of NH2 functional groups and Ti+4 is an efficient adsorbent for environmental applications to remove many contaminants, dyes and organic pollutants.

In this research, deriving optimal reservoir operation in selective withdrawal scheme considering quality and quantity aspects has been studied. Surrogate based simulationoptimization approach (SBSOA) has been applied to improve downstream water supply and enhance reservoir outflow water quality. CE-QUAL-W2 as the hydrodynamic and water quality simulation model in the river-reservoir system and multi-objective particle swarm optimization (MOPSO) algorithm as an efficient tool have been applied in simulation-optimization (SO) approach. To overcome the computational burdens of multiple calls of CE-QUAL-W2, as a numerical high fidelity model, various surrogate models have been developed to simulate reservoir outflow water quality parameters (DO, NO3, PO4, BOD, and Fe). The developed surrogate models and mass balance model have been coupled with MOPSO algorithm in SBSOA. In this study, the water quality objective function is defined as water quality index (WQI), which integrates various water quality parameters, DO, NO3, PO4, BOD, and Fe. The proposed approach has been applied in Ilam river-reservoir system to derive optimal reservoir operating strategies in the selective withdrawal scheme. The results show suitable efficiency and accuracy of the developed surrogate models in approximation of various water quality parameters compared with CE-QUAL-W2 simulation results (the approximation error of DO, NO3, PO4, Fe, and BOD has been respectively 3%, 1%, 2%, 2%, 3%). The studies indicate enhancing reservoir outflow water quality is consistent with downstream water supply satisfaction. It means, the increasing of reservoir outflow rate leads to the reservoir detention time decreasing, pollutant settling rate reductions, and chemical/biological reaction attenuation.

Regarding the complexity of WDNs, the need for computerized modelling of WDNs is felt more than ever for monitoring their performance at the operational stage. One of the most important issues in modelling is to adjust the results of modelling with the real status of the system. So it is necessary to calibrate the model by observed data. Finding a suitable method for adjusting the model's coefficients is one of the main challenges in computerized modelling. In this paper, a modified particle swarm method is presented for adjustment of water distribution network coefficients by modifying the velocity equation of the particle swarm and combining it with the mutation operator. Thus by defining the coefficients of the models, four models such as standard particle swarm optimization model (SPSO), modified standard particle swarm optimization model (MSPSO), standard particle swarm optimization model with a mutation (SPSOM) and modified standard particle swarm optimization model with a mutation (MSPSOM) are constructed. The Rastrigin test function is used for verification of the modified particle swarm equation and the two-loop network is used for verification of models and also the four-loop network and real water distribution network are used for detailed analysis. The optimization is done in MATLAB by combining the particle swarm optimization algorithm and the EPANET software. Comparison of the results of the standard particle swarm model and the modified standard particle swarm model for the Rastrigin test function showed that modifying the particle swarm velocity equation increased the model's ability to determine the actual answers and reduced the costs. The MSPSOM model finds the optimal answer for two-loop and four-loop networks with a probability of 96. 7 and 95 percent respectively. So it is the best model among all models in this criteria. Also, the MSPSO model finds the optimal answer for two-loop and four-loop networks in the lowest time compared to other models. So it is the best model among all models in this criteria. Comparing the results of the models in the Ahar water distribution network showed that the modified standard particle swarm with the mutation model has the lowest minimum and average values of the modeling data error. So it has the best performance among the particle swarm models. In general, the correction of the particle swarm velocity equation in the form of the standard particle swarm model, and the correction of the particle swarm velocity and its integration with the mutation operator in the form of a modified standard particle swarm with a mutation has a higher ability to adjust the water distribution network coefficients.

The process of spatially allocating the water demand is a potential source of errors that should be considered when building the hydraulic simulation model. There are several methods for this purpose and each has limitations and advantages. In the case of existing accurate recording of coordinates for water meters in GIS, there are several base demand automated allocation strategies for modeling the spatial distribution of water consumption in water networks. Where the spatial data for water meters is not available, conventional methods such as Thiessen and LDM (Length Dependent Method) can be used. If this data is incomplete mixed practices can be used. This study proposed a mixed method named SAWDSL (Spatial Allocation of the Water Demand based on Data of Consumers) that divides the total consumption in subgroups related with corresponding recorded water meters. This method assigns the demand of each subgroup into the nearest pipe. The simulation results of WaterGEMS software using SAWDSL, Thiessen and LDM methods, after calibration, were compared to field measurements in zone I1 of Mashhad city. RMSE between observed and simulated pressure with the SAWDSL, Thiessen and LDM methods was determined to be 0. 9, 2. 3 and 1. 4 respectively. That shows, if the incomplete data of water meters exists and there is enough time to use them, SAWDSL method is more accurate than others. Otherwise LDM method is more accurate than Thiessen method.

People’ s participation is one of the means of financing investment through which will develop investment in different sectors such as the supply of public goods and services. In this research, how to encourage people to participate in the proposed project of water transfer from Caspian Sea to Iran’ s central plateau has been studied. The paper evaluates the value of the citizens of Semnan’ s participation in the implementation of water transfer project from the Caspian Sea to the Central Plateau using the Contingent Valuation Method (CVM) and identifies effective factors on willingness to the pay by applying Logit model in the framework of Maximum Likelihood Method. Data through two-dimensional dual questionnaire that includes 384 members have been collected. The results from model estimation show that firstly, the variables of income, educational level have a positive and significant effect and the number of household members and the proposed price have a negative and significant effect on the willingness to pay of Semnan’ s citizens. Secondly, the average of per household willingness to pay, 433, 077, 096 Rials annually and the people’ s annual participation value, 30. 1 milliard Rials is estimated. Citizen’ s willingness to finance the costs of project implementation indicates citizens' responsibility in resolving the regional problems that can be presented as a good model in the performance of national plans and solving of regional problems.

Water sludge management is one of the main problems facing water and wastewater companies. Disposal of conditioned sludge by chemical polymers is restricted due to the health and environmental effects. Recently, the use of natural polymers has been investigated to reduce the side effects of chemical polymers. In this study, the effectiveness of Moringa Pergerina seed as a natural polymer in the conditioning of water treatment sludge has been studied. In this study, sludge samples from the Tehranpars Water Treatment Plant were taken daily from the sedimentation tank. Sampled sludge conditioning was performed using jar test by Moringa pergerina powder dissolved in salt water (1N NaCl). Optimization of three important factors in the jar test, including mixing speed, mixing time and optimum dosage using the Box-Behnken Design, Response Surface Design Method (RSM), was performed in Design Expert software. Results: The minimum capillary suction time (CST) and specific resistance filtration (SRF) was obtained at 30. 294 and 6. 19×1012 m / kg respectively under optimal conditions. The results were obtained in terms of speed and time of mixing 50 rpm and 3 min, 250 rpm and 100 s with an optimal dosage of 5040 mg/L of Moringa Pegerina dissolved in salt water and a desirability index of 1. 000. The best effectiveness of Moringa Pergerina for sludge conditioning was obtained in acidic media. Under optimal operating conditions, SRF and CST relative to the initial conditions of the sludge were reduced by 75% and 42%, respectively.

The limited and vulnerable water resources in the world have a special economic value with social, economic and environmental impacts. Water resources constraints and the need for optimal use of these resources show the necessity and importance of using refined wastewater. In this research, the economic evaluation of the use of treated wastewater in Zahedan green irrigation with economic and financial justification and focus on the environmental benefits of the wastewater treatment process are considered. Two scenarios are considered in this research: In the first case, according to the sales price of water equal to 3000 and 45000 Rials, an estimate has been made and in the second scenario, the environmental benefits and benefits of the project are estimated by estimating the shadow price of pollutants and pollutants from wastewater treatment. The data used in this study was based on spending patterns Water and Wastewater Company has chosen Zahedan, the capital city of Sistan and Baluchestan Province as the location of the project. The findings of the study conducted in the first scenario show that the project is not justified in this scenario, the net value of the project over a period of 20 years and a 25 percent rate of return equal to-182. 2065617 Rials as well as the benefit to cost ratio in this scenario is 0. 68 times. The second scenario examines the reduction of the environmental impact of wastewater treatment processes for the manufacture of shadow prices of undesirable and pollution control has been dealt with distance function. The average shadow price for adverse outcomes, including total biochemical oxygen demand, total chemical oxygen demand (BOD and COD) wastewater treatment ranged between 94-92 years, respectively-100. 1,-319. 75,-500. 6. Shadow price must interpret whether we want the wastewater treatment plant and produce undesirable emissions (BOD and COD) reduce. This will produce less than the desired output (treated water) or increase the use of inputs in remediation and disposal of the product is desirable.

Pharmaceutical wastewater treatment is a complicated process due to presence of various kinds of toxic chemicals and antibiotics that are harmful to any type of organism. In this paper, elimination of sulfamethoxazole antibiotic from artificial sewage was investigated. A pilot scale Rotating Biological Contactor (RBC) with three compartments, 48 discs, and total volume of 78. 75 L was employed. The antibiotic removal was measured at various COD concentrations, hydraulic retention times (HRT) and concentrations of sulfamethoxazole. The results indicated that by increasing in OLR and HRT, SMX removal efficiency was increased and in the first 12 hours of the treatment process, SMX removal efficiency is about 50%. The maximum removal occurred within the first 72 hours, which was more than 95%. Also, the obtained results demonstrated that increasing COD concentration had a positive impact on SMX removal efficiency, which was most probably due to the utilization of SMX as a nitrogen source. SMX removal efficiency in OLRs 0, 2, 4, 8, 16 and 32 g COD /L. d was 17, 44, 75, 72, 78 and 82 percent, respectively. It was also revealed that most SMX and organic matter removal occurred in the first compartment of the NRBC, that is about 57 percent. This study indicated that employing the attached growth system is a good alternative for conventional activated sludge system in pharmaceutical wastewater treatment.

Generally, circular channels are used in urban sewage systems where the flow is a three phase flow including water, air, and sediments. Accordingly, there are many studies carried out by different researchers related to flow within sewage channels. In current study, the Froude number of three phase flow within sewer channels is predicted using Extreme Learning Machine (ELM). Using parameters affecting the Froude number, 127 various ELM models were defined. The superior model was then introduced. For instance, for the superior model as a function of volumetric sediment concentration, the ratio of the particle size to overall hydraulic radius and overall friction factor for sediment load of 60% and 40% in train and test, respectively, the R2, MAPE and RMSE in testing mode were calculated as 0. 856, 0. 117, and 0. 738, respectively. In addition, the results of superior model were compared with Artificial Neural Network (ANN) and support Vector Machine (SVM) models. Analyses of modeling results showed that extreme learning machine simulated the aim function with more accuracy.