RESIDUAL METAL CONCENTRATIONS IN ENHANCED COAGULATION WITH FERRIC CHLORIDE AND ALUM FOR TOC REMOVAL

Chemical coagulation with metallic salts has traditionally been used in water treatment for turbidity removal. However, coagulation is also capable of some degree of natural organic matter (NOM) removal, with NOM functioning as a precursor to disinfection by-products (DBPs) formation. Enhanced coagulation is thus introduced to most water utilities treating surface water. Jar-test experiments were conducted to compare the effectiveness of alum and ferric chloride in removing DBPs precursors from eight synthetic water samples, each representing a different element of the USEPA’s 3×3 enhanced coagulation matrix, and the residual metal (aluminum/iron) concentration in the treated water was assessed. Coagulant type influenced the removal of total organic carbon (TOC) and which was enhanced with increasing coagulant dose. For all the treated samples coagulation with ferric chloride proved to be more effective than alum at similar doses and the mean values of treatment efficiencies were 51% and 32%, respectively. Ferric chloride was therefore considered the better chemical for enhancing the coagulation process. The results of residual metal concentration measurements in treated water showed that iron and aluminum concentrations had been increased as expected but the quality of water concerning the residual metal deteriorated much more in cases of under-dosing. Despite expecting high residual Al and Fe concentrations under enhanced coagulation, metal concentrations were frequently remained low and were not increased appreciably

RESIDUAL METAL CONCENTRATIONS IN ENHANCED COAGULATION WITH FERRIC CHLORIDE AND ALUM FOR TOC REMOVAL

Chemical coagulation with metallic salts has traditionally been used in water treatment for turbidity removal. However, coagulation is also capable of some degree of natural organic matter (NOM) removal, with NOM functioning as a precursor to disinfection by-products (DBPs) formation. Enhanced coagulation is thus introduced to most water utilities treating surface water. Jar-test experiments were conducted to compare the effectiveness of alum and ferric chloride in removing DBPs precursors from eight synthetic water samples, each representing a different element of the USEPA’s 3×3 enhanced coagulation matrix, and the residual metal (aluminum/iron) concentration in the treated water was assessed. Coagulant type influenced the removal of total organic carbon (TOC) and which was enhanced with increasing coagulant dose. For all the treated samples coagulation with ferric chloride proved to be more effective than alum at similar doses and the mean values of treatment efficiencies were 51% and 32%, respectively. Ferric chloride was therefore considered the better chemical for enhancing the coagulation process. The results of residual metal concentration measurements in treated water showed that iron and aluminum concentrations had been increased as expected but the quality of water concerning the residual metal deteriorated much more in cases of under-dosing. Despite expecting high residual Al and Fe concentrations under enhanced coagulation, metal concentrations were frequently remained low and were not increased appreciably

Removal of humic acid from aqueous solution using MgO nanoparticles

The main purpose of this work was to investigate the removal of humic acid (HA) from aqueous solutions using MgO nanoparticles as a novel adsorbent. The effect of contact time, competing anions in the aqueous solutions, for the removal of HA in batch system was studied. The nanoparticle was characterized by scanning election microscope method. Experimental results show that MgO nanoparticles can remove more than 90% of HA under optimum conditions. The results showed that the examined interfering anions influenced the HA removal. The adsorption kinetics and isotherm were also studied. The adsorption kinetics was well described by the pseudo-second-order equation, and the adsorption isotherms were better fitted by the Langmuir model

Equilibrium and synthetic studies of methylene blue dye removal using ash of walnut shell

Background and Aims: Wastewater treatment and color removal is always one of the most important measures to control pollution from industrial effluents especially in the textile and dyeing industry. This industry is one of the largest producers of organic compounds and color. For this reason, their treatment conditions are complicated and difficult. This study investigates the efficacy of ash produced from walnut shell as a natural adsorbent in color removal of methylene blue (MB) from aqueous solutions in the experimental condition.Materials and Methods: At present study, effect of various operating parameters such as pH (2-13), reaction time (30-250 min), amount of adsorbent dosage (0.2-5 g/l) and initial concentration of dye (25-250 mg/l) on color removal from synthetic wastewater were studied. Also the adsorption behavior of dyes by isotherms of Freundlich and Langmuir and synthetic of adsorption were conducted using excel program and regression coefficient.Results: Maximum removal efficiency of methylene blue (93.25%) were achieved at optimal pH 10, reaction time 150 min, adsorbent dosage 3 g/l and initial dye concentration 100 mg/l. Data of this study was fitted with Langmuir and Freundlich isotherms and more fitted with Freundlich (R=0.8500). Also, kinetic adsorption study showed that for initial dye concentrations 100, 150 and 200 mg/l, pseudo-second order kinetic is more favorable (R2=0.9900).Conclusion: More than 90% removal efficiency for MB dye showed that this adsorbent is an effective natural compound and also inexpensive for treatment processes. Hence, using this technique and process was recommended for dye pollutants removal from aqueous environments.Key words: Walnut, methylene blue dye, adsorption kinetics, equilibrium isother

Kinetic and degradation efficiency of trichloroethylene (TCE) via photochemical process from contaminated water

Trichloroethylene (TCE) is a common pollutant in groundwater and one of the priority pollutants listed by the U.S. EPA. With regard to concentration ranges in previous studies exceeding environmental levels by far with millimolar concentrations of TCE, this study deals with the degradation of TCE at micromolar concentrations by UV/H2O2. The degradation rate of TCE at different dilute solution levels, 30, 300 and 3000 g L-1 (0.22, 2.28 and 22.83 micromolar) at different initial pHs was examined. In addition, samples were taken from four contaminated wells to measure the degradation rate of TCE. It was shown that thedegradation rate of TCE increased due to the reduction of initial concentration in both aqueous solution and groundwater samples. The TCE degradation constants in groundwater samples increased by a factor of 2.05, while the initial concentration reduced from 1345.7 to 97.7 μg1 L-1. By increasing the molar ratios of H2O2 to TCE from 13 to 129, caused the degradation rates to increase in aqueous solutions. No harmful byproducts such as aloacetic acids (HAAs) were detected at these low levels of initial concentration of TCE during process. This study confirmed that application of UV/H2O2 process could be an effective method in treating contaminated groundwater by TCE at low concentrations

The survey of electrocoagulation Process for removal dye Reactive Orange 16 from aqueous solutions using sacrificial iron electrodes

ABSTRACT Discharge of textile industries colored wastewaters without enough treatment into natural water supplies cause serious damages to the environment. This study was performed to investigate the effect of electrocoagulation for dye removal from synthetic wastewater using iron electrodes. Removal of dye reactive orange 16 (RO16) by electrocoagulation using iron electrode was conducted in a batch reactor with volume 1 liter. The effect of operating parameters such as current density, initial concentration of dye, pH and contact time was studied and the electrical energy consumption was calculated. The maximum efficiency of hardness removal which was obtained in current density of 20mA/cm2, optimum concentration 50mg L-1, optimum pH 5.5, reaction time of 30 min and NaCL concentration 1.5g/l are equal to 99.27%. Also COD removal efficiency is increased to 66%. Results show, electrocoagulation process by iron electrode is an effective method for reactive dye removal from colored wastewater

Feasibility study of wastewater reuse for irrigation in Isfahan, Iran

Abstract: Wastewater reuse is one of the main options that can be considered as a new source of water in regions where water is scarce. The main purpose of this study is to determine the feasibility of Isfahan’s north wastewater treatment plant effluent for agricultural irrigation. To evaluate suitability of treated wastewater for irrigation, important indicators like Sodium Adsorption Ratio (SAR), Soluble Sodium Percentage (SSP)and Potential Salinity were investigated. In this study the SAR value for effluent was 2.62 and according to approved criteria by Food and Agriculture Organization (FAO) it was excellent for irrigation,SSPwas 39.7% so it has good quality for irrigation usage and the potential salinity was 4.81 meq/L, thusaccording to approved criteria by FAO it is medium for soil permeability.Also the EC value of effluent was 1250 µS/cm (1.25 dS/m) and according to approved criteria by FAO it was permissible for irrigatio

Increasing convergence rate in two-objective optimization of water distribution network with engineering judgment

Background: Water distribution networks (WDNs) are facilities that require massive investment and their optimization is very important. This study aimed to optimization and development of models for promoting WDNs with using engineering judgment. In this method, instead of controlling all system states, it is possible to search the optimal set of options based on engineering judgment and hydraulic and physical status of the system. Thus, the time to solve the optimization problem is greatly reduced, which is very important in widespread networks with many components. The case study was a WDN in western Tehran. Methods: To reduce the calculation size and increase the convergence rate using engineering judgment, the parts of the network where there was no possibility of parallel piping was ignored. For other parts with a low pressure problem, parallel piping was defined. A FMGA and WaterGEMS hydraulic software were used to optimize the WDN. Cost minimization and pressure benefit maximization were the objective functions and the diameters of the pipes were considered to be the decision variables. Results: The results of optimization the network showed that, the cost decreased 89.84% and the pressure in all nodes, except one node, reached within the standard range (26-60 mH20). It included 2387 m of pipe with diameters of 100, 150, 200, 250, 350, 400 and 500 mm. Conclusion: The results of optimization and modification of the network using engineering judgment confirm that the cost decreased significantly and the pressure level in all the nodes increased to above the allowable minimum pressure. Keywords: Water, Judgment, Software, Pressure, Engineerin