WATER AND WASTEWATER
Year:2013 | Volume:24 | Issue:2 (86)|Papers Count:19

Extensive use of heavy metals and their compounds in industrial processes and products have lead to discharging a large amount of pollutants (e.g. Chromium) into water sources and aquatic environment. These pollutants cause a variety of human and environmental effects including health problems. There is serious concern regarding the presence of Chromium in marine environment as it causes severe toxic effects on microorganisms and ecosystem. The purpose of this study was to evaluate the efficiency of Fenton process in the removal of chromium from electroplating industry wastewater, as a major and effective pollutant for COD and turbidity removal. This is a descriptive study, cross-sectional in nature, and was conducted within a period of three months in 2010. Wastewater samples were taken from a balancing pond located in an electroplating industry in Khazra' industrial city of Kerman. Almost 110 samples were delivered to the laboratory for analyses. Collected samples were investigated under different conditions (pH levels of 2, 5, 7, adding H2O2 with 30% weight at concentrations of 500, 1000, 1500, 2000, 2500, 3000 mg/L as well as Fe2+with concentrations of 100, 200, 400, 800, 1600 and 3200 mg/L) and various reaction times of 10, 30 and 60 minutes. All experiments were based on the Standard Methods for Examination of Water & Wastewater. The highest Chromium removal (99.7%) was obtained at pH of 5.0, optimum ratio of H2O2/Fe2+=800/2000 mg/L and the reaction time of 10 minutes. The maximum efficiency COD removal (68%) was obtained at pH of 2.0, optimum ratio of H2O2/Fe2+=1600/2500 mg/L and the reaction time of 60 minutes. The maximum efficiency for Turbidity removal (97.6%) was obtained at pH of 7.0, optimum ratio of H2O2/Fe2+=400/1500 mg/L and the reaction time 10 minutes. Our findings are in line with the results of previous studies such as Degradation of microcystin-LR toxin by Fenton and Photo-Fenton processes, Feasibility study of treatment of amoxillin wastewater with a combination of extraction, Fenton oxidation and reverse osmosis, Sonoelectro-Fenton process a novel hybrid technique for the destruction of organic pollutions in water, Fenton oxidation of RDX and HMX and Reduction of COD and removal of Zn2+ from rayon industry wastewater by combined electro-Fenton treatment and chemical precipitation. According to the results of this study, the Fenton process is an effective way to remove pollutants such as chromium, COD and turbidity from the wastewater of electroplating industries, and can be replaced by other methods of pollutant removal from wastewater.

One of the most important quality characteristics associated with wastewater reuse in agriculture, which takes into consideration, is the microbial quality. The aim of this study is determination of efficiency of wastewater treatment plants in removal of protozoan cysts and parasitic eggs of Ghasreshirin (constructed wetland), Islamabadgharb and Gilangharb (stabilization ponds). This study was accomplished during six months and sampling was done from inlet and outlet of wastewater Plants, as weekly. Totally, 144 samples were investigated for parasitic analysis with Bailenger method by Mac Master Slide (with a hole size 0.3 ml). The findings showed that mean of removal efficiency in constructed wetland for parasitic eggs and protozoan cysts are %99.7±0.23 and %100 respectively, but, any parasitic eggs and protozoan cysts in outlet effluent of both of wastewater stabilization ponds were not observed, so removal efficiency of these two parameters in these systems was %100 obtained. Ascaris lumbricoides eggs had most number of parasitic eggs in inlet wastewater and outlet effluent of all three wastewater treatment plants. According to the results, the efficiency of all three wastewater treatment plants in terms of removal of cysts and parasitic eggs are desirable and there was no significant difference between them (Pvalue>0.05). The outlet effluent quality of them in terms of nematode eggs rate is consistent with Engelberg index (number of nematode eggs: 1≥number per liter).

Phytoplankton plays a major role in monitoring aquatic ecosystems. The purpose of this study was to investigate the relationship between the density of phytoplankton and the nutrients, especially nitrates and phosphates and other effective parameters in Karaj dam as a case study. For this purpose, in 2010, Karaj dam was sampled during a year and physical, chemical and biological factors were measured. The penetration depth of sunlight into the water, was measured using Sechei disk. The results of this study demonstrated that there is a thermal stratification in Karaj reservoir. The density of phytoplankton in this lake increased in hot weather of the year and it also varies as the depth increases. In 2010, the most population in phytoplankton community of the lake was formed by Diatoma and specially Cyclotella. No relationship was found between the number of phytoplankton and the amount of chemical factors in this study.

Coagulation-flocculation is one of the most important processes for water treatment, commonly used all over the world. The use of synthetic polymers known as “Polyelectrolytes as a coagulant aid is now wide spread in water treatment plants. Tehran’s “Jalalieh WTP” has been using an anionic polyelectrolyte under the trade name of “Magna Floc LT25” for a number of years MagnaFloc LT25 (MF-LT25) is a synthetic coagulant with high molecular weight, produced in granular and powder form. The application of this coagulant aid is known to be most effective if injected to water after addition of main coagulant (Ferric Chloride in Tehran’s WTP). However the use of synthetic polymers in treatment of drinking water has always been under question due tohigh costs, availability and possible health effects. Moringa Oleifera (MO) is a tropical tree widely grown in south and south east parts of Iran, regionally identified as oily tamarisk (called “Gazrokh” by natives). The extract of MO seed contains proteins soluble in water which have high coagulating properties. This pilot scale study was performed to compare the coagulating properties of seed extract of MO to MF-LT25, The tests were carried out on Tehran’s raw water in Jalalieh treatment plant. Several turbidity ranges such as 5, 20, 100, and 200 NTU were used representing real seasonal turbidities of influent water to treatment plant. Optimum concentration of the coagulant and coagulant aid was determined within water pH values of 6, 7 and 8, using common “Jar Test” technique. The extract of Moringa Oleifera seed in optimum concentration of 10, 14, 25, 35 mg/L and optimum pH of 8 is capable in removal of 96.5, 97.4, 98.5 and 99% of water turbidity range of 5, 20, 100, and 200 NTU respectively. Under similar conditions, MF-LT25 removal efficiency were found 97, 98.1, 98.4 and 99.4% of water turbidity range of 5, 20, 100, and 200 NTU at optimum concentrations of 0.015, 0.02, 0.025, 0.03 mg/L respectively. The results also showed that the extract of Moringa Oleifera seed is a powerful coagulating agent, at alkalinity pH values, and is more effective for high turbid waters. It compared well with synthetic polyelectrolyte as a coagulating agent. Due to possibility of its production locally, and its excellent properties it could be considered as a potential substitute for more expensive imported polymers such as Magnafloc- LT25.

Nickel is one of the heavy metals in the surface water that its Harmful effects can include bone and lung cancers, cyanosis, chronic headaches, dizziness, and chest pain and body weakness. This study has been performed to determine the efficiency of reducing nickel from aqueous environments by using carbon nanotubes. Experiments were performed in batch reactor and changing effective factors such as pH, time and concentration of carbon nanotubes. Removal efficiency was investigated using a Friedman statistical test, software SPSS-16.The highest removal efficiency was 82.5% at a concentration of 100 mg/L of carbon nanotubes, pH=10, retention time of 10 min and nickel concentrations of 40 mg/L. The results showed that carbon nanotubes have a high ability to absorb high concentrations of nickel in the aquatic environment.

There are many non-wood lignocelluloses resources such as wheat, rice straw and other agriculture by- products with appropriate feature for pulp production in Iran. The most major deterrent to their use is presence of pulping black liquor that due to lignin of lignocelluloses solution contains significant amounts of color and phenol compounds. The aim of this paper was investigation of the ability to remove phenol and color as the most important organic pollutants from back liquor of agri-based pulping process using electrocoagulation method. In the electrocoagulation process aluminium electrode was used and cell potential and current intensity were adjusted on 16 V and 1700 mA respectively. The effect of various treatment time (10, 25, 40, 55, 70 min) and initial pH (3, 5, 7, 9, 10.5) of black liquor were investigated. The results showed that maximum of decrease obtained at pH 5 that has led to a remove capacity 78% of phenol and 98% of color in treatment time 70 min. electrocoagulation method can be used for black liquor treatment because of simple, effective and its low investment cost compared to other technologies.

In this work, the performance of two treatment plants in the City of Mashhad, one with an aerated lagoons system and the other one with waste stabilization ponds system were evaluated in regard to their efficiency in reduction of pathogenic microorganisms. For this purpose, over a period of one year (with 15-days intervals), samples were taken from the influent and effluent (prior to disinfection unit) of the above mentioned treatment plants. The samples then were analyzed for parameters such as temperature, pH, density of total coliforms (TC) and fecal coliforms (FC), dissolved oxygen and total suspended solids concentration. The results indicated that the aerated lagoons system was much more efficient in removal of indicator bacteria than the waste stabilization ponds during autumn and winter periods. However during the summer months, the waste stabilization ponds showed a higher efficiency in this regard. In general, the waste stabilization ponds system reduced the density of TC and FC by 0.21-2.15 log10 and 0.20-2.33 log10, respectively. In contrast, the levels of reduction in aerated lagoons system were in the range of 0.29-2.03 log10 for TC and 0.42-2.40 log10 for FC. Results indicated that solar intensity, pH and dissolved oxygen concentration were found to be the most significant parameters that reduced the microorganisms population in waste stabilization ponds, While, in the aerated lagoons system, the dissolved oxygen concentration in aerated basin and solar intensity play the most important role. In general, without receiving an adequate disinfection, the effluent from waste stabilization ponds and aerated lagoons cannot provide the microbiological standards required for irrigation of agricultural crops.

Electrocoagulation (EC) and Electrocoagulation/flotation (ECF) processes are simple and efficient in water and wastewater treatment. In recent years, many investigations have focused on the use of these processes for treating of polluted water. The purpose of this study was to investigate the efficiency of EC and ECF processes in removal of high turbidity water using different electrodes in different circumstances. In present study an electrocoagulation and electrocoagulation/ flotation reactor in a lab scale to an approximate volume of 6 liters which is equipped with four Al-AL and Fe-Fe electrodes (200 * 20 * 2 mm) was used for removing of high turbidity water. The effects of operating parameters such as type of electrodes, initial water turbidity, applied voltage (10 to 30 v), initial pH of the solution (3 to 12) and reaction times (5 to 30 minutes) were evaluated. The batch experimental results showed that initial turbidity water, initial pH of the solution, different applied voltages up to %88 turbidity as initial turbidity of 1200 NTU have been removed when using Al-Al and Fe-Fe electrodes and reaction times highly effective on the turbidity removal efficiency in these processes. In ECF process, 84% in optimum condition. However, in EC process the maximum removal was found up to 68% of initial turbidity when using Al-Al and Fe-Fe electrodes in same operation. Based on the result obtained in this study, the type of electrodes in EC and ECF processes significantly affect the removal rate of high turbid water. Also, it was found that much higher turbidity removal could be achieved by ECF process than that by EC process in the same condition.

This paper presents a simulation-optimization model integrating MODSIM river basin model and Particle Swarm Optimization algorithm for basin-scale optimal water allocation considering system's performance and equity indexes. The proposed model considers reliability, resilience, vulnerability and equity indexes in water supply and allocation directly in its objective function through which the trade-off between different indexes and their influence on water allocation results can be assessed. The model has been applied in Atrak River Basin water allocation problem as a real case study, where there are serious competition and conflicts between upstream and downstream provinces in using the basin water resources. The model has been capable of presenting good solutions in terms of all objectives compared to the best possible values obtained for each objective when ignoring other objectives.

Nickel is one of the heavy metals which commonly can be found in industrial wastewater. Many studies have been done on agricultural waste for the removal of nickel from aqueous solutions. The purpose of this study is to identify hard-shell pistachios as a local attraction for removal of nickel from aqueous solution. Nickel adsorption isotherm models are studied using shell pistachios. Pistachio shell was chosen which its particle size is between 800-600 microns. The stock solution of nickel ions was prepared mixing nickel nitrate with distilled water. The results showed that the maximum absorption efficiency occurs (73.3%) at pH=8. Also, it was shown that with increasing adsorbent dose, equilibrium time decreased within constant concentration. Examination of uptake isotherm models showed that models of Freundlich, BET, Radke-Praunitz, Redlich-Peterson and Sips describe data in 97% level of confidence well, however Freundlich and Sips isotherm models has the lowest error factor 0.10597 and 0/10598 respectively and the highest correlation coefficient (0.9785). Comparison of adsorbent capacity within removal of nickel from aqueous solution shows that Pistachio shell with special absorbent surface of 1.7 m2/g and uptake capacity of 0.3984 mg/g is proper than adsorbents of Kaolinite, Bagasse, sludgeash.

In recent decades, by increasing immunocompromised patients, disease related to nontuberculous mycobacteria, previously known as environmental opportunistic pathogen, has been raised. In this study, 85 water samples from different sources in Isfahan were evaluated for the presence of NTM. Phenotypic tests were used to identify NTM species. Twenty one out of 85 (24.7%) collected water samples had at least one NTM. Of these, 23.8% (5 isolates) and 14.3% (3 isolates) were M. furtuitum and M. smegmatis, respectively. Two cases for each isolates (9.5%) were identified as M. chelonae like organisms, M. terrae complex, M. gordonae and M. mucogenicum. One cases for each isolates (4.8%) was determined as M. avium complex, M. phlei, M. xenopi, M. fallax, and M. flavescence. The results showed the incidence of different species of NTM in this geographical region in Iran. Because of increasing immunocompromised disease in communities, and high frequency of NTM in different geographical regions, understanding the NTM distribution in environment would help clinicians to manage proper treatment strategy.

Transient flow in a conduit is an unsteady flow, followed by the change in the flow rate. Transient flow analysis is commonly based on the assumption of no air entrainment in the liquid phase. However, air entrainment in the liquid flow frequently occurs in the pipelines. Experimental study has been carried out to investigate the characteristics of transient pressure in a two-phase, air-water slug flow inside a rectangular, horizontal pipeline. Pressure surges propagating the pipeline that results transient pressure changes have been studied by rapidly closing a sluice gate inside the pipeline. The pressure variations have been recorded by installing different pressure transducers to the pipe. The results showed that increasing the air/water discharge ratio affects the transient pressure distribution in pipeline significantly. In the downstream 10% of pipeline length, pressure variation is considerably sharp, fast damping, and with higher peak. In other sections of conduit, low-frequency pressure changes were observed which were damped slowly.

The aim of this work was to investigate Bacillus sp. strain MGL-75 as biosorbent, for the fixation of Ni ion in batch reactor. Pollution of the environment by toxic metals is a major environmental concern. In a first step, biosorption kinetics and isotherms have been performed at pH 7. The equilibrium time was about 5 min and the adsorption equilibrium data were well described by the Langmuir's equation. The point of zero net proton charge (PZNPC) was found close to pH 5.7. Using the single extrapolation method, three kinds of acidic functional groups with three intrinsic pka were determined at 4.4, 6.9 and 11.2. The maximum capacity has been extrapolated to 0.52 mmol/g. Finally the effect of autoclave, 2, 4 Dinitrophenol (DNF) and Na-Azid (NaN3), and the effect of pH values, were studied. These results indicated that the Bacillus sp. strain MGL-75 is an excellent candidate for use in reactor to remove Nickel ions from polluted aqueous effluents.

Treatment of toxic organic compounds is one of the major applications of the Wet Air Oxidation (WAO) processes. The process can be defined as the oxidation of substances, either in the form of solutions or suspensions, with the use of an oxidant (oxygen or air) at elevated pressure and temperature. The aim of this paper was to study of Catalytic Wet Oxidation (CWAO) with hydrogen peroxide to improve removal efficiency of organic matter and ammonia mainly produced in Isfahan composting factory leachate. The experiment was carried out by adding 1.5 Lit pretreated leachate sample to 3 Lit autoclave reactor. Four parameters are considered: pressure (8–12 bar), temperature (100–300oC), retention time (30–0 min), H2O2 (1– mL/L).The highest removal efficiencies of COD and BOD were achieved at 300oC, approximately 44% and 48% were destroyed, respectively. On the other hand, highest ammonium removal efficiency was achieved at 100oC in which approximately 63.8% was removed. The efficiency of aqueous phase oxidation can be largely improved by the use of H2O2 as catalyst. Therefore, catalytic wet oxidation would provide an environmentally attractive option for control of organic and toxic wastes problems. Temperature was found to be the most important control variable of the wet oxidation process of leachate.

Estimation of the friction coefficient in pipes is very important in many water and wastewater engineering issues, such as distribution of velocity and shear stress, erosion, sediment transport and head loss. In analyzing these problems, knowing the friction coefficient, can obtain estimates that are more accurate. In this study in order to estimate the friction coefficient in pipes, using adaptive neuro-fuzzy inference systems (ANFIS), grid partition method was used. For training and testing of neuro-fuzzy model, the data derived from the Colebrook's equation was used. In the neuro-fuzzy approach, pipe relative roughness and Reynolds number are considered as input variables and friction coefficient as output variable is considered. Performance of the proposed approach was evaluated by using of the data obtained from the Colebrook’s equation and based on statistical indicators such as coefficient determination (R2), root mean squared error (RMSE) and mean absolute error (MAE). The results showed that the adaptive nerou-fuzzy inference system with grid partition method and gauss model as an input membership function and linear as an output function could estimate friction coefficient more accurately than other conditions. The new proposed approach in this paper has capability of application in the practical design issues and can be combined with mathematical and numerical models of sediment transfer or real-time updating of these models.

Electrocoagulation is one of the technologies which have been considered by many researchers in recent years. This process has many advantages including high efficiency, no need to chemical addition, low sludge production, capability of process control, easy to operation and maintenance. Bipolar electrodes system is one of the electrocoagulation techniques which can be used for increasing the process efficiency and better distribution of the electric current. The aim of this study was to remove hexavalent chromium from aqueous solution by electrocoagulation technique. Response surface methodology (RSM) was used to optimize the parameters involving in the process, and the effect of current density, initial chromium concentration and pH on the process were investigated. At optimal conditions, for the highest chromium removal (>90%), the optimum initial chromium, reaction time, current density and pH were found to be 117 mg/L, 50 min, 11.75 mA cm-2 and 4.5, respectively. It can be stated that electrocoagulation is an efficient technique for separation and removing high chromium concentration from aqueous solutions.