WATER AND WASTEWATER
Year:2013 | Volume:24 | Issue:1 (85)|Papers Count:16

The Anionic detergents are synthetic organic chemicals used in high volumes in household cleaning products. Alkyle benzene Solfunate (LAS) detergent is one of the most widely used anionic surfactants due to excellent cleaning properties. LAS can be toxic to aquatic organisms and bio-accumulated in some fish,and eventually spread through ecosystems using food chain. Thus it should be removed from wastewater before discharge direct to the environment. Photocatalyst degradation process is one the advanced technologies in removal of organic materials from water and wastewater. The aim of this study was the applicability of photodegradations of anionic detergent by use of TiO2 nanoparticles and their change in to the nontoxic materials such as H2O and CO2 in a slurry reactor. LAS solution (10mg/L) was prepared and in separated stages was exposed to UV and TiO2 and a combination of them. Also the effect of initial LAS concentration, TiO2 loading, pH and various type of UV irradiation on degradation rate were studied. Maximum degradation was obtained at acidic pH, 50 mg/l of TiO2 and 30 min irradiation time, It was also found 99.5% of LAS was degradated in optimal conditions. Kinetics analysis indicated that photocatalytic degradation rates of LAS can be approximated by pseudo-first order model. The mineralization of LAS was reported by measuring the initial and final COD of illuminated solution. Based on the results, UV/TiO2 process may be effectively applied in LAS removal in low concentration but for high concentration not recommended due to economic reasons.

Biosorbents have become increasingly important for removal of heavy metal from water and wastewater due to their and biodegradability low costs. Chitosan is a hydrophilic and cationic polymer product of chitin deacetylation and used as an absorbent for removal of heavy metals. In the present study, the adsorption of Pb (II) metal ions from aqueous solution by chitosan nanoparticles was investigated. Nanoparticles are formed by reacting of the free amino groups of chitosan with carboxyl groups of maleic acid as crosslinking agent. Nanoparticles were characterized by Scanning Electron Microscopy (SEM) and fourier transform infrared spectrometry (FT-IR). The average size of the nanoparticles obtained was about 65-250 nm. Adsorption experiments were performed at room temperature in batch system. The effects of pH, concentration of metal ions and adsorbent dose were conducted. Optimization of adsorption was carried out by the initial solution pH ranged from 3 to 6, the initial metal ions concentration ranged from 10 to 100 mg/l and the adsorbent dose ranged from 1 to 7.5 g/l. Under these conditions, optimal values of initial pH solution, concentration of metal ions and adsorbent dose were found at 6, 100 mg/l and 2.5 g/l respectively. The maximum removal efficiently of 86% for Pb (II) in concentration of 10mg/l was achieved. The adsorption data fairly fitted to Langmuir and Freundlich isotherms. The maximum adsorption capacity of 25.8 mg/g based on Langmuir isotherm was obtained.

Considering the surface water resources as one of the main water supplies in many regions of Iran. The application of chlorination for disinfecting drinking water has increased the rate of Disinfection By- Products (DBPs) formation. The required cost for DBPS removal motivates researchers to find a solution related to substitute the chlorination process and need for residual chlorine. Using the current Nano particles such as silver, copper and zinc in powder form is one of the best alternatives in injecting polymer and producing the pipe, but several problems such as lack of uniform distribution of Nano particles in polymer matrices, distribution of particles in the air (TLV), release of Nano particles into the system and accumulate in the body, high consumption due to reduction of filler properties and increased cost price of products led to unpopularity of this technology. Using capsulated material because of zero release and high rates and low prices can be a good choice and useful substituent. In this study various concentrations of Al2 O3 / SiO2 micro-particles, which the silver Nano particles are on these micro-particles have been used to produce sheets, and microbial tests have been done on samples of composites prepared by Iran national standard method of 10.900. And ultimately based on an amount of bacteria and retention time minimum particulate required to slow the growth of bacteria was determined as 4 percent by weight.

Silver nanoparticles have become one of the most commonly used nanomaterials in consumer products because of their effective antimicrobial properties and low toxicity toward mammalian cells. In the area of water purification, today nanoparticles are widely used for detection and removal of chemical and biological substances. Therefore by the growing use of nanoparticles, further research is certainly needed to study the behavior of them. In this study, the antibacterial and antibiofilm activities of colloidal nanosilver (average size: 40±10 nm) on the growth, cellular respiration and biofilm formation of pathogenic strains and the isolates from the cooling water of Isfahan Oil Refinery (A1 and A2) were compared with biocide E-265 which generally used in this refinery by microtiterplate method. The results showed that different concentration of biocide E-265 had no significant effects on the bacterial growth and even at 20 and 40 ppm showed 100% increase in the biofilm formation of the isolate A1. Also it is detected that low concentration of nanosilver (1-2 ppm) showed unique antibacterial and antibiofilm activities and can be suggested as a suitable biocide for the recirculating water systems.

The efficiency of modified Phragmites australis nanoparticles for nitrate removal from aqueous solution in batch and continuous conditions was studied. The effect of different operating conditions such as pH, the amount of adsorbent, and initial nitrate concentration were surveyed. Our results showed that, pH 6 could provide better condition for nitrate removal. The increase in the nitrate concentration from 5 to 120mg L-1 reduced the efficiency from 90% to 67%. Kinetics and isotherm data revealed that the nitrate adsorption successfully can be described by pseudo-second order kinetic model (R2 =1) and Longmuir isotherm (R2 =0.99), respectively. At the continuous-flow mode, column were operated at 0.98 L hr-1 and 2.27 L hr-1 with initial nitrate concentration of 15, 50 and 120 mg L-1. At the above mentioned conditions, the adsorption capacities were 13.4, 28.5 and 36.5 mg g -1 at 0.98 L hr-1 and 25.2, 60.9 and 74.3 mg g-1 at 2.27 L hr-1, respectively.

Activated sludge process is one of the well-establish methods for biological treatment of oily wastewater, which use in Iranian oil refineries. However, the process involved many problems such as low efficiency at high concentration of hydrocarbon, instability during hydraulics shocks and bulking phenomena. In this paper attached and suspended growth was used to improve conventional activated sludge treatment process. A hybrid activated sludge reactor, with 34.5 liter capacity, was used in order to treat synthetic high CODs oily wastewater and the results were compared with those obtained from conventional activated sludge reactor. Novel media used in this fixed-film biofilm bioreactor, provided a high surface area-to-volume ratio (600m2/m3). Reactor biodegradability for COD and TPH was evaluated for different hydraulic retention time (HRT) and oil pollution concentration. In optimum condition (T= 27oC, pH= 7.5, DO= 4.1mg/l, recycle sludge ratio= 1 and COD/TPH= 2.5) the removal efficiency of HASBR for TPH and COD were 90% and over 95% respectively which showed a significant difference in comparison with the conventional activated sludge reactor in the same conditions. Therefore, existing conventional activated sludge plants could be upgraded and improved by changing the reactor configuration and introducing support media into aeration tank.

Over 90 percent of the wastewater treatment plants in Iran use activated sludge process. Due to increase in organic loading rates, most of these plants do not have appropriate performance. For upgrading these systems and decreasing production of the excess sludge, a UASB reactor can be used as pretreatment for decreasing the organic loading prior to the activated sludge system. Also for improving the effluent quality, a membrane can be replaced for secondary sedimentation tank, i.e. changing activated sludge to membrane bioreactor. In this study, the effect of significant changes in feed composition, due to the introduction of UASB reactor; have been investigated on the population of filamentous bacteria, COD and TS removal efficiency and membrane fouling. The results showed that the population of filamentous bacteria increased rapidly from 5 to 100 Count/µL. However, this increase does not have considerable effect on membrane fouling. With increasing MLSS concentration, the number of filamentous bacteria increased from 100 to 400Count/µL. As a result, the trans membrane pressure was raised from 1.5 to 3kpa and overall membrane resistance was increased against the effluent flux. For reducing the filamentous bacteria, a dose of 20 g Cl2 /Kg MLSS was added in few intervals for two days. It was also found the number of filamentous bacteria decreased from 400 to 100 after 5 days without decreasing the other microorganisms’ population significantly. The trans membrane pressure was also retained without any further increase.

In this study the efficiency of anaerobic stabilization pond for treating oil refinery wastewater at different concentrations of phenol is investigated. The anaerobic stabilization pond (ASP) was built from fiberglass plats (0.2m×1m×1m and 6mm thickness). The experimental apparatus was performed at HRT (2d) with hydraulic loading rate 95L/day. After inoculation of the biomass, reactor was run at different concentrations of phenol (100, 200, 300, and 400 mg/L). Sampling is carried out from effluent after achievement of steady state condition at all experimental tests. The samples for the determination of NH3, PO4 and Phenol, were analyzed using a spectrophotometer (Varian, UV-120-02). In addition, other parameters such as TCOD, SCOD, TBOD, SBOD, and pH were determined using standard methods. The results showed that the efficiency of system reduced at phenol concentrations of 100, 200, 300, 400 mg/L. The maximum and minimum removal rates of BOD and COD were 71.75±8.14; 76.07± 10.94 and 53.5±6.03, 55.63±3.47 by the system respectively at phenol concentrations of 100 and 400 mg/l. The optimum condition for phenol removal (89.82% and 55.86%) was determined with phenol concentrations of 100 mg/L and 400 mg/L, respectively. This study showed a comprehensive efficiency of anaerobic stabilization pond as a promising system to eliminate different concentrations of Phenol, COD and BOD, however increase of Phenol concentration to 400 mg/L was decreasing of system efficiency due to phenol toxicity for biomass.

Mercury has recognized as one of the most toxic heavy metals, which many industries generate and dispose to the environment. Few studies are done about mercury accumulation in soil and bioconcentration and transfer factor of mercury in rice plant cultivated in industrial areas. In this study samples were taken randomly from 10 farms in vicinity of Amol industrial suburban area with three replications. Samples were measured by the LECO AMA 254 Advanced Mercury Analyzer according to ASTM D-6733method. Also the parameters related to the quality of the soil were measured. The mean of mercury concentration in soil, root, stem and grain were found 0.031 ±0.012 mg/kg, 0.074 ±0.0163 mg/kg, 0.058 ±0.008 mg/kg and 0.051 ±0.0083 mg/kg respectively. The calculated transfer factor of mercury to various organs and bioconcentration factor were < 1 and 2.46 respectively. Pearson correlation test showed a positive correlation between mercury concentration in soil with mercury concentration in grain and also a negative correlation between pH with mercury concentration in root and soil. It is concluded that rice plant have high potential for phytoremediation of mercury from soil.

Oil, gas and petrochemical projects are implemented to achieve the industrial development and economic benefits. The human welfare is one of the main anticipated aims for these projects. However, these projects result in vast environmental impacts. In this research, the rate of petroleum emulsion in Arvand River receiving a petroleum complex wastewater treatment effluent was investigated. Results showed that, the maximum concentrations of DO, COD and BOD were 7.2, 95.8 and 48.4 mg/L and the minimum concentrations were 1.64, 21mg/L and 4 mg/L respectively. The maximum concentration of oil and grease was 18.5 mg/L. Oil and grease content have not been observed in Arvand River during research period. It was also found the maximum concentrations of TSS, TDS and Hardness were 56, 8400 and 3762 mg/L and the minimum were 21 mg/L, 1740 mg/L and 680 mg/L respectively. The results revealed that the effluent quality from this complex does not meet the discharge standard to surface waters and the exiting treatment process is not sufficient. Therefore, a more advanced process is required and recommended.

Methods for evaluatingthe quality of groundwater resources and recognition of appropriate locations for urban and agricultural water demand has been known as an important item in water resources planning. The main focus of this paper has been addressed a new water quality mapping based on coupling of fuzzy approximation and water quality indexing. In this paper, after indexing water quality in each monitoring well, based on fuzzy reasoning a new global fuzzy indexing has been presented. In this regard, 12 water quality parameters for 217 monitoring wells in the province of Ghazvin in the north have been used. In the final step, map of fuzzy evaluation over the area of interest has been provided based on an optimized new spatial approximation via Genetic Algorithm (GA). The results showed the capability of the proposed methodology for groundwater quality mapping. The most important contribution of this paper is successful combination of fuzzy reasoning and water quality indexing as a continuous function for evaluating groundwater quality mapping.

The water resources are limited and the groundwater levels decrease due to water abuse. This causes the lack of water problem in some regions of Iran. Therefore the hydrological and statistical methods needed for prediction of the water levels at a given location, region or times. The groundwater levels are variables changing by space and time, and their data can be considered as a spatial-temporal data set. Modeling of the correlation structures of such data is a major tool, for the prediction of unknown water level at some specified locations and times. This correlation structure is specified by fitting suitable variogram or covariogrammodels to the data. In this article some nonseparable covariance models were briefly reviewed. Then the spatial-temporal variogram of underground water levels were estimated as product and sum-product models. Finally the underground water levels of Birjand region was predicted using the universal kriging and give the contour map at the selected time. Moreover the prediction precision of different models were compared numerically.

Leakage is one of the main problems in the water supply systems and due to the limitations in water supply and its costly process, reduction of leak in water distribution networks can be considered as one of the main goals of the water supply authorities. One of the leak detection techniques in water distribution system is the usage of the recorded node pressures at some locations to calibrate the whole system node pressures. Calibration process is accomplished by the optimization of a constrained objective function. Therefore, in addition to performing a hydraulic analysis of the network, application of an optimization technique is needed. In the current paper, a comparsion between the ant colony and genetic algorithm methodes, in calibration of the node pressures and leak detections was investigated. To examine the workability and the way of leak detection, analysis of the network with an assumed leak was carried out. The results showed that the effectiveness of the ant colony optimization in the detection of the position and magnitude of leak in a water network.

The aim of this study is the spatial prediction runoff using hydrometric and meteorological stations data. The research shows that usually there is a certain communication between the meteorological and hydrometric data of upstream basin and runoff rates in output basin. So, if can be extracted the rules related to historical data that recorded at stations, can be easily predicted runoff amount based on data measured. Accordingly, among the tools available, the fuzzy theory (with flexibility in developing fuzzy rules) can be provide the knowledge lies in the observed data to parameters prediction in real time. So, in this research the fuzzy inference system has been used for estimating runoff rates at stations located in the Taleghan river downstream using rain gage stations and hydrometric stations upstream. Because the inappropriate values associated with membership functions, the fuzzy system model can not provide correct value for the prediction. In this study, a combination of intelligence-based optimization algorithm and fuzzy theory developed to accelerate and improve modeling. The result of proposed model, optimum values to each membership function that related to dependent and independent variable extracted and based on it’s the runoff rates in rivers downstream predicted. The results of this study were shown that the high accuracy of proposed model compared with fuzzy inference system. Also based on proposed model can be more accurately the rate of runoff estimated for future conditions.

One of the main sources of environment pollution is the industrial wastewater which contains heavy metals and can be found in many industries such as plating industry. If these heavy metals enter in the human body, would cause many health problems. The aim of this study was to investigate the possible application of nanofiltration technology in removal of three heavy metals (nickel, zinc, and cupper) as the most representatives of heavy metals in plating effluents. The effects of different pressure, concentration, and time of filtration on removal of these elements were evaluated. Two concentrations levels of heavy metals (25 and 50 mg/L) were studied under three different pressures of 4, 6 and 8 bar. pH and temperature were considered constant in all experiments. The results showed that increasing of pressure resulted in increased in removal. This was more significant for Cu (100% removal) than Zn and Ni under 8 bar of pressure. Also, it was found increasing of concentration resulted in decreased removal of heavy metals. The results showed that Zn removal decreased from 99% in 25 mg/L to 97. 07% in 50 mg/L. Finally, the filtration time caused a positive effect in the heavy metals removal.