WATER AND WASTEWATER
Year:2012 | Volume:23 | Issue:3 (83)|Papers Count:18

In water supply systems, the accidents occurring in pipes are of the utmost importance and sensitivity. Failure of the pipes is not necessary with the end of their life and different factors namely age, diameter, material, stability and corrosion of soil and water, execution, installation and operational conditions such as hydraulic pressure are effective on it. At the same time studies show non comprehensiveness of presented relations in prediction of pipes failure rate. In this research, with regards to the available software and hardware, a structure was developed using combination of new optimization and simulation models. In this structure, theartificial neural networks were used for simulation of the pipes failure rate. Considering the point that neural networks are always consider as a black box and unable to provide the effect of each independent variable on the dependent variable, on the other hand, they are prone to incorrect training. Therefore, in this study to determine the input parameters affecting failure rate and the most appropriate structure of artificial neural network (as well as bios vectors, layers adjusting weights and the number of neurons), Genetic algorithm has been used with the aim of presentation of a structure which has the minimum error rate of simulation. In this algorithm, decision variables and properties of neural networks are the parameters affecting the failure rate. By running the developed optimization model, in addition to the effective parameters on pipe failure, the best neural network structure for simulation pipe failure rate can be determined. The advantage of the proposed method is full coordination between the input parameters and network structure in prediction of the pipes failure rate. The results of this study can be used to find the most appropriate relationship failure rate pipes with regards to the effective parameters and take necessary actions for decision making lead to resolve problems due to it. The results of this research indicating that the proposed combination method is able to extract the optimal and effective parameters on the pipes failure rate amongst the factors affecting failure rate, and also have been caused improve power capabilities and expansion of neural network structure that indicate high efficiency of the proposed method in simulation of nonlinear and complex relations.

In this study, the different methods for groundwater vulnerability assessment to pesticides contamination and their uncertainties were introduced. Then, the groundwater vulnerability of agricultural regions of Pasha-Kolaa dam (Mazandaran province) to 7 pesticides has been assessed by the mobility potential indices in the typical conditions of pesticide properties (t1/2 and KOC) and the zonation maps of groundwater vulnerability in this region have been generated in the GIS environment. According to the uncertainty of the pesticide properties and the lack of necessary data for uncertainty analysis in the region of study, the mobility potential indices in different scenarios of pesticide properties (worst and best conditions of pesticide properties) (t1/2 and KOC) have been calculated, mapped and zoned. The zonation maps in three scenarios (best, typical and worst conditions of pesticide properties) were compared. Next, according to the regional values of mobility potential indices, generated for different scenarios, the pesticides are ranked using the composite programming method. Finally, the pesticides are clustered to three groups (suitable, transitional and unsuitable) by the combination of the results of previous sections. The clustering results showed that among of studied pesticides, 2, 4 D Acid, Dimethoate and Fenvalerate are suitable, and Metsulfuron and Triclopyr are unsuitable pesticides for region of study. The other pesticides showed transitional condition.

Design of sewer networks involves many constraints and technical criteria. These issues make the problem complicated and the feasible alternatives difficult to achieve. Besides, the methods of handling these constraints play a major role in optimization approaches for the least cost design. In this work an integrated analysis-design model is developed thereby all constraints are automatically satisfied during designing. A normal design alternative is defined herein which is a vector of values between zero and one. This vector represents the sewers diameters, slopes and pump station locations. The normal alternative is then decoded to real design parameters based on the hydraulics rules and the problem constraints. Using the proposed model every normal alternative is feasible and consequently the input design parameters are totally unconditional. At the end the abilities of the model is shown introducing and solving a relatively large sewer network. Furthermore, to demonstrate the capability and easiness of integrating the model with optimization tools, a Simulated Annealing (SA) algorithm is also applied to obtain the least cost design of the example. The results show that the optimum design and the rate of optimization convergence are significantly improved using the proposed method.

Etland is one of the natural treatment methods used for municipal wastewater treatment, which could transfer the effluents to the ecosystem, safely or being used for agricultural purposes and etc. this study investigates a pilot in the form subsurface flow wetland efficiency in rural sewage result of septic tank. The constructed Wetland was built in Morad Tapeh Village, Karaj County, Alborz Province.The pilot project was executed from galvanized plates with the dimensions of (length 20 m- Depth 1 m- width 30 cm). 0.5 m from each side of the Pilot Project was covered by rubble-stones to the depth of 0.5 m and the interval was filled by screened sand, porosity degree (a=0.39), maximum 10% of them measuring 2mm, with the hydraulic conductivity Ks=1575 F3, covered by 10cm peat. The study took one year, from Sept. 2009 to Sept. 2010. The plant used in this constructed Wetland, was the common straw, scientifically named as Pharagmites Australis and role of the pilot constructed Wetland was considered refining pollution, using this type of plant. It was supposed that the said project decreases the items P, N and some other parameters including TSS, COD and BOD and brings them within limits of the ecological standards. Tests were carried out according to the method, showing following results: (1)BOD input & output averages is 57±31 and 8±4 mg/l respectively, while its average elimination percentage is %79 ±15.(2)COD input & output averages is 97±47 and 24±12 mg/l respectively, while its average elimination percentage is %70±16.(3)TSS input & output averages is 40±47 and 5±4 mg/l respectively, while its average elimination percentage is %76±16. (4)TN input & output averages is 13±6 and 4±3 mg/l respectively, while its average elimination percentage is %59±26.(5)TP input & output averages is 7±7 and 8±9 mg/l respectively, while its average elimination percentage is %86±12.

Drought is one of the important natural disasters that may happen in any climate conditions. Since drought is inevitable phenomenon, therefore familiar with that natural disaster is very important for reliable water management. Drought prediction system design is one of the efficient ways that it can minimize the drought damages. In this research for predicting the coming drought, genetic algorithm and conjoined model of neural network-wavelet is used for analyzing standardized precipitation index. The results show that genetic algorithm and conjoined model of neural network-wavelet is more satisfactory than genetic algorithm and neural network.

Arsenic which is present in the underground and surface water is one of the most toxic elements threating human health and animals. Arsenic has been removed in different type of ways. In this study Arsenic removal from drinking water and its decreasing rates were investigated by NZVI (nanoparticle zerovalent iron) to standard limit (I.e. 0.01 mg/lit). The tests were conducted on reactor containing 100 ml water containing 1 mg/L. Arsenic by virtue of Batch method. The mixture was executed in mixing was done an Oultrasnic device in order to have better mixture and complete distribution of nanoparticles in water. Then the arsenic was removed from the water by VATMAN paper of 0.45 Hm. The remained arsenic in the water was measured by ICP device. In this article the influence of the parameters including mixture time, PH, NZVI and arcenic doses were examined. Having perfomed many tests the results showed that 1 mg arsenic can be removed 100 percent by 0.05 g NZVI in 8 min. It is possible to remove by 98 percent arsenic in 5-10 PH range. Iron nanopaticle way is an effective and rapid way to remove arsenic from water and various conditions have not considerable effect on it.

The main purpose of this paper is examination of return to scale index and economics of scale index that is an argument of being natural monopoly, also investigation on states of technical changes and productivity growth rate in Shiraz water and wastewater company. This is the reason translog cost function is used to estimate the cost function of the water supply in this company. The framework of analysis is in accordance to the iterative seemingly unrelated regression (ISUR) technique. To estimate the parameters of the cost function we have used the quarterly data for the period of 1999-2006 has been used. This company uses four factors of production in its process: labor, capital, raw material and other services. The result showed that there exists decreasing return to scale and no economizing of scale that rejects the existence of natural monopoly in this company. Advance technology index indicated cost decrease as a result of advance in technology and calculation index of productivity growth showed the existence of productivity growth during the surveyed period of time.

In this study, efficiency of UV/NiO system as a forms of Advanced Oxidation Processes (AOP) to remove red poly azo was investigated. This study was conducted as a pilot scale and batch mode. Ultraviolet was achieved by 11 W low pressure lamp. Effects of various factors such as pH, different times of irradiation, different concentration of nickel oxide, primary concentration of colors were evaluated. The test results of UV/NiO system showed that no effects were observed with UV alone in photocatalysis process for removal of dye DR 80. Nickel oxide is an effective catalyst in removal of dye by the nanophotocatalytic process. The results represent that the color removal efficiency increase with pH reduction and optimum pH was found 4. Fainally, the highest removal efficiency for DR 80 dye with concenteration of 25 mg/L and 50 mg/L was obtained about 94.29% and 82.22% by the process of UV/NiO respectively. Reaction kinetic in the UV/NiO process follows pseudo secondry-order reactions. Totally UV/NiO process is an effective methode for DR 80 poly azo dye removal in aqueous solutions.

Integrated management of urban watersheds and effective productivity of its resources, especially water resources requires knowledge of its hydrology. In this among flood events and urban runoff produced at the time of floods from the point of harvesting and consumption is extremely important. In this study in order to evaluate the possibility of using the most appropriate water harvesting systems in Arak Watershed, collecting basic information was collected. At first surrounding watersheds were grouped by using cluster analysis into homogeneous areas. In each region using the rainfall - runoff SCS model runoff rate of some base time and return periods was calculated. Using a hierarchical analysis (AHP) and quantitative and qualitative criteria, different systems of urban water harvesting were determined for each homogeneous region of Arak watershed.

Chitosan, as a coagulant is used in water and wastewater treatment. It has similar performance in comparison with other conventional coagulants, and doesn’t have any disadvantages of them. However, its bactericidal property is lower than the metal based coagulants. In this study the potential synergistic effect of potassium permanganate, as a powerful oxidant, on the Chitosan fecal coliforms inactivation and turbidity removal has been investigated. Synthetic wastewater samples were prepared by mixing tap water with Bentonite and adding pure culture of fecal coliforms that provided by biological laboratory of Tehran University of Medical Sciences. After preparing synthetic samples of the wastewater and determining its turbidity and fecal coliforms concentration, various doses of Chitosan and Potassium Permanganate individually and in combination with each other, were injected to the samples. Afterwards supernatant of jar reactors were investigated for turbidity and fecal coliforms removal. Simultaneous use Chitosan and potassium permanganate has higher removal efficiency than the individual using of them. Highest applied combined dose (3 mg / L Chitosan and 1.5 mg / L potassium permanganate) reduced fecal coliform to a level less than 100 MPN/100mL, which is equivalent 4 log-inactivation of fecal coliforms. Simultaneous use of Chitosan and potassium permanganate in tertiary treatment of wastewater can led to produce lower turbidity, as well as higher microbial quality in the effluent, which can reduce the amount of required disinfectant, consequently disinfection by products formation lowered very much.

Nanophotocatalysts such as titanium dioxide (TiO2) have been successfully used to degrade pollutants during the past few years. Photocatalysts have some benefits such as non toxicity, high stability, high efficiency and low cost. In this study, photocatalytic decomposition of organophosphorus compound, triethyl phosphate (TEP), in water using nano-TiO2 powders as a catalyst has been investigated. Besides, adsorption of TEP on nano-TiO2 in different pH levels, comparison of micro-and nano-TiO2 efficiencies and effect of Hydrogen peroxide (H2O2) on TEP decomposition has been investigated. The results showed that at 30 mg/l triethyl phosphate dosage, 400 mg/l nanocatalyst, 90 watt power of radiation source, pH about 7 and 4 hours of exposure time, decomposition of over 99 percent is achieved.

The present study investigates the degradation of Acid Red 14 (AR14), commonly used as a textile dye in aqueous medium through the oxidation process by UV /S2O82- under a set of variables concentration of S2O82-, Ag+, AR14 and temperature. Commonly Ag+, heat and UV light can excite S2O82- to sulfate radical form (SO4-), a stronger oxidant (E0=2.60 V) than S2O82-, to enhance significantly the oxidation of contaminants. Also the changes in the absorption spectra of AR14 solutions during the photoxidation process showed that decrease of absorption peak of the dye at lmax=514 nm indicates a rapid degradation of the azo dye. The results of this study suggest that the oxidative treatment of AR14 by peroxydisulfate with UV is a viable option for removal of the textile dyes from effluents.

Biosurfactants have the ability to form heavy metal complexes and clean up heavy metal contaminated soils. In this work, a biosurfactant producing bacterium (Bacillus spp.) isolated from compost and Pseudomonas aeuroginosa ATCC3027 were cultured in whey in order to produce biosurfactant. Compost samples were leached by supernatant of mentioned strains. Total amount of Pb, Ni, Cr, Cd, Zn, Cu and Mn in samples were measured before and after treatment was measured. It was revealed that supernatant of P. aeuroginosa ATCC 3027 removed 52, 49, 60, 33, 25, 32 and 22% of Pb, Ni, Cr, Cd, Zn, Cu and Mn respectively. Heavy metal removal by supernatant of strain B was 45, 39, 42, 33, 40, 41 and 29% for above mentioned metals; respectively. These results indicate the potential of the biosurfactants as leaching agents for heavy metal removal from compost.

This study investigates the presence of heavy metals such as copper, iron, zinc, mercury, lead, cadmium and manganes in muscle, liver and gill of fish (L.abu) in the Karoon River, in Khuzestan province. Samples were collected in winter 2010. After the biometric data of 72 specimens were recorded the samples of muscle, liver and gill were analysed. Sample preparation and analysis was done according to MOPPAM method. The concentrations of heavy metals in the dry digested samples of tissues were measured using Atomic Absorption Spectrophotometer (AAS). The results of this study showed that the average concentrations of heavy metals were negligible and at maximum value in muscle and giil tissues, respectively. Iron concentration was showed to be higher than those of zinc, lead, manganese, cadmium, copper and mercury in different organs of fish (Liza abu). (P<0.05). Accumulation of lead, mercury, cadmium, iron and copper in muscle, liver and gill was highly significant and there were positive linear relationship between them (p<0.05). Concentration of Zinc in muscle and liver were not significantly different, but there were significant difference between muscle and liver with gills (p<0.05). Manganese concentration was determined in liver and gill showed no significant difference but it was significant difference between liver and gill with muscle (P<0.05). The results of the present study suggest that higher accumulation of heavy metals in liver and gills can be good environmental indicators of metal stress in Liza abu.