WATER AND WASTEWATER
Year:2006 | Volume:16 | Issue:4 (56)|Papers Count:11

This paper present simulation-optimization models for waste load allocation from multiple point sources which include uncertainty due to vagueness of the parameters and goals. This model employs fuzzy sets with appropriate membership functions to deal with uncertainties due to vagueness. The fuzzy waste load allocation model (FWLAM) incorporate QUAL2E as a water quality simulation model and Genetic Algorithm (GA) as an optimization tool to find the optimal combination of the fraction removal level to the dischargers and pollution control agency (PCA). Penalty functions are employed to control the violations in the system. The results demonstrate that the goal of PCA to achieve the best water quality and the goal of the dischargers to use the full assimilative capacity of the river have not been satisfied completely and a compromise solution between these goals is provided. This fuzzy optimization model with genetic algorithm has been used for a hypothetical problem. Results demonstrate a very suitable convergence of proposed optimization algorithm to the global optima.

A Genetic Algorithm (GA) method for optimization of multi-reservoir systems operation is proposed in this paper. In this method, the parameters of operating policies are optimized using system simulation results. Hence, any operating problem with any sort of objective function, constraints and structure of operating policy can be optimized by GA. The method is applied to a 3-reservoir system and is compared with two traditional methods of Stochastic Dynamic Programming and Dynamic Programming and Regression. The results show that GA is superior both in objective function value and in computational speed. The proposed method is further improved using a mutation power updating rule and a varying period simulation method. The later is a novel procedure proposed in this paper that is believed to help in solving computational time problem in large systems. These revisions are evaluated and proved to be very useful in converging to better solutions in much less time. The final GA method is eventually evaluated as a very efficient procedure that is able to solve problems of large multi-reservoir system which is usually impossible by traditional methods. In fact, the real performance of the GA method starts where others fail to function.

Cyanide, a generic term referring to all compounds containing the cyanide group -CN, is a highly potent and fast-acting poison to humans and other living organisms when exposed to high levels. Cyanide is a widely and essential chemical used in mining and minerals processing industries and many other industries such as metal processing and production of organic chemicals. While some industrial cyanide containing wastes are treated or recovered, there are cases such as certain gold extraction plants where wastes are released in the environment. The objective of this research is to study the transport and fate of cyanide in soil in vicinity of a specific pollution source. For the purpose of this study, Mooteh valley, in the vicinity of Mooteh gold mine and factory, m the north of Isfahan province, Iran, was investigated. In Mooteh's Plant, the cyanide-containing waste (slurry tailings) is discharged to tailings ponds and there is potential for cyanloe to migrate from them. Eight boreholes with 6 m depth were dug and from every 0.5 m a soil sample was taken. Statistical analysis of the results show that soil cyanide concentration decreases with distance from the tailings ponds (as a pollution source) and increases with depth. A regression model consisting of a power term for distance and an exponential term for soil depth can appropriately predict the soil cyanide concentration m the vicinity of a pollution source. As soil depth decreases, the rate of natural cyanide fate processes considerably increases. So, soil turn over practices is recommended to improve remediation of polluted sites.

Industrial contamination leakage into groundwater resources is increasing during recent years. Unlike surface water resources, lots of contaminants are stable in groundwater. Hence, several technologies, like Pump-and- Treat (PAT) and Air Sparging (AS), are being used in order to remedy contaminated aquifers. Despite of suggestions about using these two technologies together, there is no integrated simulation model for these two technologies. Using existing models for PAT simulation and combining them with AS simulation model, an integrated model for simulation of these technologies in field scale has been developed in this study. In addition to model validation, remediation of Bagher-Shahr aquifer (west of Tehran refinery) from MTBE by using AS and PAT technologies has been evaluated during a case study. Based on the suggested design for local remediation of MTBE plume in Bagher- Shar aquifer (without facility installation inside the city area) and during a five- year simulation period, mass of contaminant inside the city area is decreased to half of the initial mass.

Removal of ammonium is very important due to its toxicity to the environment and human being. The wastewater of Isfahan Steel Company (ESC) Contains high concentration of phenol (maximum 3000 mg/l) and ammonium (maximum 2000 mg/l). Therefore its effluent in the range of 1400 mg/l was used in this study as a feed. Synthetic wastewater also used for the comparison of removal efficiency. The bioremediation of ammonium in wastewater treatment of Isfahan Steel Company is very low. In this study activated sludge and compost were used to remove ammonium from effluent of Steel Company and synthetic wastewater. The results showed the maximum removal of ammonium by using activated sludge and compost in combination with mineral salts and glucose and CaCl2 in the effluent of ESC and synthetic wastewater were found 38.7% and 75.7% of respectively. The application of activated sludge and compost in effluents containing low ammonium and toxicity is very significant. Overall, due to considerable efficiency and low cost, this process could be used for ammonium removal in industrial wastewater.

The most fundamental model which is considerably used in designing of treatment plant is Monod model. Although there are some problems regarding using this model, it is frequently used by the engineers. In the present study the accuracy and precision of this model was evaluated in different range of S0/X0 ratio. The results of simulation showed that the Monod model for low ranges of S0/X0 does not have a great precision, but for high ranges of S0/X0, it shows acceptable concordance.

The disposal of excess sludge from wastewater treatment plant represents a rising challenge in activated sludge processes. Hence, the minimization of excess sludge production was investigated by increasing the dissolved oxygen in aeration basin. Units of the pilot include: Primary sedimentation tank, aeration basin, secondary sedimentation tank, and return sludge tank. Volume of aeration basin is 360 l and influent flow rate is 90 L/h. Influent of pilot is taken from effluent of grit chamber of Isfahan's North Wastewater treatment plant. The experiments were done on different parts of pilot during the 5 month of study. Results show that increase of dissolved oxygen in aeration tank affect on decrease of excess sludge. Increase of dissolved oxygen from 0.5 to 4.5 mg/L resulted in 25% decrease of excess sludge. Variation of dissolved oxygen affect on settle ability of sludge too. By increase of dissolved oxygen, SVI decreased and then increased. Value of 1-3 mg/L was the adequate range of dissolved oxygen by settles ability of sludge and optimum range was 2-2.5 mg/L. It could be concluded by increasing of dissolved oxygen up to of 3 mg/L, sludge settle ability significant decreased.

In this research, the performance of pumice stone as a fixed bed support in the biological treatment of the synthetic wastewater of sugar beet factory was evaluated. Pumice is a volcanic rock having high porosity and specific surface and in comparison with other supports, pumice has a very low price. The experiments were done on an up-flow biofilm reactor, the effective volume of which was 14.2 L, with pumice fixed bed supports. After the starting period, the reactor was operated in steady-state mode, which lasted 222 days, at hydraulic retention time of 12, 16 and 24 hours and influent COD concentration of 750, 1500 and 2250 mg/L. During the operation, the contamination removal efficiencies from 89 to 97 percent were achieved in 9 experimental runs. The results demonstrate that in organic loading rate from 750 to 4500 gr.COD/m3/day in the mentioned status the reactor's efficiency is satisfactory. In addition, some kinetic prevalent models were tested with the experimental data. Results show that according to the regression coefficients, Grau second order kinetic model and modified Stover-Kincannon model are appropriate for predicting similar reactors situations and designing new reactors, and the related equations were derived.

Unaccounted for water (U.F.W) represents water that has been produced and is lost before it reaches the customer, through leakage and, other means. U.F.W is an environmental, social, cultural and economic issue. Because loss exist in any water distribution systems, therefore it is necessary to identify the causes, effects and degrees of the problem and find the best way for reduction and control of U.F.W. In this research, the causes of UFW and estimation of it as a case study in the city of Sisakht in Kohkiloye and Boier Ahmad province has been studied. Part of Physical (water loss) and nonphysical (apparent loss) water have been presented. The approach method in non-physical section includes Identification of, illegal meter connection, meter inaccuracy, errors m water reading systems, estimation of water loss from each sources, and its effects in total U.F.W. finally the best method for control of water loss in this part is discussed. In physical part study carried out for identification of real loss causes with implementation of district meter area with installation of pressure logger, flow meter in the network and determination using the method of minimum night flow. According to the results from 1014700 cubic meter of water produced daily, about 483260 cubic meters is UFW (47.6%) which consists in physical with 349195 cubic meter (34.4%) and non-physical with 134065 cubic meters to the national scale, which is 31% the UFW in Sisakht is 16.63% higher.