WATER AND WASTEWATER
Year:2006 | Volume:17 | Issue:3 (59)|Papers Count:8

Due to the high cost of monitoring systems, budget limitations, and high priority given to water quality control in municipal networks, especially for unexpected events, optimum location of monitoring stations has received considerable attention during the last decade. An optimization model needs to be developed for the desirable location of monitoring stations. This research attempts to develop such a model using Ant Colony Optimization (ACO) algorithm and tires to verify it through a bench-mark classical example used in previous researches. Selection of ACO as optimizer was fully justified due to discrete decision space and extensive number of binary variables in modeling system. Diversity of the policies derived from ACO may facilitate the process of decision making considering the social, physical, and economical conditions.

Water management needs to decide for the water resources development project and future planning based on comprehensive and integrated views. One of the management tools is based on system dynamic approach. This technique has the capability of simulating complex water resource systems to support decision making. The undefined outcome of decisions is revealed through this methodology. The main objective of this method of simulation is its simplicity and rapid learning of system behavior in present and future conditions. In this paper, the model for water resources and urban water demand was developed with dynamic system for evaluating the trend of resources and demands and the effective parameter on them. The feedback of urban water resources due to the economic, socio and environmental aspects of supply and demand brings about a complex system which can only be analyzed through integrated and dynamic views of the system. The results of the dynamic analysis of Tehran urban water system leads to a tool for understanding and visualizing the reasons of the shortages. This model shows the trend of water balance variation in future as well as the effect of management scenario such as interbasin water transfer, collection and treatment of waste water and demand management.

Controlling the unsteady effects of fluid flow (water hammer) is one of the most important monitoring factors for structural protection of transmission pipelines. These effects are controlled by surge tanks, air chambers, pressure relief valves, and check valves. Generally, the critical points are detected by simulating the unsteady flow of the fluid, and accordingly, optimum positioning of the control devices is decided. Among the search methods, Genetic Algorithm (GA) is an effective and robust method to solve highly complex optimization problems. Here, for the first time, GA coupled with an unsteady flow simulator is used to optimize the number and capacity of surge tanks in a pipeline system. In addition, the pipeline diameters are optimized for their best performance.

Zoweircherry and Kherran plains are located in the northeast of Ahwaz in Khuzestan province. The water supply of these plains is a crucial issue and the quality of groundwater is also under the threat as a result of an increase in the use of agrochemicals. For this reason, assessing the vulnerability is an important factor in any policymaking decision for these plains. Focusing on this issue, this paper attempts to produce a groundwater vulnerability map for Zoweircherry and Kherran plains. The map is designed to show areas of highest potential for groundwater pollution on the basis of hydro-geological conditions and human impacts. Seven major hydrogeological factors (depth to water table, net recharge, aquifer media, soil media, topography, impact of vadose zone and hydraulic conductivity) were incorporated into DRASTIC model and Geographical Information System (GIS) was used to create a groundwater vulnerability map by overlaying the available hydro-geological data. The results of model exhibit that the west and southwest of the aquifer are dominated by medium vulnerability while small areas on northwest and east of the study area have no risk of pollution. Other parts of aquifer have low vulnerability. The nitrate analysis of groundwater samples shows that the existing nitrate on the west and southwest parts of aquifer is more than the existing nitrate on its other parts which, therefore, confirms the results of the vulnerability assessment.

Transient mixed flow occurs under particular conditions in closed conduits, in which both free-surface and pressurized flow come into existence simultaneously. Depending on the origin of the mixed flow, systems experiencing this phenomenon may encounter several problems. Successful simulation of mixed flows is, therefore, necessary to predict and overcome the encountered problems. Different methods are suggested for the simulation of the mixed flows. In this research, transient mixed flow in closed conduits has been analyzed by slot method. The model is further used for the prediction of transient mixed flow in a real world pipeline system. The results are then used for devising some operational guidelines.

Organic manures are the source of many pathogenic bacteria which could be dangerous for human health. In this study, the effects of soil texture and structure on transmitting and filtering of manure-borne Escherichia Coli were investigated. The intact soil samples (25 cm in height and 16 cm in diameter) were taken from a sandy clay loam soil and a loamy sand soil. Three manures including: cow manure, poultry manure and sewage sludge was applied on the surface of the soil cores at the rate of 10 Mg ha-1 on dry basis. With controlled steady-state unsaturated water flow, the influent and effluent concentration of Escherichia Coli were determined vs. time up to four pore volumes (PV). In spite of greater adsorptive sites of sandy clay loam soil, more bacteria have been transmitted and polluted the effluent of the soil. The loamy sand soil filtered more Escherichia Coli compared with the sandy clay loam soil. The effluent contamination of poultry manure-treated columns was greater than the cow manure and that of treated sewage sludge. In the majority of the columns, the difference between cow manure and sewage sludge was negligible. The filtration of Escherichia Coli in loamy sand soil was greater due to weaker structure and discontinuity of pores which are responsible for Physical filtering. In sandy clay loam soil, the stable structure and preferential pathways are believed to cause funneling of the bacteria towards the bottom of the columns and the early appearance of Escherichia Coli in the drain water. The results demonstrated the importance of soil structure and preferential (macroporous) flow in bacteria transport which could diminish the impacts of soil texture and adsorptive sites on the transmission mechanisms.

Every year more than 700,000 tons of dyestuff is produced, 50% of which is azo. Azo dyes contain one or more azo bonds (-N=N-) and are among the most important synthetic dyes because they are produced in high amounts and also have many applications in different industries especially in textile industries. This study was done to Investigate dye removal of dyed effluents in textile industries as well as COD removal through advanced photochemical oxidation by the application of UV/ H2O 2. A low-pressure 55-watt (UVC) mercury ultraviolet lamp as radiation source and H2O2 30 % (Merck) as oxidant was used. Dyestuff of C.I. Direct Red 80 of azo group was selected as model due to its high use and application. Some important parameters such as the effect of DV, duration of DV radiation, H2O2 concentration, dyestuff concentration and pH were studied in five separate stages based on the standard methods. The results showed that after 20 minutes, UV individually could remove 33.3 and 18.4 percent of color and COD, respectively; while, H2O2 could remove only 5.7% of color and 3.5% of COD after 24 hr. In UV/ H2O2 system, color removal reaches 100% in optimum conditions after 5 min radiation; however, after 20 min of radiation, COD removal was 77.3 %. Optimum conditions for color removal (30 mg/L) and the COD resulting from the color in H2O2 process included 150 mg/L of pure H2O2, neutral pH and low concentrations of color. Therefore, DV/H2O system proved to be an effective method for removing color and the COD produced by color. However, removal efficiency of UV radiation and H2O2 individually was not appropriate because they can not individually generate enough OH° radicals, which are the main decomposing agents.

This paper is intended to illustrate the application of the results concerning the latest researches in surface water hydraulics and hydrology for flood control project planning. In this paper, after describing flow tracing algorithms and the logics for programming in GIS environment, the transfer of GIS output to a hydrologic model and its application to a flood control project planning has been demonstrated. In this research, Behbahan flood control project has been used as the case study, HEC-GEOHMS with D8 algorithm in Arc View as flow tracing model and HEC-HMS as the hydrologic mathematical model. Case study results reveal that using a hydrologic mathematical model linked to flow tracing methods embedded in GIS can show approximate locations of outlets and gives an acceptable estimate of design flood magnitude in each node and scenario. The difference in final results before and after the application of the new methodology is noticeable.