IRAN-WATER RESOURCES RESEARCH
Year:2014 | Volume:10 | Issue:2 (30)|Papers Count:12

According to the rapid population growth and increasing need for clean and reliable water, wastewater treatment plants play an important role in providing a reliable source of water. In this regard, the reliability of a wastewater treatment plant is a critical issue while the effluent is reused or discharged to water resources. Main factors that affect the performance of a wastewater treatment plant are the variability of the influent, inherent variability in the treatment processes, deficiencies in design and mechanical equipments and operational failures. Thus, meeting established reuse and discharge criteria would require assessment of plant reliability. Amongst many techniques developed in system reliability analysis, Fault Tree Analysis (FTA) is one of the popular and efficient methods. FTA is a top down, deductive failure analysis in which an undesired state of a system, including failure to achieve system goals, is analyzed.The case study in this article is West Town wastewater treatment plant in Tehran which is a conventional activated sludge process and the effluent is used in irrigation of downstream green areas. The FTA components in this study include the violation of BOD from the standard limit for irrigation as the top event and cases such as operator fault, malfunction of the equipments and failure in the plant design as the basic events. The probabilities of basic events were determined based on available data and the experts’ and operators’ opinions and the probability of the top event was calculated. According to the obtained results, the probability of effluent BOD violation is estimated about 29% in which human error specially operator’s fault has the highest share in its occurance. Subsequently the mechanical, climate (influent wastewater quantity and quality) and factors related to collection network are placed in the following order. In this regard, to increase the reliability and management of the risk, some measures with the priority of focusing on reduction of human faults and incresing the level of supervision and inspection was recommended.

Determination the suitable pattern according to the system mechanism is one of the key issues in modeling and forecasting time series. It is common to use linear time series models without investigating linearity or nonlinearity of using system. In this study streamflow processes of Nazlu Chai, Shahar Chai and Baranduz Chai rivers located in the West Azarbaijan province and west of Lake Urmia investigated by BDS test in annual, monthly and daily time scales. Stationarity of series, as the main assumption of this test, has been done by ADF and KPSS methods. It is found that as the timescale decreases, the nonlinearity will increase. So that for annual series (due to the linearity test) linear ARMA models can be used at the acceptable significance. Whereas to increase accuracy of forecasted monthly and daily streamflow series of studied rivers, nonlinear models such as Bilinear, TAR and ARCH should be used. Linear and nonlinear models for each river in the different time scales on the basis of BDS test results proposed.

A variety of optimization models have been developed in the last decades to solve complex problems in water resources management. Thought that some of these methods are unreliable and do not improve the water resources management problem in reality, it is thus essential to investigate and compare the capabilities of these models. One of the most general and well-known optimization problems in water resources is the Dynamic Programming (DP) which can be solved using continuous and/or discrete solution approaches. Since the discrete solution techniques is computationally burden and inefficient in complex problems, the continuous solution techniques takes much attention recently. In this paper a continuous solution of dynamic programming model, called Constraint State (CS) method is adopted to solve a problem related to reservoir operation and its results are compared with those obtained from two different discrete solution methods, called DP and SDP methods. The reliability of these techniques for reservoir operation is investigated using a set of reliability indices. The results show that the CS solution method can even improve the reliability of system, as a comparison with the SDP method.

Social changes and water shortagecreate serious problems for policy makers to distribute water justly that lead to water conflictsin small and large social levels. So, this research was done toexplore the relation between social relations and hydrological parameters and to determine the strengths and weaknesses of social relations network in Homag-E payin village located in Hormozgan province. A questionnaire was used to collect the required data and then cooperation network among people to solve the problem of water shortage in Homag-E Payin village was delineated. Authority and role equivalence indices and Visone and Ucinetsoftware packages were used to delineate and to analyze the networks. Results revealed that former relation patterns in Homag-E payin village that were based on the kinship relations have changed following the water shortage problem in this village andnew grouping between residents of this village has shaped based on hydrological parameters. In this regard, policy-makers and planners must be attended more and more into the relations of all issues and their interactions in a watershed; specially, social issues that interacted to all other parameters in a watershed and sometimes, those are the most affective parameters.

The Markov chain used for statistical analysis events that are not independent and are related to their previous events. In this study, events possibility of serial dry and wet days were analyzed by Markov Chain method for 15 synoptic stations with different climates of coldest arid climates to its moderate humid in Iran. For this purpose was used daily precipitation data (1978-2009) for Kerman, Mashhad, Shiraz and Bandar Abbas stations, (1978-2008) for Tabriz, Khorramabad, Isfahan, Tehran, Zahedan, Ahwaz, Ardabil, Gorgan stations, (1978-2007) for Zanjan station, (1987-2008) for Yasouj stations and (2000-2008) for Sari station. These data are arranged according to frequency matrix of rainy days and without rainfall, then probability matrix was calculated by maximum likelihood method. The respectively produced the Probability contour maps during the dry monsoon. In the study stations, results showed that lack of precipitation probability has variable, 0.811- 0.909 in the arid climates, 0.685- 0.84 in the semi-arid climates and 0.695- 0.728 in the moderate and humid climates.

Management practices of equity allocation for water in water user associations (WUA), requires the use of decision support system as effective tool for supply and demand analysis. The river management model MIKEBASIN is one of these systems which developed for simulation and water allocation management in river basin. The objective of this study is evaluating the application of this model as a decision support system in Alborz integrated land and water management project. In this regard, the project area is divided into 20 water user associations and water resources in this area respectively are surface water, Ab-bandans and groundwater. As a matter of water allocation to WUAs, the simulation of resources and demand was done monthly in 28 years with the data of main catchment runoff and sub-catchment, reservoir and demand of WUAs, groundwater and Ab-bandans. In assessing the condition of water resources allocation by MIKEBASIN model in WUAs, demand volume with the aim of minimizing the deficiencies and spatial priorities on the basis of any association was evaluated. Accordingly upstream WUAs received more water. Also the result showed that demand of 460 MCM of WUAs, 277.02 MCM is supplied from surface water and 131.01 MCM from groundwater and remaining (1.92 MCM) is from Ab-bandans. According to criterion of 85% supply, the evaluated deficiency is 13.5 MCM. Finally, the result of this research was in accordance with the results of other studies.

Design of flood control systems are subjected to different kinds of uncertainties of hydrologic, hydraulic, geotechnical, and economic along, due to inherent behavior of flooding and random errors associated with measurement. The purpose of this paper is sensitivity analysis to determining the effect of uncertainties on the dimensions of design parameters.Therefore, using LINGO software a nonlinear optimization model based on risk analysis in both deterministic and probabilistic scheme have been developed for design of one of the most common structural flood control measure. In The probabilistic design , each of uncertainties once separately and once again all together are applied and Monte Carlo simulation for uncertainty analysis has been used. In this paper a reach in the Moali-abad river at north of Shiraz city, has been considered as case study. According to the results of probabilistic and deterministic models, the optimum return period equal to 20 years. Unlike the deterministic model that every output (design parameters) is single valued, stochastic model gives a range for each parameter that its value affected by the uncertainty imposed. The results show that applying the hydrologic uncertainty in the design is more efficient than economic uncertainty, and the economic one is more efficient than the hydraulic uncertainty. In the situation of limited time and budget, it has suggested that at least hydrologic uncertainty has been considered in design.

In present study the effects of transverse waves modes 1, 2, 3 and 4 in a staggered obstacles arrangement on suspended sediment load transport in a rectangular flume was investigated. The results show that in no transverse wave condition, the concentration of suspended sediment at downstream obstacles zone is more than the part of no obstacles zone but it was reduced in the case of existing transverse wave. In the same condition of discharge, diameter and perpendicular and transversal distances of obstacles, increasing of transverse wave mode caused to decrease of this difference. Also, the percentage of decreased suspended sediment concentration in obstacles zone rather than no transverse wave condition was decreased. In fact the concentration of the transported suspended sediment in obstacles zone for wave modes 1, 2, 3 and 4 rather than no transverse wave condition was decreased about 6.2%, 3.9%, 3.6% and 3.1%, respectively and in this condition, suspended sediment was deposited at upstream of the obstacles zone for transverse wave modes 3 and 4. However, 1% and 3% of this sediment was transported to no obstacles zone for wave mode 1 and 2. Also, according to findings, the ability of wave for decreasing of suspended sediment concentration at downstream obstacles zone rather than part of no obstacles zone is increased by increasing of the wave amplitude.

Modeling as an effective approach, with the least cost, assist to managers to study complexity of groundwater flow. Always, identification of optimized withdrawal from aquifer was the one of complex problems for water science engineers. The main goal of this research was the management of optimized withdrawal from Uromiyeh coastal plain and identification of optimized pumping rate of extraction wells, to rescuing the Uromiyeh Lake from increasing drying with preventing of unlimited groundwater withdrawal. In this study, firstly groundwater flow model of case study region was designed using Visual MODFLOW (Ver 4.2) software. Afterwards,the abstraction wells of Uromyieh coastal aquiferwas clustered according to Hydraulic Conductivity and Specific Storage coefficients variations. Finally, with using of genetic algorithm, the pumping rate of extraction wells was optimized.