WATER AND WASTEWATER
Year:2017 | Volume:28 | Issue:4 |Papers Count:12

The vital role and significance of water for all lif forms، and for human beings in particular، make it essential to determine its real value. This study was carried out in 2014 with the objective of making an estimation of the value of agricultural surplus water and the parameters determining the general preferences of Isfahani citizens to use this water for drinking purposes. To realize these objectives، the contingent valuation method and the Logit Regression model were used. Results showed that the individuals’ willingness to pay a surcharge for the surplus water had a significantly negative relationship with such variables as per capita water bill، family size، and the proposed price while it had a significantly positive relationship with the individual’ s education. Family size and ethical appreciation of environment were found to promote the highest acceptance and the greatest effect on one’ s willingness to accept the surcharge on their water bills. Estimation of the Logit function revealed that the average monthly water consumption of each Isfahani family (with an average size of 4) was equal to 27. 57 cubic meters and that they would pay a monthly surcharge of 5201. 8 Rials for one cubic meter of agriculturtal surplus water.

Heavy damages might be inflicted upon national infrastructure due to a variety of disasters caused by natural events or human activities. One example of such vital infrastructure at risk is the water supply system. At the time of crises، the water supply system is expected to continue supplying water to citizens، or the crisis will be augmented. This warrants the potential threats and their effects on the system to be identified and evaluated in an attempt to determine the vulnerable systems and sites toward proper solutions. In this study، the assets and the associated threats of the water supply are identified followed by a vulnerability analysis. The RAMCAP method is then employed to determine values for the risks associated with each of the assets including dams، water storage systems، pumping stations، treatment plants، water wells، and building units. Methods are proposed to reduce these risks before a crisis occurs. In addition، basic threats due to air-missile and Cyber attacks are also considered.

Groundwater is the only vital source of water for millions of people around the world and its contamination has dire impacts on human health، industrial activities، agriculture، and the environment. The drinking water in the City of Qom is supplied from neighboring water basins transferred by interbasin water transimission facilities and from water wells within the city. The growing demands and the consequent increasing water scarcity have augmented and foregrounded the significant role played by the water wells in this city. Nitrate as a widespread pollutant originates from human activities and the dumped wastes that lead to the gradual degradation of groundwater resources، which might go undetected for years. On the other hand، remediation of polluted aquifers is a formidable، cost-intensive، and، at times، impossible endeavor. In this study، groundwater resources in the city of Qom were investigated in terms of their nitrate concentration. For this purpose، 600 groundwater samples collected from 2006 to 2013 by the Qom Water and Sewage Company were used، 136 of which were found to be polluted with nitrate. In order to validate the data thus obtained and to identify the contaminated areas، additional samples were collected from 27 wells in December 2013 and subjected to the relevant analysis. The latter analysis revealed a mean nitrate concentration of 74 mg/L and a standard deviation of 37 mg/L، with nitrate contamination detected in 19 wells accounting for 70% of the sampling sites. Generally، the results indicate that the aquifers within the city of Qom suffer from nitrate contamination.

Transient flows naturally occur in piping systems due to operation exigencies. It is، therefore، essential to analyze water distribution networks under transient flow conditions in an attempt to enhance their reliability. The accuracy of such an analysis highly depends on such input parameters as pipe wall roughness، wave speed، and unsteady friction loss coefficients. As these parameters vary from system to system and in different flow conditions، they cannot be definitively determined in practice. Generally، the parameters are determined by engineering judgments and trial-and-error estimations. For complex pipe networks، this can be very burdensome and time-consuming. Moreover، there are great numbers of dynamic parameters in water supply networks and their interactions are so complicated that it is extremely difficult to explicitly determine the role of each one in the system responses observed. This calls for mathematical simulation models to predict systems responses accurately. In this study، an inverse transient analysis model is introduced for the calibration of input parameters. A reverse method based on a series of measurements and computations was used for the solution of the calibration problem and efforts were made to reduce the value of the objective function by finding the optimum solution. However، the model introduced in this work differs from other similar ones in that inverse transient analysis models are often used in the time-domain while the current work uses the transfer matrix method to analyze the system in the frequency-domain. The frequency analysis of a pipe network not only provides a deep insight into the system performance but also speeds up the simulation and optimization computations. Finally، the model is applied to a lab-scale pipe network from the Technical University of Lisbon as a reference model. The parameters with dynamic effects are calibrated and compared with available data obtained from massive experimental observations and numerical trial-and-errors in the time domain. Results indicate not only that the model is adequately simple and faster than its counterpart model in the time domain but that it is capable of successfully calibrating the network with results in good agreement with observed data.

Triangular channels have different applications in many water and wastewater engineering problems. For this purpose investigating hydraulic characteristics of flow in these sections has great importance. Researchers have presented different prediction methods for the velocity contours in prismatic sections. Most proposed methods are not able to consider the effect of walls roughness، the roughness distribution and secondary flows. However، due to complexity and nonlinearity of velocity contours in open channel flow، there is no simple relationship that can be fully able to exactly draw the velocity contours. In this paper an efficient approach for modeling velocity contours in triangular open channels with non-uniform roughness distributions by Adaptive Neuro-Fuzzy Inference System (ANFIS) has been suggested. For training and testing model، the experimental data including 1703 data in triangular channels with geometric symmetry and non-uniform roughness distributions have been used. Comparing experimental results with predicted values by model indicates that ANFIS model is capable to be used in simulation of local velocity and determining velocity contours and the independent evaluation showed that the calculated values of discharge and depth-averaged velocity from model information are precisely in conformity with experimental values.

It is observed that physical changes in the filter as bed media size variation، nozzle breakage، or water temperature variations lead to changes in the backwash regime throughout the year. The remedy proposed in this article is to use variable speed pumps in order to maintain a constant and steady optimum regime. In this study، experiments were performed using a full-scale single-layer rapid sand filter to find the optimum bed expansions of 7-8%. In addition، previous research has shown that air and backwash water flows need to be slowly and gradually increased to the optimum design values in order to avoid sand boil. In a typical treatment plant، this is normally controlled by globe valves، which results in the waste of energy and variation in pump and blower pressures. Application of variable speed pumps has the advantage that a constant pressure can be maintained throughout to yield an optimum backwash regime. Variable speed pumps provide various backwash regimes which enable design engineers and water plant operators to determine the optimum expansion in sand bed filters. This range of optimum bed expansion was found to lead to such improvements as shorter filter ripening، reduced effluent turbidity to levels below 0. 3 NTU، conservation of backwash water by up to 15‒ 20%، and savings in backwash pump power consumption by up to 30-50%.

In this study، the phytoremediation capacity of the hydrophilic tree species populus deltoides and Taxodium distichum and their ability to absorb cadmium (Cd) are investigated as a method for addressing the need for the removal of heavy metals from contaminated water and soil resources as a measure to counteract their environmental effects. For this purpose، a completely randomized design was used with 4 treatments (namely، 0، 50، 100، and 150 mg kg-1 of cadmium) and 3 replications. Results showed that Cd concentrations in the organs of the two species increased with increasing soil Cd content. The highest Cd concentrations in the leaves، stems، and roots (18. 6، 35. 33، and 89. 06 in T. distichum and 29. 44، 61. 56، and 104. 6 in p. deltoids، respectively) were observed for a Cd concentration of 150 mg Cd kg-1. The highest and lowest values of Cd concentration were observed in the roots and leaves، respectively، for all the Cd concentrations examined. Cd concentration exhibited a decreasing trend moving from roots to stems and leaves. The translocation factor increased in both species compared to the control and its greatest values (1. 1065 and 1. 006) were observed in the treatment with 50 mg Cd kg‒ 1 for p. deltoides and T. distichum، respectively. Given the importance of biological wastewater treatment and the removal of contaminants، especially heavy metals، from the environment aimed at optimal use of soil and water resources as goals of sustainable development، the cultivation of the hydrophilic species of p. deltoides and T. distichum may be recommended due to their high biomass production while the species also offer a high potential for phytoremediation and a great capacity for stabilizing soil cadmium.

Disposal of effluents containing dyes into natural ecosystems pose serious threats to both the environment and its aquatic life. Malachite green (MG) is a basic dye that has extensive industrial applications، especially in aquaculture، throughout the world. This study reports on the application of the central composite design (CCD) under the response surface methodology (RSM) for the optimization of MG adsorption from aqueous solutions using the clinoptilolite nano-zerovalence iron (Cl-nZVI) nanocomposites. The sorbent structures produced are characterized by means of scanning electron micrograph (SEM)، energy-dispersive X-ray spectroscopy (EDS)، and vibrating sample magnetometer (VSM). The effects of different parameters including pH، initial MG concentration، and sorbent dosage on the removal efficiency (R) of MG were studied to find the optimum operating conditions. For this purpose، a total of 20 sets of experiments were designed by the Design Expert. 7. 0 software and the values of removal efficiency were used as input response to the software. The optimum pH، initial MG concentration، and sorbent dosage were found to be 5. 6، 49. 21 mg. L-1، and 1. 43 g. L-1، respectively. A high MG removal efficiency (57. 90%) was obtained with optimal process parameters. Moreover، a desirability value of 0. 963 was obtained for the optimization process.

There is an increasing demand for effl uents of higher quality from wastewater treatment plants due to the more stringent quality standards as well as the increasing pressure on water resources worldwide، which calls for effluent recycle and reuse. Membrane bioreactors (MBRs) have been recently gaining rapid popularity as a promising technology for wastewater treatment. In order to improve the quality of the effluent from Shiraz wastewater treatment plant، an on-site pilot-scale membrane bioreactor was operated for 9 months. The pilot plant built at Shiraz wastewater treatment plant consisted of an aerobic reactor and a membrane compartment containing one submerged hollow fiber membrane module. In this study، eleven different aerobic hydraulic retention times (HRT) ranging from 2 to 12 hours were tested to determine the membrane capacity and to investigate the performance of the system in removing total ammonia nitrogen، organic matter، total suspended solids، and turbidity. The system recorded a perfectly stable removal efficiency over the whole experimental period، except for the 2-hour aerobic HRT، so that its COD and BOD reductions exceeded 95% and 99%، respectively. Moreover، the system achieved complete nitrification in a stable manner during the whole study period، except for the 2-hour aerobic operation period. TSS concentration was almost zero and turbidity was less than 1 NTU. Membrane capacity measurements showed an average flux of 5. 5 Lm-2h-1 with a mean trans-membrane pressure difference of 30 kPa. Results showed that the MBR outperformed the conventional sewage treatment processes. Additionally، it was not affected by aerobic HRT changes (12، 10، 8، 6، 4، and 3h). Based on the effluent qulity، teh system may be recommended for application toward water reuse in industrial and agricultural settings

Application of sewage sludge as a fertilizer on farmlands is a common practice in most countries. Although the practice may play a positive role in plant performance، the organic amendments introduced may increase the soil heavy metals content. This study was conducted in Arak، Iran، to investigate the effectiveness of DTPA chelate on corn Cd availability in a sewage sludge treated soil. The treatments consisted of sewage sludge (0، 15، and 30 t ha-1) polluted with cadmium applied at 0، 5، 10، and 15 mg kg-1 as well as DTPA applied at 0 and 1. 5 mmol kg-1 soil. Corn plants were then grown in the soil in each treatmnent and، on day 60، the physic-chemical characteristics and Cd quantities were measured ion both the corn plants and soil samples. Application of 1. 5 m mol of DTPA chelate in soil contaminated with 5 mg Cd led to a significant increase in the soil available Cd content. It was also observed that application of DTPA chelate to soils containing 30 t ha-1 of sewage sludge polluted with 10 mg Cd increased root and shoot Cd concentrations by 17 and 25%، respectively. Results indicated the effectiveness of DTPA chelate in reducing Cd phytoremediation with increasing sewage sludge loading rate. This was evidenced by the lowest phytoremediation effectiveness observed for the treatment with the greatest sewage sludge loading (30 t ha-1) and the lowest cadmium pollution (5 mg Cd).

The instabilities over the past two decades in governing water resources have led to the need for an integrated approach to the problem. Moreover، the decent and sustainable governance of water resources has come to be recognized as the supplement to the integrated management of water resources. The present study strives to develop a conceptual model of water reources sustainable governance with emphasis on training and capacity-building. For this purpose، expert views presented to different international meetings and world conferences on water were reviewed to develop a comprehensive and all-embracuing conceptual model of sustainable governance for the integrated management of water resources with a focus on training and capacity-building. In a second stage of the study، both internationally published literature and the regulatory documents on water management approved at the national level were consulted to derive appropriate standards، criteria، and indicators for the implementation of the proposed conceptual model. The relevance of these indicators was validated by soliciting expert views while their stability was calculated via the Cronbach’ s alpha formula to be 0. 94. The third stage of the study involved the ranking and gradation of the indicators using the relevant software in a fuzzy decision-making environment based on interviews with 110 senior water executives، academics working in the field، senior agricultural managers، water experts in local communities، and NGO activists. The emerging model finally consisted of 9 criteria and 52 indicators، amongst which the criterion of public participation and the indicator of training and capacity-building won the highest scores. It may be claimed that the proposed conceptual model is quite relevant and adapted to the sustainable governance presently sought. The key roles in this model are played by public participation as well as training and capacity building that must be on the priority list of all policy makers and stakeholders in their decision making and planning efforts.