WATER AND WASTEWATER
Year:2018 | Volume:29 | Issue:6 |Papers Count:12

Major investments and high operational expenditure are the special characteristics of the water and wastewater industry in the context of organizational mission. Planning the production and improving the efficiency of production factors by quantitative models are among the conventional methods in the management of investments, costs and financial resources. This research aimed to identify the share and elasticity of the urban water production factors and partial and total productivity in the context of production planning. The data used are panel data according to size of production and production factors (labor, capital stock and energy). The data on 34 urban waters and wastewater companies in the period of 2006-2016 (374 samples) were used and the fixed effect econometric method was applied to estimate the Cobb – Douglas production function. The results indicated that in the water and wastewater industry the elasticity of the labor, the capital and the energy was 0. 32, 0. 42, and 0. 21, respectively. The research findings showed that the productivity of capital and energy as well as the total factor productivity declined in the years 2015 and 2016 while the efficiency of labor remained constant. The findings can be used by the top management of the industry as a strong tool for strategic planning of production of a high level of reliability.

In the past decades, urban development and the increase in densely populated urban areas have led to expansion of the impervious surfaces. This resulted in an increase in the volume and peak discharge of runoff. To face the intensified urban floods problems worldwide, many management practices have been proposed and implemented. This study attempted to investigate and prioritize suitable urban runoff management scenarios for Bojnord city. Based on a thorough literature review on international experiences and examples, local experts’ opinions, and operational feasibility, a total of six management alternatives including Bioretention, Infiltration Trench, Pervious Asphalt, Pervious Paver Blocks, Green Roof, and Rain Barrels were chosen. The hydrological, social and economic implications were then assessed for these alternatives for the Bojnord city. A total of 60 questionnaires were filled out by face to face interviews with citizens. Likewise, an extra set of 30 questionnaires was filled out by the relevant experts and authorities. The cost of each management alternative along with their potential to reduce the runoff volume resulting from a rainfall with a five-year return period was analyzed using SWMM. The Multi Criteria Decision Making Method (MCDM) was used for prioritizing these alternatives. Then MCDM in this study used TOPSIS technics and was performed using different weighting conditions (equal weighting, Delphi, Shannon entropy, emphasizing on hydrologic, social and economic criteria). The result of this study indicated that when applying equal weighting method, Delphi and social criteria, Infiltration Trench scenario were considered as the most compatible option to ideal solution. While Rain Barrels scenario was considered as the top priority when Shannon entropy and economic criteria were emphasized. And finally, applying a hydrologic criterion put the Green Roof scenario on top priority

Network reliability is one of the most important parameter when evaluating the efficiency of water distribution networks (WDNs). WDN reliability is calculated based on the mechanical, hydraulic and water quality aspects under normal and also abnormal conditions such as system failures. In this paper, hydraulic reliability was calculated through the ratio of satisfied nodal demands. In this regard, hydraulic simulation is performed based on the proposed EPANET-IMNO algorithm based on a Pressure-Driven Simulation model. This algorithm is written in Visual Studio through C++ code. The mechanical reliability of the network was evaluated by means of BDD algorithm based on probability of having a connection between the source nodes and consumption nodes. DNA and RNA tools are used to evaluate the mechanical reliability based on BDD method. Finally, an integrated reliability is proposed for optimum design and operation of WDNs. A looped WDN with nine nodes and a branched WDN were considered in this paper. The results showed that besides the hydraulic reliability the evaluation of mechanical reliability index is very important in the design of WDN to improve the operation of WDNs. Adding 4 loops to the branched WDN increased its reliability by 18. 3%. Also, it was determined that under a looped WDN eliminating one pipe in the worst case may reduce the network reliability by28%.

Having a reliable rehabilitation plan with sufficient operational data is crucially important for the operation and maintenance of a water distribution systems. This research was conducted to develop a prioritization model for planning the rehabilitation of pipes in water networks when minimum structural data is available. To accomplish the main objective of the study, WDSR-Min model with Fuzzy TOPSIS technique capability was used to prioritize the pipes rehabilitation. The proposed model was used for the prioritization of pipes rehabilitation in a two-loop water distribution system. The prioritization of pipes rehabilitation were evaluated under two methods by using: 1) the pre-defined template of the WDSR-Min model, and 2) the template consistent with the conditions of the study area. The results showed that the rehabilitation plan obtained from WDSR-Min was aligned with the real needs for rehabilitation in the water network pipes. Furthermore, it was found that to prioritize the pipes rehabilitation it was preferred to localize the model criteria for the conditions of the study area, while to determine the pipes rehabilitation strategies the use of the pre-defined template of the WDSR-Min model was preferred. Using the proposed model in this work makes it possible to determine the prioritization/strategies of pipes rehabilitation using the minimum structural data of water distribution networks and independent of operational data.

Lack of water along with environmental problems have put focus on wastewater treatment and its potential for reuse. This study aimed to study the photo catalytic impact of using zeolite and garnet in purification of the organic pollutant from industrial wastewater. In summer of 2016 samples were taken from the industrial wastewater of station number 13 in the Khuzestan steel factory. A pilot with the scale of 1: 150 (10 × 24 × 100 cm) was built with hydraulic conditions of this station. The pilot was built of fiberglass material and was divided into 5 ponds with the internal dimensions of 10 × 24 × 20 cm, equipped with outlet valve. There was 5 cm of different amounts of zeolite and garnet inside each pond with three replications including: G100, Z100, G50Z50, G70Z30 and G30Z70. The aggregation was 0. 2 mm and the wastewater was shed to the remaining 5 cm of the height in each pond and was laid in the light of the sun. After 2, 4 and 6 days, the wastewater of each pond was evacuated and sampled through the outlet valve and was replaced with new wastewater. Then, the amounts of BOD, COD, TSS, TDS, EC, SS, turbidity, pH and OIL were measured with the standard methods. The results showed that the applied levels caused reduction of BOD, COD, TSS, SS, OIL, and turbidity in the output wastewater respectively to the amount of 94. 1, 94. 94, 84, 90. 59, 92. 84, and 87. 26 percent. The amount of TDS and DO were increased by 1. 9 and 1. 2 times respectively. The results of the tests related to the levels represented the good performance and proper efficiency of this system, particularly in the case of levels containing garnet and they showed the ability of doing photo catalytic process for removal of existent organic pollutants from the industrial wastewater.

Treatment of the produced water, as a major wastewater in oil and gas industry, is concerned with reduction of the wastewater volume or providing water for some applications such as agriculture. Since membrane technologies play an important role in the separation of dissolved and emulsified oil droplets, forward osmosis (FO) was used in this research as a novel process to reduce the volume of such wastewater. A cellulose commercial flat membrane was applied in a FO laboratory system. The results showed that by increasing the concentrations of the most important inorganic solutes in produced water from 0 to 20 g/L, water flux decreased from 11 to 6. 6 L/m2. h due to an increase in feed osmotic pressure. In the presence of 1000 and 3000 mg/L oil in deionized feed water, 12 and 15 percent reduction of the water flux was observed, respectively. This was due to the increased viscosity of feed and the precipitation and adsorption of emulsifed oil particles on the membrane surface. On the other hand, adding oil to the solution with different salt concentrations, led to a further reduction in the water flux. This was a result of the increase in feed osmotic pressure and changes in the condition of oil-water emulsion in the presence of salts. The salts increased the surface tension of the solution, which caused coagulation of oil droplets and higher fouling in the membrane surface.

Due to the high solubility of nitrate in water, conventional treatment methods fail to remove it. This research investigated for the first time in national and global level, the efficiency of functionalized PAMAM-Go nanocomposite for nitrate removal from aquatic solutions. GO was synthesized by modified Hummers method. AFM images were used to characterize the GO and the AGO. Experiments were performed in a batch reactor and the main factors of pH, reaction time, and concentration of PAMAM_GO were investigated. The highest removal efficiency was obtained as 84% at 5 mL/L functionalized PAMAM_GO, pH of 3 and 25 min reaction time. The results showed that nitrate removal by functionalized PAMAM-Go nanocomposite is directly correlated with nanocomposite concentration and contact time while it is inversely correlated with pH and initial concentration of nitrate. It seems that ion exchange between nitrate and chloride is the main mechanism of nitrate removal by functionalized PAMAM_GO nano composite according to functionalization of PAMAM-Go using hydrochloric acid. This method can be used as a suitable method for in situ treatment of nitrate and many pollutants in water and wastewater, due to its easy operation, no need for high levels of expertise and sophisticated equipment, no need for large space of construction, low initial investment, low price, availability of raw materials, simple synthesis of graphene oxide and easy to functionalize.

Organic contaminants in industrial wastewater are mostly non-biodegradable, so advanced oxidation processes (AOPs) should be used as a promising alternative for conventional treatment processes. In this investigation, degradation of an organic dye was studied in a fluidized bed reactor, using Fenton heterogeneous process. Application of fluidized bed reactor in this process makes it more effective because of high mass transfer and turbulence rate. Pyrite is a natural mineral ironstone which is abundant on earth and is known as a sustainable catalyst for AOPs. In the first part of this study, computational fluid dynamics (CFD) simulation was prepared, which showed a good agreement with the experimental results in dye removal efficiency and hydrodynamics of the reactor. In the second part of the study, a kinetic model was developed for evaluating the hydrodynamic effects on the heterogeneous Fenton reaction in a fluidized bed reactor. Unlike the CFD model, the provided kinetic model does not contain the momentum and mass transfer balances. The CFD results were more similar to the experiment results than the kinetic model. It showed that some of the components that were involved in this process had smaller eddy dissipation rate compared to the kinetic rate.

The concentration of elements such as calcium, magnesium, barium and silica would gradually increase in the wastewater treatment using RO systems. Reusing this wastewater in a second RO would cause precipitation of such elements on the surface of membrane and would decrease its permeability. Zero liquid discharge (ZLD) is the most advanced management technique for saline wastewater of RO systems. The aim of this study was to determine a mathematical model to estimate barium and silica removal from RO wastewater in ZLD multistep process. This research was conducted on samples from the effluent of the RO system in Tang-e Alhad in Hajiabad, Zarin Dasht in Fars Province, Iran. The experiments consisted of chemical precipitation, fluidized bed crystallization (FBC) and fluidized bed crystallization with chemical precipitation. During different ZLD processes, a correlation was observed between critical elements removal. The correlations between Ca with Ba and also SiO2 with alkalinity were observed in all experiments. According to the results the mathematical models for removal of barium and silica were determined according to the initial and final concentrations of barium, calcium, and silica and alkalinity. The results showed a very suitable correlation (R2=0. 99) between these concentrations and removal of silica and barium.

Agricultural irrigation with treated wastewater effluent may be used for crop production, but due to elevated of certain contaminants (e. g. nitrate or nitrite) may adversely impact the quality of groundwater. This research was carried out to investigate the transfer of nitrate in deep soil that was planted with corn fodder crop using treated effluent from the sewage treatment plant in the city of Neyshabur during 2012-2013. The study data were collected in pot cultivation with the same condition and under a completely randomized design. The irrigation with wastewater effluent and conventional raw water was performed at four levels comprised of: 100% irrigation capacity and 80% irrigation capacity for two irrigation periods of 8 and 10 days and 3 replications. The result of this study showed that irrigation levels and irrigation periods affected the absorption of nitrate by corn. Comparison of the amount of nitrogen in wastewater effluent and conventional raw water before and after irrigation showed that the nitrate absorption in the plant was low (below the standard level) and there is no significant health issue for the users of the corn forage components in the food chain. Also, the average nitrate concentration (on mass basis) of wastewater effluent after irrigation (drainage water) was about 64 mg/kg and the nitrate content in the soil under irrigation was about 59 mg/kg. Irrigation of corn with treated wastewater does not increase the health hazards of the crop and the soil, but there is still a high risk of nitrate pollution for the water resources in the area.

Nowadays the proficient maintenance of water network infrastructure is vital in sustainable urban development and is among the obligations of urban management which should be considered by responsible organizations. Accordingly, in this paper, by using the performance benchmarking method, Tabriz water utility was compared in graph basis to seven US water utility infrastructures based on the main indicators including: 1. Water resources, 2. Personnel information, 3. Physical components, 4. Service quality, 5. Executive performance, 6. Customer Services, and 7. Financial performance. The results showed that in comparison, Tabriz water utility suffers from major problems in terms of uncontrolled use of water resources in Tabriz city, high quantity of water loss, absence of wastewater recycling, erosion in network and water reservoirs in some areas, increased water demand due to the construction of new townships, and lack of adequate funding for network development. Accordingly, funds and investments are required to prevent the consequences of the aforementioned issues based on the proposed methodology. This methodology is found to be a very effective tool for decision makers and experts and can be applied for other cities and regions.