WATER AND WASTEWATER
Year:2011 | Volume:22 | Issue:2 (78)|Papers Count:18

Optimum operation of water distribution networks is one of the priorities of sustainable development of water resources, considering the issues of increasing efficiency and decreasing the water losses. One of the key subjects in optimum operational management of water distribution systems is preparing rehabilitation and replacement schemes, prediction of pipes break rate and evaluation of their reliability. Several approaches have been presented in recent years regarding prediction of pipe failure rates which each one requires especial data sets. Deterministic models based on age and deterministic multi variables and stochastic group modeling are examples of the solutions which relate pipe break rates to parameters like age, material and diameters. In this paper besides the mentioned parameters, more factors such as pipe depth and hydraulic pressures are considered as well. Then using multi variable regression method, intelligent approaches (Artificial neural network and neuro fuzzy models) and Evolutionary polynomial Regression method (EPR) pipe burst rate are predicted. To evaluate the results of different approaches, a case study is carried out in a part of Mashhad water distribution network. The results show the capability and advantages of ANN and EPR methods to predict pipe break rates, in comparison with neuro fuzzy and multi-variable regression methods.

Reverse Osmosis (RO) is one of the most useful techniques to improve the elimination of organic and mineral Substances from ground and surface water after primary purification processes such as coagulation, sedimentation and filtration. This System provides the required water quality characteristics to somehow. However, in selection RO systems civil management decision and general public opinion along with cost and health impact must be considered. This study was done in 2010. Statistical methods have used to gather data about of families who used RO In their private homes and mode of eliminate of the wastewater generated by this process. The results indicated that in the normal operational conditions such as pressure 6- 10 kg/cm2 the, optimum recovery % 30 and flow rate 1lit/min, and water temperature 4- 38Co, an Amount of 14191200 kwh of power energy have been consumed to produce 157680 m3/year treated water required for 36000 families. This has also generated 367920 m3/year of wastewater being disposed without any management and environmental considerations. Apart from that more than 198000 of filters have been ejected to the environment. Also regarding health aspects, reducing the hardness and fluoride levels in treated water could be undesirable. It could be concluded that increasing the number of local water distribution points and speeding up the water supplying project from Dez river to Qom can decrease the investment on RO system.

The scarcity of water is the result of the recent successive drought in most country's districts. The increase of demand due to the increase of population and also inappropriate growth of supply according to the high cost of production process and therefore distribution, arise a big concern for the water and wastewater companies. Therefore the provision of water supply for consumers emphasizes on the urge of the management policies more than ever. Knowing the consumer behavior, in this regard, is the first and the most important step. In this study, to reach this objective, the function of household water demand in structure of block pricing in Tehran was estimated by using household budget data, through discrete - continues choice model and maximum likelihood approach. The results show that price and income parameters have expected sign. The calculated unconditional elasticties show that consumers’ sensitiveness for price fluctuations in the structure of block pricing are against zero. Therefore, the policy of price reform in the structure of block pricing can be used as an effective tool in the management of consumption.

Removal of particles by filter is a complex process in water treatment. Several factors are involved such as shape and size of filter grains, suspended particle concentration, filtration velocity and filter bed depth. The objective of this study was to evaluate effects of filtration velocity and rapid sand filter bed depth on removal efficiency of suspended particles. Four filtration velocities (0.086, 0.11, 0.14 and 0.17 cm/sec) and three depths of filter bed (25, 50 and 60 cm) were used in this study. Kaolinite concentration in inlet suspension above the filter bed was 100 ppm in each experiment. Silica sand was used as the filter medium with an average diameter of 0.51 mm. The results showed that removal efficiency of suspended particles was greater in low filtration velocity (i.e. 0.086 cm/sec) than high filtration velocities in the filters with specific bed depth. Removal efficiency of suspended particles increased with increasing filter bed depth from 25 to 50 cm in all of the experiments but there was no significant difference between obtained results in the filter bed with 50 and 60 cm depths (a=0.01). Head loss development was greater in low velocities than high velocities. Head loss development was greater in 25 cm depth than 50 and 60 cm depths in all of the filtration velocities. Favorable depth and filtration velocity was obtained 50 cm and 0.17 cm/sec, respectively.

Iron is the 4th abundant elements of the earth’s crust which high sub standard quantity of it in water distribution systems causes improper effects .The main objective of this research is to use Pumice stone for eliminating or decreasing of soluble Iron in water and to study in detail the effect of its factors. Three levels of Iron concentrations were prepared (0.3, 1 and 5 mg/L) and poured in a batch system in two Levels 10 and 20 g of Pumice stone. The pH were set at three levels (3.5, 7 and 10) .The remaining Iron concentration was measured in each step of process by taking a sample in every 10 minutes using spectrometry method. The results showed that adsorption rate had a direct relation with adsorbent and soluble pH. Also in this method the used Pumice stone can be reused and regenerated. Iron absorption data can be presented by freundlich isotherm model. According to the results obtained, Pumice stone can be used with high efficiency in adsorption process of Iron from water and wastewater. Also low cost and easy accessibility of Pumice stone along with its possibility for reused and regeneration are other advantages of this stone for full-scale application.

Water Treatment is among the most important water quality management criteria in recirculating aquaculture systems (RAS). Nitrogenous wastes are the main pollutants in RAS. Ion exchangers, namely zeolites and clays are widely used in wastewater treatment industries. Due to negative charges within their structural network, they are used frequenty. Through superficial modifications this process can be applied to remove anions as well as cations. In the present study, modification of superficial and layered structures of zeolite and clay were carried out using the organic compound, tetradecyltrimethylammonium bromide and different ambient conditions of temperature (10, 15 and 20oC) and pH (6.0, 6.5, 7.0, 7.5 and 8.0) were examined. Results showed that ambient factors such as temperature, pH, ion concentration, presence of excess anions and interfer ions could affect the extent of ion uptake. It was revealed that higher temperatures increased ion uptake by modified Bentonits. Temperature rise significantly affected nitrite uptake of both absorbents (p<0.05). Higher pH significantly influenced nitrate absorption of both absorbents in a positive manner, while in the case of nitrite it was not depicted. Results indicated that use of modified ion exchangers as a effective tool for anion uptake in RAS is feasible.

In this study, removal of para-nitrophenol (PNP) from synthetic wastewater by Alcaligens faecalis was investigated for the first time in an external airlift bioreactor. The effect of factors such as pH (6, 7 and 8) and nitrogen source (yeast extract, peptone and urea) as well as initial PNP concentration (50, 75, 100 and 125 mg/lit) on PNP removal and bacterial growth was first examined in shake flask experiments. Then, performance of airlift bioreactor was studied at various aeration rates (1, 2 and 4 l/min) and initial PNP concentrations (50, 75 and 100 mg/lit). In shake flask experiments, yeast extract and pH value of 8 led to the highest bacterial growth and PNP removal. In all bioreactor experiments, PNP removal was higher and biodegradation time was lower compared to shake flask experiments. The maximum of 40 and 60% PNP removal were obtained in shake flask and bioreactor experiments at 50 mg/l initial PNP concentration respectively. Among examined aeration rates, 2 L/min resulted in the highest PNP removal percentage at all initial PNP concentration.

In dairy industries large amount of water is utilized and major parts disposed as wastewater. The concentration of organic substance in this wastewater is relatively high. For example in Tehran Pegah Dairy Complex (TPDC) as the biggest Iranian a dairy producer, around 3500 cube meter of wastewater generated for processing of 1000 tons milk, per day. The concentration of chemical oxygen demand (COD) and 5-days biological wastewater demand (BOD5) is about 3000, 1000 mg/L respectively. In this paper the effects of applying ultrasonic wave irradiation on hydrolysis of chemical oxygen demand in TPDC with 20 kHz operational frequency was investigated. The Samples were taken during one working day from 8 a.m. to 4 p.m. Samples were taken every two hour using composite sampling with constant volume from the outlet of equalization tank. Analysis of experimental data showed that it is possible to transfer some part of insoluble COD and BOD5 to soluble form by applying ultrasonic wave. The maximum of this conversion was about 52% which observed at 480s contact time and output power 300 W. For 300 and 600 W output power with extending contact time in the range of 60 to 480s, hydrolysis of organic matter showed ascending trend, but at 900w output powers find out different behavior. Therefore, when hydrolysis of organic matter consider, it is recommended to use low output power and long contact time. And it is important to considering that by this conversion, achievement the high level of treatment become more feasible and a reduction in the cost of treatment obtained consequently.

This study was carried out to evaluate the secondary effluent disinfection of the Isfahan north municipal wastewater treatment plant using filtration and UV technology in current operational condition. The combined system was used in series in pilot scale including: Pressure Sand Filter + Low Pressure (LP) + Medium Pressure (MP) UV Lamps. The UV dose varied according to the initial intensity of lamp, flow rate and influent transmittance. Total coliform (TC), fecal coliform (FC) and fecal streptococcus (FS) were analyzed as microbiological parameters in all effluent samples. TSS, BOD5, COD, VSS, pH and transmittance (UVT percentage) were tested as physicochemical parameters, before and after the units. Results showed that the filtration with loading of 1050 lit/m2.hr, followed by MP lamp with dose of 230 mW.s/cm2 is an effective alternative to reduce the TC/FC and FS in the secondary effluent. The combined disinfection processes that were used in this study, could be met the standards of 1000 TC, and 400FC/100ml for effluent discharge to receiving waters or restricted reuses in the agriculture. This process can also inactivate the FS down to 6-log.Using low-pressure lamps due to low dose radiation for disinfection is not cost-effective. In this study, parasite egg counts due to lack of access to accurate identification techniques for alive cyst detection was not examined.

Phenol is a carbonic compound that is dangerous for humans at a concentration of 0.5 ppm in the environment. The best phenol removal from coal tar wastewaters is achieved by bioremediation. In this study, we isolated indigenous bacteria from phenolic wastewater and adapted it to a high concentration of phenol for its removal from wastewater. We also investigated the growth and removal curves of the bacteria in media with 2000 and 4000 ppm of phenol. It was observed that after lag phases of 24 and 48 hours, they grew and removed all of the phenol concentration over 264 and 312 hours. It was also found that this isolate was able to remove 2233 ppm of phenol in natural wastewater over a period of 120 hours. Identification tests showed that it is a gram-negative bactetium possibly belonging to the pseudomonas species. Phenol concentrations in wastewater can be reduced over a shorter period of time by using either this isolate alone or a group of them.

Sludge from wastewater treatment plants is a valuable source of nitrogen, phosphorus and potassium which are necessary for the plants growth. The purpose of this research was to control sludge quality to use it for soil improvement in Kish Island, Iran. Because of soil with low qualified for agricultural activities and high import expenses of fertile soils from outside of the Island, application of sludge as a cheap source of soil amendment is an easy and economical mean to improve the soil in Kish Island. Comparison of laboratory data of domestic sludge with global standard has shown that it has suitable for application on landscapes and agriculture from the point of view of fertility and heavy metals concentration. Biological data has also shown that the sludge was in class A or B of EPA standard, to fecal coliform, based on the ambient conditions such as water, air, temperature, sun radiation and storage time. The soil test data indicated that salinity, sodium and calcium ions were between 5000-7000 mg/kg which cause a decrease in plant’s growth. Transplanting of garden petunia in the region has been done in different samples mixed with sludge rate of 0, 25, 50, 75 and 100 ton/ha during December 2008 to March 2009. In the first period of the growth study, the results have shown a decrease in the amended soil with sludge retard in comparison with control plant, but after 5 months probably because of spring rains and decrease in the salinity of amended soil, the plant has shown very good growth in leaves and petal, whereas the control plant was dried. Soil and plant analyses were also approved the results because physical (humidity increase) and chemical (EC decrease) characteristics of the amended soil with sludge were improved. Most of the time, the concentrations of micro-nutrients such as iron, manganese, zinc, copper and nutrients in soil and leaves showed an increase in values by an increase in the rate of applied sludge. Other results were not shown considerable variation in accessible phosphorus but noticeable decrease in potassium. Of course, in some special cases, negligible changes in cadmium and lead concentrations of the plant have been observed. In addition, the soil phosphorous content had negligible changes and the soil potassium content had a decreased rate in the amended soil. Finally, it is concluded that for sludge application, it is necessary to check agronomic nutrients levels and heavy metals accumulation. However it is also recommended to use any kind of salt resisted native plants for landscapes. In case of sensitive plant, sludge should be added at least 6 months in advance to ensure that soil physical and chemical condition are achieved.

Estimation of the flow discharge under sluice and radial gates is an essential problem in many water engineering works. The results obtained from previous studies showed a lot of controversy and therefore need further research on this subject. In this investigation, the energy equation was used and the concept of increasing the pressure head created by water surface profile under the gates was considered. A semi theoretical equation was obtained for the estimation of the contraction coefficient (Cc) of flow under the sluice gates. This method decreased the mean absolute error of Cc less than 3%. To estimate the free flow discharge under radial gates, an analogy approach between sluice gates and radial gates has been presented. Semi-experimental equations, for both gates, were obtained by using some known data of other investigators. Field and laboratory data of many researchers were also used for the verification of the presented method. Results of this investigation showed that the presented equations are perfectly suitable for both sluice and radial gates.

In this study, hydraulic behavior of Shiraz plain aquifer, with an area of ~300 km2, was simulated using PMWIN model. The performance of recently constructed drainage system in the plain was modeled and parameters affecting hydraulic behavior of the aquifer were analyzed. Measured rainfall and evaporation rates in the plain, recharge and discharge rates through the aqueducts, Khoshk and Chenar Rahdar rivers, as well as amount of water discharged from production wells and recharge due to returned wastewater were considered in the model. Plain hydrodynamic coefficients were estimated via calibration and sensitivity analysis of the model was performed for four important parameters. Results showed that the model is most sensitive to recharge rate and hydraulic conductivity, respectively, such that a small variation in these two parameters causes a dramatic change in hydraulic head distribution in the plain. Furthermore, specific yield coefficient influences the seasonal water level fluctuations, but the aqueducts conductance coefficient only affects the aqueduct radius of influence with little effect on the overall hydraulic behavior of the plain.

Forecasting and monitoring droughts are important elements of optimum water resources management specifically in the metropolitan areas. Tehran as the biggest city of Iran and its five dams (Amirkabir, Lar, Latyan, Mamloo and Taleghan) are also exposed to drought hazards. In the current article, monthly meteorological data in the geographic area covering [0o, 60o] Northern latitudes and [0o, 90o] Eastern longitudes with 10×10 degree resolution including air temperature and geopotential height at 1000, 850, 700, 500 and 300 mbar levels are used as the model predictors. These data recorded in the period of 1948 to 2008 have been used to develop a model for forecasting SPI (Standardized Precipitation Index) values in Winter and Winter-Spring seasons with 2.5 and 4.5 months leadtime. This model has been calibrated using 31 years of data. Mutual Information (MI) index has been used to select the inputs (predictors) for each basin in each season. Fuzzy Inference System (FIS) has been used to formulate the model. The fuzzy membership functions have been selected based on sensitivity analysis and engineering judgment. The results of the study have shown that geopotential height in 850 and 300 mbar levels are the best predictors for forecasting SPI values in the selected seasons. The model results have had enough accuracy to be used for forecasting SPI values in Winter and Spring seasons in Karaj and Taleghan basins and SPI values in the Winter season in Mamloo, Latyan, and Lar basins.

Withdrawal of ground water resource in Rafsanjan plain is about 450 million cubic meters in 1974. In this year, according to the hydrological calculation approximately, 98 million cubic meters of capacity permitted the table, has been added to harvest. Therefore, Rafsanjan region been forbidden region since 1974. According to statistics data, in 2003, extraction rate of ground water are recorded about 750 million cubic meters. But approximately 250 million cubic meters per year had added to the harvest in stored groundwater. For this rezone the level of groundwater falls down 80 cm per year. This has been introduced of agent to loss of farm land residential areas of failure. Down the level of groundwater decreased water quality including high and rising Ec, so that not to meet the standard value. In the Rafsanjan plain the geological layers are different, then, in this region, opening layers of earth is horizontally and vertically. This phenomenon alongs with techtonic movement may be resulted to a tragic event in this area.