جستجوی مقالات مرتبط با کلیدواژه « تصفیه خانه فاضلاب » در نشریات گروه « مهندسی آب »

Nowadays, the importance of ensuring the effluent standards of wastewater treatment plants is obvious. It is necessary to pay attention to the selection of the biological wastewater treatment process by considering different and diverse criteria. Because, the incorrect choice of the process increases costs and does not achieve the desired result. In this research, the technique of analytical hierarchy process and its combination with Taguchi method was used. By weighting and prioritizing the criteria and options by two groups of experts, including the scientific group and the executive group, the weight of each criterion and option was calculated. In the present study, options (in two cases including 7 conventional options and 7 advanced options), criteria (4 items) and comprehensive and complete sub-criteria (13 items) for selecting biological wastewater treatment processes in rural areas under various conditions have been considered. Finally, it was concluded that in both perspectives, the sub-criteria of providing disposal criteria and standards and the ability to reuse wastewater and climatic conditions were placed in the first and second priority. These sub-criteria received weights of 0.113 and 0.108 from the scientific point of view and 0.122 and 0.106 from the executive point of view. Also, the present study showed that the model of combining AHP and Taguchi method is a successful model for determining the method of biological wastewater treatment for various conditions. Finally, according to the results of this study, the prioritization of biological wastewater treatment options for wastewater treatment in Ahar village was done as a case study and the output results showed that the first priority of all experts is the artificial wetland method and MBBR, from a scientific point of view, Extended Aeration and ABR-Wetland, and in the executive point of view, artificial wetland and A2O methods were prioritized (conventional and advanced methods, respectively).

One of the important issues along with water shortage and demand in cities is the issue of wastewater disposal and treatment. When it comes to wastewater and its treatment, the first thing that comes to mind is the discussion of the environment and its protection from pollution because wastewater is always a major polluting parameter in human and natural environment The construction of a wastewater treatment plant is a civil-environmental activity whose main purpose is the proper and hygienic disposal of wastewater, which, if neglected, will have irreparable consequences. The first effective step for the construction of these facilities is to identify their suitable location, which is done by considering various factors and criteria. For this purpose, multi-criteria decision making (MCDM) methods have been used. Here, according to the existing conditions, hierarchical decision making (AHP) and Delphi (delphi) decision methods have been selected to solve the problem. In this research, Farooj city, which is one of the cities of North Khorasan province, was studied for the construction of a wastewater treatment plant.

Separate sewer networks are designed and built to collect foul sewage from buildings and convey it to wastewater treatment plants (WWTPs). However, due to some holes and cracks on the pipes or unsealed pipe joints, a volume of ground or subsurface water that is placed in saturated or unsaturated zones intrudes sewers and WWTPs. In a condition that the wastewater level in the sewer stands higher than the groundwater level, wastewater leaks into the soil and groundwater and this phenomenon is called sewer exfiltration. Moreover, during a rain event, a part of the precipitation gets into the sewer system through the illicit connection of the yard drains and roof downspouts to the building’s lateral, and this part of the flow is called rainfall-derived inflow and infiltration (RDII). In this research, infiltration, exfiltration, and RDII were evaluated in a 16-month period to show the range of inflow and infiltration in the sewer network under the service of the South Tehran WWTP. Results show that the infiltration constitutes the major volume of the total inflow and infiltration. But the RDII leads to more operational problems due to its nature as an intense flow. After calculating the range of inflow and infiltration, results show that the average infiltration rate that entered the WWTP in the year 2014 was 0.0175 L/s/ha that is much less than the values mentioned in Criterion No. 118. Furthermore, total inflow and infiltration in five hours of the study period crossed the upper limit of the inflow and infiltration range (0.6 L/s/ha) in Criterion No. 118 that shows the high percentage of illicit connections in Tehran and a high volume of rainfall that enters the sewer network. Accordingly, the inflow and infiltration range in the Criterion No. 118 seems to be an unsound range and it needs some revisions.

Due to the water shortage crisis, the reuse of municipal wastewater is essential. Planting plants in the wastewater treatment process is appropriate and can help to reduce and eliminate pollution in urban and rural wastewater. This study aimed to determine the phytoremediation of lead and nickel from Ahwaz wastewater treatment plant. In this study, a completely randomized design with 4 treatments and 3 replications was used, and the laboratory activities were performed in the soil laboratory of Islamic Azad University, Ahvaz Branch. Heavy metals were measured by atomic absorption method and PG Instruments Ltd. The average amount of lead and nickel in the effluent of Ahvaz was 96.35 and 102.57 μg/kg. The amount of lead metal in the studied treatments was 17.85-96.86 ppb, and nickel content was 18.91- 102.87 ppb. In this study, the percentage of the Lewis plant's removal of lead and nickel was 62.66% and 70.18%, respectively. Also, the removal efficiency of the studied parameters by the seven herbaceous plants was 29.26% and 44.22%, respectively. The amount of nickel adsorbed by plants was higher than that of lead metal. The removal efficiency of lead and nickel metals from municipal effluent obtained by Typha Latifolica was higher than Polygonum aviculare. In total, Typha Latifolica and Polygonum aviculare plants had the ability to purify lead and nickel metals from urban effluents so that the amounts of these metals were reduced in the second and fourth treatments within 90 days.

Nowadays, the using of treated wastewater in diverse purposes such as agriculture, industry and irrigation is converted to an appropriate solution for water shortage. Despite the advantages of water reuse, due to various pollutants in wastewater and lack of complete treatment in accordance with the standards, it is always risky. Therefore risk assessment should be conducted in order to determine the reliability of system and offer solutions to enhance the reliability of wastewater treatment system. Risk is the possibility of occurrence an adverse event and the severity of the negative effects of it. In the present study, Bayesian network approach is used for risk assessment of wastewater treatment plant. In this method the possibility of an event can be obtained by creating cause and effect relationship between the components of the system.
Wastewater treatment plant of industrial complex of Moorchekhort is selected for case study in this study. The fouling, corrosion and biofilm of using treated wastewater for industry have been determine as final events. The model input datas have been formed by experts, specialists and laboratory datas from wastewater treatment plant of industrial complex of Moorchekhort. The reliability of wastewater treatment system analyzed by Bayesian network model showed %70. The efficiency of Bayesian network in order to determine elements of failure and estimate the risk of wastewater treatment system that is not adapted to effluent standards for the industry is shown in this study.

Performance of wastewater treatment plants (WWTPs) in Urmia, Khoy, Miandoab, Salmas, and Bookan were evaluated during the years 2008 to 2011 based on the reliability approach. The approach predicts the overall performance of WWTPs and their processes and, thereby, makes the screening of treatment technologies possible. The required BOD5, COD, and TSS data were collected using the records available at West Azerbayejan Water and Wastewater Company, local surveys, and interviews with operators. Statistical analysis was performed by SPSS. The valid Niku modeling was employed to calculate the Rmeasured, Revaluated, COR, and expected percentages of compliance with discharge standards and a significant relationship was found among these parameters. The results also showed the log normal distribution of effluent characteristics. Furthermore,SBR and biolac processes exhibited higher values of Rmeasured (90-100%), Revaluated (93-100%), and expected percentages of compliance with the discharge standards (95-99.97%) in all the WWTPs studied but lower values of COR (0.41-0.64) than those in aerated lagoons. The coefficients obtained in this study can, therefore, be used for the development and construction designs of similar systems.

Measuring the amounts of pollutants in the treated wastewater represents the level of performance and efficiency of the Wastewater Treatment Plant (WWTP). In this cross-sectional study, an attempt was made to monitor the performance of partialmix aerated lagoons in Miandoab WWTP for a period of 9 months in the summer, fall and winter of 2012. The sample was selected from both the input and output of WWTP during daylight hours once a week. The results showed that the performance of the treatment is influenced by weather conditions and the efficiency of the system will decrease if the weather is cold which will lead to a slowdown in the biological activities. The analysis of the system's performance indicated that the elimination efficiency of the pollutants from wastewater is higher in summer in comparison with other months. The Removing Percentage of BOD5, COD, TSS in summer was 5.9, 6.4 and 6.6 percent higher than those values in winter. The comparison of the concentration of the effluent of WWTP with the standards of Iran's Environmental Protection Agency showed that the output of the plant can be used for agricultural irrigation.

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.

Listeria and in particular Listeria monocytogenes is considered a ubiquitous foodborne pathogen which can lead listeriosis in human and animals. Listeriosis can be serious and may cause meningitis، septicemia and abortion in pregnant women. Although wastewater or sludge may contaminate foods of plant origin، there are no data on occurrence of Listeria spp. in wastewater and sludge in Iran. The purpose of current investigation was to study the occurrence of Listeria spp. in various samples of wastewater and sludge in Isfahan North wastewater treatment plant. Influent، effluent، raw sludge and dried sludge samples were collected from Isfahan North municipal wastewater treatment plant. L. monocytogenes were enumerated by a three–tube most probable number (MPN) assay using enrichment Fraser broth. A total of 65 various samples from five step in 13 visits were collected. The presence of Listeria spp. also was determined using USDA procedure. Then، phenotypically identified L. monocytogenes were further confirmed by Polymerase Chain Reaction amplification. L. monocytogenes isolated from 76. 9%، 38. 5%، 84. 6%، 69. 2% and 46. 2% of influent، effluent، raw sludge، stabilized sludge and dried sludge respectively. The efficiency of wastewater treatment processes، digester tank and drying bed in removal L. monocytogenes were 69. 6%، 64. 7% and 73. 4% respectively. All phenotypically identified L. monocytogenes were further confirmed by Polymerase Chain Reaction. The results of present study have shown that Listeriaspp. and L. monocytogenes in particular، were present in wastewater treatment plant effluents and sludge at high level. The bacteria may spread on agriculture land and contaminate foods of plant origin. This may cause a risk of spreading disease to human and animals.

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.