مجله آب و فاضلاب
پیاپی 150 (فروردین و اردیبهشت 1403)

Today, customer satisfaction is one of the main issues that water and wastewater companies must consider. In this regard, it is crucial to identify effective strategies to increase customer satisfaction. Therefore, the aim of this research was to evaluate the satisfaction of the subscribers of Shiraz Water and Wastewater Company. For this purpose, the combined Delphi and Kano model was used. The method used in the current research was descriptive-analytical and qualitative-quantitative in terms of the type of the data. With this objective in mind, according to the Delphi method, 37 satisfaction factors of the subscribers of Shiraz Water and Wastewater Company were selected according to the opinion of the company's and other experts, and were investigated as the main variables of the research. In the following, using a research questionnaire based on the Kano model, information was collected from the statistical population; then, using an evaluation table, the subscriber's needs were identified, and the coefficient of satisfaction and dissatisfaction was calculated and analyzed. Based on Kano's model, customer satisfaction factors are mainly classified into three categories: must-be one-dimensional and attractive requirements. In this research, 10 factors were identified as must-be requirements, 9 factors as one-dimensional requirements, and 18 factors as attractive requirements, which were ranked based on the level of satisfaction and dissatisfaction of subscribers. Based on the results, Shiraz Water and Sewerage Company should focus more on the characteristics of attractive requirements instead of must-be or one-dimensional requirements in order to gain a competitive advantage and focus on customer satisfaction.

Municipal waste is a cost-effective and valuable source of organic matter for agricultural soils. In recent years, MSW compost has been widely used in agriculture as a soil conditioner and fertilizer. However, the excessive use of organic and mineral fertilizers in the production of greenhouse crops leads to the accumulation of heavy metals in the soil and health risks for humans. Therefore, this study investigated the effect of the municipal waste and manure application on heavy metals in the soil. Also, the health risks for humans were evaluated through the consumption of cucumber cultivated in these soil. In this study, the concentration of heavy metals Cd, Cu, Ni, Pb and Zn in soil, mobility of metals, bioavailability, fractionation of metals, effects of pollution in the greenhouse soil and uptake of these metals by cucumber plant following 3 cultivation years of application of municipal waste compost and manure were studied in a randomized complete block design with three replicates in a greenhouse located in the south of Theran province. Also, environmental pollution risks were evaluated. The results showed that the application of municipal waste compost and manure increased both the total and available concentration of heavy metals in the soil. However, the concentration of the measured metals was at the permissible limit of the concentrations of heavy metals in Iranian soils. Copper and Zn were detected as the most mobile metals in control and treated soils with municipal waste compost and manure, respectively. The amount of Pb (2.26 mg kg-1) and Cd (0.06 mg kg-1) in cucumber in treated soil with municipal waste exceeded the limit value for edible vegetables. Based on the results obtained from the health risk index, Pb and Cu represented a high potential risk for the health of adults and children by consuming cucumbers in compost-treated soils. The results of this study showed that despite the three-year application of municipal waste compost and manure, the concentration of heavy metals measured was not higher than the allowed guideline level. However, considering the high bioavailability of heavy metals, repeated application of municipal waste compost would carry a risk of gradual accumulation in the soil over time. Therefore, measuring the total and extractable concentration of heavy metals and metal mobility when assessing likely effects on plant yields and metal uptakes and setting soil quality criteria is important.

It is more important to improve and complete the wastewater process in order to reuse and return it to the production line. In this study, the hydrogen peroxide/ozone process (Peroxone) was investigated as a supplementary step in paper mill wastewater treatment to reduce the amount of chemical oxygen demand and remove E. coli. In this regard, using the Box-Behnken Design method based on the response surface method to optimize and investigate the effect of three variables governing the ozonation process, including the amount of hydrogen peroxide consumed (ml), the amount of ozone input (mg/min) and ozonation time (min) were used. The results showed that the amount of ozone and hydrogen peroxide had the greatest effect for reducing COD (up to about 75%). Also, all three variables have played a significant role in increasing the efficiency of the Peroxone process and even completely eliminating E. coli. In determining the optimal conditions, the amount of ozone (146 mg/min), the amount of hydrogen peroxide (2ml) and the duration of ozonation (23 min), the lowest amount of residual COD (73 mg/L) and the highest efficiency (75% removal of E. coli) are predicted. The results showed that due to the interaction of ozone and hydrogen peroxide, the peroxone process performance was less efficient than the ozonation process alone.

The entry of large volumes of industrial effluents containing organic pollutants and dyes into water has made pollution an important issue and led to more attention being paid to advanced oxidation processes for industrial wastewater treatment. Cavitation, due to its ability to produce active free radicals, is a technique that has been considered to increase the efficiency of water and wastewater treatment processes in order to remove organic chemical compounds and decompose pollutants resistant to biological decomposition. The purpose of this research is to use hydrodynamic cavitation to remove the methyl orange dye and optimize the operating parameters for color removal efficiency. For this purpose, cavitation was produced through the use of a pump and an orifice plate with a 4 mm diameter hole, and methyl orange with a concentration of 2 mg/L was tested at each stage. In the following, the effect of operating parameters, including pressure in the range of 0.5 to 6.5 bar, temperature in the range of 8 to 40 °C, pH in acidic, neutral, and alkaline conditions after 135 minutes was determined to achieve the maximum decolonization in optimal conditions. In this study, optimal conditions for achieving the highest removal efficiency (51.7%) were obtained at an inlet pressure of 5.5 bar and a cavitation number of about 0.14 (Ca≈0.14). The results of this investigation showed that the decomposition and removal of methyl orange dye using the hydrodynamic cavitation method is sensitive to the pH of the solution, especially in acidic conditions, which are more suitable conditions for the production of hydroxyl radicals than in alkaline conditions, and has higher efficiency in acidic conditions. Also, increasing the temperature of the solution due to the effect on the saturated vapor pressure will increase the decolonization rate.

Antibiotic-resistant bacteria have increased in livestock and poultry over recent years. However, to date, there have been few studies that have investigated the antibiotic resistance bacteria among environmental and animal samples. Hence, the main purpose of this research was to isolate Enterobacteriaceae from the wastewater of poultry farms and investigate the pattern of antibiotic resistance in these bacteria. In this study, 100 wastewater samples were isolated from different poultry farms. These strains were identified using biochemical tests. The antibiotic resistance pattern was determined by the disk diffusion method (Kirby–Bauer). The isolated bacteria were investigated in terms of resistance patterns to cephalexin, tylosin, doxycycline, and erythromycin. A total of 170 Gram-negative bacteria from the Enterobacteriaceae family were isolated from poultry wastewater samples. The most isolated strain was Escherichia coli (35.33%), followed by Klebsiella (17.65%). According to this study, the most resistance was to cephalexin and doxycycline antibiotics. The results of this research indicate a high level of antibiotic resistance in bacterial isolates from wastewater. This is probably be due to the improper use of antibiotics in the poultry industry.

With the increase in maintenance and repair costs, as well as changing expectations towards the growth of efficiency and increasing the life cycle of equipment, detecting the possibility of failures before they occur and reducing the time of breakdowns and stops, maintenance and repairs and condition monitoring of equipment have become more important. Reliability-centered maintenance is one of the methods and strategies that are systematically related to equipment maintenance and repairs. Since the pumps are the center and axis of the treatment plants, their study can be of great significance. This is because the output of the water and sewage industry is very important because of its connection with people's lives. The current research is focused on investigating the impact of RCM strategy on water treatment plant pumps by using the Analytical Hierarchy Process. Questionnaires were designed based on objectives and criteria, and the weighting of data was done by the AHP method. Also, information worksheets and RCM decision worksheets for pumps were designed and completed. In total, the MTBF index of clear water pumps was investigated in two time periods (from June 2021 to June 2022 and June 2022 to June 2023). The data analysis shows that the value of this index increased in the second period compared to the first period, which indicates the positive effect of Reliability Centered Maintenance activities.