Iranian Journal of

Background and Objective: Wastewater treatment and stabilization always imposes costs and consequently a lot of energy on wastewater treatment plants. To achieve the purification and stabilization of as much sludge as possible, breaking complex components into simpler components is considered a critical step. Therefore, this study aimed to evaluate the feasibility of treating the produced sludge in the municipal wastewater treatment plant using ozonation method.
Materials and Methods: In this study, sludge was obtained from the return line of activated sludge from the wastewater treatment plant in the south of Tehran. An ozonation generator with a discharge rate of 3 L/min and an ozone concentration of 40-35 mg/L was discharged to the reactor and the residual ozone concentration was measured by iodometric method. Finally, the total suspended solids and volatile, soluble chemical oxygen demand, total organic carbon, and biochemical oxygen demand during ozonation processes were measured using the Standard Method.
Results: The results of this study showed that the amount of TSS and VSS in the activated return sludge decreased from 4060 to 2100 mg/L and from 3300 to 1850 mg/L during the ozonation process, respectively. However, SCOD, TOC, and SBOD had an upward trend of about 18, 11.7, and 14 times in the same reaction time, respectively.
Conclusion: According to the results of this study, it can be concluded that the ozonation system can be proposed as a suitable process for the decomposition of sludge produced in wastewater treatment plants and increasing the biodegradability of these sludges.

Background and Objective: The purpose of this study was to use the HELP model to estimate the leachate generation rate and its pattern in a landfill located in the semi-arid region of Iran.
Materials and Methods: The input data for the model were collected through fieldwork. To evaluate the accuracy of outputs, the actual amount of leachate production has been measured on-site for 10 months. In addition, sensitivity analysis was conducted to find out the most important parameters in leachate generation in the landfill.
Results: The results showed that the model was able to estimate the rate of leachate generation with an accuracy of 75.5% and the correlation between the model's estimated values and actual values was 60%. In addition. the sensitivity analysis showed that the most important factors affecting the leachate generation in the landfill were waste moisture content and rainfall, respectively.
Conclusion: The model showed satisfactory performance in the prediction of leachate generation in the arid area. The model showed that the moisture content of the waste significantly contributes to leachate generation in Karaj landfill and therefore, it is suggested to identify and implement procedures to reduce the moisture content of the waste at the source of generation.

Background and Objective: Microbial fuel cell (MFC) is a new green technology that uses the catabolic ability of microorganisms to produce bioenergy while simultaneously removing organic matter and other wastewater contaminants. Electrode material is one of the factors affecting the performance of microbial fuel cells. The aim of this study was to investigate the performance of microbial fuel cells in COD removal and bioenergy production from synthetic and real beverage wastewater.
Materials and Methods: In this research, a two-chamber microbial fuel cell with Nafion membrane and aerated  cathode was set up using two electrodes made of carbon felt and flat graphite after being contacted by synthetic wastewater with a concentration of COD 5000  mg/L and real beverage wastewater. Organic matter removal efficiency and voltage, power density and maximum current were determine.
Results: Experimental results showed that maximum COD removal efficiency of 92 % was achieved in synthetic wastewater and with a carbon felts electrode. In this condition, maximum voltage, power density and output current density of 469 mV, 175.28 mW/m², and 855 mA/m², were obtained, respectively. However, by using real industrial wastewater (beverage), maximum removal efficiency of COD, voltage, power density and output current density, related to carbon felt electrodes ‎were obtaines as 84 %, ‎460 mV, 91/65 mW/m², and 635 mA/m², respectively.
Conclusion: The findings showed that synthetic wastewater outperforms microbial fuel cells in terms of bioelectric production and organic matter removal as compared to real wastewater (beverage). The reason for the decrease in the cell performance might be the presence of solids and other confounding pollutants in real wastewater.

Background and Objective: As pharmaceutically active compounds (particularly antibiotics) are known emerging contaminants (EC), their occurrence in the environment has high health risks for the living organisms and the public. The effluent of wastewater treatment plants (WWTPs) is the most important source of residues of these compounds in the environment. The urban wastewater of Bandar Abbas is discharged into the marine environment of the Persian Gulf at the rate of 500 to 700 L/s, which could be a potential source of pharmaceutical contamination for the marine ecosystem.
Materials and Methods: In this research, two main wastewater discharge stations at Gursuzan and Suru were sampled during three phases between December 2020 to February 2021. The concentration of Erythromycin residues, as the first antibiotic clinically used to treat human infections, was assessed by high performance liquid chromatography (HPLC) method.
Results: Data analysis showed that mean (± 95% CI) concentration of Erythromycin in Suru and Gorsuzan stations were 16 ± 1.53 and 19 ± 5.86 μg/L, respectively; which their differences did not differ significantly (p>0.05). Pooled data also indicated that the wastewater discharge contained 13.2 to 23.50 μg/L of Erythromycin (α=0.05). Considering the discharge of high volume of Bandar Abbas wastewater effluent into the Persian Gulf (500-700 L/s) as well as the data obtained from this study, the results of the simulation model showed that 5184×10⁴ L Bandar Abbas municipal wastewater is discharged into the Persian Gulf marine ecosystem daily. This volume contains 0.877×10³-1.02×10³ g active residues of Erythromycin antibiotic (α=0.05).
Conclusion: The present study is the first report of contamination of residues of medicinal compounds into the Marine Environment of the Persian Gulf by urban wastewater. Regarding the high volume of wastewater discharged, which calls for immediate actions to be taken.

Background and Objective: Various aspects including the environmental burdens, social and economic consequences of the waste management(WM) scenarios must be considered to come up with a comprehensive WM plan. Life Cycle Assessment (LCA) approach is a systematic method to quantify the environmental burdens of each WM scenario.
Materials and Methods: This study used an LCA approach to develop a decision support system to analyze different scenarios of WM. Local and global databases were used to develop a comprehensive life cycle inventory database. The model comes with a graphical user interface in Persian to make it easier to use by a wide range of customers. Finally, to evaluate the model, three scenarios were assessed in Karaj city, Iran.
Results: To the best of our knowledge, this model is the first attempt to automate the process of waste management scenarios evaluation in Iran. The model enables users to easily and quickly simulate a wide range of scenarios. All calculations will be carried out by the software in the background and the user only needs to determine his/her scenario of concern which is very easy owing to the user-friend GUI of the software. The model was evaluated by analyzing the current WM in Karaj. The results showed that the waste collection system is the main source of environmental pollution of the WM in Karaj city due to the inefficient system of the waste collection and poor fleet fuel efficiency.
Conclusion: This tool allows users to gather detailed information about the waste management systems. In this way, the user can make informed decisions about the most suitable waste management scenario in a city.

Background and Objective: Changes in the quantity and quality of waste produced as a result of compliance with health protocols are the result of the COVID-19 outbreak. The present study aimed to determine the quantity of personal protection equipment produced in Tehran and people’s knowledge of its management.
Materials and Methods: The present cross-sectional and descriptive-analytical study was carried out on 2560 participants in Tehran through an online survey in spring 2020. Based on the percentage of using masks and gloves, the amount of produced waste was calculated, and Mann-Whitney and Kruskal-Wallis statistical tests were run to explore the relationship between the variables.
Results: The overall Cronbach's alpha coefficient of the questionnaire was 0.94, and the rate of mask and glove use was 90.7% and 65.7%, respectively. 70.3% and 52% of the population used two masks and one pair of gloves on a daily basis. The number of daily produced masks and pairs of gloves was 14530407 and 5262666, respectively. Mann-Whitney U-test showed a statistically significant difference between gender and marital status with people’s knowledge of waste management (p <0.05). Kruskal-Wallis test showed a significant difference between the economic status and people’s knowledge of separating the produced waste (p <0.05). People with an increasing income tended to separate the waste more.
Conclusion: Due to the high volume of personal protective wastes and the lacking knowledge of one-third of the participants about the transmission of the virus through contaminated waste, it is necessary to raise awareness of breaking the virus transmission chain.

Background and Objective: Dolochar is the residual ash from the production of sponge iron in the process of direct reduction of iron ore by the coal-based method. In Iran, this waste is transported to the nearest landfill. However, these methods are a major environmental concern due to the fineness of the waste and the presence of heavy metals in its composition. The aim of the present study is to investigate the methods of reusing dolochar in order to solve the environmental problem and further use it as auxiliary materials in applications such as road construction and wastewater treatment.
Materials and Methods: In depth investigation of the word “Dolochar” in Science Direct, SID, and MagIran databases showed that there is no long history of reusing it. Only 14 English articles were found, all of which were used in research; Therefore, the present article deals with the issue of reusing Dolochar in Iran for the first time.
Results: By reviewing previous studies, reuse of Dolochar has been classified into five sections. Dolochar use in wastewater treatment (removal of copper, chromium, paint, phosphate, nitrate, surfactant), removal of chromium from mine effluent (more than 94%), as a synthesis gas, as a filter medium (three times better than sand filters) and it is also used in construction and road construction (alternatives to aggregates).
Conclusion: The high capacity of Dolochar in waste absorption and wastewater treatment shows that it is necessary to reuse it in Iran instead of burying or leaving it in the environment.

Background and Objective: Pharmaceutical wastewater has a high level of pollution load that should be treated before discharging to the environment. Integrated processes using different mechanisms are one of the most fruitful methods in wastewater treatment. In this study, combined Integrated Fixed Film Activated Sludge (IFAS) and photocatalytic processes are utilized using of Fe₃O₄/TiO₂ nanocatalysts to decrease the COD value of pharmaceutical wastewater.
Materials and Methods: In this study, the variables of each process are optimized using Response Surface Methodology (RSM). In the IFAS process, the variables were dissolved oxygen (DO), media filling percentage and hydraulic retention time (HRT); while in the photocatalytic process, the effects of pH of wastewater, catalyst dose and reaction time were investigated.
Results: In optimal conditions (DO 3 mg/L, HRT 24 h and media filling percentage 65%), COD removal rate was obtained 59.15%. With the initial concentration of 1725 mg/L COD and the mentioned efficiency, the concentration of COD in the effluent diminished to 704 mg/L. However, in the photocatalytic process, during optimal conditions (pH 6.8, reaction time 105 min and catalyst dose 60 mg/L), The efficiency of the process was determined 81%, which by considering the input COD (704 mg/L), the output concentration was reduced to 134 mg/L.
Conclusion: According to the standards provided by the Environmental Protection Agency (EPA), the effluent from the combined process can be discharged into the environment.
 

Background and Objective: Nowadays, in metropolitan areas, principled and hygienic waste management is very important. Recycling is one of the most appropriate options in waste management. Hereof, the present study was aimed to investigate the possibility of using textile waste fibers in the manufacture of Medium Density Fiberboard (MDF).
Materials and Methods: This experimental study was performed on lab-scale. Fabric waste was prepared by separation method at source from a clothing manufacturer in Tehran and converted into fibers. Test boards were made with weight percentage of mixing textile waste fibers to industrial fibers at three levels of 0:100, 10:90 and 15:85, respectively, 10% urea-formaldehyde adhesive, with 16 mm thickness and 0.7 g/cm³ density by hot press. Then, properties of the boards were measured including bending strength, modulus of elasticity, internal bond, hardness, water absorption and thickness swelling. The results were analyzed with ANOVA test.
Results: The results of ANOVA showed that the effect of textile waste fibers on the bending strength, modulus of elasticity and swelling thickness of 2 and 24 hours of boards made at 5% probability level was significant. Additionally, the highest values of physical and mechanical properties are related to made boards with 10% of textile waste fibers.
Conclusion: The results showed that it is possible to make MDF with textile waste fibers. The use of wastes such as fabrics in the production of new functional products can be considered as one of the strategies to reduce waste and thus to maintain human health and the environment.
 

Background and Objective: barbershops are one of the most important public places for beauty activities, which requires attention to health issues (personal and environmental), and non-compliance with health standards and procedures can be a threat to public health. The level of awareness and performance of employees can affect the management of waste production. This study aimed to investigate the level of knowledge of personnel about waste production and performance in southern Tehran in 2021.
Materials and Methods: This descriptive cross-sectional study was conducted in southern Tehran with a statistical sample of 330 places. In this study, a questionnaire was used which comprised of three sections; demographic information, the level of awareness and performance of personnel, and the information was completed after interviews with hairdressers. Data were analyzed by Kolmogorov-Smirnov, Chi-square, Pearson correlation coefficient, one-sample t-test, and Mann-Whitney using SPSS software (IBM-v.26).
Results: The average scores of awareness and performance of individuals in waste management were 43.18 and 48.27, respectively, and based on the results of qualitative analysis, the scores of awareness and optimal performance of individuals in waste management were 53.6% and 72%, respectively. Also, 46.6% and 28% of the participants obtained unfavorable scores on knowledge and practice in waste management, respectively. People's knowledge about the management of waste produced in hairdressers had a significant relationship with gender, history of health education, history of health crimes, education and performance of people about the management of waste produced in hairdressers with gender and history of health education. There was no significant relationship between knowledge and practice with other variables.
Conclusion: Barbershop is a place where paying attention to environmental health is effective in promoting community health and disease control. Ignoring this issue can lead to the spread of various diseases. In general, the results of this study showed that the level of awareness is effective in the performance of barbers regarding the management of waste production. Additionally, health education was known effective in the level of awareness and performance of hairdressers in this field, so the improtant roles of these variables should taken into consideration. 
 

Background and Objective: With increasing population growth and water pollution, fresh water supply sources are declining and can not meet today's human needs. Thus, energy conversion systems with high efficiency and low pollution such as desalination microbial cell have been considered. Therefore the aim of this research was to investigation the efficiency of microbial desalination cell (MDC) for desalination and treatment of salt wastewater.
Materials and Methods: To address this issue, the decision was taken to use saline synthetic wastewater with different initial salt concentrations (2, 5, 7 and 10 g/L NaCl) and, different hydraulic retention times (1, 2, 3 and 72 h) in open circuit voltage (OCV) and closed circuit voltage (CCV) continuous mode.
Results: The results showed that highest EC removal was 11.2% and 14.3% with 10 g/L NaCl in open and closed circuit mode, respectively. Maximum COD removal of 68.7% was achieved in CCV mode that was obtained at 10 g/L NaCl. Additionally, Escherichia coli, Bacillus, Enterobacter, Staphylococcus aureus, Pseudomonas and Citrobacter were diagnose as effective bacteria in decomposing wastewater.
Conclusion: The obtained results proved that MDC desalination microbial cell technology is Emerging technology that has many unknown aspects; however, it is expected to be an appropriate technique for wastewater treatment and desalination.
 

Background and Objective: It is important to determine the quality of the compost to use compost properly. The aim of this study was to determine the effect of mixing ratio of bulking agent on stability and maturity indices in poultry waste compost.
Materials and Methods: Two piles of sawdust mixture with poultry wastes and volume ratios of 1:1 (W1) and 2:1 (W2) were prepared by Windrow method and a pile containing poultry manure was used as control (W0). In order to determine the stability and maturity indices in compost, the most important physicochemical and biological parameters were studied.
Results: The thermophilic phase lasted about 7 weeks for W1 and about 4 weeks for W2. The initial C/N ratios in the W0, W1 and W2 were 27.10, 31.40 and 56.24, respectively, which eventually reached less than 20. The reduction of organic matter in the three piles was 8.30%, 62.59% and 85.53%, respectively. The thermophilic phase caused a sharp decrease in the population of indicator and pathogenic microorganisms in all piles. The highest dehydrogenase activity in W1 pile was 2.95 mgTPF/gDW.h and by decreasing temperature until the last day, its value decreased to 0.29 mgTPF/gDW.h.
Conclusion: The best ratio for mixing sawdust with poultry manure was 1:1 (v:v). Microbial and enzymatic activities are useful parameters for monitoring poultry composting process and determining the rate of compost stability, and the use of this compost in agriculture will improve soil quality.
 

Background and Objective: Based on its unique characteristics, oil industry wastewater must be treated before discharging into the environment. The study aimed to optimize the catalytic sonopraxone process in the treatment of petroleum wastewater using a statistical method.
Materials and Methods: The synthesis of Iron Oxide-Zinc Oxide was carried out by air oxidation and layer-by-layer self-assembly method. XRD, SEM, EDAX, FT-IR, BET, DRS, VSM and TGA techniques were used to investigate the structure. In this study, applied CCD method optimization of pH parameters, reaction time, ozone gas concentration, hydrogen peroxide concentration and catalyst amount in the process. In optimal conditions, BOD₅ and TPH removal values, reaction kinetics and synergistic effect of mechanisms were studied. COD, TPH and BOD₅ were measured by spectrophotometer (DR6000), GC-FID and incubator, respectively.
Results: The results indicated that the Fe₃O₄@ZnO structure is well formed. A quadratic model was proposed to model the process based on the correlation coefficient. Based on ANOVA analysis and p and f indices, the proposed model was reported to be significant. Optimum conditions include pH 6.4, ozone concentration 1.3 mg/L.min, hydrogen peroxide concentration 2.5 mL/L, reaction time 51 min and catalyst amount equal to 0.64 g/L. In these conditions, the amount of COD reduction was 82.3 and 70% theoretically and experimentally, respectively. Also, in optimal conditions, BOD₅ and TPH removal rates were 90.5% and 85.8%, respectively. The kinetics of the process follows the kinetics of the first order (R²=0.98) and the presence of different mechanisms together causes a synergistic effect and increases the efficiency of the process.
Conclusion: This process can improve the quality of oil effluent based on COD, BOD₅, and TPH removal.
 

Background and Objective: The consequence of using coagulant materials such as aluminum sulfate and ferric chloride in the coagulation unit of conventional water treatment plants can generate plenty of sludge that contains large amounts of coagulant, which in addition to environmental risks, will also possess disposal costs. Today, intending to preserve the environment and reduce treatment costs, researchers emphasize the recovery and reuse of coagulants from sludge. In this regard, the present study was proposed and implemented to recover and reuse water treatment plant sludge as a low-cost coagulant in wastewater treatment.
Materials and Methods: This research is an experimental-laboratory study. In order to recover the coagulant from the collected sludge, acid hydrolysis method was used. The physicochemical characteristics of the recovered sludge were also determined using FTIR, FE-SEM, and BET analysis. Moreover, the efficiency of recovered sludge in different doses (50 to 300 mg/L) on wastewater treatability in terms of COD, TSS, VSS, turbidity, phosphorus, and coliform indices was compared with aluminum sulfate, ferric chloride coagulants, also the results of the study were analyzed and presented using Excel software (version, 2016).
Results: According to the results, the prepared sludge had no crystalline structure with amorphous morphology. In addition, recovered coagulant from water treatment sludge has demonstrated high efficiency for wastewater treatment, so 66.6%, 82.49%, 79.66%, 80%, 65 %, 99.18% of COD, turbidity, TSS, VSS, phosphorus, total coliform were removed at the highest dosage of recovered coagulant (300 mg/L), respectively. Furthermore, the recovered coagulant dosage had a significant effect on the performance of the coagulation and flocculation process in wastewater treatment.
Conclusion: The results showed that recovered coagulant from the sludge of the water treatment plant can be considered an acceptable option with appropriate effectiveness in the wastewater treatment processes.
 

Background and Objective: The critical step of policymaking and planning for the local governments to select appropriate waste management methods, is comprehensive information on solid waste generation. Waste generation rate and composition may vary from year to year because many factors influence it. This research identified the most important factors influencing the future of household waste generation and composition in Tehran, and how these factors affect each other.
Materials and Methods: This research is based on future studies methods which are carried out using a combination of quantitative and qualitative models. Due to the nature of this research, structural analysis, Micmac software and Delphi survey were used.
Results: In this regard, after holding many meetings with 22 of the experts as the statistical population of the research, 14 effective factors were identified. The influential factors were then analyzed in the framework of the Cross-impact matrix in the Micmac software. The results showed that what can be understood from the state of the dispersion page of the variables indicated the system instability, with most of the variables dispersed around the diagonal axis of the screen.
Conclusion: Finally, considering the high scores received by direct and indirect influences, 10 key factors were identified. “Economic Growth”, “Digital Transformation and Technological Advances”, “Amendment of Existing laws, Enactment and Implementation of New and Specialized Laws”, and “Increased Awareness about waste and Attraction of Citizen Participation through Education and Provision of Information” were identified among these 10 factors as the driving forces influencing generation and composition, of household waste in Tehran in the Next Twenty Years.
 

Background and Objective: Today, the issue of health aspects in urban waste management, especially recycling, has received a lot of attention during Covid-19 around the world. Therefore, the purpose of this research is to investigate the knowledge, attitude, and performance of workers of one of the waste recycling centers in Tehran metropolis regarding health aspects during the spread of Covid-19.  
Materials and Methods: This was a descriptive-analytical cross-sectional study and the study population was all workers working in one of the recycling centers of Tehran Municipality. The data collection tool was a researcher-made questionnaire with validity and reliability in four sections: demographic, knowledge, attitude, and practice of workers toward Covid-19 and solid waste.
Results: Findings of the study showed that the highest number of workers employed were in the age group of 20 to 40 years (60 percent). The level of knowledge was about 80 percent and the lack of awareness was 20 percent. The level of workers' positive attitude, negative attitude, and lack of attitude were 79.71, 14.56, and 5.72 percent, respectively. The level of positive practice among workers was about 67.43 percent and the negative practice was 32.57 percent.
Conclusion: The results clarified that in order to succeed in waste management programs in recycling centers, municipal waste managers should pay more attention to educational aspects, especially through the focus on programs and their development and adaptation for different age groups, especially 20 to 40 years.
 

Background and Objective:  One of the important environmental problems is the mass production of urban waste, which has increased per capita household waste production with the ever-increasing population growth; Therefore, nowadays, the use of intelligent systems has been expanded as a new solution in the analysis of environmental issues. Estimation of household waste through modeling, including the use of the fuzzy-neural network, leads to its better management. Therefore, the current research was conducted to investigate the socioeconomic factors on household waste production using the Adaptive Neural Fuzzy Inference System (ANFIS) in Tabriz city.
Materials and Method:   In this research, by using the adaptive neuro-fuzzy inference system (AFNIS) with the Fuzzy C-Means (FCM) method, domestic waste generation in Tabriz city has been predicted. According to the nature of the subject and the investigated indicators, the information collected in descriptive research was collected from the students of schools in Tabriz using a questionnaire. Also, socio-economic factors were statistically analyzed using SPSS version 26 software, and parameters affecting domestic waste production in Tabriz city were used for modeling in MATLAB software.
Results: The results of the study showed that the adaptive neuro-fuzzy inference system with the Fuzzy C-Means method has acceptable performance for domestic waste production in Tabriz city.
Conclusion:  According to the results obtained based on the statistical index, the forecasted model in domestic waste production in the Fuzzy C-Means method with the highest R (0.75) and the lowest error has an acceptable performance model in predicting the production of dry domestic waste in the studied area.

Background and Objective: Due to the presence of heavy metals (HMs), sludge produced in industrial wastewater treatment plants (WWPT) is classified as special waste and can cause adverse health effects. The present study aimed to identify special wastes and assess the risk associated with the presence of HMs in the sludge of WWTP from an Industrial City.
Materials and Methods: Identifying the special wastes was conducted using a checklist, and classification was performed in accordance with the Basel Convention. Ecological risk assessment was done by determining the geo-accumulation and ecological indexes. The estimation of health risk was done by determining HQ and ELCR indexes.
Results: The highest amount of special waste was allocated to sludge with a value of 3900.0 kg/month. Chromium was detected in the highest concentration (95.89 ± 52.15 mg/kg). The level of chromium and nickel pollution was evaluated in the low range, and cadmium was very severe. The ecological risk of lead was estimated in a significant range and was very high for cadmium. The HQ was less than 1, and the ELCR for inhalation and dermal exposure was estimated to be lower than the acceptable risk level of WHO.
Conclusion: The present study showed that the largest amount of special waste is dedicated to sludge. Although the concentration of  HMs was lower than the acceptable limits, the sludge had a high ecological risk level. Therefore, the accumulation and transfer of sludge must be carried out under the provisions of the Basel Convention and environmental considerations.

Background and Objective: Mining is one of the important economic activities all over the world. It causes the release of various emissions, especially heavy metals in the soil, due to the weak exploitation and improper disposal of mineral wastes. Different techniques are used for soil remediation and heavy metal extraction; including the electrokinetic method (so effective in fine-grained soils). In this research, the electrokinetic process was used to extract copper from the waste of the mine in Birjand.
Materials and Methods: In this research, a 24 cm long PVC reactor was used. The retention time was 2, 4, and 6 days and the voltage gradient was 1 V/cm. Graphite electrodes and electrolyte solutions of nitric acid and citric acid were investigated for copper extraction. The electrode polarity was alternately changed in order to pH control and improve the extraction process.
Results: According to the results, the highest removal efficiency (54%) was obtained after 6 days using 0.1 M citric acid and distilled water in the anode and cathode reservoir, respectively. Further, by 24-hour polarity reversing, the copper removal efficiency increased to about 60%.
Conclusion: The use of citric acid in anode was more effective than nitric acid, leading to more copper removal. In addition, by periodically polarity change and keeping the soil pH in the neutral range, further dissolution of the metal and reducing its sedimentation in the soil occurred. As a result, the rate of its transfer outside the treatment area and removal efficiency increased.
 

Background and Objective: Employees of wastewater treatment plants are exposed to various harmful factors in the work environment that can threaten their health. In this research, the health status of the employees of Mashhad sewage treatment plants has been evaluated to help by implementing intervention programs to improve the health of employees.
Materials and Methods: In this descriptive-analytical study, (bioaerosols, UV rays, heat stress, and hydrogen disulfide gas) were measured in 5 treatment plants in Mashhad. All study variables, including health status, clinical tests, and job stress, were analyzed analytically in two operational and administrative employee groups. The standard HSE occupational stress questionnaire was used to investigate the state of occupational stress. All data were transferred to the computer and data analysis was done with the help of software SPSS20.
Results: The amount of pollutants except H₂S gas was lower than the national occupational exposure limit. The number of smokers, diabetics, knee pain, and hearing loss was higher among operational than administrative employees, and hypertension, increased cholesterol, back pain, and skin disease were also more common in office workers than operational workers, but there were no statistically significant differences. Obesity and overweight (p<0.009) and increased triglycerides (p<0.05) were more common in administrative than operational workers, which had statistically significant differences. The state of job stress in operational employees was statistically significant compared to administrative employees regarding role (p<0.018) and communication (p<0.002).
Conclusion: Appropriate occupational health interventions to reduce pollutants, implement ergonomic programs and improve nutrition and increase physical activity and stress management can play an effective role in improving the health of employees of these units.