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

Wastewater treatment plants are systems that can contribute to the health of the industry and the environment provided that they function properly. Mathematical and statistical simulators coupled with various models can be used to alleviate the costs of monitoring and managing wastewater treatment systems.

This is a retrospective descriptive- analytical study. Considering the complexity of biological processes along with the advances in data processing methods, algorithms (ANN) and M5 model tree were used in this study in order to make a modelto estimate the effluent COD in the sanitary wastewater treatment plant of one of the country's refineries. ANN and M5 were developed through learning and testing stages based on daily data of five consecutive years (2015-2020). Various statistical indicators such as MSE and R were used to evaluate the models. Ethical considerations were observed in all stages of the study.

In the ANN model with 100 hidden layers, through the training step, the amount of MSE and R respectively decreased and increased, compared to the two modes of 10 and 30 hidden layers. This is why 100 layers were chosen for this model. Also, in the M5 tree model, R-SqOptimal = 0.6147 was calculated by selecting independent data as input, which is significant at the 0.05 level. In other words, with 95% confidence, the developed model is considered sufficiently logical for predicting CODout. The results showed that the ANN model outperformed M5 model tree for predicting effluent COD with a coefficient of determination equal to 0.90 and 0.61, respectively.

Both models have high robustness, reliability and generalizability. Therefore, ANN and M5 model tree data mining techniques can be successfully used for environmental decision-making and estimation of lost data in wastewater treatment plants.

Since 2019, the spread of the coronavirus has caused an epidemic worldwide, and the transmission of the disease through respiratory droplets has been declared as the primary method of transmission in 2020. However, in this study, the indirect transmission of the virus through sewage has been investigated.

Wastewater related to hospital and urban wastewater treatment plants in 5 regions of Ardabil province (northwest of Iran) were investigated. A total of 22 samples were kept in pre-test conditions (temperature -20 degrees Celsius) and were used to identify the viral genome. Specific primer and chain reaction probes targeting ORF1ab and N (nucleoprotein gene) genes were used.

In this research, out of all the samples collected, the result of 3 samples was positive. All three positive samples are related to incoming sewage.

The results of this research showed that sewage epidemiology (WBE) can be considered a cost-effective method for diagnosing and predicting pathogenic agents and an effective method for making decisions to protect citizens' health.

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.

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.

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).

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.

Due to the expansion of agricultural activities and the occurrence of successive droughts, the utilization of urban effluents for agricultural purposes is a suitable and economical way. However, the safely and responsibly use of these resources is essential. The purpose of this study is to investigate the possibility of using the effluent of the Borujen municipal wastewater treatment plant for agricultural irrigation.

In this descriptively-analytically study, the physical, chemical and microbial properties of the effluent of Borujen municipal wastewater treatment plant were measured according to the standard methods for the examination of water and wastewater, for 6 months and then was compared with the standard of Institute of Standards and Industrial Research of Iran (IRNDOE) and The Food and Agriculture Organization (FAO).

The mean concentrations of Biological Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), and Total dissolved solids (TDS) parameters in the effluent were 10.00 ± 1.17, 39.19 ± 4.10, and 513.0 ± 8.7 mg/L respectively. The average of chemical parameters including Cl-, SO42-, PO43-, NO3-, NO2-, Na, Mg, Sodium adsorption ratio (SAR), HCO3-, CO32-, Ca, and alkalinity was within the standard range of IRNDOE and FAO. The average of turbidity in the effluent was 54.27 ± 16.47 NTU. This effluent, in terms of SAR and EC was in the great and acceptable water group respectively. The average concentration of heavy metals was less than the permissible level for these metals. The mean concentration of total coliform, fecal coliform were higher than the standard set for these parameters. Also, no parasite eggs were detected in the effluent.

The results showed that the average chemical parameters of effluent of Borujen wastewater treatment plant were within the standards of effluent use in agriculture. However, the concentration of biological parameters of the effluent was higher than the standard level; and in case of more microbiological purification, it can be used for irrigation of edible agricultural products.

Today, plastics have a special place among the various issues that are considered as sources of pollution. Most of these plastics are in the dimensions of Micro and Nano. One of the most important sources of Microplastics transfer is wastewater treatment plants, where a large amount of these particles, which are not removed in the treatment process, enter the receiving environment. The purpose of this study is to first determine the optimal method of identifying and extracting particles from wastewater for counting and then to investigate the amount of removal and also to determine the amount of particles leaving the treatment plant.Sampling of inlet and outlet of wastewater treatment plant located in Mazandaran province was done seasonally in three seasons of spring, summer and autumn to determine in which season of the year, the amount of microplastics in wastewater increases or decreases. Also, the extraction and identification method is based on acid washing operation and based on creating a density difference, which has resulted in a favorable result with optimization and innovation.Using this method, the amount of Microparticles and microfibers along with the size and shape of the particle was determined and it was determined to what extent the normal treatment process is able to separate Microplastics from wastewater. The treatment plant can remove an average of 95% of the particles, which means that the remaining 5% of the particles are removed with the effluent and enter the aqueous environment.Finally, it was found that the determined laboratory method can identify and extract Microplastics in very small sizes to a very desirable extent. Also, determining the appropriate parameters of liquid volume, salt consumption and the use of dual capacity iron increased the efficiency compared to other methods and led to the identification of smaller particles than previous research.

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.

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.

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.

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.

Emission of bioaerosols from wastewater treatment plants is a potential hazard to human health. In this study aimed at investigating the effects of surface and deep aeration techniques on density and type of airborne bacteria and fungi in two municipal wastewater treatment plants. This descriptive cross-sectional study was done in two wastewater treatment plants in Tehran equipped with surface and deep aerations. Microbial samples were taken from air beside aeration tank, grit chamber, secondary sedimentation basin and two control points (upwind and downwind) every 6 days during summer and autumn 2017. Samples were analyzed for density of bioaerosols and types of bacteria and fungus applying standard methods. Wastewater treatment plant with surface aeration tank had the greatest effect on emission of bioaerosols than the plant with deep aeration. Mean values for density of bacterial bioaerosols and fungal emission were 6845 and 15784 CFU/m2/h in summer and 535 and 899 CFU/m2/h in autumn, respectively. Different gram-positive and gram-negative bacteria were identified in both wastewater treatment plants investigated. According to current study, emission of bioaerosol in wastewater treatment plants with surface aeration is more than that of those with deep aeration and has greater potential hazard.

Wastewater treatment plants represent one of the most important approachs for water conservation. On the other hand, wastewaters can act as a source of antibiotics in aquatic environments. The aim of this study was to evaluate the performance of the Yasooj municipal wastewater treatment plant for removal of Escherichia coli, Pseudomonas aeruginosa and Listeria monocytogenes and also the antibiotic resistance pattern of these bacteria. In this cross sectional study, samples of inlet, outlet aerated lagoon, outlet settlement lagoon and outlet effluent were collected from the wastewater treatment plant in order to count, isolate, and identify E. coli, P. aeruginosa and L. monocytogenes. Antibiotic resistance pattern was investigated using disk diffusion method for 6 different antibiotics according to CLSI reference method. E. coli, P. aeruginosa and L. monocytogenes were isolated and identified in all levels of purification of wastewater treatment plants. The effectiveness of sewage treatment processes to remove E. coli, P. aeruginosa and L. monocytogenes was 54.17-99.33 in the outlet effluent. The bacterial isolates showed high rate of resistance against cefixime and trimethoprim-sulfamethoxazole and low resistance to imipenem. Multidrug resistance pattern (double and triple) was observed in bacterial isolates. This study showed that antibiotic-resistant bacteria in the outlet effluent are discharged into the environment. Further research needs to be undertaken to improve sewage treatment technologies, thereby producing a better quality treated sewage effluent.

Antibiotics are a group of emerging contaminants in the aquatic environment. Antibiotic residues threaten the human health and ecosystem in the low concentrations found in the environment. Hence, the present work has been conducted to investigate the occurrence and removal efficiency of most prescribed antibiotics including amoxicillin, penicillin, cefixime, cephalexin, ciprofloxacin, erythromycin and azithromycin detected in two urban wastewater treatment plants (WWTPs) in Tehran. The present work is an applied research based on USEPA method no. 1694, to investigate pharmaceuticals residues in water by HPLC/MS/MS in year 2016. The differences between target antibiotics residues were investigated statistically. After the calculation of the removal efficiencies, the normality of the data was assessed. Then, parametric and non-parametric tests were used to compare the removal efficiencies in both WWTPs. There was not a significant difference between the influent and effluent concentrations of cefixime and azithromycin (in Ekbatan WWTP) and cefixime (in southern Tehran WWTP). There is a significant difference between the removal efficiencies of cephalexin (p=0.005) and erythromycin (p=0.002) in two WWTPs. The Highest median removal efficiencies were observed for cephalexin 94.41 and 99.47 in Ekbatan WWTP and southern Tehran WWTP, respectively. In addition to the type of treatment processes, it is physicochemical properties of the selected compound has a significant influence on removal efficiencies.

One of the reuses of wastewater in industries is irrigation of green space. Therefore, with proper treatment and reduction of environmental pollution of wastewater and in compliance with environmental standards, it can be used for irrigation purposes. The present study was aimed to evaluate the performance of Noosh Azar Wastewater Treatment Plant by the online monitoring station in 2016.
This descriptive cross-sectional study was performed at Noosh Azar Waste Water Treatment Plant (WWTP) in Tehran. The effluent outlet parameters include COD, BOD, TSS, TOC, Turbidity, pH and temperature which were measured 12 times/day by the online monitoring station of the refinery according to the standard methods (the Examinations of Water and Wastewater), and reported at the end of each month. Data were entered into SPSS software and analyzed using statistical indices including mean and standard deviation.
The average total of BOD/COD ratio in the wastewater was 0.8. The results of the study showed that the average concentration of COD, BOD and TSS of the wastewater was 1624.91 ±134.85, 1310±75.38 and 283.58± 39.76 mg/L, respectively. The average of total outlet parameters of turbidity, COD, BOD, TSS and TOC were 12.78±2.21, 83.73±12.90, 41.26±6.65, 6.70±2.14, 46.03±7.08 mg/L, and pH=7.80±0.35. The total average of removal efficiencies of COD, BOD and TSS were 93.92±3.62, 96.57±1.002 and 97.57±0.936, respectively.
Regarding the proper performance of the activated sludge system of Noosh Azar Company, the effluent parameters such as COD, BOD, TSS, TOC, turbidity and pH, were in accordance with the standard of the Iranian Environmental Protection Agency for irrigation use. However in order to ensure the quality of the wastewater for reuse, the microbial parameters should also be considered.

With attention to the existence numerous numbers of industrial towns and them volume of generated wastewater and problems of shortage of water in the Yazd province, therfore the proper wastewater treatment and efficient management of waste water of industrial towns for reuse of them is one of the most important of program for reducing & saving in water consumption. Hence, this study aimed to the feasibility of the reuse of waste water of industrial town of Jahan Abad Maybod for agricultural and irrigation uses.
This study is a descriptive crosssectional research. At this study, it is used the mean values ​​of the results of sampling and tests of output waste water of Jahan Abad Maybod treatment plant in 2012 (July to January). Then the mean values ​​of the BOD, COD, TSS and ... parameters compared with the standards values of the EPA and analyzed by Excel software.
The results show that the mean values ​​of quality parameters of the output waste waterof treatment plant such as COD, BOD5, TSS, SO4, pH and turbidity are respectively 312, 160, 92, 162(mg/L), 8/2 and 31/4(NTU).
The results showed that the mean values ​​of the quality parameters of the studied output waste water except BOD5 and COD are in the standard range for the uses of agriculture and irrigation which it may has the negative & inappropriate environmental operation of these two parameters.

Odors are one of the problems of water and wastewater treatment, especially in the vicinity of residential areas. Hydrogen sulfide and ammonia, mineral compounds in waste water treatment plants are odorous. These gases have unfavoraitable effects on humans and the environment.
This Cross-sectional study was conducted in the Faculty of Health, Qazvin University of Medical Sciences. After field visits around the plant, the number of 12 sampling stations was determined. Sampling stations are selected in four geographical directions with regard to permanent trade winds that are zero, two and four kilo meters from the plant to Residential settlements. Sampling was performed in the morning and evening during the four seasons and 192 samples were provided.
Results showed that the concentration of ammonia and hydrogen sulfide gas was more in warm seasons significantly and more odor caused (P=0.011, P=0.004) and the maximum emission is in the summertime. According to the results, the highest concentration of these gases was in the evening during the day.
According to the results, the concentration of hydrogen sulfide and ammonia gases in all the seasons except winter is within the threshold. Concentration of hydrogen sulfide in the summer and ammonia concentrations in all the seasons were higher than US. EPA standards and World Health Organization guidelines.

Background and Today, hospital waste is one of the problems facing human societies. Hospital waste contains toxic and dangerous compounds, infectious substances, biological microorganisms, toxic chemicals effluents (resulting from x-ray film processor and disinfectants) and pharmaceutical compounds. The absence of treatment and improper disposal can be a very dangerous to the environment and human’s health. The purpose of this study was to evaluate the performance of wastewater treatment and disposal condition and the quality of hospitals effluent of Hospital in Giulan and Tehran.
This cross-sectional descriptive research studied the wastewater treatment and disposal systems condition and effluent quality in heshmat rasht, aria rasht, rasol akram rasht, 12 Bahman Tehran, erfan tehran, alghadir tehran, fayazbaghsh tehran, hospitals. testedTested for pH, BOD5, COD, TSS and TC in the effluents of wastewater treatment plants using the current standard methods.
The Mean values of pH, TSS, BOD, COD, Total Coliforms and Fecal coliforms in wastewaters- outlet from the studied hospitals were 12 bahman (290 total and 150 fecal) alghadir ( 460total and 240 fecal) erfan (298 total and 171 fecal) fayazbaghsh (290 total and 150 fecal) aria ((>1100 total and >1100 fecal) heshmat (>1100total and >1100 fecal) rasol akram ( >1100 total and >1100 fecal) respectively.
The mean value of TSS, BOD, COD and TC in the wastewater- outlet of the studied hospitals Especially the hospitals studied, Gilan province Higher than the standard output of the country has been approved by the environmental protection agency Of reducing the effectiveness of sewage purification systems remove dirt by at these centers. Therefore, the basic overview in order to improve the effectiveness of this type of treatment in the areas of design, operation and maintenance.

In order to prevent water pollution, protect public health, and reuse of the treated wastewater; controlling on quality of the wastewater treatment plant effluent has been considered a necessary.
To compare the quality of wastewater treatment plant effluent in Lia industrial zone with Iranian environmental protection standards.
This cross-sectional study was performed in one of the industrial zones in Qazvin (Lia). Samples were collected from wastewater treatment plant from May to September 2015 and analyzed in the laboratory. Chemical oxygen demand (COD) parameters were determined twice per week when the pH values were daily measured by pH meter. Sampling was carried out weekly to determine other important operational parameters including biochemical oxygen demand (BOD), total suspended solids (TSS), total coliform (TC) and fecal coliform (FC). Sampling and experiments were done according to the latest standard methods. The data were analyzed with SPSS 16 software (T-Test a single group).
Findings: The average of BOD, COD, TSS, FC, TC in effluent were achieved to 73.3±13.2, 156.2±42, and 76.43±50.8 mg/L 1.1×103,1.1×103 MPN/100 ml respectively. The total average of removal efficiencies for BOD, COD and TSS were calculated 92.41%, 92.75%, and 87.46%, respectively.
The results obtained that the wastewater treatment plant systems can be used as an efficient system for reduction of common pollutants by providing the Iranian standards for irrigating when the most important such as BOD, COD, TSS and PH are considered. The quality of the treated wastewater was found to be within the permissible Iranian standards for irrigating. However, it is important to keep in mind that reduce microbial contamination within standards is needed to be considered.

Recently contact with bioaerosols has been presented as an important problem which endangers human being’s health. The aim of this investigation is to compare potential of separation of fungal aerosols in the air around Tehran’s Milad hospital, blood transfusion organization and waste water treatment plant of Tehran’s Shahrake Ghods. this cross-sectional investigation was done in Milad hospital, blood transfusion organization and Tehran’s Shahrake Ghods waste water treatment plant within for 4 months. The sampling was done passively for 1 hour and once in 6 days. The culture medium was Sabouraud dextrose agar. comparing selected sampling stations the most fungal density was for 100 meters after the last unit of waste water treatment plant (67 CFU) and the least density was for Milad hospital (30 CFU). Dominant genera of fungal in waste water treatment plant and blood transfusion organization was related to Cladosporium (in order of 49% and 84%) and in air around Milad hospital was related to Alternaria (47%). according to the results processing and operating sections in waste water treatment plant can be effective in fungal density and separation of bioaerosols. Therefore it seems to be vital that the responsible organizations should do necessary actions to develop guidelines and standards related to bioaerosols. Also appropriate administration of environmental health in waste water treatment plant can be an important factor in reduction of aerosol separation.

Background and Wastewaters are the most important sources of antibiotics entrance into the aqueous environments. Conventional wastewater treatments cannot eliminate these micropollutants and antibiotic resistant bacteria. The aim of this study was to determine the antibiotic resistance pattern in bacteria isolated from untreated sewage and effluent of municipal wastewater treatment plant in Tabriz. In this cross sectional study, in addition to counting the number of different types of bacteria in raw sewage and municipal wastewater effluent, various bacteria including Enterobacteriaceae and Staphylococcus, Bacillus and Pseudomonas were identified using specific mediums, API E20 kits and biochemical tests. Susceptibility test of bacteria to antibiotics was determined by Kirby-Bauer's disc diffusion. The results showed lower than one log removal efficiency for coliforms bacteria by the wastewater treatment plants. The difference in the number of colonies apart from staphylococci was not significant in wastewater influent and effluent. Aeromonas and staphylococci were the most frequent bacteria in wastewater influent and effluent, respectively. Enterobacteriaceae were generally more sensitive than other bacteria. Resistance to antibiotics was found to be higher in the penicillin member of antibiotics. Resistant to four antibiotics including cephalexin, ampicillin, methicillin and amoxicillin were between 60 to 100%. The resistance of all species increased in the effluent of wastewater treatment plant. Growth and survival of antibiotic resistant bacteria increases in wastewater treatment plants and conventional treatment processes do not demonstrate enough efficiency for removal of these strains.

In recent years exposure to bioaerosols has been an important matter of concern; causing danger to human health. This study aimed to determine bacterial and fungal pollution in ambient air of Tehran’s Shahrake Ghods waste water treatment and investigate its relations to environmental parameters. This cross-sectional study was done in Tehran WWTP for 4 months. 440 samples were taken from grit chamber, aeration tank, aerobic digester, 100 meters apart from the last unit of the treatment plant, and management building of treatment plant by a passive method using 9cm plates. Soy agar and dextrose agar were used for sampling of Trypticase and Sabouraud, respectively. Concentrations varied from 62 to 1823 CFU/Plate for bacteria and from 1 to 50 CFU/Plate for fungi. The highest concentration of bacterial pollution was observed in aeration digester with an average of 3303 CFU/Plate and the lowest one related to grit chamber with an average of 586 CFU/Plate. In terms of fungal pollution, respective highest and lowest numbers were quantified in grit chamber with an average of 61 CFU/Plate and aeration system with an average of 41 CFU/Plate. Dominant species for bacterial were Bacillus, Staphylococcus, and Micrococcus and for fungi were Cladosporium, Alternaria and Penicillium. According to the results, operational and processing units of WWTP influence pollution load and dispersion of bioaerosols. Therefore, appropriate environmental health management in WWTP could be one of the important factors reducing dispersion of bioaerosols.

the existing aerosols in air can be a factor for separation of microorganisms. Bio aerosols are one of the most important ways of infectious illnesses separation. The aim of this investigation is to compare potential of separation of fungal aerosols in air around Tehran’s Milad hospital, Tehran’s shahrake gharb waste water treatment plant and blood transfusion organization. This cross- sectional investigation was done in Milad hospital, blood transfusion organization and Tehran’s sharke ghods waste water treatment plant from Mars 2012 until June 2013. The sampling was done passively according to EPA sampling calendar in the year 2013, for 1 hour once every 6 days. The culture medium for fungal samples was sabouraud dextrose agar and for bacterial samples was Trypticase Soy agar. After sampling, they were transferred to laboratory, and they were analyzed. At the same time, the temperature, humidity, wind speed and UV light indexes were measured in the sampling areas. Comparing selected sampling stations, it was shown that the most bacterial density was for aeration digester of waste water treatment plant (3303CFU/plate), and the least density was for100 meters after the last unit of waste water treatment plant (529 CFU/plate). Dominant type of fungal in Milad hospital and blood transfusion organization was related to Staphylococcus (46% and 49.6% respectively), and it was related to Bacillus (36.3%) in waste water treatment plant. The most fungal density was for 100 meters after the last unit of waste water treatment plant (67 CFU/plate) and the least density was for Milad hospital (30 CFU/plate). Dominant genera of fungal in waste water treatment plant and blood transfusion organization was related to Cladosporium(in order of 49% and 84%)and in air around Milad hospital was related to Alternaria (47%). According to the results of the study, microbial aerosol density in the air around processing and operating sections of waste water treatment plant was more than milad hospital and blood transfusion organization. In another words processing and operating sections in waste water treatment plants affect microbial density. Appropriate administration of environment health in waste water treatment plant can be an important factor in the reduction of aerosol separation. Also it seems to be vital that the responsible organizations should do the necessary actions to develop guidelines and standards related to microbial pollutions.

Background and There is no specific standard on the compost maturity time of biosolids of wastewater treatment plants in Ïran; therefore, the researchers made an attempt to employ different chemical and biological methods to assess the compost maturity time. Ïn this study, the sludge was obtained from the drying beds of South Ïsfahan Wastewater Treatment Plant and was then mixed with sawdust and windrow type of composting was performed to stabilize the sludge. The height, width and length of windrow were 1.2, 1.5, and 2.5 m, respectively. The windrow turning was done manually for 7-10 days. The results showed that, Ç/N ratio after 100 days of composting reached 15.1 and the NH4/NÔ3 ratio decreased with increase in the time of dewatered sludge compost. The content of volatile solids decreased up to 28.8 percent with composting time and the number of fecal coliforms reached 898 MPN/gram of total solids.Çonclusion: Thus, biosolids compost in this study was mature and ready for use as an agricultural substrate after 100 days of composting.

Considering importance of wastewater treatment and disposal in contemporary societies as well as the possibility of effluent discharge of Wastewater Treatment Plants (WWTP) to water courses, or reusing it; this study conducted to assess efficiency of Zanjan WWTP in 2008. This cross-sectional study was performed from June to March 2008 in Zanjan WWTP. Sampling was accomplished from inlet and outlet flow of treatment plant and measurement of TSS, BOD5,COD, MLSS, MLVSS, and SVI indices in aeration ponds were done based on standard method version 20. Removal efficiency of TSS, BOD5, and COD was 77.91, 87.25 and 87.29 percent with respective average concentration of 30.2, 18.63 and 33.37 milligram per liter in outlet flow. These results are in accordance with standards of Iranian Department of Environment to be used for agricultural purposes. efficiency of pollutants removal in Zanjan WWTP is around 84 percent which complies with Iranian regulation, thus the flow is suitable for reuse or discharge to water courses.