نشریه مهندسی بهداشت محیط
سال هشتم شماره 2 (پیاپی 31، زمستان 1399)

Trace elements are the common pollutants of soils, sediments and street dust in the urban environment, which pose a potential threat to public health. Therefore, this study was conducted to potential ecological risk assessment of As, Cd, Cr, Cu, Pb, Ni and Zn in street dust collected from industrial, commercial and residential areas of city of Hamedan in 2019 using ecotoxicological criteria.

In this descriptive study, a total of 378 street dust specimens were collected from 18 sampling sites. After acid digestion of dust specimens, the element contents were determined using ICP-OES. Also, potential ecological risk factor (Er), risk index (RI) and the ecotoxicological criteria were calculated. All statistical analyses were done by SPSS software.

Based on the results obtained, the mean contents of the examined elements in dust specimens (mg/kg) were 2.31, 0.225, 41.3, 48.8, 65.2, 79.2 and 211 for As, Cd, Cr, Cu, Pb, Ni and Zn, respectively. The computed values of Er showed that, factor values were decreased in the order Cd > As > Pb > Ni > Cu > Zn > Cr. Also, the mean values of RI with 77 represented that, all the examined elements have the "low potential ecological risk". Moreover, the computed values of the ecotoxicological criteria showed that the street dust specimens of the study area were non-polluted with trace elements.

Although the examined elements have been shown the low potential ecological risk, Cd with 38.2% of the mean values of RI showed significant potential to occurrence the ecological risk, therefore, source identification and sources control of this element and also periodic monitoring of contaminated soils are recommended for maintenance of public health.

The contamination of water by organic pollutant viz. 2,4 DNP compound is recognized as most common environmental concern due to their highly toxic nature, worldwide. Adsorption has attracted much attention as a new technique to remove these contaminants from water and wastewater. The purpose of this study was to introduce an inexpensive adsorbent, dried waste sludge, for removal of 2,4 DNP compound.

At first, sludge was dried at temperature 60 °C. Next, CaCl2 was used to improve adsorption capacity. The removal efficiency of 2,4 dinitrophenol were determined by HPLC at wavelength of 360 nm. In addition, the effects of influencing factors including pH, initial pollutant concentration, contact time, and adsorbent dose were examined. The equilibrium binding were described by Langmuir or Freundlich isotherms and kinetic models.

The results obtained from adsorption process indicated that was 60 min is the equilibrium time. The optimum pH for adsorption for both adsorbents was found to be 7. The optimum concentration of 2,4-DNP was found to be 10 ppm. The results obtained from the present research showed that the removal of the contaminant using modified sludge sorbent was increased from 40.4% to 77.9% when dosage increased from 0.1 to 1.5 g. Equilibrium adsorption data for 2,4 DNP were fitted by using Langmuir, Freundlich and Freundlich adsorption isotherms model, respectively. Also it has been found that adsorption kinetics can be described according to the Pseudo-second order model.

According to results, chemically modified waste sludge showed reasonable adsorption capacity. Therefore, it and can be used as a native alternative to 2,4 DNP compound removal from aqueous environments.

Landfill is one of the most common methods of waste disposal in developing countries. Determining burial sites is a difficult and complex process in which social, environmental and technical parameters are involved. The purpose of this study is to select a suitable landfill for waste disposal in Sardasht.

The type of research is a descriptive-analytical research method. Geographic tools and techniques, GIS software, word, and AHP (hierarchical) model have been used in setting up information and calculations in this research. Using GIS software, different layers of information were scored and divided into completely appropriate, appropriate, completely inappropriate and inappropriate categories.

Based on the field study, about 61% of the study sites were found to be completely unsuitable for landfilling. Selected locations were scored based on evaluation criteria and compared by weighting these criteria, comparisons were made between them. Then, 20% of the remaining places were considered as a better option. In the end, after reviewing these places, a place was selected as the suggested place. This place is located at a distance of approximately 12 km from Sardasht city, has a suitable side road and slope, which is a suitable distance from the villages and the city, and was selected as a suitable option due to its location outside the aquifer.

This study showed that with the help of AHP model and GIS software, a suitable place for landfilling of municipal waste can be selected so that the factors affecting the selection of a suitable place can be applied.

The performance of ozone in water disinfection depends on process factors as well as the design parameters of the ozone unit that improper design of ozonation unit and an imbalance between ozone doses with the quality of the water used is causing changes in water quality. The overall goal of this study is to investigate the effect of ozonation process factors on drinking water quality parameters. 

This study is on a pilot scale in four different scenarios to evaluate the effectiveness of ozonation process factors on the simulated water quality parameters (turbidity, color, chlorophyll a, pH and TOC) was performed. In all scenarios, ozone doses between 1 and 5 grams per hour are considered. Contact time (minutes), temperature (degrees Celsius) and pH are equal in scenarios 1 to 4, respectively; 5, 23.9 and 5.6-4 (Scenario 1), 10, 23.8 and 6.8-5.6 (Scenario 2), 15, 23.8 and 6.8 (Scenario 3) and 20, 23.6 and 8.6 (Scenario 4).

The results of data in different scenarios showed that, injectable ozone dose, ozone contact time with water, pH and temperature it has the greatest effect on ozonation performance. The average removal rate of turbidity, TOC, color  and chlorophyll a parameters in scenarios 1 to 3 is equal to; (Scenario 1; 12.85, 1.05, 5.3 and 41.8%), (Scenario 2; 14.35, 12.3, 12.75 and 60), (Scenario 3; 31.65, 16.3, 18 and 67.3) . Studies showed that in scenario 4 with an alkaline pH (10.6) and an average temperature of 23.6 ° C with an injection ozone dose of 5 grams per hour and a contact time of 20 minutes, the removal rate of quality parameters of water samples including; Turbidity, TOC, color and chlorophyll a was higher than other scenarios and are equal to: 44.07%, 32.6%, 39.8% and 92.7%, respectively.

The results showed that among the process factors governing ozonation, temperature and pH have the greatest effect on water ozonation, So that with the decrease of temperature and increase of pH, the removal rate of parameters increases. The contact time and the dose of injected ozone have a direct effect on the removal of parameters, So that the effect of these two parameters depends on the hydraulic conditions of the ozonation tank and the quality of raw water. Reviews various scenarios showed that in the optimal ozonation conditions, the highest removal rate of parameters is related to chlorophyll a, turbidity, color and TOC, respectively.

Soils have a key role in establishment and growth of biota and also are as a natural resource, national capital and life substrate in any country. Therefore, every contamination can be transferred from soils to higher food levels with its negative impacts. Therefore, the purpose of the present study is to investigate oil pollution in soils caused by the establishment of Shahid Tondgovian Oil Storage in Zanjan province. The depot has three storage tanks with capacity of 47, 35 and 26 million liters of oil and gasoline and kerosene, respectively.

Soil samples were collected from a depth of 5-15 cm at 20 sites and the values ​​of EC, pH and PAHs were measured. Then T-test was used to compare the results with standards and control sites.

The mean of pH and EC results were 8.24 and 281 µ/cm, respectively. The results showed PAHs values ​​were lower than the standard and there was no statistically significant difference between the study sites and the control one (P > 0.05). Also, the amount of benzo (a) pyrene compound, used as an indicator of total PAHs to study carcinogenic effects, was lower than standard in study area. Therefore, there is no health risk for the oil residents in collected samples from Shahid Tondgoian Oil Storage.

Currently, oil pollution is not observed in the soils around the study area and there is no health risk for the residents in the suburbs.

Water supply systems and various parts of dentistry unit have the ability to aggregate biofilms and thus the transmission of dangerous diseases to staff and patients. The aim of this study was to determine the bacterial contamination of surfaces and water lines of dental units of health center (Qods 2) in Divandareh city.

This cross-sectional descriptive study was conducted on dental units of the health center (Qods 2) in Divandareh city in 2019. 125 samples were collected from different parts of the units including unit lamp handle, lamp ON/OFF power button, open/close bolt of unit water, setting switch button (before and after disinfecting), and the inlet and outlet water of units. The samples were tested for Staphylococcus aureus, Pseudomonas aeruginosa, Coliforms and Escherichia coli.

The results of this study showed that all samples collected from the studied parts of the units including unit lamp handle, lamp ON/OFF power button, open/close bolt of unit water, and setting switch button were positive as presence of Staphylococcus aureus, Pseudomonas aeruginosa, and coliforms before and after disinfection. Also, the unit lamp handle and setting switch button were positive as Escherichia coli. The inlet and outlet water were also positive for all the studied bacteria. The number of Staphylococcus aureus bacteria in the handle of the unit lamp before disinfection (210±80.5 CFU/ml) and in the ON/OFF button of the lamp after disinfection (300±82.6 CFU/ml) were higher than the permissible amount (200 CFU/ml). Also, the number of Pseudomonas aeruginosa bacteria detected in setting switch button, before disinfection, was higher (200±75.2) than the allowable value.

According to the obtained results, the contamination level of water and surface of the studied dental units was high. Also, identifying of the considerable number of bacteria at the different surfaces of the units, indicating the improper use of the disinfectants and the possibility of biofilms presence in the unit waterlines.

Non-metallic industries such as tile and ceramics, in addition to production and economic development, cause many environmental problems, including air and soil pollution and waste production. Industrial environments, by their very nature, are exposed to serious damage and hazards that are potentially expanding in line with the increasing growth of technology. This study was conducted with the aim of identifying and assessing the environmental risks of Eram Tile and Ceramic Industrial Company in Ardakan City by combined method of PHA and William Fine.

First, based on field visits to Eram Ardakan Company, environmental hazards were identified by PHA method and based on the work unit, performance of existing machinery, and human activities. Then, using the William Fine method, environmental risk assessment was performed and corrective solutions for high risks were presented.

Based on the findings of this study, 241 environmental hazards were identified, which were classified into 6 groups of environmental hazards (pollutants entering water, pollutants entering soil, pollutants entering air, loss of water and energy resources, generation of noise, and the generation and dispersion of industrial waste). The Risk Priority Number (RPN) of natural risks was 166, abnormal risks 52, and high risks 23. The highest RPN was 560 related to the operation of the crusher, spraying, operation of the furnace and dryer, press, and suction, while the lowest was 1, related to the excessive watering of trees and plants and uploading of animal manure.

the assessment of hazards in the ceramics industry, while helping identify technical deficiencies and human errors, emphasizes the need for training and change the attitude of managers and personnel working in this industry and environmental inspections to maintain and promote environmental health.

Membrane bioreactor (MBR) is known as new technology for domestic wastewater treatment. This research aims on the performance evaluation of MBR in pollutants removal and membrane fouling in different operational conditions.

For this purpose, a pilot with 140 L net volume and flat-sheet membrane was started up and continuously fed with real wastewater in Ekbatan wastewater treatment plant. It has been operated for 100 days with different organic loading rates (OLR) of 0.58, 0.71 and 1.55 kgCOD/m3.d and aeration conditions of DO>4 mg/L and DO<1.5 mg/L.

The results show that MBR can remove more than 96% of BOD, COD and TSS of wastewater in all operating conditions. This performance is rather constant and verifies the high reliability of system in different operating conditions. Nevertheless, the maximum removal efficiency of total nitrogen (TN) and total phosphorous (TP) is 31% and 66%, respectively, while it degrades about 15% in aerated condition (DO>4 mg/L). In addition, membrane fouling increases whenever OLR is increased or the aeration is reduced. Actually, the trans-membrane pressure (TMP) is statistically correlated with OLR (R2=0.91).

The findings reveal that MBR is an efficient technology for domestic wastewater treatment and performs rather constant in times of aeration reduction or OLR enhancement. However, it requires supplementary techniques for TN and TP removal.