Due to the recent outbreak of COVID-19, the problem of protecting the individual against airborne transmission has become of great importance. This transmission occurs when virus-containing droplets enter the respiratory tract. Accordingly, the inactivation of airborne viruses plays significant role in mitigating the threat posed by a human-to-human infectious disease. The use of gasbased treatments such as ozone to decontaminate indoor air containing viruses has been increased. Ozone is a strong oxidizing agent that can be used to inactivate broad-range viruses that might be resistant to other disinfectants. The purpose of the study is to bring attention to the ozonizing of indoor air as a novel treatment for the inactivation of viruses. This review study showed that enveloped viruses (e.g., SARS-CoV-2) are more sensitive to oxidizing agents such as ozone than to non-enveloped viruses. Furthermore, some viruses such as coronaviruses have cysteine containing a sulfhydryl group that reacts with ozone gas. The study indicated that more free radicals will be formed when air humidity is higher, which could lead to higher virus inactivation. Air disinfection by ozone gas can be a promising approach for the viral deactivation of contaminated spaces in hospitals, health-care centers, dental offices, sport clubs, hotels and transportation sector, as well as all other places where viral disease outbreaks occur.

This study surveys the possibility to optimally produce active chlorine from synthetic saline solutions using electrolysis by Response Surface Methodology (RSM). Various operating parameters, such as sodium chloride concentration, electrical potential and electrolysis time were evaluated. Central composite design (CCD) was applied to determine the optimal experimental factors for chlorine production. The experimental design, statistical analysis of the data and optimization were performed using R 3.5.3 software. The results showed that the optimum value of electrical efficiency (42 mg Cl 2 /kj) was obtained at the electrical voltage of 15.73 V during 15.63 min in the presence of 63.42 g/l of sodium chloride. The optimum point for current efficiency was 38.40%, which was obtained at the electrical voltage of 10.76 V during 6.70 min in the presence of 34.65 g/l of sodium chloride. Moreover, generated active chlorine was optimized based on energy consumption, which was 77 mg/l for the energy consumption of 0.2 kWh/l at a current density of 2000 mA/cm 2 . The electrochemical production of the chlorine gas from saline or brine water can be extensively used for water disinfection.

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Effective disinfection is a particular stage of drinking-water treatment and is an important process for the removal of pathogenic microorganisms from the water. Germs resistant to common disinfectants are a major challenge in drinking water treatment across the world. The present study was conducted to compare the electrochemical removal of Escherichia coli and spores of Bacillus subtilis as indicative and resistant bacteria in drinking water, respectively. A reactor designed with a capacity of 200 cc and containing steel electrodes was selected for the reactions. The number of bacteria (CFU/ mL), the electrochemical reaction time (min), the voltage (v), the electric current intensity (mA), ambient temperature of 25°C and natural pH of drinking water (7.4) were fixed as the operating parameters of the study. Based on the findings of this study, after applied voltage, reaction time is the most effective factor in increasing microbial removal efficiency. The optimal reaction time for the removal of Bacillus subtilis spores, Bacillus subtilis and E. coli was 5, 90 and 120 min, respectively. By establishing a potential difference of 4.5 and 8 V in the reactor, the number of Bacillus subtilis spores after the expiry of 2 h was 2 CFU/mL and 0 CFU/mL, respectively.

Background: Nowadays, volatile organic compounds (TVOCs) are considered as one of the most wellknown air pollutants, especially in the indoor environments. The aim of this study was to measure the amount of TVOCs in indoor and fresh air around the intended kindergartens and investigation the association between indoor and outdoor concentrations. Materials and Methods: The measurement was done in four kindergartens in Ahvaz city in five days between 9 to 10 o'clock in the morning. Overall, 40 samples were collected.The PhoCheck PID Detector portal device was used for activity sampling in this study. Also, the results were reported by SPSS16 Software and descriptive statistics. Results: The mean of measured TVOC in the indoor and outdoor air were 50 µg/m 3 (SD= ±74) and 495 µg/m 3 (SD= ±310) respectively. The analyses conducted by the paired-samples t-test and it indicated that the amount of fresh air is not effective on the indoor environment values. Conclusion: The measured values in indoor air of these kindergartens depend on internal factors and appropriate ventilation is slightly had been effective.