M Gholami, A Sabzali, E Dehghani Fard, R Mirzaei, D Motalebi,
Volume 4, Issue 3 (1 2011)
Abstract
Background and Objectives: One of the complete treatment processes for industrial and municipal wastewater treatment is membrane bioreactor process which has dominant potential in process and operation sections. This study was conducted to compare the performance of extended aeration activated sludge (EAAS) with submerged membrane bioreactor (SMBR) systems in the treatment of strength wastewater, in the same condition.
Materials and Methods: The initial activated sludge was brought from the Plascokar Saipa wastewater plant. The Plexiglas reactor with effective volume of 758 L was separated by a baffle into the aeration and secondary sedimentation parts with effective volumes of 433 L and 325 L, respectively. The chemical oxygen demand (COD) concentration of the influent wastewater of the EAAS and SMBR systems were between 500-2700 and 500-5000 mg/L, respectively.
Results: Results showed that the SMBR system produced a much better quality effluent than EAAS system in terms of COD, biochemical oxygen demand (BOD5), total suspended solids (TSS) and ammonium. By increasing the COD concentration, the concentration of mixed liquor suspended solids (MLSS) and the removal efficiency of organic matter in the SMBR system, were increased regularly, however the removal efficiency of COD in the EAAS system was irregular.
Conclusion: The average BOD5/COD ratio of effluent in the EAAS and SMBR systems were 0.708±0.18 and 0.537±0.106, respectively. These show that the organic matters in the effluent of the SMBR system was less degradable and thereupon more biological treatment was achieved. Nitrification process was completely done in the SMBR system while the EAAS system could not achieve to complete nitrification.
Aram Arpanaei, Sina Attarroshan, Sima Sabzalipour, Iman Arpanaei,
Volume 13, Issue 4 (2-2021)
Abstract
Background and Objective: Pollutants emitted from industries can endanger human health if they enter the food chain, so environmental monitoring is essential. The aim of this study was to investigate the bioaccumulation of heavy metals including lead, copper and nickel and the level of air pollution tolerance index in Prosopis juliflora and Conocarpus erectus tree species during one-year period (1399-1400) in Mahshahr city.
Materials and Methods: In order to investigate the bioaccumulation of heavy metals by two species of Prosopis juliflora and Conocarpus erectus, 15 stations were selected separately. After recording the coordinates of each tree (station), 4 leaveas were taken from each tree that accounted for total 60 samples. The samples were then transferred to the laboratory and digested then analyzed using atomic absorption spectrometer. For statistical analysis, K.S test was used to normalize data and independent t-tests were applied to determine the level of significance. The correlation between variables were tested by Pearson correlation. Spatial distribution of heavy metals was performed using Ver.10.4 Arc GIS software.
Results: Conocarpus erectus established the highest adsorption value for metals such as lead (0.1223±0.35 mg/kg), copper (0.2101±0.053 mg/kg) and nickel (0.2023±0.094 mg/kg). No significant correlation was observed between heavy metals. Evaluation of air pollution tolerance showed that Conocarpus erectus (6.53±0.026 mg/kg) was more tolerant than Prosopis juliflora (4.77±0.029 mg/kg). Spatial distribution revealed that heavy metals accumulation in the leaves of trees were more obvious in the southest area of the city.
Conclusion: Conocarpus erectus is more tolerant of air pollution than Prosopis juliflora. Therefore, it can be used in areas with the high levels of pollution. Moreover, the spatial distribution of heavy metals’ bioaccumulation illustrated that the south and southeast parts of the city (due to industry concentration) are more affected by the heavy metals pollution which call for more palnting trees.
