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Optimization of Wastewater Treatment Plant by Activated Sludge Method Using GPS-X Software
Seyed Mahdy Mirian, Afshin Ebrahmi,
Volume 19, Issue 2 (7-2023)
Abstract
Background: The purpose of this study was to model a real wastewater treatment plant in operation with GPS-X software. In the following, the verification of the output results of the software was done with the results of the effluent tests of the discussed sewage treatment plant. Then, the rate of return sludge, recycled sludge, and disposed sludge of the wastewater treatment plant was optimized by Modified Ludzack-Ettinger (MLE) method, so that it has the greatest effect on the quality of the effluent, especially chemical oxygen demand (COD) and nitrate (NO3) parameters.
Methods: First, using the available data of an operating wastewater treatment plant, the processes of the treatment plant were modeled in the software and the compatibility of the model with the existing treatment plant was checked. After the validation of the software, in order to check the parameters affecting the activated sludge process, including return sludge rate, excess sludge rate, and internal recirculation sludge rate in the treatment of organic matter and nitrogen, COD, NO3, and ammonia parameters were investigated as indicators of pollution. In addition, the MLE process for nitrogen removal was modeled in the software. After performing the modeling by changing the parameters and checking the resulting outputs, the results regarding the effect of increasing the sludge recirculation rate on the COD concentration in the effluent and the effect of increasing and decreasing the internal recirculation rate and the disposal sludge rate on COD removal were examined. In addition, the mutual effect of changes in internal sludge recycling and return sludge and the amount of excess sludge disposal on NO3 removal was shown by different graphs.
Findings: In this study, while validating the software, the results of the experiment design showed that the return sludge rate and the internal recirculation rate had mutual effects on each other in the removal of COD and NO3, and in the optimal mode of operation and design, the ratio of 0.54 for return sludge and one-time internal recycling and ratio of 0.021 for disposal sludge had the greatest effect on COD and NO3 removal target efficiency and increasing the effluent quality.
Conclusion: GPS-X software can be used in the modeling and optimization of wastewater treatment processes.

Status of Sorbic Acid and Its Derivatives as Food Preservative in Iran: A Systematic Review
Arghavan Madani, Zahra Esfandiari, Yadolah Fakhri,
Volume 21, Issue 2 (7-2025)
Abstract
Background: Food preservatives have an important role in food industry and are widely used in many products. Sorbic acid and its salts lead to maintaining the quality and improving the shelf life of food by preventing the growth of microorganisms and preventing chemical and enzymatic changes. However, health organizations involved in monitoring food products have set permitted limits for the use of these compounds in food industry. Due to probable high usage and long-term application of preservatives such as sorbic acid and its derivatives, they may have adverse effects on human health.
Methods: The present study is a systematic review of the measured amount of sorbic acid and its derivatives in different foods in Iran. In the following, the extracted measured amounts of sorbic acid and its derivatives were compared with the permitted amount mentioned in the Iran National Standard Organization (INSO) and Codex Alimentarius Commission (CAC).
Findings: Literature reviews showed that most of the examined products were in an illegal state in terms of sorbic acid content in INSO. According to INSO, the highest rate of non-compliance with the appropriate concentration range was related to dairy and bakery products. Since the food standard limit of INSO is stricter than CAC, the products that were within the permissible limits set by CAC were included in a larger share. It should be mentioned that the limits of some food products in CAC were not define.
Conclusion: In general, in this study, it was found that the amounts of sorbic acid and its derivatives were not within the range approved by the INSO in many food products. But they were within the CAC limit. Nevertheless, continuous monitoring of preservatives in food, specifically in highly consumed food products, is suggested.

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