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Research Article Occurrence of Phthalates in Sewage Sludge from Three Wastewater Treatment Plants in Istanbul, TurkeyPhthalates are considered priority pollutants because of their potential adverse effects on ecosystems and human health. The objectives of this study were to determine the occurrence of five phthalates (DMP, DEP, DBP, BBP, and DEHP) in sewage sludge and to determine the seasonal variability of these contaminants at three (Bahçeşehir, Paşaköy, and Tuzla) full-scale municipal and domestic wastewater treatment plants (WWTP) in Istanbul, Turkey. Mass balance was also calculated for DEHP at Tuzla WWTP sludge treatment units. DMP, DEP, DBP, BBP, and DEHP concentrations in sewage sludge ranged from 1.4 to 2.7 mg/kg dry weight (dw), 1.1 to 2.8, 0.6 to 4.6, 2.8 to 6.2, 18 to 490 mg/kg dw, respectively. Phthalate concentrations from the Bahçeşehir and Paşaköy WWTPs met the limit (100 mg/kg dw) of Turkey national sludge regulation and the Europe Union draft of sludge directive for land application, whereas phthalate concentrations from Tuzla WWTP exceeded the maximum permissible concentration. Phthalate concentrations did not show seasonal variations for Bahçeşehir and Paşaköy WWTPs, which receive mainly household wastewater while some fluctuations were observed DEP, DBP, and DEHP at Tuzla WWTP which has a lot of industrial wastewater contribution. The mass balance showed that approximately 17% of DEHP in the primary and secondary sludge was removed by anaerobic digestion, while 43% returned back to the beginning of the WWTP and 40% remained in the dewatered sludge. This study suggests that phthalates in sludge from WWTPs with industrial wastewater contribution may limit the use of sludge for land application.

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Effectiveness of ultrasonication, microwave technologies, and enzyme addition prior to anaerobic digestion is investigated using sludge samples taken from the secondary settling tank of a domestic wastewater treatment plant to improve methane production, enhance dewaterability characteristics of the sludge, and to reduce excess sludge. Microwave pre‐treatment (1500 W, 10 min at 175 °C) results in better extra digester performance (compared to the control reactor) in terms of methane production (25 m3 ton−1 suspended solids (SS)) than ultrasound (no improvement) and enzyme pre‐treatment (11 m3 ton−1 SS). While methane production is not improved as a result of ultrasonication pre‐treatment (15 000 kJ kg−1 SS), a noticeable increase (19%) is observed in the case of microwave pre‐treatment. Higher compactibility values are obtained after ultrasonication and microwave application compared to the control (i.e., from 7.1 to 8.7 and 9.2%, respectively) before anaerobic digestion. Although ultrasonication and microwave application decrease the dewaterability of the raw sludge (capillary suction time (CST) from 827 to 1364 and 2290 s, respectively), similar dewaterability results are obtained at the end of the anaerobic digestion process for all pre‐treated sludge samples. An economic assessment of this study shows that pre‐treatment with microwave results in more than 10‐fold less net cost compared to the enzyme application.

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In this study, the amount of medical waste generated in a high-populated city in Turkey between January 2018 and August 2021 was evaluated, and the effect of the COVID-19 pandemic on waste amounts and waste production rate was investigated. While a total of 79,027 kg/month of medical waste was produced in the city before COVID-19, this value reached 116,714 kg/month after COVID-19. The increase in the amount of medical waste due to the COVID-19 pandemic in the province was calculated as 48% on average. It was determined that 75% of this waste amount originates from public hospitals in the city. While the production of medical waste was 0.86 kg/bed day in the pre-COVID-19 period, this value increased to 0.96 kg/bed day in 2020 and to 1.34 kg/bed day in 2021 with the COVID-19 pandemic. According to the results obtained, the amount of medical waste reached in the province due to COVID-19 is the amount of medical waste expected to be generated in the 2040s under normal conditions. It is a very important issue in terms of public health that the capacity of waste disposal in medical waste management in cities is flexible to respond to severe epidemic conditions. Based on the information obtained within the scope of the study, changes in the amount of medical waste in a city with a dense population under pandemic conditions can be obtained based on real data and projections regarding disposal capacity can be made more realistically. Supplementary Information The online version contains supplementary material available at 10.1007/s10163-022-01428-3.