3个污水处理厂脱脂设施中油脂含量的检测

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克里特岛污水处理厂油脂能量含量的分离与测定Isolation and determination of the energy content of grease and oil in Wastewater Treatment1st International Conference on Sustainable Chemical and Environmental Engineering31 Aug – 04 Sep 2022, Rethymno, Crete, Greece Isolation and determination of the energy content of grease and oil in Wastewater Treatment Plants on the island of Crete 克里特岛污水处理厂油脂能量含量的分离与测定 N. Tatas1, A. Manali1 and P. Gikas1 1Design of Environmental Processes Laboratory, School of Chemical and Environmental Engineering, Technical University of Crete, Chania, Greece Corresponding author email: pgikas@tuc.gr keywords: wastewater treatment plants; degreasers; fats and oils; extraction; calorific value. Introduction Food preparation in households and in restaurants generates significant quantities oil and grease (O&G), which often end up at the Wastewater Treatment Plant(WWTP). Crete is not an exception to the above rule, with O&G maximizing during summer, due to the increase of tourists. Even if there are companies collecting O&G in Crete, and most municipalities in Crete have enforced the use of degreasing facilities at the restaurants(prior to wastewater discharge into the sewer), large amounts of O&G are entering the sewers. The O&G separated at the WWTPs are usually disposed, however they could be used as raw materials to produce alternative fuels such as biofuel (biodiesel) (Srivastava et al., 2018). The present study aims in estimating the production of O&G in the island of Crete, and determining their energy content, by measuring their heating value. Materials and methods O&G samples were collected form the degreasing facilities of the three largest WWTPs of Crete, treating the wastewater of municipalities of Chania, Rethymno and Heraklion. Although the sampling points were always the same for each WWTP, the samples had large heterogeneity, so they were managed as liquid or solid depending on their composition. Three samples had been collected between September 2021 and January 2022. All the studied WWTPs are equipped with aerated degritting/degreasing facilities, located downstream of the screening facilities. O&G were extracted from the samples using the 5520 Standard Method (APHA, 2017), using Gerhardt's Soxtherm apparatus, with petroleum ether as solvent. The Higher Heating Value (HHV) of O&G was determined by the XRY-1A Oxygen Bomb Calorimeter. Results and discussion The average O&G content in liquid samples was measured as: 23.1 ± 8.4, 19.4 ± 5.1 and 7.9 ± 3.4 g/L for the WWTPs of Heraklion, Rethymno and Chania, respectively (Figure 1). According to previous studies, the concentration of fats and oils in raw municipal wastewater ranges from 0 to 15 g/L (APHA, 2017; Williams et al., 2017). However, the O&G concentrations measured from the WWTPs of Heraklion and Rethymno were measured above the concentrations reported by the literature, which is probably due to inadequate removal of O&G by the onsite degreasers. Solid samples had been collected only from the Chania and Rethymno WWTPs, resulting to an average O&G content of 490.6 ± 246.4 and 122.2 ± 7.7 mg/g, respectively (Figure 2). No solid sample was collected from the WWTP of Heraklion. Figure 1. Average concentrations in liquid samples of O&G at WWTPs in Crete. Figure 2. Average concentrations in solid samples of O&G at WWTPs in Crete. The HHVs of the O&G isolated from the samples were measured as: 43.6 ± 0.7, 42 ± 1.8 and 40.2 ± 3.2MJ/kg, for the WWTPs of Heraklion, Chania and Rethymno, respectively. HHV values of other typical oils, such as oil from corn, soybean, sunflower, olive, and eucalyptus, range from 37 to 43 MJ/kg, which is quite similar with the values found for Ο&G. Despite the differences monitored in O&G concentrations in the samples, the HHVs are quite similar. This may be because the chemical composition of fats and oils is similar no matter the source. Also, the high energy content of the isolated fats and oils shows that they can be used as raw material to produce alternativefuels,suchasbiodiesel,byfollowingtheprocessofesterification/transesterification.The produced biodiesel is valuable for the coverage of the energy needs of WWTPs, and particularly for the aeration process, which is responsible for 45-90% of the total energy consumption of a WWTP(Rosso et al.,2008). Conclusions The O&G concentrations in the samples found to be quite different, ranging from 7.9 to 23.1 g/L for the liquid samples, and from 122.2 to 490.6 mg/g for the solid samples. Despite the large heterogeneity of the samples (liquid or solid), their HHV values, and therefore their energy content, found to be quite similar, varying between 40.2 to 43.6 MJ/kg. References APHA, 2017. Standard Methods for the Examination of Water and Wastewater, 23rd Edition. Rosso, D., Stenstrom, M.K. and Larson, M.K. 2008. Aeration of large-scale municipal wastewater treatment plants: state of the art. Water Sci. Technol., 57(7), 973–978. Srivastava, N., Srivastava, M. and Gupta, V.K., 2018. Recent development on sustainable biodiesel production using sewage sludge. Biotech, 8, 245. Williams, J.B., Clarkson, C., Mant, C., Drinkwater, A. and May, E., 2012. Fat, oil and grease deposits in sewers:Characterisation of deposits and formation mechanisms. Water Research, 46(19), 6319-6328.