Application of machine learning algorithms and feature selection methods for better prediction of sludge production in a real advanced biological wastewater treatment plant.

Although the management of sewage sludge is an important and challenging task of wastewater treatment, there is a scarcity of studies on the prediction of waste sludge. To overcome this deficiency, the present work aims to develop an appropriate model providing accurate and fast prediction of sewage sludge. With this aim, different machine learning (ML) algorithms were tested by data obtained from a real advanced biological wastewater treatment plant located in Kocaeli, Turkey. In modelling studies, a data set from January 2022 to December 2022 composed of 208 daily measurements was considered. The flow rate of the plant (Q), polyelectrolyte dosage (PD) and removed amounts of total suspended solids (TSS), chemical oxygen demand (COD), biological oxygen demand (BOD), total phosphorous (TP), total nitrogen (TN) were assigned as input parameters to predict sludge production (SP). The precision of the models was evaluated in terms of Mean Square Error (MSE), Mean Absolute Percentage Error (MAPE), Root Mean Square Error (RMSE), Mean Absolute Error (MAE), and correlation coefficient (R2). Among the various tested models Kernel Ridge Regression provided the best accuracy with R2 value of 0.94 and MAE value of 3.25. Mutual information-based feature selection (MIFS) and correlation-based feature selection (CFS) algorithms were also used in the study in order to enhance the model performance. Thus, higher prediction accuracies were achieved using the selected subset of features. Furthermore, importance contribution of features were calculated and visualized by SHapley Additive exPlanations (SHAP) technique. The overall results of the work indicate the feasibility of ML models for describing the dynamic and complex nature of SP. The process operators may benefit from this modelling approach since it enables accurate and fast estimation of sewage sludge by using fewer and easily measurable parameters.

Treatment of real printing and packaging wastewater by combination of coagulation with Fenton and photo-Fenton processes.

Printing and packaging process wastewater (PPPW) with high flow rates causes severe damage to the environment due to high organic pollution (3830.0 mg O2/L of COD and 813.6 mg/L of TOC) and turbidity (9110 NTU). This study examined the efficiencies of coagulation, Fenton, and photo-Fenton procedures, and their combinations in the treatment of PPPW. The three inorganic salts (FeCl3, Al2(SO4)3, and Fe2(SO4)3) were used in a wide range of pH (2.5-10) as a coagulant, and FeCl3 was chosen as the optimum coagulant. The 71.3% of TOC removal and the decreasing of turbidity up to 5.8 NTU were obtained at 0.5 g/L FeCl3 and pH of 6.0. Then, Fenton and photo-Fenton processes were applied to the effluent of the coagulation process. The Fenton process engaged the TOC removal efficiencies up to 85.2% in the presence of 7.350 g/L iron catalysts and 36.0 mL/L H2O2. The combined coagulation and Fenton process is a promising way to decrease the COD up to 119 mg O2/L, meeting the wastewater discharge standards of COD (200 mg O2/L) in Turkey. However, adding UV sources to the Fenton process showed a little bit of engagement (only %1.4 extra removal). When evaluated for PPPW, it is seen that the usage of combined coagulation and the Fenton process is an important treatment alternative. Furthermore, Zeta potential measurements and size exclusion chromatography were used to understand the removal mechanism.

Towards zero-waste airports: a case study of Istanbul Airport.

In this day and age, an important indicator of sustainable waste management is zero-waste index. Zero-waste approach is adopted by many organizations in different sectors. In this context, implementation of sustainable waste management at airports, which have become the most vibrant centers of the transportation sector in the globalizing world, is one of the important environmental issues. In this study, the activities carried out in the Istanbul airport in 2019-2020 within the scope of sustainable waste management were evaluated within the framework of zero-waste approach. For this purpose, waste characterizations for different zones in the airport have been presented. When the methods used in the disposal of the wastes were examined, it was seen that recycling (43-49%) and landfilling (50-57%) took the first place. The results of the study reveal that the pandemic restrictions implemented in 2020 have caused significant differences in the amount and composition of waste generated. The highest decrease in waste generation occurred in Zone A where terminal activities are located, with 76%. This change was also reflected in the zero-waste index determined depending on the waste management strategies applied, and the values calculated for 2019 and 2020 were found to be 0.35 and 0.26, respectively. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10163-021-01308-2.

Possibility of the most cost efficient choice: a divided process approach to method and location selection for municipal solid waste management.

As studies on municipal solid waste management increased in recent years, many new mathematical models and approaches with a focus on determining the best treatment and disposal scenario were developed and applied. In this study, a mixed integer linear programming model was developed to be used as a facilitative tool for the cost minimisation of municipal solid waste management practices. Since municipal solid waste mass is a mixed composition of various types of waste components with different physical and chemical properties, the model was designed to include all the suitable treatment and disposal methods for these different waste components. The method alternatives with multiple waste inputs, such as aerobic biological treatment and the thermal processes, were divided into a number of inputs to remove their non-linear structures. This way, linear programming could be used, and the linear cost function could be minimised over a set of linear constraints with integer variables. The model was applied to the city of Kocaeli, which will require a new waste management application in the future, beginning from 2015. The results obtained for different haul distance constraints in the study area were presented and assessed. The results showed that all the information required for a comprehensive management task could be modelled by a linear optimisation model with a divided processes approach easily.

Application of Taguchi L32 orthogonal array design to optimize copper biosorption by using Spaghnum moss.

In this work, Taguchi L32 experimental design was applied to optimize biosorption of Cu(2+) ions by an easily available biosorbent, Spaghnum moss. With this aim, batch biosorption tests were performed to achieve targeted experimental design with five factors (concentration, pH, biosorbent dosage, temperature and agitation time) at two different levels. Optimal experimental conditions were determined by calculated signal-to-noise ratios. "Higher is better" approach was followed to calculate signal-to-noise ratios as it was aimed to obtain high metal removal efficiencies. The impact ratios of factors were determined by the model. Within the study, Cu(2+) biosorption efficiencies were also predicted by using Taguchi method. Results of the model showed that experimental and predicted values were close to each other demonstrating the success of Taguchi approach. Furthermore, thermodynamic, isotherm and kinetic studies were performed to explain the biosorption mechanism. Calculated thermodynamic parameters were in good accordance with the results of Taguchi model.

Comparison of 3D dose distributions for HDR 192Ir brachytherapy sources with normoxic polymer gel dosimetry and treatment planning system.

Radiation fluence changes caused by the dosimeter itself and poor spatial resolution may lead to lack of 3-dimensional (3D) information depending on the features of the dosimeter and quality assurance of dose distributions for high-dose rate (HDR) iridium-192 ((192)Ir) brachytherapy sources is challenging and experimental dosimetry methods used for brachytherapy sources are limited. In this study, we investigated 3D dose distributions of (192)Ir brachytherapy sources for irradiation with single and multiple dwell positions using a normoxic gel dosimeter and compared them with treatment planning system (TPS) calculations. For dose calibration purposes, 100-mL gel-containing vials were irradiated at predefined doses and then scanned in an magnetic resonance (MR) imaging unit. Gel phantoms prepared in 2 spherical glasses were irradiated with (192)Ir for the calculated dwell positions, and MR scans of the phantoms were obtained. The images were analyzed with MATLAB software. Dose distributions and profiles derived with 1-mm resolution were compared with TPS calculations. Linearity was observed between the delivered dose and the reciprocal of the T2 relaxation time constant of the gel. The x-, y-, and z-axes were defined as the sagittal, coronal, and axial planes, respectively, the sagittal and axial planes were defined parallel to the long axis of the source while the coronal plane was defined horizontally to the long axis of the source. The differences between measured and calculated profile widths of 3-cm source length and point source for 70%, 50%, and 30% isodose lines were evaluated at 3 dose levels using 18 profiles of comparison. The calculations for 3-cm source length revealed a difference of > 3mm in 1 coordinate at 50% profile width on the sagittal plane and 3 coordinates at 70% profile width and 2 coordinates at 50% and 30% profile widths on the axial plane. Calculations on the coronal plane for 3-cm source length showed > 3-mm difference in 1 coordinate at 50% and 70% and 2 coordinates at 30% profile widths. The point source measurements and calculations for 50% profile widths revealed a difference > 3mm in 1 coordinate on the sagittal plane and 2 coordinates on the axial plane. The doses of 3 coordinates on the sagittal plane and 4 coordinates on the axial plane could not be evaluated in 30% profile width because of low doses. There was good agreement between the gel dosimetry and TPS results. Gel dosimetry provides dose distributions in all 3 planes at the same time, which enables us to define the dose distributions in any plane with high resolution. It can be used to obtain 3D dose distributions for HDR (192)Ir brachytherapy sources and 3D dose verification of TPS.

Energy content of municipal solid waste bales.

Baling technology is a preferred method for temporary storage of municipal solid waste (MSW) prior to final disposal. If incineration is intended for final disposal of the bales, the energy content of the baled MSW gains importance. In this study, nine cylindrical bales containing a mix of different waste materials were constructed and several parameters, including total carbon (TC), total organic carbon (TOC), total Kjeldahl nitrogen, moisture content, loss on ignition, gross calorific value and net calorific value (NCV) were determined before the baling and at the end of 10 months of storage. In addition, the relationships between the waste materials and the energy contents of the bales were investigated by the bivariate correlation analyses. At the end, linear regression models were developed in order to forecast the decrease of energy content during storage. While the NCVs of the waste materials before the baling ranged between 6.2 and 23.7 MJ kg(-1) dry basis, they ranged from 1.0 to 16.4 MJ kg(-1) dry basis at the end of the storage period. Moreover, food wastes exhibited the highest negative correlation with NCVs, whereas plastics have significant positive correlation with both NCVs and TCs. Similarly, TOCs and carbon/nitrogen ratios decreased with the increase in food amounts inside the bales. In addition, textile, wood and yard wastes increase the energy content of the bales slightly over the storage period.

Evaluation of material heterogeneity dosimetric effects using radiochromic film for COMS eye plaques loaded with (125)I seeds (model I25.S16).

PURPOSE: (1) To measure absolute dose distributions in eye phantom for COMS eye plaques with (125)I seeds (model I25.S16) using radiochromic EBT film dosimetry. (2) To determine the dose correction function for calculations involving the TG-43 formalism to account for the presence of the COMS eye plaque using Monte Carlo (MC) method specific to this seed model. (3) To test the heterogeneous dose calculation accuracy of the new version of Plaque Simulator (v5.3.9) against the EBT film data for this seed model. METHODS: Using EBT film, absolute doses were measured for (125)I seeds (model I25.S16) in COMS eye plaques (1) along the plaque's central axis for (a) uniformly loaded plaques (14-20 mm in diameter) and (b) a 20 mm plaque with single seed, and (2) in off-axis direction at depths of 5 and 12 mm for all four plaque sizes. The EBT film calibration was performed at (125)I photon energy. MC calculations using MCNP5 code for a single seed at the center of a 20 mm plaque in homogeneous water and polystyrene medium were performed. The heterogeneity dose correction function was determined from the MC calculations. These function values at various depths were entered into PS software (v5.3.9) to calculate the heterogeneous dose distributions for the uniformly loaded plaques (of all four sizes). The dose distributions with homogeneous water assumptions were also calculated using PS for comparison. The EBT film measured absolute dose rate values (film) were compared with those calculated using PS with homogeneous assumption (PS Homo) and heterogeneity correction (PS Hetero). The values of dose ratio (film∕PS Homo) and (film∕PS Hetero) were obtained. RESULTS: The central axis depth dose rate values for a single seed in 20 mm plaque measured using EBT film and calculated with MCNP5 code (both in ploystyrene phantom) were compared, and agreement within 9% was found. The dose ratio (film∕PS Homo) values were substantially lower than unity (mostly between 0.8 and 0.9) for all four plaque sizes, indicating dose reduction by COMS plaque compared with homogeneous assumption. The dose ratio (film∕PS Hetero) values were close to unity, indicating the PS Hetero calculations agree with those from the film study. CONCLUSIONS: Substantial heterogeneity effect on the (125)I dose distributions in an eye phantom for COMS plaques was verified using radiochromic EBT film dosimetry. The calculated doses for uniformly loaded plaques using PS with heterogeneity correction option enabled were corroborated by the EBT film measurement data. Radiochromic EBT film dosimetry is feasible in measuring absolute dose distributions in eye phantom for COMS eye plaques loaded with single or multiple (125)I seeds. Plaque Simulator is a viable tool for the calculation of dose distributions if one understands its limitations and uses the proper heterogeneity correction feature.

Temporal variation of decomposition gases from baled municipal solid wastes.

In this study, after nine cylindrical bales containing a mix of different waste materials were constructed, they were stored in the open air and temporal variations of CO(2), CH(4), O(2), and N(2) were monitored over 10 months. In each bale, different waste fractions were considered in order to represent different moisture contents. The results showed that CO(2) increased within very few days to approximately 80% and stabilized later in the range of between 10% and 35% in a month. The O(2) levels dropped from approximately 15% to significantly less than 1%. There was no significant anaerobic decomposition since CH(4) did not exceed 5% during the whole test period. N(2) exhibited an opposite pattern with CO(2). In addition, relationships between waste species in the bales and gas formations were determined by a bivariate correlation analysis. An empirical prediction model for the maximum CO(2) production was also developed.