Date

2021-12

Author

Yıldız, Adile Umut

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Sludge treatment and management is a growing challenge for countries globally. The quantities of sludge continue to increase as new wastewater treatment facilities are built and the existing ones are upgraded to keep up with the growing population. Associated costs are expected to increase with the increasing sludge amounts, and with stricter regulations that require further treatment. Knowing the cost of sludge treatment constitutes approximately half of the cost of wastewater treatment, one of the significant issues to be considered in selecting the appropriate sludge management option for wastewater treatment plants should be optimizing the total cost of sludge management. The main objective of this study is to find the optimal combinations of sludge management options for each integrated WWTP in Gediz Basin for land application. Considered options included different drying and stabilization combinations. A cost-based optimization model was developed comprising of management costs relevant to sludge drying, stabilization, vi transportation, and land application. In this study, stabilization methods are assigned to WWTPs as anaerobic digestion or aerobic composting depending on sludge production rates; anaerobic digestion for WWTPs producing greater than 1 tonnes/day, aerobic composting for lower rates. 3 different scenarios are considered: land application following on-site sludge drying, off-site drying, and without sludge drying. Best land application locations for each WWTP and optimum costs were determined. The developed optimization model was run using the ArcGIS Model Builder tool. The suitability of lands for application of sludge and real travel distances were determined with the overlay analysis and network analysis via ArcGIS platform, respectively. As a general result of the study, the total investment and operating maintenance costs for sludge management on a scenario basis for WWTPs with high sludge amount appear to be over $100,000. However; It is seen that this cost decreases as the amount of sludge decreases. Also, for WWTPs with high sludge amount, compared to plants with low sludge production; scenario costs were found to be close to each other. Results indicated that the sparse distribution of off-site sludge drying facilities and the wider distribution of suitable agricultural lands for sludge application increased costs. In addition, when the sludge application dosage is adjusted to remain on the safe side, there is no capacity restriction in Gediz Basin in terms of sludge application in agricultural lands. Sensitivity analysis applied on unit costs showed that there may be changes in the optimal pathway of sludge management for WWTPs when there is a change in unit cost

Subject Keywords

Wastewater sludge, Sludge Treatment, Optimization

URI

https://hdl.handle.net/11511/95235

Collections

Graduate School of Natural and Applied Sciences, Thesis