To determine the supply of wastewater solids, the state has been divided into districts made up of one or more counties, with boundaries determined by existing municipal service areas and geological surveys. Estimates of wastewater solid production are drawn from the number of customers served by each sewage system [2], the average household size by county [3], and an estimated rate of 0.16 pounds of dry solid waste generated per person per day [4]. Additionally, major soil types and primary crops in each district are identified using USDA soil surveys and 2022 agricultural census data [5,6]. These datasets are utilized to determine specific nutrient demands in farms (e.g., nitrogen, phosphorus, and potassium), enabling the production of fertilizers that match local agricultural needs. To extract the nutrients from wastewater, we investigate the use of conventional fertilizer facilities, anaerobic digestion, and the integration with a novel integrated precipitation and membrane separation process developed by Piash et al. [7].
The optimal locations for fertilizer production facilities are then determined using a mixed-integer linear optimization (MILP) model, which incorporated multiple factors, including the supply and distribution of wastewater solids, transportation costs to and from the fertilizer facilities, and the varying demand for fertilizers in different districts. The objective is to minimize overall costs by determining the optimal placements, following the approach of Niziolek et al. [8]. This model will supply the costs and most beneficial locations of the fertilizer facilities for West Virginian farms. This research highlights the advantages of diverting wastewater solids to agriculture. Utilizing these materials as fertilizer feedstock reduces the need for synthetic fertilizers and helps prevent further landfilling and eutrophication. Optimally placed fertilizer production facilities could allow these benefits to become reality for West Virginia.
References
[1] National Biosolids Data Project. WV Biosolids. (2018) https://www.biosolidsdata.org/west-virginia
[2] WV Infrastructure and Jobs Development Council. Needs Assessment. (2023) Appendix B - Existing Sewer Customers.
[3] US Census Data: Household size by WV County. (2020)
[4] Stehouwer, R. Penn State Extension: What is Sewage Sludge. (2023)
[5] USDA Web Soil Survey https://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx
[6] United States Department of Agriculture. Agricultural Census, West Virginia. (2022)
[7] Piash, K. S., Anwar, R., Shingleton, C., Erwin, R., Lin, L. S., & Sanyal, O. (2022). Integrating chemical precipitation and membrane separation for phosphorus and ammonia recovery from anaerobic digestate. AIChE Journal, 68(12), e17869.
[8] Niziolek, A. M., Onel, O., Tian, Y., Floudas, C. A., & Pistikopoulos, E. N. (2018). Municipal solid waste to liquid transportation fuels–part iii: An optimization-based nationwide supply chain management framework. Computers & chemical engineering, 116, 468-487.