Application of Upflow Anaerobic Sludge Blanket Reactor coupled with Trickling Filters for Municipal Wastewater Treatment: Technical, Environmental and Economic Assessment in the Tropical Developing Country of Ghana
Creators: name: ARTHUR, PHILOMINA MAMLEY ADANTEY
Publisher: name: Zenodo
Year: 2023
Subjects: Economic assessment; Environmental assessment; Ghana; Municipal wastewater treatment; Technical assessment; Trickling filter; UASB reactor

description: Wastewater management remains one major challenge in most developing countries in sub-Saharan Africa (SSA) due to the lack of adequate infrastructure for wastewater disposal, collection, and treatment. This challenge has been exacerbated by rapid population growth, urbanization, and industrialization. Meanwhile, untreated wastewater contains pollutants such as toxic compounds and pathogens which put at risk public health and the receiving ecosystems. Wastewater is, however, composed of rich resources such as freshwater, nutrients and energy, which can be harnessed using modern and eco-friendly technologies that employ circular economy principles, promoting sustainable wastewater management. The Upflow Anaerobic Sludge Blanket (UASB) reactor has been identified as an efficient and low-cost wastewater treatment option which has been widely implemented in several regions of the world, especially in Latin America and India. This technology is, however, less represented in SSA despite the favourable climatic conditions. This study, therefore, evaluated the technical, environmental, and economic sustainability of a full-scale UASB reactor coupled with Trickling Filters as post-treatment units in Accra, the capital city of Ghana in the West African sub-region. The technical assessment revealed satisfactory system performance with over 70% removal efficiency for solids, organic matter, and microbial loads, whilst post-treatment further enhanced the removal of these contaminants to acceptable limits set by the Environmental Protection Agency (EPA), Ghana. However, the system could not adequately remove nutrients, with nitrogen and phosphorous compounds far exceeding discharge limits. Daily biogas production was between 101 Nm3/d and 1673 Nm3/d, with an average daily production of 613 ± 271 Nm3/d, corresponding to a specific yield of 0.14 ± 0.07 m3biogas/kgCOD removed. Biogas produced contained 65% of methane. However, 23% of the methane generated remained dissolved in the effluent, reducing biogas energy recovery potential. Environmental assessment employed the IPCC GHG inventory methodology to measure the carbon footprints of the full-scale municipal wastewater treatment plant. It was found from the study that the total greenhouse gas (GHG) emissions from the operations of the Mudor Plant were estimated at 39,619.36 tCO2eq/yr. CO2 emissions from energy consumption were estimated at 165.74 tCO2eq/yr, constituting 8.5% of the total emissions. Dissolved methane in the effluent was identified as the single most significant source of GHG emissions, with over 90% contribution at 37,676.67 tCO2eq/yr. A cost-benefit analysis was employed for the economic assessment. Cost analysis revealed that staff management was responsible for the highest percentage (37%) of the operational cost, whilst energy consumption of the anaerobic-based wastewater treatment plant was only 7.3% of the total operational cost. Benefit analysis carried out employing resource recovery revealed that energy recovery potential (534.1 MWh/yr) from biogas and sludge generated by the Plant could completely offset the total Plant energy demand (392.7 MWh/yr). Additionally, it was found that the nutrient-rich effluent had lower heavy metals concentration with acceptable microbial load count for urban irrigation. Thus, the UASB reactor technology presents an efficient, economically feasible and sustainable wastewater treatment alternative that can be implemented in developing countries towards the attainment of sustainable wastewater management for sustainable development in this part of the world.