Description
A Master of Science thesis in Civil Engineering by Hadeer Abdalla entitled, “Experimental Assessment of Microbial Fuel Cells for Treatment and Nutrient Recovery from Different Wastewaters”, submitted in May 2022. Thesis advisor is Dr. Kazi Fattah and thesis co-advisor is Dr. Mohamed Abdallah. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).
Abstract
Wastewater is an abundant renewable source of nutrients such as nitrogen and phosphorus. However, current recovery methods require large amounts of energy and chemicals. Consequently, these processes pose economic and environmental burdens and is therefore often not implemented. Microbial fuel cells (MFC) are one of the bio-electrochemical wastewater treatment technologies that has potential for nutrient recovery as it can reduce chemicals cost while at the same time treat the wastewater and produce electricity. However, there is limited knowledge of the optimum operation mode of MFCs and the effect of the substrate on nutrient recovery. This study investigates the efficiency of struvite formation for nutrient recovery in a MFC using various wastewater substrates, such as, urine, centrate, and greywater (phase I) and different operating modes (phase II). In phase II of the experimental run the system was operated by recirculating the treated anolyte to the cathode compartment. The performance of the 700ml-volume dual-chamber cells was assessed based on electricity output, organics removal in terms of soluble chemical oxygen demand (sCOD), and struvite recovery. The highest sCOD removal efficiency of over 95% was achieved with the centrate-fed cell. The sCOD removal efficiency increased by 24% from the single operation (phase I) to the recirculation stage (phase II). The highest maximum power density generated from the urine, centrate, and greywater fed MFCs for phase I were found to be 1.7, 1.5, and 0.95 mW/cm², and 1.18, 0.82, and 0.73 mW/cm² for phase II, respectively. The urine-fed 700ml cell produced the highest struvite precipitate quantity (1.5g), followed by centrate (1.3g) and greywater (0.3g) in phase I, while the urine sample yielded 1.7g in phase II. The highest phosphate recovery efficiencies of over 55% (phase I) and 20% (phase II) were found for the cell treating urine, while efficiencies of other substrates were 36% (for centrate) and 48% (for greywater. Morphological and chemical analysis of the precipitate formed confirmed that the nutrients were recovered primarily as struvite. The results of this study verify the potential for implementing MFCs for nutrient recovery and anolyte recirculation.