Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Chemical and Biochemical Engineering

Supervisor

Bassi, Amarjeet

Abstract

Heavy metals in wastewater streams negatively affect the environment due to their high toxicity. Non-conventional heavy metal removal methods show higher efficiencies for the remediation of these pollutants. In this investigation, a two-step approach using micellar-enhanced ultrafiltration (MEUF) and microbial fuel cell (MFC) was investigated to remove copper, manganese, and zinc from a synthetic salt wastewater containing magnesium, sodium, and phenol. This synthetic solution was used to simulate refinery wastewater streams such as desalter effluent. The study was carried out in three phases. In the first phase, a flat plate polyether sulfone membrane was investigated for the MEUF process with different concentrations of rhamnolipid biosurfactant. The process was performed using a transmembrane pressure of 2.5 bar for an average time of 2 h. MEUF showed a maximum heavy metal removal efficiency of 99% for copper with a rhamnolipid concentration of 300 mg/L. In the second phase, a dual chamber MFC inoculated in the anode with Shewanella oneidensis MR-1 demonstrated a maximum removal efficiency of 93% and 98% for copper in the anode and cathode chambers, respectively. During the operation, the biofilm produced bacterial nanowires on the surface of the carbon felt electrodes. These bacterial nanowires enhanced electron transport, and maximum open-circuit voltages (OCV) of 516.6 mV in the anode and 127.7 mV in the cathode were obtained. Finally in the third phase, the complex rhamnolipid metals mixture was applied to the MFC system. A maximum metal removal of 84% for manganese was observed. Furthermore, it was found that MFC efficiency was lower and bacterial growth was inhibited at high rhamnolipid concentrations. In conclusion, a rhamnolipid concentration of 100 mg/L was optimal for bacterial growth in the MFC, resulting in a maximum OCV of 335.5 mV. Moreover, the synthetic wastewater solution in the anode chamber facilitated the formation of bacterial nanowires. The bacterial nanowires are formed due to the higher toxicity of heavy metals. The specific growth rate for the wastewater was 0.11 h-1. The study led to a novel combined approach using MEUF and MFC for heavy metal remediation.

Summary for Lay Audience

Heavy metals in wastewater harm the environment due to their high toxicity. New approaches for heavy metal removal show higher efficiencies for the remediation of these pollutants. In this investigation, a two-step approach using filtration and bacterial-based technology was investigated to remove copper, magnesium, manganese, and zinc from synthetic salt wastewater containing hydrocarbons. The study was carried out in three phases. In the first phase, a filtration membrane was investigated with biosurfactant. The process showed a maximum heavy metal removal efficiency for copper. In the second phase, a battery based on bacteria demonstrated a maximum removal efficiency for copper as well. In the third phase, the battery based on bacteria showed a higher removal efficiency for manganese, using the discharge wastewater from phase 1. Finally, the bacterial battery demonstrated voltage generation and metal removal for phases 2 and 3. The study demonstrated an efficient method for metal remediation and voltage production using two different processes.

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