Microbial Process Biokinetics under DC Electrical Field for Bio-Electrochemical Wastewater Treatment Related Applications

Abstract

The application of electro-technologies in the UAE existing biological treatment methods requires further understanding of the behavior of the microorganisms (biodegraders) to enhance the treated effluent's water quality. Therefore, the primary objective of this research study was to evaluate the microbial communities present in bio-electrochemical reactor under different operating conditions such as current density and exposure time to electricity to achieve system process stability. This study was divided into two Phases. In Phase 1, a laboratory scale study was conducted at different current densities ranging between 5 and 20 A/m2 continuously supplied with no addition of substrate (Stage 1) and with addition of substrate (Stage 2). Phase 2 evaluated the bacteria count, substrate utilization rate (organic removal), and microbial process biokinetics (bacteria growth rate and doubling time) at continuous supply of electric field at different current density (Stage 1), and at intermittent supply of electric field at constant current density of 15 A/m2 (Stage 2). The results from Phase 1 revealed that the continuous supply of electric field had significant stimulation effect on microorganisms at low current density of 5 A/m2 (bacteria count has increased from 80,000 (initially) to 1,686,600 CFU/mL after 12 h) when compared to the bacteria count at high current density of 20 A/m2 (bacteria count has increased from 80,000 (initially) to 263,600 CFU/mL after 12 h). Moreover, in Phase 2 – Stage 1, the bacteria count in the bioreactors has increased from 200,000 CFU/mL (initially) to 540,000, 920,000, 1,460,000 and 320,000 CFU/mL at 15, 10, 5, and 0 (control) A/m2, respectively. However, the growth rate of living microorganisms at intermittent supply (Phase 2 – Stage 2) of electricity at 15 A/m2 was also higher (0.1 1/h) when compared to the control reactor through which no electric field was supplied (0.08 1/h). A similar observation was reported with respect to substrate removal as the concentration of sCOD was 35, 25, 25, 24, and 54 mg/L at 5 min ON yet with 10, 15, 20, 30 min OFF, and Control, respectively. The success of this study would contribute to the implementation of electro-technologies in the wastewater treatment plants in the UAE.

Date of Award	2014
Original language	American English
Supervisor	SHADI Hasan (Supervisor)