|Ph.D Student||Miller Efrat|
|Subject||Examination of Macro-Encapsulated Bacteria as a Mechanism of|
Confined Environment for Water and Wastewater
|Department||Department of Civil and Environmental Engineering||Supervisor||Professor Emeritus Carlos Dosoretz|
|Full Thesis text - in Hebrew|
The main objective of this research was to examine the process of bioaugmentation through the application of advanced macrocapsules in order to streamline wastewater treatment and groundwater detoxification processes. Encapsulated was performed in macrocapsules in the centimeter range, thereby facilitating fixation of bacterial populations in confined environments that guarantee their survival throughout the decontamination process. The capsules included a built-in inner nutrient core that supports essential growth needs of the microorganisms while preventing excessive use of nutrients (nitrogen and phosphorus).
In order to test the efficacy of the capsules by means of biodegradation, two pilot systems were designed and built as part of this research: (i) A copiotroph system for the treatment of wastewater in a membrane bioreactor (MBR); (ii) An oligotroph system for the treatment of groundwater contamination mimicking a permeable reactive bio-barrier (PRBB). In both systems, capsules were integrated within the systems as a bio-barrier to the flow trajectory of the fluid and compared with controls without capsules.
The first part of this research aimed at characterizing the capsule’s sheath permeability. Threshold permeability was determined and indicated that the capsules are easily penetrated by small molecules and fairly permeable to oligomers (< 500 nm). Bacteria, with an average size of 1 μm, were safely retained within the capsule whereas exogenous bacteria could not penetrate it. Biofouling of the capsule’s outer membrane did not affect flux of soluble components.
The second part of this research aimed at testing the influence of the macrocapsules for removing toxic pollutants in a copiotrophic system mimicking municipal wastewater treatment. 3-Chlorophenol at 600 and 800 mg/L was chosen as target pollutant for its biodegradable characteristics and molecular structure (single halogenated aromatic) that facilitates effective tracking of its biodegradation pathway. This array of experiments involved the use of a commercial bacterial blend capable of removing phenol and polyphenols compounds. The immediate influence of the capsules was evident.
The third part of this research was aimed at testing the influence of the macrocapsules for biodegrading toxic pollutants in an oligotrophic system mimicking groundwater treatment under aerobic conditions, with 3-chlorophenol at the model compound ranging at 350-500 mg/). 3-Chlorophenol degradation was tested with either exogenous nutrient supply or a built-in nutrient core within the macrocapsules which ensured the endurance of capsule activity. In these experiments, pure cultures of Pseudomonas putida were encapsulated based on their metabolic ability to biodegrade the target pollutant. The capsules served as the obstructing biological medium in the PRBB pilot system. Removal performance of 3-chlorophenol ranged at 72-85% compared to 15-30% in the control system. The built-in nutrient core resulted advantageous since the water effluent was free of nutrient contamination.
To conclude, bioaugmentation through targeted macrocapsules can be implemented in both copiotrophic and oligotrophic systems exposed to stress conditions. In oligotrophic systems, the possibility of managing a built-in nutrient core presents a significant environmental advantage controlling excess nutrient release, i.e., nitrogen and phosphorous, while enabling required growth of microorganisms within the capsule at the expense of the treated pollutant in the water.