|M.Sc Student||Dekel Oz Anat|
|Subject||Study of Bacterial Communities by Molecular Methods as|
a Tool for Developing an Attached Growth
Treatment Process for Greywater
|Department||Department of Civil and Environmental Engineering||Supervisors||Professor Eran Friedler|
|Dr. Malka Halpern|
|Full Thesis text - in Hebrew|
Greywater has a great potential for on-site reuse due to its availability and the low pollutants concentrations as compared with combined residential sewage. However, greywater contains various contaminants including pathogens and thus has to be treated before reuse.
The goal of this research was to develop an extensive treatment unit with a small footprint, suitable for treating greywater in density populated urban areas.
Two innovative attached growth bio-reactors, with "BIOROCK" ? media of high specific surface area were constructed. These biological filters were operated under unsaturated flow regime. One reactor was fed with synthetic greywater at controlled discharges and organic loads. The second was fed with real "light greywater" originating from fourteen flats. The operational parameters and chemical properties of the greywater influent and effluent were characterized. Microbial DNA samples were collected from the reactor media, the influent and the effluent and analyzed by "Denaturing Gradient Gel Electrophoresis" (DGGE) and pyrosequencing.
COD removal efficiency was 80-88% depending on the influent type and the organic load, and removal efficiency of turbidity was 83-99%. Under all operation modes (various organic loads and discharges, synthetic & rael greywater), nitrification occurred. Increasing the organic load resulted in initiation of denitrification. Nitrogen mass balance for nitrification-denitrification was confirmed by the alkalinity changes in the reactor.
Microbial communities' dynamics in the media, influent and effluent was characterized using DGGE fingerprint and 454 pyrosequencing technologies. Even after a steady state was reached in regard to removal efficiency of COD, significant changes were observed in the DGGE fingerprints and in the pyrosequencing results. This implies that performance based on chemical parameters alone cannot serve as an index for microbial population stability.
The bacterial communities identified within the reactors could not be attributed to one habitat. Most of the species found were unknown. Classification of the pyrosequencing indicated that the most prevalent phylum was Proteobacteria and the dominant genus (according to DGGE and pyrosequencing) was pseudomonas.
The media physical properties enabled support of diverse bacterial communities, and consequently efficient degradation of organic matter was observed. Relationships were found between the identified microbial population and changes in the main chemical quality parameters along the treatment unit.
In conclusion, the present study contributed to the understanding of relationships between processes occurring in unsaturated flow biofilters treating greywater and operational parameters and chemical quality, and the microbial communities. These relationships allows to design better greywater treatment systems.