When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.
Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.
The conventional wastewater treatment processes in cold–climate regions are not adequately effective; they experience moderate seasonal removal of pollutants, if any, since biological and chemical treatment processes are severely affected by low temperatures. Biomass responsible for the transformation of nitrogen species are usually washed-out as a result of low-temperature impacts. Chemical processes during low temperatures increase dosage of coagulants, leading ultimately to substantial increase of operational costs. To overcome these problems, a membrane electro–bioreactor (MEBR) was coupled with an anaerobic ammonium oxidation (anammox) process in this research to improve treatment facilities in cold weather. Main objective of this study is investigating and designing of a MEBR/anammox considering variety of temperatures. To achieve research objective, 3 research phases were proposed, which included an optimization of operation electrical and biological processes. Furthermore, characterization of microbial community structure and bio-stimulation were investigated in temperatures between 22 and 8 oC.
First phase of study has already revealed that application of DC field to a series of batch tests permitted to define relationships between different current density, temperature variation and microbial growth, phosphorus removal as well as sludge quality. Tests in phase II considered a design of anammox side-stream device enhanced with the submerged electrodes and DC power supply, where rapid anammox biomass enrichment with adequate ammonium removal was achieved. Generated outcomes have been replied to continuous flow MEBR/anammox in order to achieve carbon and nutrient removal at a superior level independently on temperature.
The addition of a low direct current (DC) and anammox process inside the MBR in the third phase study, realizing an anammox membrane electro-bioreactor (MEBR/anammox), increases the effectiveness of the treatment system, improves sludge characteristics and reduces membrane fouling at low-temperature environments compared to conventional treatment systems. At lower operating temperatures, the removal efficiencies of ammonium, total nitrogen, phosphorus and COD in the MEBR-anammox were 94.46%, 88.62%, 95.60% and 90.76%, respectively. The new MEBR/anammox system showed superiority over conventional MBR in respect to membrane fouling, sludge filterability and settleability by 45.12%, 14.36% and 19.67%, respectively. At lower temperatures, the sludge volume index (SVI) had reduced from 362 to 117 mL/g, while time-to-filter (TTF) had decreased from 18.2 to 7.3 min. MEBR/anammox system substantially enhanced sludge flocculation, where zeta potential changed from -32 to -12.7 mV. This high performance of the MEBR/anammox system was attributed to the synergistic effects between biological, electrochemical and membrane filtration processes, where COD removed through biomass oxidation and flocculation, while phosphorous removed by electrocoagulation process and phosphorus accumulating organisms (PAOs) growth. TN removal was mainly due to the growth of all diverse types of nitrogen-removing bacteria, where novel MEBR/anammox system allowed to the development of simultaneous nitrification, anammox and denitrification (SNAD) processes in the same reactor. The MEBR/anammox system showed the potential to greatly reduce capital and operating costs, while energy requirements were less than 0.83 kWh/m3 with a total energy cost of CAD $0.042/m3.