Can Induced Magnetic Field Enhance Bioprocesses? - Review

Augustine Chioma Affam, Wong Chee Chung, Wong Chee Swee, M. Raza Ul Mustafa, I. Bin Othman, M. Latheef, D. Bayu Endrayana, N. Zulaikha Bt Yusof
2018 MATEC Web of Conferences  
This review presents a compilation of works with particular interest in the application of static magnetic field (SMF) to biological systems, wastewater treatment and few available reports on microbial granulation technology. It also highlights the effects of SMF on biological systems and wastewater treatment process. With an increasing need for environmentally conscious solutions to water purification and disinfection, wastewater treatment, bioremediation and other cheap alternative means, the
more » ... ernative means, the application of SMF in biological water and wastewater treatment without increase in chemicals required may become an attractive option. Application of SMF has been reported to be successful in a number of fields including treatment of wastewater. However, there are sparse reports on SMF application in the formation and development of microbial granule and production of extracellular polymeric substances (EPS). Achieving a short start-up time in a bioreactor towards the development of microbial granule is of paramount importance in granulation technology. Ascertaining how effective varying strength of SMF and other input variables may enhance the microbial granule with respect to its physical, chemical and biological characteristics requires further research. The performance of UASB reactors in terms of removal of organic matter from municipal and/or industrial wastewater has been reported [5] . Aerobic microbial granulation has been reported as well. They are known to develop faster and effectively under desirable conditions [6] . Aerobic granulation could be carried out mainly in sequencing batch reactors (SBRs) [7] . It has been used for the treatment of low to high strength wastewater containing organics, phosphorus, nitrogen, and toxic substances contained in wastewater [8] [9] . Granulation technology is known to be one of the most promising treatment processes. The success of microbial granulation in the treatment of wastewater has been reported [10] [11] . Well documented review on trends in aerobic and anaerobic granulation [5, [12] [13] and the physicochemical characteristics of microbial granule [14] have been also reported. In order to aggregate bacteria and subsequently develop granules, some vital conditions would be required to be fulfilled [10] . Attempts to reduce the start-up time has led to an increase in the volumetric loading rate of the reactor [15], applying sludge washout strategy [16] , trying suitable inoculation sludge and a variety of bioreactors [17] . Also, the nature of substrate composition, hydrodynamic shear force, hydraulic retention time, settling time, aerobic starvation, presence of calcium and other ions, intermittent feeding strategy, dissolved oxygen, pH, temperature, seed sludge selection, reactor configuration, presence of inhibitory compounds, amongst others are factors that could affect the time needed for the biogranule development. Aside these strategies a likely promising alternative is the application of static magnetic field (SMF) to biological wastewater treatment so as to accelerate the biological activity. This is possible by exposing the bioreactor to a created magnetic field during the treatment process. All organisms are generally said to possess internal magnetism. The magnetic field inside organisms known as magnetic biologic effect can bring about metabolism of the living organism [18] . The magnetic biologic effect has been applied in wastewater treatment and its effect on microorganism has been reported [18] [19] [20] [21] . The biologic effect in organisms has a relationship with the biomass metabolism, cell membrane permeability and enzyme activity, etc. Although the physiology of magnetic biologic effect on the microorganisms is not completely understood, some investigations have indicated that additional magnetic field is a promising approach in the enhancement of biological activity. Some factors have been identified to stimulate bacteria to secrete more EPS such as organic loading, hydrodynamic shear force, substrate composition, hydraulic retention time, substrate composition and settling time amongst others have been demonstrated to stimulate bacteria to secrete more EPS. [22] [23] . This is similar to factors which could reduce bioreactor start-up time as mentioned before. There may be need to further elucidate on the effect of SMF on the granulation process. However, one study observed that SMF could improve granule development and also enhance the EPS production [24] . The operating conditions of a reactor such as organic loading rate, solids and hydraulic retention times, etc., and probably the wastewater composition can affect the eventual granular anaerobic or aerobic sludge characteristics. To achieve a stable operation of the reactor, appropriate design of the reactor based on the expected granular sludge characteristics would be required to be done. In addition, it is important to highlight the bioaggregation process and the development of the microbial granule. More so, it is important to mention reported external effects such as the magnetic field presence and its potential magnetic field intensity range (milli Tesla (mT) to Tesla (T)) in biological systems. On another hand, whether it is an anaerobic or aerobic process, some drawbacks exist. The slow growth of microorganisms in the anaerobic process is the major drawback in the operation of the anaerobic granular reactor as the start-up time of the reactor is pretty much longer, but it is followed by a later rapid development of anaerobic granules [25] . In the case of aerobic granular sludge reactors, the limiting factors for scale up of the process includes effluent high suspended solids (SS) and relatively high cost associated with
doi:10.1051/matecconf/201820303007 fatcat:ch2ehspcbvf2vgffkqbvtguo4u