Study On The Effects Of Low-intensity Steady Magnetic Field On Wastewater Treatment With Biofilm Reactor

The processes of low organic degradation load need a large occupancy area and high investment on infrastructure due to the slow biodegradation rate in biological wastewater treatment.Therefor it is significant theoretically and valuable in practical application to research the enhancing microbial activity by adopting biological method. Two biofilm reactors were designed according to the biological effects of magnetic field, the magnetic bio-reactor which was assembled with a set of solenoid coil applied to dispose simulated domestic wastewater for the comparative study.A solenoid was designed that can generate a steady magnetic field, its heating value can be controlled and magnetic induction ranged from OGs to 400Gs. Natural pumice can be applied as biocarriers, the start-up and film formation properties of the reactor was studied under the action of magnetic field.The results indicated that inoculation sludge with high activity and high external temperature beneficial to the biofilm culturing in a smaller reactor, especially under the action of 50Gs magnetic field, but there had little difference on organic removal effect of two biofilm reactors. The effects of different magnetic field on wastewater treatment with biofilm reactor were studied after the success in the biofilm culturing, the research results showed that,the microbial growth was inhibited and the organic removal effect was reduced under the action of 100Gs magnetic field; the organic removal effect can be improved under the action of 200Gs,260Gs or 320Gs magnetic field, and the increased range of organic removal rate was largest and the cycle of biofilm which reached steady-state operation was shortest (26d) under the action of 260Gs magnetic field.Then the characteristic of biofilm were studied, which were extracted from two continuous operation reactors.â‘ Comparing the weight of the desquamated biofilm as well as mensurating the viable counts,oxygen consumption rate(OUR and SOUR) and extracellular polymeric, the results showed that the variation of biomass presented a characteristic curve of "V" shape and the variation of biofilm activity was reverse with increasing of magnetic induction intensity, and the extremum appeared on the condition of 260Gs.â‘¡Observing the magnetic field effect on biological phase of biofilm by optical microscope and electron microscope, the results showed that the biofilm was dense as well as even density by SEM under the action of 260Gs magnetic field. The composition of microorganism population was diverse. With increasing magnetic induction intensity, it formed dominant microorganism population of different metabolic types, triggered fluctuations of microorganism population of high trophic level in the food chain, and led to a succession of alternate dominant species.â‘¢A 230bp DNA fragment was amplified from all samples by optimized PCR reaction system and program,the signal of sample with magnetic was stronger than non-magnetic one in the third period. The results of DGGE showed the similar patterns in eight samples, but there were certain differences in structure of microbial community between two biofilm reactors.The results showed there had certain strengthening effect on microbial activity under the action of 200Gs,260Gs or 320Gs magnetic field, and the 260Gs had the greatest effect.