Development Of Multi-parameter Tunable High Voltage Pulser And Algae Removal Experiments

Circulating cooling water system is the essential equipment for heat transfer oflarge-scale installations in industrial production. Due to good conditions for microbialbreeding in circulating cooling water system, bacteria and algae breed rapidly. Thecombination of microbial metabolites and impurities in water causes lots of biologicalslime and corrosion in the circulating cooling water system, which results in decline ofheat transfer efficiency. So bacteria sterilization and algae removal are both important toensure the long-term and normal operation of circulating cooling water equipment. Atpresent, the electromagnetic pulses’ killing objectives are mostly microorganisms suchas Escherichia coli and other bacteria, other microorganisms especially the algae arescarcely reported so that it is lack of experimental data.This paper presents a power supply topology based on Marx pulse generatorand bridge type solid state modulator. Circuit design and parameters calculation for theMarx generator, full bridge solid-state modulator, the control circuit are completed.Then, devices’ selection and hardware circuits’ match, assemble and adjust are donesuccessfully. Finally, a multi-parameter tunable pulse source is developed withfollowing parameters: output voltage is pulse wave with variable polarity, number ofpulse per second is from1to1000pps, peak voltage scope is0~6kV, pulse width scopeis1~5us, the instantneous maximum output current is12A.After carefully selecting test sample of algae, we used orthogonal experimentalmethod to design the algae removal experiments. Meanwhile, detection equipments andrelated materials were prepared. Both algae liquid and parameters of pulsed electricfield during treatment were monitored continuously for several days in culture chambers,the absorbance value after treatment liquid of algae, algae cell density, biomass as themain parameters were concerned. According to the obtained data, we analysed theeffectiveness of suppressing the algae along with weight variable parameters of theelectric field. Combining the corresponding changes over time in algae growthcondition after the treatment, further study focused on the mechanism of electric pulses’inhibiting the growth of algae. According to the experiment data, they show pulsedelectric field’s significant inhibitory effect on the growth of algae,. For example, afterthe electric field treatment, reduction rate of cell density of two experimentalmicroalgae, namly, Chlorella pyrenoidosa and Microcystis algae, is up to94%and86% respectively. Even if volume and shape are similar to each other, their tolerances topulsed electric field treatment are not exactly the same. Comparison between the meanvariance analysis and the processing parameters on the results of the different levels ofalgae removal rate were made and attained the results that electric field intensity is oneof the most important factors for inhibiting microalgae’s growth among four parameterssuch as electric field intensity, duration, frequency and treatment period. Increasingelectric field intensity can significantly enhance the inhibition effect on the growth ofalgae. Finally, the most optimum processing parameters were selected according to theorthogonal experimental method.