Effects Of Electrohydraulic Technology On The Inhibition Of Algae Blooms By Treating Dormant Algae

The excessive input of nutrients in lakes and reservoirs has accelerated the eutrophication of water bodies and promoted the outbreak of cyanobacteria blooms because of the frequent increase of human activities in recent years.Cyanobacteria blooms and their by-products seriously affect water the survival of vivid plants and human health.So far,many scholars at home and abroad have carried out researchs on the control of cyanobacteria blooms,but most of the control measures are limited to cyanobacteria in the water body,ignoring the dormant cyanobacteria in the surface layer of the sediment,so they are only suitable for emergency.The liquid-phase high-voltage pulse discharge technology(referred to as electrohydraulic technology,ET)has the characteristics of energy saving and environmental protection,which can produce a series of physical,chemical,and mechanical effects,and can act on sludge and broken rocks.Therefore,we optimize the processing parameters of ET under experimental conditions,and exploreed the feasibility of using ET to inhibit the resuscitation of dormant algal in the surface layer of sediment,then we evaluated the effect of ET on aquatic organisms in the process,and analyzed the effect of ET on algae removal and algae suppression and water quality improvement by treating dormant body of wild algae in Taihu Lake based on the optimization of the best processing parameters in the laboratory.The results obtained are as follows:(1)We constructed a high-voltage pulse discharge device in liquid independently,and investigated the effects of working voltage(8 k V,10 k V,12 k V,14 k V),working depth(3cm,6cm,9cm,12cm)and working time(3min?6min?9min?12min)on the algae-removing and algae-reducing effects of overwintering dormant algae on the surface of simulated sediment under the conditions of laboratory research.The results show that under the optimal conditions of operating voltage of 14 k V,action depth of 6cm,and an action time of 12 min,the removal rate of dormant algal in the surface layer of the sediment was 81.60%,and the inhibition rate of Microcystis aeruginosa reached 95.51% after 49 days of recovery,and the algal toxin was not detected.It can be considered that when Microcystis aeruginosa is in the wintering stage,the use of ET can effectively remove the wintering dormant algal in the surface layer of the sediment,and inhibit its recovery.(2)Taking some aquatic organisms as research objects,the effects of ET on aquatic organisms in the process of treating wintering dormant algal in the surface layer of sediment were preliminarily discussed.The results show that the inhibiton rate of Microcystis aeruginosa was 99.29% after 14 days of treatment at an operating voltage of 14 k V for 5 min,and the chlorella was almost unchanged.Meanwhile,there were no obvious abnormalities in the surface and morphology of the three aquatic organisms including koi fish,freshwater monoporous earthworm and Chinese round snail.Moreover,the MDA and SOD levels of the groups were basically the same on the 7th day after treatment when the electrode was treated with an operating voltage of 14 k V for 12 min at a distance of 6 cm from the surface of the sediment,These results show that the ET has not caused serious harm to aquatic organisms in the process of wintering dormant algal under our experimental conditions.(3)The wild dormant algal and in-situ lake water in the surface sediments of Meiliang Bay in Taihu Lake in winter were taken and treated with ET to analyze its algae-removing effect and water quality improvement of the wild dormant algal.The results showed that the inhibition rate of Taihu Lake's wild algae treated by the ET reached 93.47%,and the degradation of TN,TP,and COD in the treatment group was significantly lower than that in the control group.Our findings show that the ET can not only inhibit or prevent the outbreak of algae blooms,but also effectively improve water quality.