Production And Release Of Microcystin-LR In Chemical Treatment Of Microcystis Aeruginosa

Blooms of toxic blue-green algae outbreak not only poses a serious harm to the ecosystem,but also brings a serious threat to human health.Chemical algaecide is a kind of effective and fast algal-killing technology.However,the production and release of algal toxin poses a huge threat to water safety as well as the ecosystem.Therefore,it is essential to study the effects of algaecide on water safety and algal toxin production and release.High performance liquid chromatography(HPLC)for determining algal toxins concentration have been optimized,by testing the condition of microcystin-LR(MC-LR)extraction.The typical algaecide of copper sulfate was used in this study.The experimental results indicated that copper sulfate had a good performance on algal inhibition and killing,due to its serious destructiveness on algal cells integrity.Copper sulfate can cause a release of intracellular material,since the TOC in filtrate increase from 26mg·L-1 to 48 mg·L-1 after the use of the algaecide.Also,algal toxins and algal cell metabolism were of close relationship in growth and cell division.Therefore,to kill algal efficiently while controlling the release of algal toxin,the ideal dose of copper sulfate was 1.5 mg·L-1.Also,dosing should process in the early stage of algae outbreak.The most significant effect of copper sulfate arised after 1-2 days of dosing.However,modulation of pH(8-11)or light intensity(250-2000 lux)showed little improvement in algal inhibition and killing.It is figured out that algaecides show various performances in algal inhibition and killing.From the view of algal killing effect,aluminum silicate agent >microbial agent >copper sulfate>pyrogallic acid.Meanwhile,to simply considering their less impact on the release of MC-LR,aluminum silicate agent >copper sulfate>microbial agent > pyrogallic acid.Furthermore,studies on the transport of MC-LR in river showed that ultraviolet in natural light had a significant effect on MC-LR degradation.And the degradation effect was enhanced with an increase of lightning duration.Removal rate could reach 22% under 254 nm UV irradiation for 8 hours.Aeration has little effects on the degradation of MC-LR.Removal rate only reached 6% under aeration for 10 hours.Sediment could absorb MC-LR,but demonstrating an unsteady performance,the removal rate was between 13% and 30%.