Combination Of Allelopathic Modifier Modified River Sand Fall Effect Research

In recent years, with the development of urbanization, agriculture, industry andeconomy, eutrophication is becoming more frequent and serious, which imposed greatimpact on our life and health and aroused wide public concern. Eutrophication couldresult in the excessive growth of algae, and then lead to algal blooms which wouldfurther pollute the water. Therefore, doing more researches on settling algae isimportant and has great application potential.Cyanobacteria is the mainly kind of algae during algae blooms, so this studyselected Microcystic Aeruginosa,which was in logarithmic phase, as research object.Using riversand form Three Gorges Reservoir as carrier, the effects of settling algaewith different combined allelochemical modifiers were studied. Five allelochemicals(p-hydroxybenzoic acid, linoleic acid, anthraquinone, catechol and gallic acid) and twomodifiers (polyacrylamide and chitosan) were used in this study, and the combinationof different allelochemical and modifier could produce different allelochemicalmodifier. By studying the influencing factor in the modifying process and settlingalgae effects with different allelochemical modifiers, the best operating condition, theratio of the modifier and allelochemicals, feeding time and feeding pattern weredetermined.The results show that:(1) all of the five allelochemicals could allelopathicallyinhibited the Microcystic Aeruginosa to some degrees, and p-hydroxybenzoic acid hadthe strongest allelopathic inhibition ability. After careful analysis, the following reasonmay explain the p-hydroxybenzoic acid’ strong allelopathic inhibition ability:p-hydroxybenzoic acid could increase the number of oxygen free radical on algal cells’surfaces, and then the oxidation of oxygen free radical would damage algal cells.(2)The effects of settling algae using riversand modified by allelochemical modifiermade from the combination of polyacrylamide acid and allelochemicals were poor, andthe settling efficiency of algae was only20%. Hence, polyacrylamide was not asuitable modifier in this study.(3)Riversand modified by allelochemical modifier madefrom the combination of chitosan and allelochemicals (RMCA)could settle algaeeffectively, and the best ratio for allelochemical modifier is that:0.05g chitosan,5mlhydrochloric acid (1%),0.06g p-hydroxybenzoic acid and1g riversand pretreated byhydrogen peroxide; When the RMCA was feed into the solution of algae in suspendedstate, after shaking, the settling efficiency of algae was100%;the dosage of suspended RMCA for treating100ml solution of algae was1ml;When the algae was inlogarithmic phase and stationary phase, adding suspended RMCA into the solution ofalgae could achieve95%and settling efficiency, respectively.In RMCA the allelochemicals and riversand were wrapped by chitosan, and thenthe flocculation of chitosan would integrate the algae and riversand. Due to the gravityof riversand, this flocculating constituent would settle to the bottom. As time passed,chitosan would hydrolyze to monosaccharides, and then the allelochemicals couldinhibit the growth of algae cells and prevent the happening of new algae blooms.In summary, RMCA was a good algaecide technology and all of the usingmaterials in this technology were natural and would not new pollution. Therefore,RMCA had a good prospect of application.