Experimental Study. Flocculation Treatment Of Ships' Ballast Water Algae

The introduction of invasive marine species into new environments has been identified as one of the Four Greatest Threats to the world's ocean and its main spread source is the ballast water. But MEPC and GloBallast think that there are not efficient shipboard treatment options till now. As part of the Project "Study on the Killing of Microorganisms in Ballast Water with Flocculation Coordinated other Technique Method", this dissertation, taking the world's status of treating the invasive marine species of ballast water into account, utilizes the flocculation method. By organic modification to clay mineral, its molecular layer construction is modifed, as well as absorbing and extinguishing capability changed, and all these provide an ideal new approach to managing invasion spread of non-indigenous biology.Three representative oceanic harmful algae are chosen to analyze in this dissertation. Through experiments, we discover that the eliminating efficiency of organic soil with HDTMA as modification reagent is 93.6%, far more than that of original soil-24.7% and organic soil with TMAB (Tetra-n-methylammonium Bromide) as modification reagent-71.6%. This is mainly because: First, the charges on the modified clay particles surface are positive and their static gravitation and flocculability are strengthened. Second, Quaternary Ammonium Compounds (QAC) absorbed on the clay surface still can extinguish the algae flocculated and decrease their mobility. Now, eliminating harmful algae by natural minerals as flocculants is considered one of the most bright future methods. To disadvantages of low efficiency and high dosage with clay minerals, the dissertation discuss the modified clay as flocculant in the study of harmful algae control in the ballast water. The result indicates that HDTMA modified clay is a high efficiency extinguishing material to harmful algae and has no obvious harm to breed aquatics. Experimental result indicates that flocculating, absorbing and extinguishing the harmful algae in ballast water is an effective, feasible, safe and non-pollutive innovative approach to control harmful algae in ship ballast water.