Study On The Removal Of Brown Tide

Brown tide is a type of harmful algal bloom caused by picoplanktonic algae. Ithas occured continuously since2009and caused significant economic losses in theBohai Sea. Controlling and reducing detrimental environmental and economic lossesin affected ecosystems become an urgent problem in situations where accurateprevention and pre-control systems are not available. Mitigation of HABs by clays isan important and widely used control method. A variety of original clays&modifiedclays were tested on the brown tide species-Aureococcus anophagefferens and fivetypical clays were chosen as the main experimental material. A series of experimentsthat employed original and modified clays to remove Aureococcus anophagefferenswere tested. The results showed that removal efficiency of Aureococcus blooms maybe limited due to their small size and cellular density. The removal efficiency variedwith the type of clay and kaolinite indicated better removal ability as compared tomontmorillonite. After modification by inorganic method, all types of clays showedsignificant improvement with more than three folds in removal rates. Additionally,application procedures that increase the concentration of original and modified clays,select the appropriate clay particle size and use fresh water as dispersion mediumwould achieve higher cell removal efficiency. Through a lot of experiments, we foundthat the dispersion medium （eg: deionized water or seawater） of the modified clay had a big effect on removal efficiency. When modified clay dispersed in seawater itshowed lower removal efficiency and was unfavorable for the field test. In this case,the impact of dispersion medium on the algae removal efficiency remained furtherresearch and the result showed that the0.01mol/L of SO₄^2-and CO₃^2-could decreasethe removal efficiency significantly.Combining the previous result with the development and application of theflocculation theory, the improved method adding trace amount of organic polymer-polyacrylamide（PAM） in inorganic modified clays was proposed. Through theexploration and research, we produced a new kind of efficient, environment friendlyand compound modified clay to removal Aureococcus anophagefferens. The impact ofdosage of compound modified clay, preparation conditions and the dispersion mediumwere studied. The result showed that the new modified clay with PAM had20%higher removal efficiency compared to the inorganic modified clay. The componentdosages, preparation conditions and the dispersion medium can affect the algaeremoval efficiency. Preliminary studies indicated a very promising result that theremoval efficiency can be improved significantly by adding trace amount of H⁺to thenew modified clay. Overall, our study initiated a new approach to explore moreefficient, environmentally removal materials and technologies that can be used asemergency control strategies for brown tide in coastal waters.