Effect of a ballast water treatment system on survivorship of natural plankton community collected from the Jangmok bay

Abstract

This study investigated the survivorship of natural plankton population in order to explore the biological efficacy of electrochemical reactor for approval of ballast water management systems. The biological efficacy test was carried out using the types of round and rectangular. Following the treatment of electrochemical reactor, the survivorship of planktonic zooplankton was assessed immediately through direct observations, while phytoplankton and bacteria survivorship were assessed by immediate observations through green filter and through 48h incubations. Under the condition of 75 ampere (NaOcl: 10 ppm) of round and rectangular types, dominant phytoplankton, Skeletonema costatum, Ceratium fusus, Thalassionema nitzschioides, turned from red into green after they passed the reactor, indicating no live chlorophyll-a remained. And no live E. coli and coliform bacteria were remained after being passed through the reactor. With respect to zooplankton, live copepods were not observed in the post-reactor samples. The remove efficiency of phytoplankton and copepods was up to 100% by using the electrochemical reactor. In contrast, cirripedia larvae showed the efficacy less than 10%, suggesting that 10ppm NaOCl was not effective concentration to the cirripedia larvae. However, this showed the instantaneous value, thus it will increased if the larvae is exposed continuously to the NaOCl in the tank during the extended period of cruise.