Evaluating Water Purification Capacity of Patinopecten yessoensis Shells Inoculated with Effective Microorganisms

Abstract

In Japan, the installation of biotopes, defined as aquatic systems aiming to recreate a natural environment, has been popular since the 20^th century. Due to the closed character of many biotopes and high nutrient inputs, one of the main issues related to water quality in a biotope is the occurrence of blue-green algae. In this environment, reduction and control of the blue-green algae cannot be done by chemicals. Water quality must be maintained by other non-chemical means. Therefore, this study aims to investigate the effectiveness of patinopecten yessoensis shells inoculated with effective microorganisms as a method for nutrient and water quality control in a biotope environment. In Japan, huge numbers of patinopecten yessoensis shells are left out in the open because they cannot be properly handled. At the same time, patinopecten yessoensis shells are porous and have been studied for water purification. Accordingly, this research has focused on the water purification capacity of patinopecten yessoensis shells inoculated with effective microorganisms. In the study experiment, patinopecten yessoensis shells inoculated with lactobacillus, bacillus subtilis var. natto, and saccharomyces cerevisiae were used to purify water samples taken from a pond in Yatoyama Park in Kanagawa Prefecture, Japan. To compare nitrogen removal capacity, the experiments consisted of 8 treatments in total. In the first group of four treatments, patinopecten yessoensis shells were burned at 600 degrees to increase pore size and distribution, and were then inoculated with the aforementioned microorganisms. In the second group of four treatments, patinopecten yessoensis shells were not burned, and were only inoculated with the microorganisms. Uninoculated burned and unburned shells were used as control treatments. The experimental results showed total nitrogen removal rates of 42% for unburned and uninoculated shells, 0% for lactobacillus-inoculated unburned shells, 45% for bacillus subtilis var. natto-inoculated unburned shells, and 58% for saccharomyces cerevisiae-inoculated unburned shells. Regarding the burned shells, results showed 51% nitrogen reduction at the uninoculated shells treatment. Lactobacillus-inoculated burned shells reduced nitrogen by 47%, bacillus subtilis var. natto-inoculated burned shells reduced by 34% and saccharomyces cerevisiae-inoculated burned shells reduced the nitrogen in the water sample by 69%. Since this was a short-term experiment, a long-term experiment as well as field-applicable methods need to be discussed in the future.