Studies on the Water Purification in the Coastal Areas of Inner Bay Using Nitrifying and Denitrifying Bacteria in the Tidal Bottom-Mud

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The purposes of the present research are to clarify the relationships between the biological activity of nitrifying and denitrifying bacteria and various environmental factors in the tidal bottom-mud, and to use the nitrification and denitrification processes maintained by the metabolism of these bacteria in order to purify water of the coastal areas in the inner bay. The conclusions obtained by the present research during three years from 2001 to 2002 are summari zed as follows :(1)A kind of nitrifying bacteria and two kinds of denitrifying bacteria with high biological activity were selected and isolated from the tidal bottom -mud i n the Ariake Sea. Moreover, the properties of these bacteria were clarified.(2)The relationships between the nitrification and denitrification rates in the tidal bottom -mud and control factors such as substrate concentr ation, temperature, pH, reduction potential were clarified. A Mechaelis -Menten equation was valid for the relation between nitrification and denitrification rates, substrate concentration and temperature. This equation indicated the optimum temperature for nitrification and denitrification rates and these Timit values.(3)A method for removal of inorganic nitrogen compounds i n the waste water using the tidal bottom-mud. where many nitrifying and denitrifing bacteria with high biological activity lived was proposed. Moreover, a trial device for its removal based on this method was made.(4)The relationships between N-removal rates of this trial device and NH_4^+ concentration, temperature, flow, mud-content, pH and number of nitrifying and denitrifying bacteria were commanded experimentally.(5)The utility of the removal device was verified and the extent power of water purification of the tidal bottom -mud in the Ariake Sea was confirmed. On the other hand, the issues for the practical use of the removal device were also found.