Device and method for reducing the hydrogen peroxide and peracetic acid content in a water flow

Abstract

A device comprising a measuring device for determining the flow rate of a water stream, a measuring device for determining the concentration of hydrogen peroxide in the water stream, a measuring device for determining the concentration of peracetic acid in the water stream, a metering device for metering a reducing agent into the water stream downstream of the measuring devices for the concentrations, and a control device which, from the flow rate of the water stream, the concentration of hydrogen peroxide in the water stream and the concentration of peracetic acid in the water stream, calculates an amount of reducing agent for reducing the content of hydrogen peroxide and peracetic acid to a desired value and actuates the metering device for metering the reducing agent, makes possible reliable reduction of the content of hydrogen peroxide and peracetic acid in a water stream. The device is suitable for reducing the content of hydrogen peroxide and peracetic acid in a water stream which is withdrawn from ballast water tanks of a ship.

1 - 10 . (canceled) 
     
     
         11 . A device for reducing the content of hydrogen peroxide and peracetic acid in a water stream, comprising:
 a) a first measuring device for determining the flow rate of said water stream;   b) a second measuring device for determining the concentration of hydrogen peroxide in said water stream;   c) a third measuring device for determining the concentration of peracetic acid in said water stream;   d) an additional measuring device for determining the salinity in said water stream;   e) a metering device for metering a reducing agent into said water stream downstream of the second and third measuring devices; and   f) a control device which, from the flow rate of said water stream, the concentration of hydrogen peroxide in said water stream, the concentration of peracetic acid in said water stream and the salinity, calculates an amount of reducing agent for reducing the content of hydrogen peroxide and peracetic acid to a desired value and actuates the metering device for metering the reducing agent.   
     
     
         12 . The device of  claim 11 , wherein the measuring device for determining the concentration of hydrogen peroxide in said water stream comprises an amperometric sensor. 
     
     
         13 . The device of  claim 11 , wherein the measuring device for determining the concentration of peracetic acid in said water stream comprises an amperometric sensor. 
     
     
         14 . The device of  claim 11 , wherein the measuring device for determining the salinity comprises a conductivity sensor. 
     
     
         15 . The device of  claim 11 , wherein the metering device for metering a reducing agent comprises a storage vessel and a controllable metering pump for liquid reducing agent. 
     
     
         16 . The device of  claim 11 , wherein the second and third measuring devices are arranged in a side stream of said water stream. 
     
     
         17 . A method for reducing the content of hydrogen peroxide and peracetic acid in a water stream, comprising metering a liquid reducing agent into the water stream using the device of  claim 11 . 
     
     
         18 . The method of  claim 17 , wherein said water stream is withdrawn from ballast water tanks of a ship. 
     
     
         19 . The method of  claim 17 , wherein the liquid reducing agent is an aqueous solution of sodium sulphite.