Method of measuring chemical oxygen demand (cod) in seawater

A method of measuring chemical oxygen demand (COD) in seawater, comprising:

• dialyzing the seawater comprising chloride ions and at least one organic compound with an electrodialysis unit to form a processed seawater having at least 25% less chloride ions than the seawater;
• mixing the processed seawater with an oxidizing agent to oxidize the at least one organic compound and heating to 100-200° C. for 1-5 hours to form a digested solution;
• cooling the digested solution and adding an indicator to form a titration solution;
• performing a colorimetric titration on the titration solution with a reducing agent so as to reduce any excess of the oxidizing agent and reach an equivalence point based on the indicator;
• and
• calculating the COD in the seawater based on an amount of reducing agent used in the colorimetric titration,
• wherein the digested solution and titration solution do not comprise a chloride masking agent,
• wherein the electrodialysis unit, comprises in order:
• an anode compartment;
• a first cationic membrane;
• a first buffer compartment;
• a first anionic membrane;
• a dialyzer compartment;
• a second cationic membrane;
• a second buffer compartment;
• a second anionic membrane;
• and
• a cathode compartment;
• wherein adjacent compartments are configured to allow passing of ions between compartments through anionic or cationic membranes,
• wherein the anode compartment and the cathode compartment are connected to a power supply,
• wherein the power supply provides a direct current voltage of 5-30 volts (V), and
• wherein the dialyzing comprises:
• pumping the seawater through the dialyzer compartment;
• pumping a buffer solution through the first buffer compartment and the second buffer compartment;
• and
• pumping an electrolytic solution through the anode compartment and the cathode compartment,
• wherein the pumping the seawater, the buffer solution, and the electrolytic solution are at a same or different flow rate between 1-10 milliliters per minute (mL/min), and
• wherein the electrolytic solution comprises sodium sulfate and sulfuric acid each having a concentration of 0.01 to 1 molar (M).