Water quality chemical oxygen demand determination method

Abstract

The invention belongs to the technical field of environment monitoring, particularly to a water quality chemical oxygen demand determination method which comprises the following steps: determining a dilution ratio f value; acidifying the water sample with 98% sulfuric acid; putting an acidified water sample into a digestion tube, sequentially adding a potassium dichromate standard solution, a mercury sulfate solution and a silver sulfate-sulfuric acid solution, and uniformly shaking; putting the digestion tube into a heater at 165 + / -2 DEG C for heating and digestion; completely transferring the solution in the digestion tube into a conical flask, taking ferroin as an indicator solution, and titrating with an ammonium ferrous sulfate standard solution until the color of the solution is brown; performing a blank test according to the same steps; and calculating a chemical oxygen demand (COD) result. The method disclosed by the invention is simple and easy to master in operation process, short in sample pretreatment time, capable of realizing batch treatment, small in amount of generated waste liquid, energy-saving and environment-friendly.

Description

technical field [0001] The invention belongs to the technical field of environmental monitoring. Specifically, it relates to a method for determining the chemical oxygen demand of water quality. Background technique [0002] Chemical oxygen demand, also known as chemical oxygen demand (Chemical Oxygen Demand, COD), is an important parameter in wastewater testing and an index to measure the content of organic matter in water. The greater the chemical oxygen demand, the more polluted the water body is by organic matter. serious. The so-called chemical oxygen demand refers to the mass concentration of oxygen corresponding to the strong oxidant consumed by the dissolved substances and suspended solids in the water sample when treated with a certain strong oxidant under certain conditions, expressed in mg / L of oxygen , is also an indicator of the amount of reducing substances in water. Reducing substances in water include various organic matter, nitrite, sulfide, ferrous salt,...

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Problems solved by technology

The potassium permanganate index method uses potassium permanganate as an oxidant to measure the COD value, and the measured value is the potassium permanganate index, but these two methods have their own shortcomings. The dichromate method has a long oxidation time and needs to be carried out. 2.5h, the space occupied by the backflow device is large, the water and electricity consumption is large, the operation is inconvenient, and it is difficult to quickly measure in large quantities

However, the potassium permanganate index method has the following problems: the oxidation ability is weak, and it can only reflect 20-30% of the chemical oxygen demand in the water body; the manganese ion has secondary pollution to the environment during the reflection process; the reagent consumption is large, and it needs 120ml at a time

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