Online BOD analyzer in stock The main measurement methods include: five-day cultivation method (GB7488-87), pressure sensor method, reduced pressure Coulomb method, microbial electrode method (HJ/T86-2002), etc.The general total biochemical oxygen demand is recorded as BODu, but the widely used 20 ℃ five-day cultivation method (BOD5 method) at home and abroad to determine BOD values generally does not include the nitrification stage. The BOD5 of domestic sewage is about 70% of BODu, and the difference between the two is significant in industrial wastewater.

BOD is a comprehensive indicator that reflects the degree of organic pollution in water bodies. It is also an important parameter for studying the biodegradability and biochemical treatment efficiency of wastewater, as well as for designing and studying the kinetics of biochemical wastewater treatment processes.

Online BOD analyzer in stockFive day cultivation method

Also known as standard dilution method or dilution inoculation method. The measurement principle is that the water sample is diluted and then20±1℃Cultivation under conditions5Tian, calculate the dissolved oxygen content in the water sample before and after cultivation, and the difference between the two isBOD₅A relatively clean water sample (with a five-day biochemical oxygen demand not exceeding)7mg/L）No need for dilution, can be directly measured.

Most water bodies, especially wastewater samples, are generally diluted using the dilution ratio method. In addition, for industrial wastewater with little or no microorganisms, such as acidic wastewater, alkaline wastewater, high-temperature wastewater, or wastewater treated with chlorination, the dilution ratio method is used for determinationBOD₅Vaccination should be carried out to introduce microorganisms capable of degrading organic matter in wastewater. When there are organic compounds or substances in the wastewater that are difficult to degrade at a normal rate by microorganisms in general domestic sewage, domesticated microorganisms should be introduced into the water sample for inoculation.

Biosensor method

This method is an analysis method that combines microbial technology with electrochemical technology. Microbial sensors are composed of oxygen electrodes and microbial membranes. The principle is that when the sensing electrode is inserted into a bottom liquid with a constant temperature and saturated dissolved oxygen, due to the constant respiratory activity of microorganisms, the rate at which dissolved oxygen molecules in the bottom liquid diffuse into the oxygen electrode through the microbial membrane will also remain constant. At this time, the microbial electrode outputs a steady-state current; If the bottom liquid contains certain organic substances, organic matter molecules will diffuse into the microbial membrane together with oxygen molecules. Due to the assimilation of organic matter by microorganisms in the membrane, a certain amount of oxygen is consumed, resulting in a decrease in the number of oxygen molecules diffusing onto the surface of the oxygen electrode, that is, a decrease in diffusion rate, a decrease in the output current of the electrode, and a decrease to a new steady-state value within a few minutes. In a certain wayBODWithin the range, the decrease in output current is related toBODThere is a linear correlation between concentrations.

Other measurement methods

determineBODThere are also Coulomb method, pressure measurement method, and activated sludge aeration degradation method