Reasons for the sudden rise of effluent COD detector

- Aug 20, 2020-

1. The reasons for the increase in COD value of the effluent from the activated sludge process are as follows: The reason for the low visibility is when large flocs appear behind the diving wall or in the outlet channel, or when the visibility in the secondary settling tank is very small or reduced , Caused by suspended matter. When the effluent visibility is lower than 1.5m, it is caused by the content of dissolved sewage. When the surface load of the secondary settling tank is too high and the solid content in the activated sludge is too high, it must be noted that the sludge content in the activated sludge must not be reduced by more than 25% within 24 hours, and the sludge cannot be increased due to the extraction of the remaining sludge. The content of NH4+N in water.

COD 

2. Reasons for the increase of COD effluent value in activated sludge treatment process:


The sludge index is too high. When the reflux ratio is sufficient, when the water depth in the clear water area is less than 1 meter and the sludge index exceeds 150ml/g, measures must be taken to improve the sludge index. The reflux ratio is too small, the reflux ratio is at least 50-70% of the inflow. RV<0.5(=50%)→Increase the return flow of activated sludge→change the mud surface height of the secondary settling tank. If the mud level does not decrease, check the sludge volume load q.  

 

3. Reasons for the increase of COD effluent value in activated sludge treatment process:


Fragmentation of flocs can lead to high concentration of filterable substances in the effluent, (>30mg/L or 12TE/F), insufficient degassing capacity, gas formation, and long residence time of sludge in the secondary settling tank. The removal rate of diving walls and floating objects is not effective. The temperature difference between the inlet and outlet water of the secondary sedimentation tank is too small. The pipeline is blocked. The influent COD load of the water quality analyzer is too high.

 

4. Reasons for the increase of COD effluent value in activated sludge treatment process:


The ammonium nitrogen value of the effluent is too low; the turbidity is increased; the inflow is too high; the return sludge pump is malfunctioning; the PH value is too low or too high; the sludge is mechanically crushed; the nitrite content is increased. 

COD 

1: Influent PH value is high> 8.5; alkaline sewage is discharged to damage or inhibit microorganisms;  

 

Emergency measures: Lead the sewage into other empty tanks (rainwater overflow tank, primary sedimentation tank, accident tank), and continuously measure the pH value of the nitrification zone. When the pH value is higher than 9, increase the aeration intensity. Add iron salt or aluminum salt to neutralize alkaline sewage and reduce PH value.  

 

2: When the PH value of the inlet water is lower than 6;   

 

The discharge of acidic sewage can damage or inhibit microorganisms; there is a risk of eroding structures, and the discharge of organic acids will increase the load of organic pollutants and increase oxygen consumption. 

COD Water test

Emergency measures: Lead the sewage into other empty ponds (rainwater overflow ponds, primary sedimentation ponds), and continuously measure the pH value of the nitrification zone. The only feasible measure is to add alkaline substances to neutralize it. In an emergency, dry slaked lime can be used.  

 

3: The temperature of the inlet water increased significantly;  

 

Hot production wastewater is discharged, and other substances are usually discharged. Formation of foam and floating sludge; if foam and floating sludge suddenly appear in the range of the activated sludge tank or the secondary settling tank, it may come from the impact load of the surfactant, the impact load of the detergent and other easily degradable substrates, usually From the food industry.  

 

4: There is oil film in the inlet water:  

 

Disposal measures when mineral oil products are discharged and there is no danger of explosion, the sewage is led into other empty pools (rainwater overflow tank, primary sedimentation tank, accident tank), and the transportation of return sludge and circulating sludge is stopped. Stop the stirring device in the unaerated zone, and install an oil baffle at the exit of the denitrification zone (or anaerobic zone). If oil appears in the aeration zone, stop aeration and sprinkle the binder. Recognition feature 5; the gas has the smell of alcohol, etc.;  

COD tester  

Sometimes related to sewage covering; contains flammable and explosive gases and liquids. 

 

Emergency measures: use alarm equipment to measure the explosion hazard, lead sewage into other empty pools (rainwater overflow pool, primary sedimentation pool), stop all engines and electrical equipment in all explosion danger zones; turn off all heating equipment and extinguish open flames . Close the doors and windows of sewage-free structures and stop the operation of the ventilation equipment in the blower room, but some blowers operate as usual to extract harmful substances. As far as possible, remove the sealing coverings of pools and drains. Stop the suction of suspended sludge and excess sludge.