Questions regarding atmospheric and vacuum distillation units
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The COD level of the oily wastewater from the atmospheric and vacuum distillation units is above the standard; what could be the reasons for this? Could it be the electrodialysis system?
Crude oil properties, common anti-corrosion measures for reducing pressure, electrodialysis, and so on are all relevant.
For the oily wastewater from atmospheric and vacuum distillation units, only the oil content and pH value are controlled; there is no specification for COD.
The oil content in the oily wastewater is too high: the main reason for oil being present in the water is likely faulty levels in the electrodialysis tanks and the initial separation tanks, which leads to oil being carried along with the water. There’s nothing else really. Here, oil leakage from pump seals into the gutters can also cause this issue. I’m not sure what’s the situation where you are. Additionally, the wastewater might be contaminated by fluids from adjacent equipment.
During electrocoagulation water treatment, poor quality of the oil can cause the COD level to exceed the limit, sometimes reaching 3000 mg/l
The wastewater from the atmospheric and vacuum distillation units that has the highest COD level is mainly the overheads wastewater, which also contains a high amount of oil. Upon inspection, if it is the overheads wastewater that affects the COD level of the unit’s wastewater, it is recommended to reinject the water after electrodialysis treatment; this can help reduce the COD level and the oil content in the wastewater, thereby improving the quality of the wastewater from the unit.