API separator foaming issues in asphalt refinery wastewater

[chemebabak]

Engineers,

Currently our client's wastewater treatment plant (WWTP) receives wastewater from crude overhead, Vac tower overhead, caustic scrub, Sulfatreat flush water (intermittent) and storm water (intermittent). The wastewater passes to the API separator, then to the DAF. The water is pumped to outfall and the DAF floc is pumped to a holding tank.

The API has experienced an oily foam that requires the API to be shut down once a week for cleaning. As a remediation, our client has installed filters upstream of the API separator. These filters are replaced every 1-2 hours.

Because the oily floc contains a large percentage of water (40%) the client pumps it back to the API, mixed with the wastewater, for a second pass. The client also has stated that the it is very difficult to separate the oily floc from the water. This is most likely due to the polymers and coagulants in the floc.

I would like to know what are your suggestions for improving the WWTP operation. I believe that improved DAF separation is one important step and not recirculating that Floc to the API would be a second important step. My next thought is that there needs to be some sort of additional action regarding the wastewater. As I wrote, the filters upstream of the API are continuously clogged and require constant replacement. The client believes that to be the sludge contained in the wastewater.

Thank you for your comments.

 

[bimr]

You need to check the pH of the water. The ideal pH should be approximately 5.3 units or so. As you move away from that pH, the efficiency drops off.

 

[chemebabak]

bimr,

Do you mean that the wastewater feed to the API should be 5.3?

 

[bimr]

The ideal pH to break oil emulsions is approximately 5.3. As you get away from that ph, the treatment effective will drop off.

There may have been some process change that is affecting the pH.