Foaming at outlet of UASB reactor

[sgoel]

Hello everyone

We are operating UASB reactors for treatment of waste waters from a petrochemical plant. We are observing foaming at the outlet (Treated water) from the reactor. We also observe effervescence of gas from the foam. Request for possible reasons which may be resulting in this.


Shashank

 

[bimr]

Not much to go on with such a limited description.

New or old installation?

Operating parameters?

Does the wastewater contain surfactants?

Have you tried anti-foam?

 

[sgoel]

Thanks Bimr

The installation has been in service for about eight months now. OLR is 2Kg COD/M3/Day, upflow velocity 1.5m/hr. Temperature is 38 Deg C. TSS in outlet is 100 ppm

Wastewater does not contain surfactants

Anti foam has not been tried.

 

[ashtree]

Without knowing all the details of the installation your loading rate at 2kg/m3/day is at the lower end of what would normally be expected and your up flow velocity is higher than most. The temperature at 38 C is also on the top end of the mesophilic operating range.

Here are some questions you might like to consider.
Is your pH in the range around 6.6-7.6. Processes vary a bit based on what is actually being treated but most UASB would operate best in that range
If the pH is much lower than that has the alkalinity of the raw water been considered? The alkalinity requirements will vary depending upon what is being treated but if your pH is low you may have insufficient alkalinity.
Has there been any analysis of trace nutrient requirements or toxicity done on the feed water? Some wastewater from a narrow industrial process can be deficient in certain elements that microorganisms require to grow. Likewise some substances can be toxic or rate limiting under all or some operating conditions.
Is your HDT too short? Given that you have a high up-flow velocity is your flow too high and the HDT too short even though you have a low biological load.
Are you able to operate at a slightly lower temperature?
What are the main components of the waste you are treating?


Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[bimr]

The operating manual states that: "Foaming can also be an indication of a macronutrient imbalance."

Many of these systems add nutrients. Has the biomass been inspected to check for nutrient deficiency?

 

[QualityTime]

what is the dissolved oxygen level profile in the tank.

 

[ashtree]

One would hope there is no dissolved oxygen in the tank at all. After all it is an UASB with A meaning anaerobic.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[bimr]

Upflow Anaerobic Sludge Blanket reactor (UASB).