I am trying to solve foaming issue in our snack plant. At API Separator, there is always sludge on the surface, the question is if it`s working properly, we should not have any foam or sludge on the surface of the API Separator, because sludge need to be on the bottom in order to take it out by auger at the bottom side of API Separator. In addition, there is always foaming at Hydrotreat where we measure the pH.
Everyday, I check the pH, inlet flow rate to the system, and checking the capacity, to determine optimum process condition. But I have never checked BOD, DO,COD, TSS, and other parameters.
Usually when it foams, I use defoamer, but this is an expensive way. So I am trying to figure out what can cause sludge on the surface of the API Separator and Hydrotreat.
Done some research, EPA recommends to check process condition, and if process not allows to get rid of foaming and then use defoamer.
In my opinion, we have problem on API separator. API separator cleaned like 1 year ago. Does it has to be clean in a certain time?
Is there any way to make our process to work properly, and reduce sludge and foaming on the surface?
Thanks,
Mehmet Akbas
with the data, because it is difficult to understand but, maybe you have in your output products that form the foam, not fat, or other long chain that solidify etc.
Martin Guevara thanks for the comment. There is for sure some cleaning issue, like they have never cleaned api separator, and hydrotreat. But there should be an easy way to solve this problem, I just do not want to use any chemical to reduce foaming. Maybe starch cause foaming, but the color of the foam is usually dark brown, or gray. API separator is dirty and it needs to be clean first, maybe It’s overloaded. the process has capacity, like if we keep api separator dirty all the time, TSS gonna increase and all the solid particles will be on the surface. Just trying to figure out the main problem.
Dear Mehmet Ali A.
To control activated sludge bulking you need to control filamentous bacteria. For me I doubt this is sludge but it is a foam for sure. Foam comes mainly from detergents and surface active agents. Sludge comes from biological treatment and as API is a physical treatment which must precede the biological treatment then it is only foam not sludge. Please refer to the links:-
https://wtp-operators.thewaternetwork.com/article-FfV/filamentous-bacteria-problems-and-solutions-r94HLW1n20o4ygPMhB7D4A
https://www.processingmagazine.com/control-of-activated-sludge-including-troubleshooting/
https://en.wikipedia.org/wiki/API_oil%E2%80%93water_separator
There are three types of bacterium that produce biological foams within wastewater treatment plants.
The three species thrive when the treatment plant does not contain a fat trap, allowing for a percentage of the grease and oils within the aeration process.
But they differ among themselves in conditions appropriate to their respective growth
Nocardia SP grows when it has a long life inside the aeration tanks with medium temperature rise inside the aeration tanks (c17 --- 40C)
While M Pravicella grows when it has a long lifespan within the aeration tanks but does not prefer high temperatures grow and thrive in the cold atmosphere. Type 1865 grows when the feces inside the aeration tanks are low.
Nocardia SP:
Bacteria that branch out into strands in its later stages; spend longer in the system compared to other bacteria; cannot grow in anaerobic conditions or in the presence of nitrates and nitrite.
The cells in the advanced phase of their growth are fully subdivided into branches very similar to tree roots; with a high level of surface tension due to the presence of a ratio of grease and oils within the extended aeration tanks floating on the surface in the form of a sticky biological foam with a dark brown color.
Thus, reducing the age of the sludge helps to separate the early phase of the Nocardia cells before they can reach the advanced stage in a stratified form; however, this may lead to incomplete undergrowth within the extended aeration tanks.
Further reduction of oils and grease prior to arrival in the extended aeration tanks works to reduce the appearance of bio-foam directly on the surface of the pelvis.
The concentration of oxygen within the aeration tanks should be reviewed at a level of 2ppm and that oxygen should not be lower than this level because some reduce aeration to reduce foam; however, this leads to further growth in the long-term Nocardia yarn.
Foaming can be caused by a temperature change and lysing of bacteria, but this should not be a factor in an API separator. Are there a gas release or chemical reaction that could be occuring?
Harlan Glen Kelly Thanks for sharing your knowledge. On a research, it says that 'Putting defoamer on Nocardia film is like adding gasoline to fire. The Nocardia may retreat for 30 minutes, but the foaming will just come back worse '. And our plant uses the defoamer to get rid of Nocardia Filaments. That may cause to have high foaming at API tank and at Hydrotreater. The other chemicals that we use acid and Sodium Hydroxide.
If you take a look at the picture, waste water goes into Wet Well after that API tank, and after that to Centrifuge, after that Hydrotreater, and at hydrotreater if pH is in-spec, then it sends to City, if pH is out of spec, it recycles the waste to wet well. (Min pH spec is 6.00, max pH spec is 10.00)
2 days ago we cleaned entire treatment plant. It start foaming again today. API separator usually 96% full. The system capacity is 200gpm, and centrifuge feed flow rate usually at 140gpm, and bowl speed 2390rpm. There might be issue here, because the flow rate from wet well to API separator usually between 180-200 gpm, but centrifuge feed flow rate usually around 140-150gpm. What if we increase the centrifuge flow rate, would it help us to increase the separation and to reduce foaming?
I am trying to solve the problem but there might be other factors, like incorrect equipment usage.
Temperature effects on it too, but there is always foaming in this treatment plant.
Isam Issa Omran Thanks for sharing your knowledge. I will send sample to lab to identify which bacteria causes that. I am not exactly sure, nocardia or other bacteria.
There might be some processing issue. Currently, I am trying to determine optimum process capacity. So, seeking long term solution for this problem. There is some chemicals that will help to get rid of this foam, but It`s an expensive method.
Nabeel Hameed Al-Saati thanks for sharing your knowledge. You are right, it is for sure foam, but when it sits there for a long time, it gets like muddy. EPA shared some information how to reduce foaming by making adjustment in process.
Harlan Glen Kelly what if we reduce loading capacity, would it help to reduce foaming?
Last time, I noticed that there was no foaming at hydrotreat, when flow rate was 183gpm (Wet well to API Separator), and inlet flow rate to Centrifuge was 139gpm. And pH was 6.40. And API Separator was 84% full. But there was foam in API Separator. Is this approach correct?
Thanks,
Can you analyze the foam composition? Is the foam a mixture of gas and solids. What are they? Can you simply turn the plant into a flotation device and remove the foam by scrapers or other means for futher processing?
Harlan Glen Kelly Thanks for sharing your knowledge Sir, I have sent samples to lab to identify the composition of the foam. Turning the plant into flotation device and remove foam by scrapers is a great idea. Once I get lab results, I will share it here.