High COD on the final efflent

[drogones12]

Hi guys,
I have high COD on my final effluent. What could be the issues? My plant has coarse screen-grit vortex chamber-primary clarifier-fine screen-Bioreactor (anaerobic-anoxic-aerobic-anoxic)-Mixed liquor-ultra membrane permeating trains-carbon contactor-uv light-post aeration-final. Of course there is return activated sludge right after ultra membrane permeating trains.
Some of our operators think we should do more recovery clean on our trains.

Any suggestion will be appreciated?

 

[bimr]

Are you playing Twenty Questions?

You need to provide more details such as type of wastewater, how long the problems has been going on, what is happening with the BOD, etc. Otherwise, it is just a guessing game.

 

[drogones12]

Hi Bimr,

We are treating 4.5MGD domestic wastewater daily. This wastewater plant has been running since 2007.The COD has increased constantly since october of 2011. We don't have BOD test yet. also, we are thinking of purchase new carbon for the carbon contactors. any wild idea will be appreicated.

 

[drogones12]

COD is normal before it going to Bioreactor Basin(secondary), COD goes high at the Mixed Liquor Channel

 

[bimr]

Based on what you have posted, one would surmise that the carbon may be exhausting.

What was the reason that the carbon contactor was installed as it is a little unusual to see a carbon contactor on domestic wastewater? Are you removing dissolved organics or nitrifying with the carbon.

Has the COD been increasing on the influent?

Is the effluent BOD increasing?

Have you compared the influent and effluent on the carbon contactor?

Do you have seasonal issue to contend with?

 

[bimr]

After reviewing your last post, it would seem that the COD removal would have to be related to the F/M ratio and fouling of the membrane process.

If you have higher COD in the biological reactror and the membrane removes a percentage, you would expect a higher effluent COD when operating at a higher biomass concentration.

Have the loading changed?

Have you reviewed this with the supplier of the process?

 

[drogones12]

Thank you very much Bimr