Anoxic Tank / sludge floating / Alum Dosing / MBR

[cen3aak]

Our process configuration for the domestic Sewage treatment plant is as follows:

Fine screen – Anoxic – MBR with a recycle rate between 3 to 4 times of the feed flow

The design requirement is to reduce the nitrate levels to < 10 mg/l and phosphorus from 15 mg/l to < 2.0mg/l and as normal BOD levels < 5.0 mg/l

-The permeate TSE BOD levels is < 5.0 mg/l
-For the nitrate the anoxic zone is doing the required Job and the nitrate levels are < 4.0 mg/l
-For the phosphorous removal we are utilizing Alum Dosing and it is being dosed at the outlet of the Anoxic tank ( inlet to the MBR tank) phosphorous levels are < 2.0 at the permeate outlet
-We may have some extra FOG levels as shock loads of max 60 mg/l
-We are dosing caustic to increase the PH level in the Anoxic tank


The current observation is sludge floating in the Anoxic tank (cake sludge of around 12-15% solids concentration with around 300 mm thick layer). No sludge floating in the MBR tanks

The sludge accumulation on the top of the Anoxic tank is not affecting the treatment process for now but we think this will have future bad effects on the Anoxic tank

Any suggestion; How to overcome this problem ? and is the Alum dosing causing this problem? any Advice?

 

[bimr]

Do you have mixers in the anoxic zone?

 

[cen3aak]

Yes, mixers are provided and designed only to keep solids in Suspens

MLSS in the Anoxic Tank is 12,000 mg/l and in the MBR is 14,000 mg/l ( Desing)

 

[cen3aak]

please note that we have Just tested the sludge the Sludge is 8% concentration havign very high levels of MLVSS and high levels of Aluminium