Modifications in conventional activated sludge process:-

Need for modification of the conventional activated sludge process:-

• To make the waste water treatment more effective.
• To reduce the time duration of the treatment.
• To reduce the cost of operation.
• To control the problems related to temperature shock changes in pH, changes in COD loading.

Modification in the conventional activated sludge process:-

• To overcome the problems mentioned above contact stabilization method is used, For modification two separate tanks are used or one single tank with different compartments, which are constructed for this purpose are constructed.

• The activated sludge which is stabilized is mixed with the waste water which comes from the contact tank.

• This mixed liquid is allowed to settle till the settling basing in the other tank.

Plub flow:- conventional method:-

• The feed to the aeration tank are properly mixed by using diffused aeration or the mechanical aeration.

• This helps to have better mixing and good distribution of oxygen in the tank.

• This process helps to have better and quick absorption and oxidation of the organic matter by the micro organism present in the system.

• The solids are then separated in another settling tank.

Taped aeration:-

• This is a different design which is based on the conventional plug flow system.

• In this process various aeration rates are applied by adjusting the aerator motor speed.

• Generally taped aeration is applied using air diffusers which are spread throughout the tank. This has very high efficiency.

The step feed activated sludge aeration:-

• the incoming sewage or waste water into the aeration pond if introduced at several points, it is called as step feed activated sludge aeration system.

• This method helps to get better F/M ratio and reduces the BOD that to at one single point, at the feed point only.

• To run this system a number of built in channels are required to be constructed to divert the inflow of waste water into the aeration tank.

• This construction and its maintenance , increases the cost of the system but it gives better and efficient results in the long run.