Intermittently Decanted Extended Aeration

Intermittently Decanted Extended Aeration (IDEA) applies modifications to a Conventional Activated Sludge Plant (CASP). The IDEA treatment process consists of 3 phases: Aeration, settling and decanting.

The first phase, aeration, involves rapid surface mixing to mix the influent with the activated sludge. The mixing action aids in dissolving oxygen into the water whilst forcing the sludge into suspension from its settled state. Alum is added to bind the phosphorous present in the sewage, allowing it to settle out. Nitrification also occurs at this stage to convert ammonia to nitrite.

Settling occurs when the surface aerators are stopped, which allows solids to migrate to the bottom of the tank. At this stage, anoxic conditions predominate in the sludge due to the lack of molecular oxygen, which cause the bacteria in the sludge to use oxygen the bound in nitrates (NO3) for metabolism. This results in the effusion of nitrogen as a gas.

During decanting, a trough is skimmed across the top layer of the tank, collecting the water to be sent off for further processing in downstream processes.

CRS can design, manufacture, install and commission plants based on IDEA technology to meet standards set out by clients.