Suppose that a person tries to showel up sand on a table..
In the beginning, all the sand will stay on the table.
But after a while, it starts pouring over.
And in the end, the same amount falls down as he tries to put on the table.
This is a steady state.
More thoroughly, the HEAP (Hampered Effluent Accumulation Process) effect can be described with the diagram below:
- Saturation phase: The storage (Q) increases lineary as a function of flux (J) (until the heap has reached the border of the table).
- Accumulation phase: The leakage (kQ) increases, which leads to a slower increase of the storage (Q).
- Steady state phase: When the leakage (kQ) equals the flux (J), there is no further build-up of the storage (Q). (The sewage plant, however meticioulus, has failed)