Various interactions of sewerage and waste-water treatment are discussed for the typical situation in the Netherlands.
Sewerage and waste-water treatment are no longer necessary when each house has its own integrated waste-water system; however, costs seem to be high.
The same applies for small-scale waste-water treatment versus centralisation.
However, centralized waste-water treatment plants suffer from specific problems due to high fluctuations, not only in hydraulic but also in biological load.
With stringent effluent standards the need increases for complete treatment instead of by-passing the peak flows.
Besides, the application of buffering tanks may change in favour of an increase in the hydraulic capacity of the waste-water treatment plant.
Finally, a new, integrated, attitude on water-cycle problems must be advocated.