Dear Marina, Apparently ...
Published by Bruno Peeters, managing director at Model Engineering
Dear Marina,
Apparently this summary refers only to municipal sewage treatment plants (STP's) as opposed to the many more industrial wastewater treatment plants (WWTP's).
The "why" question can largely be answered by the delays in the required STP upgrade investments by the local or regional authorities. State-of-the-art proven technology is readily available to meet the present EU water quality standards.
For sustainable water reuse with ultralow levels of residual BOD, COD, TSS, turbidity, .... enabling reuse as potable water after further multiple barrier purification, we retrofit upgrade conventional CAS to advanced activated sludge AAS biological treatment. This upgrade boosts the microbial activity and diversity along with the density of the biosludge as to adsorb and biodegrade the slowly biodegradable and recalcitrant fraction of the sewage which would otherwise pass through the CAS based STP's.
Regards, Bruno