Today's article deals with the topic of hygiene in small sewage treatment plants; in detail, membrane and UV modules.

If nowadays the authorities require a small sewage treatment plant "according to the state of the art", then it is usually an activated sludge plant of the common effluent class C; if necessary, an individual effluent class N or even D is required. Additional hygienisation (H) is usually only required in sensitive environmental zones or water protection areas.

But what does "state of the art" actually mean? Wouldn't we have to join the canon of those authorities that demand the latest state of technology as standard? The best waste water treatment that can be achieved by technical means should be used, right?

Or perhaps you - like us - are of the opinion that the opposite of "good" is often "well-intentioned". A solid effluent class C is always better than a permanently defective ultrafiltration in which the waste water leaves the reactor untreated.

For many years, membrane activated sludge plants have been the top class for wastewater hygiene and industrial water recovery in small sewage treatment plants. However, the number of successful manufacturers and operators of such plants is continuously shrinking.

More than 11 years ago, we at ATB also had the idea of making ultrafiltration usable in a KKA. However, the selection of suitable membrane modules for removing the permeate and the resulting disinfection posed a major challenge.

Be that as it may; after the OWL-Lippe University of Applied Sciences was on board, ATB developed the maxipur® plant based on experience with various pilot and test plants, which stood out due to its superior cleaning performance - but also due to a significantly higher market price than usual and an immensely high power consumption. The service life of the membrane modules also proved to be significantly shorter than predicted. Last but not least, it proved to be relatively problematic to keep the used modules permanently moist on their way to "refreshing". In short: the maxipur® systems simply did not want to develop into a success.

Many other manufacturers have tried their hand in this area, and - if you allow us to make this claim - almost all of them have got themselves a "bloody nose".

UV disinfection has proven to be a more practical alternative for small sewage treatment plants. Already more than 10 years ago ATB made this possibility available in its modular system (The further options of the modular system like phosphate precipitation, GSM module etc. will be the subject of this blog at a later date).

The UV unit downstream of a proven SBR system such as the AQUAmax® or the PUROO® works quite smoothly and can be offered at reasonable prices. Of course, the power consumption is also significantly higher here than for systems without a hygiene unit.

Nevertheless, we at ATB consider the combination of a simple, functionally reliable sewage treatment plant in combination with a UV module to be the most practical solution.

But how useful are H+ systems? In the district of Kleve, various membrane systems are currently being replaced with KKA systems with effluent class N at the instigation of the Lower Water Authority. Obviously there is solidarity with annoyed operators, who in the past were shaken enough by badly functioning plants and whose electricity costs escalated exorbitantly.

What is your opinion on this topic? Are you perhaps a friend of membrane technology and wonder where the problem actually lies? Or do you have completely different experiences or preferences? Then please share your experiences with us!