Contamination of the environment by micro pollutants has clearly been proved by now. Due to the high concentration of microorganisms and the contamination by antibiotics coming from animal breeding, hospitals and ambulant applications, elimination of micro pollutants in biologically treated wastewater becomes more and more important.
At present a combination of powdered activated carbon and subsequent sand filtration is mainly used to eliminate micro pollutants. This process is able to reduce trace substances like drug residues in the effluent of a wastewater treatment plant, however, it is disadvantageous that the sand filter does not ensure complete separation of activated carbon particles. Thus besides treating wastewater by activated carbon adsorption and sand filtration further treatment steps must be implemented.
The membrane process that is presented in the following combines adsorption of micro pollutants on activated carbon and membrane filtration. The membrane filtration step takes over the job of separating (powdered) activated carbon, micro plastics and (multi-resistant) germs. Hence this process ensures not only compliance to threshold values for drug residues and other trace substances as discussed so far, but also ensures compliance to expected concentration limits for multi-resistant germs and micro plastic in effluents of wastewater treatment plants. In Huenxe (Germany) a German association for sewage treatment (Emschergenossenschaft/ Lippeverband*) operate a municipal wastewater treatment plant with a capacity of 17,000 PE (population equivalents). This plant is divided into an MBR plant and a conventional biological treatment plant, each with a capacity of 8,500 PE.
The tests outlined here were carried out with the effluent of the conventional treatment plant in the frame of a master thesis of University Dresden in cooperation with the local association for sewage treatment.
The test plant consists of a filtration tank equipped with a with a BIO-CEL® membrane module. The filtration tank of the test stand is fed with the effluent of the sedimentation tank. Activated carbon is added from a receiver tank and concentrated in the filtration tank. Activated carbon is separated by the BIO-CEL® membrane module and the permeate is transferred to the final effluent. The experiments showed that, as a matter of principle, the combination of activated carbon adsorption and carbon separation by an immersed ultrafiltration module works well and activated carbon is reliably separated.
The increasing concentration of activated carbon had no impact on the membrane performance, and also no change of retention capability could be detected during the entire test period.
The above described combination of activated carbon adsorption and immersed membrane filtration has proven an alternative to the established activated carbon/precipitation/sand filtration process. The advantages are especially given with respect to the separation of multi-resistant germs and micro plastics, which both will be more and more in the focus. Initial cost estimation of the above described process show the competitiveness in relation to the established activated carbon/precipitation/sand filtration process.
Exhibitor: MICRODYN-NADIR GmbH