New process for micropollutant removal is trialled using MICRODYN-NADIR's BIO-CEL® membrane module
Due to high concentrations of micro-organisms and contamination by antibiotics from animal breeding, hospitals and other medical applications, elimination of micropollutants in biologically treated wastewater is becoming more and more imperative.
Micropollutants are currently often eliminated by a combination of powdered activated carbon and subsequent sand filtration. This process is able to reduce trace substances such as drug residues in the effluent of a wastewater treatment plant. However, it is disadvantageous in that the sand filter does not ensure complete separation of activated carbon particles. Therefore, as well as treating wastewater by these two unit processes, further treatment steps must be implemented.
MICRODYN-NADIR has announced that its BIO-CEL® membrane module has recently been used in tests as an alternative to the established activated carbon clarification process. This trial was recently carried out using the effluent of the conventional treatment plant at Huenxe, Germany as part of a University of Dresden Masters' thesis project, in cooperation with the local association for sewage treatment.
The German association for sewage treatment (Emschergenossenschaft/ Lippeverband) operates the municipal wastewater treatment plant at Huenxe 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.
In the trial membrane process, adsorption of micro pollutants on activated carbon is combined with membrane filtration. The membrane filtration step separates (powdered) activated carbon, micro plastics and multi-resistant micro-organisms. This process would ensure not only compliance to threshold values for drug residues and other trace substances, but also to expected concentration limits for multi-resistant micro-organisms and micro plastic in effluents of wastewater treatment plants.
The test plant consisted of a filtration tank equipped with a BIO-CEL® membrane module. The filtration tank of the test stand was fed with the effluent of the sedimentation tank. Activated carbon was added from a receiver tank and concentrated in the filtration tank. Activated carbon was separated by the BIO-CEL® membrane module, and the permeate transferred to the final effluent. The experiments showed that, in principle, the combination of activated carbon adsorption and carbon separation by an immersed ultrafiltration module worked well and the activated carbon was reliably separated.
The increased concentration of activated carbon had no impact on membrane performance, and no change in retention capability could be detected during the entire test period.
In this trial, the combination of activated carbon adsorption and immersed membrane filtration proved to be an advantageous alternative to the established activated carbon/precipitation/sand filtration process for micro pollutant removal. The combination proved particularly advantageous with respect to the separation of micro-organisms and micro plastics. In addition, MICRODYN-NADIR says that initial cost estimates indicate it is competitive when compared with the established activated carbon clarification process.
Image credit: German water works 'Emschergenossenschaft/Lippeverband'