Novel process concept alternatives for improved removal of micropollutants in wastewater treatment

Significance 

Pharmaceuticals and pesticides are micropollutants that can be toxic to aquatic life. Typical activated sludge processes have been extensively applied in the treatment of municipal wastewater nowadays.  However, these systems are not designed for micropollutants removal.

As opposed to typical activated sludge processes, membrane bioreactors are more efficient for micropollutants removal from municipal wastewater. This is mainly based on the fact that high sludge retention times are used in membrane bioreactors than in typical activated sludge processes.  Unfortunately, even though higher sludge retention times often leads to some degradation of compounds with low biodegradability, it does not necessarily lead to efficient removal of micropollutants when using membrane bio-reactors alone.

Membrane technology, for instance, reverse osmosis has been proposed as a post-treatment process after conventional activated sludge and membrane bioreactor for effective removal of micro-pollutants. In addition, advanced oxidation processes, including ozonation, fenton, and photo-fenton have also been proposed as advanced micro pollutant treatment options. However, it has been found that advanced oxidation processes and reverse osmosis come with high operational costs, particularly due to high energy consumption, and high chemical adjustments.

The operational costs can be cut by replacing reverse osmosis with nanofiltration. As for the advanced oxidation processes, pulsed corona discharge oxidation has been found to be as twice energy efficient as the conventional ozonation. Therefore, the concept of implementing membrane filtration and/or advanced oxidation processes after typical activated sludge or membrane bioreactors seems promising for micro pollutants removal.

PhD researcher Kimmo Arola, Professor Mika Mänttäri, and Associate Professor Mari Kallioinen at Lappeenranta University of Technology in collaboration with Henry Hatakka at Wapulec Oy and a water treatment plant in Finland examined two novel processes for enhanced micropollutants removal from wastewater. Their decision to select the unit operations was centered on the objective to come up with a cost-efficient process, which could remove about 90% of the studied micropollutants while maintaining an appreciable removal of organic compounds as well as nutrients in order to mitigate eutrophication effect in the receiving waters. Their research work is published in journal, Separation and Purification Technology.

The authors examined two alternatives for the removal of micropollutants. They did the tests on a pilot scale with real wastewater of a small municipality. In the first alternative, they combined a membrane bioreactor process without phosphorus precipitation with a high permeability nanofiltration. In the other alternative, they combined membrane bioreactor with phosphorus precipitation with advanced oxidation applied by pulsed corona discharge.

The authors noted limited removal of unreadily biodegradable micropollutants such as diclofenac and carbamazepine in both membrane bioreactor processes. They recorded over 84% removal with nanofiltration for all the studied pollutants, apart from caffeine and hydrochlorothiazide. The performance of the pulsed-corona discharge oxidation, which was over 90%, surpassed that of nanofiltration.

High micropollutants removal was realized with the second alternative due to the high efficiency of the pulsed corona discharge oxidation. However, total removal of organic compounds was realized in the first setup where nanofiltration was adopted to refine the membrane bioreactor permeate. The authors recorded over 98% phosphorus removal in the two concepts. However, the first process alternative utilizing nanofiltration also allowed the recovery of phosphorus from nanofiltration concentrate. The findings of Lappeenranta University of Technology researchers will be useful for future wastewater treatment processes, considering that both of the studied concepts improved the quality of the effluent water significantly.

 improved removal of micropollutants in wastewater treatment-Advances in Engineering

About the author

M. Sc. (Technol.) Kimmo Arola is a R&D Project Leader at InOpSys NV and a Junior Researcher at the LUT School of Engineering Science, Lappeenranta University of Technology. He received his B.S. in Chemical Engineering from Lappeenranta University of Technology in 2011, and his M. Sc. In Chemical Engineering from Lappeenranta University of Technology in 2013. From 2013 he has conducted PhD research under topic advanced technologies for enhanced micropollutant removal and nutrient recovery in municipal wastewater treatment and aims to defend the PhD thesis during 2018.

His research relates to the examination of membrane technologies (tertiary nanofiltration or reverse osmosis, shear enhanced membrane filtration and electrodialysis) and advanced oxidation for the improved treatment of municipal wastewater. Research is focused on the fate of micropollutants such as pharmaceuticals in municipal wastewater and their removal as well as nutrient recovery from municipal wastewaters. During his research career he has published 9 publications related to topics such as municipal wastewater treatment, pulp and paper industry effluent treatment, membrane concentrate treatment, micropollutant removal and nutrient recovery from municipal wastewaters. At the beginning of 2018 he started to work as a R&D Project Leader in a Belgium start-up company InOpSys NV, which focuses on sustainable industrial wastewater treatment and circular economy. At InOpSys he pursues to continue his research oriented work and continue to find innovative technological solutions for challenging wastewater treatment.

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About the author

Professor Mika Mänttäri received his Doctor of Science (Technology) degree from the Lappeenranta University of Technology (LUT), Finland, in 1999. He currently holds professorship in membrane technology at LUT. He also leads the LUT SAWE Research Platform at LUT. His research concerns separation and purification processes, especially membrane based processes. The main focus areas are biorefineries, water treatment, food, mining and metallurgic industries and development of separation materials.

He is interested in refining novel products from biobased materials such as lignocellulosic materials and converting wastewater to value added products. He aims to renew wastewater treatment more toward utilisation of wastewater compounds than only to degrade and dispose of them. Prof. Mänttäri has published about 100 peer-reviewed articles and book chapters and is an inventor in 10 patents.

About the author

Dr. Mari Kallioinen is Associate Professor in Membrane Technology and the Head of the Department of Separation and Purification Technology in School of Engineering Sciences at Lappeenranta University of Technology (LUT). In addition, she leads the LUT Re-Source research platform at LUT. She received her Doctor of Science (Technology) degree in 2008 at LUT.

Her research is focused in the development of sustainable membrane based processes, which could enable the improvement of resource efficiency especially in the use of biomass and in comprehensive utilization of different waste and size streams. The main application areas are biorefineries, water treatment and mining and metallurgic industry. She is also working for improved understanding on membrane fouling and for development of new real-time monitoring tools for fouling detection. She has published more than 40 peer-reviewed articles and book chapters.

Reference

Kimmo Arola, Henry Hatakka, Mika Mänttäri, Mari Kallioinen. Novel process concept alternatives for improved removal of micropollutants in wastewater treatment. Separation and Purification Technology, volume 186 (2017), pages 333–341.

 

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