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Publikation Tradeoff between micropollutant abatement and bromate formation during ozonation of concentrates from nanofiltration and reverse osmosis processes(Elsevier, 2022) Wünsch, Robin; Hettich, Timm; Prahtel, Marlies; Thomann, Michael; Wintgens, Thomas; Von Gunten, UrsWater treatment with nanofiltration (NF) or reverse osmosis (RO) membranes results in a purified permeate and a retentate, where solutes are concentrated and have to be properly managed and discharged. To date, little is known on how the selection of a semi-permeable dense membrane impacts the dissolved organic matter in the concentrate and what the consequences are for micropollutant (MP) abatement and bromate formation during concentrate treatment with ozone. Laboratory ozonation experiments were performed with standardized concentrates produced by three membranes (two NFs and one low-pressure reverse osmosis (LPRO) membrane) from three water sources (two river waters and one lake water). The concentrates were standardized by adjustment of pH and concentrations of dissolved organic carbon, total inorganic carbon, selected micropollutants (MP) with a low to high ozone reactivity and bromide to exclude factors which are known to impact ozonation. NF membranes had a lower retention of bromide and MPs than the LPRO membrane, and if the permeate quality of the NF membrane meets the requirements, the selection of this membrane type is beneficial due to the lower bromate formation risks upon concentrate ozonation. The bromate formation was typically higher in standardized concentrates of LPRO than of NF membranes, but the tradeoff between MP abatement and bromate formation upon ozonation of the standardized concentrates was not affected by the membrane type. Furthermore, there was no difference for the different source waters. Overall, ozonation of concentrates is only feasible for abatement of MPs with a high to moderate ozone reactivity with limited bromate formation. Differences in the DOM composition between NF and LPRO membrane concentrates are less relevant than retention of MPs and bromide by the membrane and the required ozone dose to meet a treatment target.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Phosphorus recovery in an acidic environment using layer-by-layer modified membranes(Elsevier, 15.07.2019) Remmen, Kirsten; Müller, Barbara; Köser, Joachim; Wintgens, ThomasPhosphorus (P) is a limited natural resource and essential for global food supply, particularly given our ever-growing world population. However, natural P deposits are restricted to just a few countries and the quality of exploited primary sources is declining. Phosphorus recovery from sewage sludge or sewage sludge ash leached by acids is hence gaining importance. During P recovery the removal of impurities is a challenge that can be addressed by nanofiltration retaining e. g. multivalent metals and allowing phosphoric acid to pass. However, currently available membranes show low permeability and limit this process option economically. Layer-by-layer (LbL) membrane synthesis is a technology that allows membrane performance to be tailored to individual filtration tasks. Little is known for such membranes with respect to acid resistance, acid permeability and impurity rejection. We show that LBL membranes based on PDADMAC/PSS show the desired passage of phosphoric acid with retentions values below 10%, aluminum retention was always above 95%. Permeabilities up to 4 L/(m2 h bar) were reached even up to a phosphorous recovery of 75%. Overall permeabilities were 16 times higher than a commercial benchmark membrane. Initial stability tests and upscaling into a larger module show the viability of the proposed modification approach.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Phosphorus recovery from sewage sludge by nanofiltration in diafiltration mode(Elsevier, 04/2015) Schütte, Thérèse; Niewersch, Claudia; Wintgens, Thomas; Yüce, SüleymanPhosphorus containing mineral fertilizers are frequently used in agriculture. The global resources of phosphorus rock are limited, which makes the use of alternative phosphorus sources increasingly promising. In this work, a process for phosphorus recovery from sewage sludge was studied. The focus lies on a nanofiltration process for the removal of metals and heavy metals from the product stream. In all cases, it was shown that metals were almost entirely retained by the membrane, while phosphorus permeated to a high degree. The phosphorus yield could be improved significantly by approaching diafiltration conditions.01A - Beitrag in wissenschaftlicher Zeitschrift