I am a postdoctoral researcher with a background in environmental engineering - in the area of wastewater treatment, organic waste recycling, energy and nutrient recovery. I conducted research on nutrient recovery from biogas digestate with biochar and zeolite during my joint PhD at University of Copenhagen and Wageningen University. In my previous postdoctoral work at University of Freiburg, my project focused on a new concept for the integration of microbial fuel cells into membrane bioreactors. Currently, I work at the Department of Environmental Process Engineering, Bremen University.
Skills and Expertise
Research Items (13)
The liquid fraction after liquid/solid separation of biogas digestate has a high potential as a fertilizer due to its high nutrient concentration. However, the direct application of digestate in agricultural fields results in practical problems due to its voluminous nature. One solution to this could be to concentrate nutrients onto sorbents such as biochar or zeolites, which can subsequently be used as a fertilizer. This study investigated the ability of biochar and zeolite ‘clinoptilolite' enriched with digestate nutrients to supply nitrogen (N) when used as a fertilizer. A pot experiment with ryegrass was conducted to test the effect of a nutrient‐enriched biochar and clinoptilolite by determining plant biomass growth and N uptake. This included untreated biochar and clinoptilolite as controls and two levels of N application (15 and 45 mg N per pot) each at two initial loading ratios (low and high). Nutrient‐enriched biochar and clinoptilolite increased plant biomass yield (up to 1.02 and 2.39 g per pot) and N uptake (up to 11.23 and 39.94 mg N per pot) compared to the untreated sorbents treatments. Initial loading ratio had a significant effect on plant biomass response and apparent N recovery (ANR) for enriched clinoptilolite, and lower initial loading ratio improved plant growth. In contrast to clinoptilolite, higher initial loading ratio resulted in higher ANR. In conclusion, our results reveal that N released from enriched clinoptilolite and biochar could be taken up by the plants, clinoptilolite performed more effectively than biochar, and initial loading ratio affected the performance of the sorbents when used as a fertilizer.
Recently, it has been shown that combining a bioelectrochemical system (BES) with an anaerobic membrane bioreactor (AnMBR) to produce electricity can reduce the overall energy consumption of wastewater treatment. In this study, we tested the recently proposed concept that integrates a microbial anode into an AnMBR, under application relevant conditions, for the treatment of synthetic brewery wastewater. We developed two system configurations: a filtering anode with stainless steel filter plate; and a hybrid anode, in which a polymeric membrane is combined with stainless steel mesh. As fouling is problematic in AnMBRs, we investigated the effect of two fouling mitigation methods, namely electrochemical cleaning and application of a turbulence promotor, on the permeate fluxes and current densities. We also investigated the effect of cathode (counter electrode) position on the permeate fluxes and current densities in filtering and hybrid anode. Our results revealed that permeate fluxes were influenced by the membrane pore size; and dropped below 5 L m−2 hr−1 on day 3 with filter grade 0.5 μm; whereas similar values of permeate flux were observed after 5 days of operation with the membrane with filter grade 0.1 μm. COD removal across the membrane reached up to 644 mg L−1 indicating improvement in energy efficiency and effluent quality of the AnMBR. The location of cathode did not influence permeate fluxes and current densities, but permeate pH was largely affected. Electrochemical cleaning improved permeate fluxes more than 2-fold (18.9 L m−2 hr−1 after 7 days of operation) compared to the operation of the 0.1 μm membrane without a cleaning procedure. Application of a turbulence promotor increased permeate fluxes and current densities in filtering anode. The hybrid anode resulted in similar current densities, but higher permeate fluxes as compared to the filtering anode, which dropped below 20 L m−2 hr−1 only after 8 days of operation. The hybrid anode configuration is an attractive option that combines high permeate fluxes on conventional non-conductive filters with current generation on an inexpensive conductive material. In summary, our results demonstrate that combining BES with AnMBR is a promising approach toward an energy efficient wastewater treatment.
- Apr 2017
The direct application of the liquid fraction of biogas digestate to agricultural fields as a fertilizer may result in practical and environmental problems. Concentrating nutrients onto clinoptilolite and subsequently using clinoptilolite as a fertilizer could be an alternative solution for the management of nutrients in the liquid fraction of digestate. In this study, the use of clinoptilolite to recover ammonium, potassium and orthophosphate from the liquid fraction of digestate was investigated. The optimal preconditioning of clinoptilolite and the optimal initial nutrient-to-clinoptilolite loading ratio was determined to achieve the highest nutrient removal efficiency. Preconditioning of clinoptilolite had no significant effect on the total ammonium and potassium removal from the liquid fraction of digestate. An increase in the initial loading ratio significantly increased nutrient concentrations on the clinoptilolite, but decreased nutrient removal efficiencies from the liquid fraction of digestate: removal efficiencies ranged from 40 to 89 % for ammonium, 37 to 78 % for potassium and 64 to 80 % for orthophosphate at various initial loading ratios. Overall, the increase in the concentration of nutrients on the clinoptilolite was relatively low, however, nutrients could be removed from the liquid fraction of digestate with high removal efficiencies. This indicated that the use of clinoptilolite could be a solution for improved management and utilization of the liquid fractions of digestate.
- Sep 2016
Concentrating nutrients on sorbents such as biochar and clinoptilolite and subsequently using the nutrient-enriched sorbents as a fertiliser could be an alternative way to manage nutrients in the liquid fraction of digestate. In this study, we investigated the use of biochar and clinoptilolite columns in removing ammonium, potassium, orthophosphate and dissolved organic carbon (DOC) from the liquid fraction of digestate. Our objectives were to investigate the effect of the initial loading ratio between liquid and biochar on nutrient removal, and to investigate the effect of combining biochar with clinoptilolite on nutrient and DOC removal efficiency. Increasing the initial loading ratios increased nutrient concentrations on biochar to 8.61 mg NH4-N g⁻¹, 1.95 mg PO4-P g⁻¹ and 13.01 mg DOC g⁻¹. However, an increase in the initial loading ratio resulted in decreasing removal efficiencies. Potassium removal was not possible since biochar released potassium into the liquid fraction of digestate. The combination of biochar and clinoptilolite resulted in improved ammonium, potassium and DOC removal efficiencies compared to biochar alone, but did not significantly change PO4-P removal efficiencies. Removal efficiencies with combined sorbents were up to 67% for ammonium, 58% for DOC and 58% for potassium. Clinoptilolite alone showed higher removal efficiencies compared to biochar alone, and combining clinoptilolite with biochar only improved total P removal efficiency. Nutrient removal from the liquid fraction of digestate with clinoptilolite and biochar may be an option for concentrating nutrients from the liquid fraction of digestate when both sorbents are available at a low cost.
- Jun 2016
The liquid fraction of digestate contains nutrients which makes it a valuable fertiliser in agricultural crop production systems. However, direct application of digestate may raise practical and environmental problems. Therefore, processes to concentrate nutrients have been proposed aiming not only to treat the liquid fraction of digestate to overcome the problems related to direct application, but also to recover the nutrients of which natural reserves are being depleted such as phosphorus and potassium. In this thesis, the focus was on the evaluation of the use of clinoptilolite and biochar for nutrient recovery from the liquid fraction of digestate; and to investigate the further use of these nutrient-enriched materials as fertiliser. This thesis showed that sorption with clinoptilolite and biochar can be a promising technology to recover nutrients from liquid fraction of digestate. Using biochar and clinoptilolite provides concentration of nutrients and, thereby, volume reduction which allows for savings on storage, transport and application of the voluminous liquid fraction of digestate. The end-products are digestate-enriched clinoptilolite and enriched biochar can act as N fertilisers.
- Jun 2013
- 15th RAMIRAN International Conference
- May 2012
Within the context of Ecological Sanitation (ECOSAN), human urine has been the subject of research and practice as a potential fertilizer in the recent years. Although quite a lot had been done with original undiluted urine with promising outcomes, not much appears in the literature which concentrates on dilute solutions of urine. This is important because unless waterless toilets are employed, urine will be diluted with flush water in actual use. In this work, dilute solutions of urine are investigated with emphasis on the recovery of plant nutrients. A natural zeolite namely clinoptilolite was loaded with nitrogen, phosphorus, and potassium as an indirect route of processing urine. The results have revealed that hydrolysis is completed in shorter times in dilute samples. Clinoptilolite could successfully remove plant nutrients from all dilute solutions. Nitrogen could be recovered up to 86% with higher efficiencies at higher concentrations in general. Recovery of orthophosphates increases with increasing concentration to reach 96%, however, potassium could not be recovered. The preliminary experiments with grass have revealed that nutrient loaded clinoptilolite was as effective as chemical fertilizers while direct application of original and diluted solutions of urine had shown inferior yields.
- Jan 2011
- WEF/IWA Nutrient Recovery and Management Conference
The natural zeolite clinoptilolite exhausted with ammonium is proposed as an alternative fertilizer. Two different sources of exhausting clinoptilolite with ammonium, and recovery of the surface accumulated ammonium were investigated. The two sources were conventional domestic wastewater and separately collected human urine. The feed solution was contacted with clinoptilolite for transfering ammonium onto the solid phase in laboratory scale columns. Subsequently, the exhausted clinoptilolite was contacted with tap water to observe the release of ammonium into the wash water. The results have revealed that over 90% of ammonium in conventional domestic wastewater and human urine could be transferred from the liquid phase onto the solid phase. High levels of recovery from surface accumulated ammonium could also be achieved, suggesting that the exhausted clinoptilolite may be used as a potential fertilizer. Surface concentrations in both cases were comparable at the level of 9.5±0.5 mg NH4 +/g clinoptilolite. Recoveries of ammonium from both sources were comparable, i.e. 8.46 – 9.07 mg NH4 +/g clinoptilolite and in all cases were over 90%, going up as high as 96%. In summary, the recovery of ammonium from exhausted clinoptilolite was high and comparable regardless of its source, indicating that the use of clinoptilolite loaded with ammonium as an alternative fertilizer is a promising suggestion.
Collection of wastewater in segregated streams is one of the new concepts in domestic wastewater management. One such stream is yellow water which is mainly human urine. Direct use of this richest fraction in terms of nutrients on plants as fertilizer is one of the recommendations as the final end use. Indirect use of urine as fertilizer may also be exercised after various modes of processing. One of those is processing with clinoptilolite to transfer plant nutrients onto the zeolite and then to recover them subsequently. One of the significant factors in this process is the initial nutrient loading with which clinoptilolite is charged. This paper aims to investigate the transfer of ammonium and potassium from source-separated urine onto clinoptilolite, concentrating upon surface concentrations attained and removal efficiencies under various initial ammonium loadings. The results have indicated that variations in initial loading have no significant effect in terms of removal efficiencies up to 10 mg NH(4) (+)/g clinoptilolite. Highly acceptable efficiencies could be attained up to 15 mg NH(4) (+)/g clinoptilolite after which the efficiency goes down as initial loading is increased. Overall, increased initial loadings result in higher final surface concentrations but decreased removal efficiencies.
Awards & Achievements (2)
Grant · Sep 2012
Stable Isotopes PhD course, Cost Action- SIBAE Training School Grant
Scholarship · Sep 2011
Erasmus Mundus- Agricultural Transformation by Innovation