Students

The increasing demand for metals marked the tremendous growth of metal extraction and refining operations worldwide. This growth resulted in the discharge of large volumes of wastes containing significant amounts of metals that can still be recovered. Applying the conventional metal recovery processes to wastes, practical applications are limited by certain factors, such as economics. This led to the development of alternative processes, which include biosorption and bioleaching. Most bio-based processes, however, are still at the lab scale. Therefore, more studies are needed to design and optimize these processes for application on real waste streams. To do this, the development of a high throughput experimentation platform would be very advantageous. Thus, this research aims to set up and optimize a high throughput experimentation platform for biosorption and bioleaching of metals; and to apply this platform for selective recovery of technology-critical elements from industrial wastewaters and valuable metals from mine tailings.

Autogenerative High Pressure Anaerobic Digestion systems (AHPD) have been used to produce biogas with improved quality (90-95% methane content) and at a pressure suitable for high grade use. This technology has also proven to produce other metabolites (carboxylates), that by themselves or through further conversion, could be of interest for the chemical industry. It is expected that specific pressure effects influence the kinetics of mixed culture fermentations (e.g. role of the CO2 partial pressure) and eventually the product spectrum. This project aims to further address these effects and determine to what extent they can be exploited to improve the production yield and increase the selectivity of a HPD system for carboxylates production. The feasibility of treating simple and complex substrates, mechanisms for controlling the product spectrum as well as the requirements for process parameters optimization, reactor design and alternatives for downstream processing will be further addressed along the research.

Trace elements are crucial constituents of cofactors and enzymes, and as such, they affect metabolism of microorganisms in anaerobic reactors. In practice, trace elements are often present in sufficient amounts, but their uptake by microorganism may be hindered by low bioavailability. The objective of this topic is to determine the trace elements deficiency in anaerobic membrane bioreactor for wastewater treatment. Moreover, we will study also trace elements limitation in the post-treatment of anaerobic effluent, i.e. during nitrogen removal. The expected deficiencies will be determined in respect to metal bioavailability and speciation in both liquid and solid phase. Furthermore, the possible solutions for overcoming potential deficiencies will be proposed.

My PhD topic is titled: model-based knowledge buildup of mixing behavior in anaerobic digesters in view of maximizing performance. Anaerobic digesters (AD) at full scale often do not reach their full potential of biogas production. It is postulated that this is caused in large extent due to incomplete mixing, resulting in heterogeneities and stratification, thus inducing reduced performance.  Dedicated rheological and density experiments with AD influent, sludge and mixtures will be performed as well as at different locations in AD.  This will lead to new process insight and is to be used as input in computational fluid dynamics (CFD). The modelling work will be initiated by studying the behavior of Anaerobic Digestion Model 1 (ADM1) in conjunction with a continuous stirred tanks (CSTR) and Tanks-in-series (TIS) approach. Next, a CFD model will be developed to model hydrodynamics full scale AD reactors of different design to optimize the mixer impeller (blade number, speed, position, and etc.). Computed CFD is used to derive a more accurate compartmental model (CM) based on velocity patterns. This work lead to process insight and potential actions for process optimization. The optimal CM needs to be translated into an AD and a mixer design. The ADM1 model will be linked to frozen CFD solutions to get an idea about the impact of incomplete mixing on the distribution of different process rates in the reactor and the possible occurrence of stratification or even short-circuiting. 

Selective separation of Inorganic salts and organic matter has a wide variety of applications ranging from drinking water purification to industrial wastewater treatment and desalination. In this context, The present study aims at developing novel Nano-filtration (NF) membranes as energy efficient and flexible alternatives to address this need.

Hydrogen sulfide as a toxic gas is formed during anaerobic treatment of sulfate-containing wastewater. Deterioration of biogas quality, inhibition of methane formation and corrosion of downstream facilities are some of the problems associated with hydrogen sulfide. Therefore, minimizing the hydrogen sulfide content of the anaerobic bioreactors and controlling its emission with biogas is necessary. 

Micro-aeration as the controlled dosing of a small amount of air into the anaerobic reactor to promote H2S oxidation, is a simple process that has been demonstrated to reach high H2S removal efficiencies. By this, sulfides are oxidized mainly biologically to elemental sulfur. Nevertheless, several challenges are still associated with the micro-aeration processes, such as a lack of knowledge regarding the exact chemical and biological processes contribution to the micro-aeration effect; their mechanisms; fate of produced elemental sulfur; effect of operational conditions like hydro dynamics, reactor geometry, etc. A better understanding of these effects will result in efficient online control strategies to minimize the undesired effects and optimize this process.  This PhD project aims to tackle these challenges through several short-term and long-term lab-scale and full-scale experiments. Moreover, a mathematical model will be set up to design appropriate control strategies and increase process efficiency.

The overall PhD’s objective is to provide sustainable wastewater treatment in rural areas by combining CWs with BES and recover valuable resources by doing so. CW are an economic and ecologic alternative for conventional wastewater treatment in small settlements and will be the main technology assessed in combination with BES - particularly Microbial Fuel Cells (MFC’s) and Microbial Electrolysis Cells (MEC’s). In MFC’s and MEC’s, active bacteria break down and remove organic matter from the wastewater while producing electricity. When incorporated in a CW, these BES can increase the treatment efficiency and thereby reduce the area required for purification. BES might also used as a biosensor, for example, to monitor the content of organic matter and other biologically active compounds throughout the CW system.

Urbanization, as a major and continuing megatrend implies that large quantities of wastewater are generated in cities and accumulate a variety of different substances. The PhD project aims for supporting the design and development of more sustainable wastewater management strategies that are based on a resource recovery perspective. Conventional and innovative wastewater treatment technologies can promote value creation and contribute to sustainable development if wastewater derived products can become re-integrated into existing material and energy flows. In this context, a strategical framework that provides guidance to exploit the resource recovery potential of existing urban wastewater systems is needed. In addition, bottlenecks for the implementation of innovative wastewater resource recovery pathways shall be revealed like e.g. economic constraints or social acceptance barriers for recoverable products.

My PhD topic is “closing the micronutrient: exploration of micronutrient-rich bioproducts generated from wastewater as environmental-friendly micronutrient supplements and fertilizers”. The objective of my project is to 1) develop and apply sustainable, biobased methods which are able to selectively remove essential trace elements from wastewaters and 2) test micronutrient-rich materials produced by these methods for their potential use as micronutrient fertilizer or food/feed supplement by studying the bioavailability and bioaccessibility of micronutrients contained in these products.