Doctoral dissertation

Mathematical modelling of trace elements dynamics in anaerobic digestion environments

Bikash Chandra Maharaj
ADM1 based novel dynamic models for precipitation, complexation and sorption of trace elements during anaerobic digestion.

Mitigation of global climate change and energy crunch requires adaptation of sustainable green technologies. In this regard, energy from biomass is one of the most promising options. Anaerobic digestion (AD) has proved to be a robust technology to harness energy from biomass in form of biogas. Apart from being an energy source, effluents from AD are also an excellent source of biofertilizers.

Although AD is an efficient technology, the changing nature of the waste influents necessitates constant technology improvisation in order to set up a stable AD process and meet environment, energy needs and cost demands. Most research efforts have been directed towards process optimization, which involves in many cases essential micro nutrients dosing. Micronutrients in form of trace elements (TEs) such as Fe, Ni, Co, Mo, W, Mn and Se are structural components of active sites in essential enzymes of AD pathway, particularly methanogenesis. Unfortunately, experimental quantification of the dynamic behavior of these micro nutrients or TEs is difficult and prone to errors due to the low resolution limit of instruments and operational limitations.

In his doctoral dissertation Bikash Chandra Maharaj proposed and recruited new mathematical models to predict the concentration and fate of various biogeochemical species in AD. The mechanistic models were developed progressively taking into consideration the major physicochemical processes involving trace elements, i.e, precipitation, complexation and adsorption, in addition to biochemical processes.

The main objective of the study was to propose, develop and establish a new mathematical modelling framework to quantify the effect of TE speciation on biodegradation processes. The first model focused on TE precipitation dissolution processes and its effect on cumulative methane production was predicted. In the next attempt, TE complexation reactions with EDTA and VFAs were considered. Finally, sorption/desorption of TEs on biomass, inert and mineral precipitates were taken into account to develop a TE speciation model able to mimic the physicochemistry of TEs in AD systems. Suitable model scenarios were considered to test the model predicting capability in terms of change in TE speciation and cumulative methane production.

Public defense of a doctoral dissertation on Tuesday, 10th of December

Bikash Chandra Maharaj’s dissertation in the field of environmental technologies entitled ADM1 Based mathematical models for accessing the effect of trace element dynamics on solid waste anaerobic digestion will be publicly examined at University of Paris-Est, (address: meeting room; Batiment IFI) on Tuesday, 10th of December 2019 at 15h00. The opponents will be Prof. Patrice Chatellier from French Institute of Science and Technology in Transportation, Planning and Networks, Paris (France), Prof. Lorenzo Bertin from University of Bologna (Italy) and Prof. Blaz Stres from University of Ljubljani (Slovenia). Prof. Patrice Chatellier will also act as the chairman.

Bikash Chandra Maharaj’s doctoral research has been conducted in the framework of the Advanced Biological Waste to Energy Technologies (ABWET) Innovative Training Network (ITN) European Joint Degree Programme. ABWET has four partner organizations: University of Cassino and Southern Lazio (Italy, coordinator), Université Paris-Est (France), IHE Delft (the Netherlands) and Tampere University of Technology (Finland). The Examination Committee of Bikash Chandra Maharaj’s doctoral dissertation includes one representative from each partner organization.

Bikash Chandra Maharaj comes from Talcher (Odisha, India) and worked as a researcher in the Department of Civil and Mechanical Engineering at the University of Cassino and Southern Lazio, Italy. A part of his research was carried out at the Department of Mathematics and Applications, “Renato Cacciopoli”, at University of Naples Federico II, Italy and IHE Delft Institute of water education, Delft, The Netherlands.

The dissertation is available in the faculty of Engineering and Natural Sciences (Konetalo building K2222A) at Tampere University and by request from the address: suvi.ikonen [at] tuni.fi