BioXtreme – Anaerobic wastewater treatment under extreme conditions

By: PDEng. Ir. Julian Muñoz Sierra

Research objectives
The aim of the study is to understand the bioconversion of model organic compounds (toxic/recalcitrant) existing in industrial wastewaters streams under extreme conditions. The research will focus on the most suitable technology for this purpose (i.e. anaerobic membrane bioreactors, AnMBrs) to encourage reclamation of process waters for reuse. Attention will be paid to the bioaugmentation of specific microbial communities and their growth dynamics in highly filterable sludge. An online control strategy will be proposed for the mitigation of membrane fouling within a long term operation of the AnMBRs.

Project outline
Industrial wastewaters generated in oil and chemical industries are often characterized by extreme conditions such as the presence of refractory and hazardous chemical compounds, high salinity, high temperatures. Particularly for these extreme types of wastewaters the conventional biological technologies have many limitations, but granular or membrane assisted bio-treatment offers many advantages such as in-reactor bio-augmentation of the required bacterial species and maximized sludge retention times (SRT), ensuring high metabolic conversion properties per unit of reactor volume. In case auto-immobilization or sludge granulation is difficult, application of membrane technology for pre-treating industrial process waters has several striking advantages: i) system compactness, allowing installation at or even inside the industry; ii) production of suspended solids free effluents, simplifying effluent upgrading techniques; iii) full retention of specific bacterial communities that are required for conversion of complex, recalcitrant and hazardous compounds.

There is an urgent need for sustainable and cost effective treatment technology that can make this water suitable for (re-)use. BioXtreme is aiming to deliver such a technology. If industrial effluents are properly treated, pollution can be prevented, and water produced can serve as an alternative source for existing freshwater resources or industrial processes.

A selection of waste streams of interest is made, i.e. at those industries where increased water efficiency is considered but hampered by the nature of the organic pollutants present. The treatability of the process water stream will be researched under controlled lab conditions and synthetic wastewater making use of down-scaled reactor systems. Relevant aspects of interests will be addressed such as biomass retention/bio-augmentation, conversion/toxicity of organic compounds, microbial population dynamics, filterability, and fouling potentials. Trials will be conducted with different phenolic compounds. Phenol is a key intermediate in the anaerobic conversion of a wide variety of aromatics, and, therefore, is of particular interest. Anaerobic treatment of phenol-containing wastewater has been mostly carried out using granular reactors, and its application has been limited under mesophilic and ambient temperature making the anaerobic degradation of phenolic compounds under thermophilic condition a challenge for AnMBRs. 

In the last phase of the research, water reclamation possibilities for industrial wastewater under extreme conditions will be evaluated.

Experimental set-up
The experiments are performed using three laboratory scale anaerobic MBR reactors with an effective volume of 7 L, and using an ultra-filtration (UF) membrane modules. The systems are equipped with feed, recycle and effluent pumps, pH and temperature sensors and a gas meters. Biogas recirculation pumps are used to mix the liquor. The temperature of the jacketed reactors is controlled at 35.0 ± 0.8 °C by thermostatic water baths. Currently, tubular PVDF membranes with 5.5 mm inner diameter and 0.64 m length are employed. The experimental system is connected to a computer running LabView software to control all pumps and collect pH, temperature, pressures and biogas flow data on-line.

Figure1. Experimental Set-Up.

Scientific relevance
Extreme conditions in the process water and wastewater of the industrial sector encourage the development of non-conventional biological treatment solutions. The research will increase the understanding of how the complex compounds are converted by the microorganisms, what is the influence of different conditions on the microbial community and functionality, and how the process is addressed within the technology selected (AnMBR). Findings are compared with current technologies, elucidating the added advantages of the developed extreme bioreactor concept, including new process configurations and water reuse possibilities.

Enabling An-MBR application to a wide range of industrial processes with the potential of water reuse.

Finding the optimum operational condition for maximised bioconversion under extreme conditions, without being limited by reduced membrane fluxes. 

Social relevance
In the Netherlands, about 80% of the fresh water use is industrial use. The research is focused on fundamental and applied research into the wastewater treatment and reuse technologies for application in the industry to compile know-how for optimizing the industrial water cycle and reducing its water footprint. Research with the final aim  in water recycling has the potential to improve the effectiveness of the existing technologies and invest in the future well-being of the world’s population.


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