Delft University of Technology
Section Sanitary Engineering Department Water Management
Faculty of Civil Engineering and Geosciences
HIGHLIGHTS
Anaerobic Membrane Bioreactors under
Extreme Conditions
Julian Muñoz*, Merle de Kreuk, Henri Spanjers, Jules Van Lier
Introduction
Membrane bioreactors ensure biomass retention by the application of micro or ultrafiltration processes. This allows operation at high sludge concentrations. Previous studies have shown that anaerobic membrane bioreactors is an efficient way to retain specialist microorganisms for treating wastewaters from different industries such as coke, textile, food, and chemical. However, few research has been found into the use of membrane bioreactors for anaerobic treatment of wastewater under extreme conditions. The latter would enable their application to a wide range of industrial processes with the potential purpose of water recycling. The challenge for future research is finding the optimum operational conditions to control maximised bioconversion under extreme conditions such as high salinity and high temperatures, without being limited by reduced membrane fluxes.
Motivation
•At extreme conditions maintaining stable granules can no longer be guaranteed, and alternative technology is required.
•Knowledge gaps on anaerobic treatment under these conditions. Anaerobic MBR is a potential option that needs to be considered.
Research Objective
The aim of the study is to understand the bioconversion of model organic compounds (toxic/recalcitrant, e.g. phenol, phenolic compounds) existing in industrial wastewaters under extreme conditions. The research will focus on the most suitable technology for this purpose (i.e. anaerobic membrane bioreactors) to encourage reclamation of process waters for reuse.
Approach
•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 such as biomass in-situ bio-augmentation and
conversion/inhibition/toxicity, microbial ecology dynamics, filterability, and controlling fouling potentials will be addressed.
The proposed research will increase the
understanding of how complex compounds are converted by the microorganisms, what is the influence of different conditions on the microbial community, functionality and biomass properties, and how the process is addressed within the technology selected (An-MBR).
Figure 2 – Experimental Setup
Section Sanitary Engineering / Department of Water Management *J.D.MunozSierra@tudelft.nl
Extreme condition Effects on anaerobic process Advantages of AnMBRs Challenges of AnMBRs High salinity Reduced biological
activity Poor granule stability, low settleability. Long adaptation time
Bacteria are retained regardless of settling/granulation properties. Retention may
improve adaptation.
Bacterial decay products due to osmotic pressure stress affect filtration performance. Aromatics Compounds /Toxicity Inhibition of SMA Biomass decay Long acclimatization time Biomass loss If a CSTR bioreactor is used it provides a better dilution under a toxic shock load. No biomass loss Bioaugmentation of
specialized bacteria is more suitable.
Suspended cells systems are more susceptible for toxicants than biofilm or granular sludge based systems. Thermophilic conditions Difficulty in granulation of anaerobic biomass. Biomass retention is not dependant on granulation. A higher flux may be
achieved due to reduced viscosity of the sludge.
Temperature fluctuation can cause stress on biomass and increase membrane fouling. A compact cake layer
may cause lower fluxes when compared to mesophilic conditions. Biomass acclimatisation/Bioagumentation Microbial Ecology Phase I AnMBR-I
(tubular) AnMBR-II(tubular) Sludge Shell Sludge Purac Phenol Phenol Salinity Salinity Thermophilic Phase II Biomass properties Coagulant
dosing Coagulantdosing Polyphenols
Online control strategy
Bulk Biofilm Bulk Biofilm
Figure 1 - Problem identification scheme
BioXtremeProject
Table 1 – Advantages and challenges of anaerobic MBRs under extreme conditions
Figure 3 – Methodology overview Figure 4 – Factors affecting the An-MBR performance
Factors affecting the An‐MBR performance Hydrodynamic conditions: Effects of shear Cross‐flow velocity Gas sparging Backwashing Biological system: Biomass concentration Particle size distribution EPS/SMP Microbial community Bioreactor operating conditions: Organic loading rate Hydraulic loading rate Temperature Toxic Shock Influent variability (salinity, aromatics) Process Performance: Bioconversion Effluent quality Membrane flux Pressure drop Chemical system: Coagulation (induced) Membrane /Cake layer: Surface morphology Porosity Thickness Industry: Petro‐Chemical and Coal/Coke Main pollutants: Aromatic Compounds Wastewater harsh conditions: High concentrations, salinity, pH, T° Biodegradability Toxicity Inhibition Feasible bio‐treatment Sludge Filterability Water reuse possibilities Energy concerns concerns Technology selection An-MBR
