Packaging material in bio-filtration systems: Woodchip vs. Pumice

1. Packing material in
biofiltration systems:
Woodchip vs. pumice
Presenter: Dr. Wan Li Low
Date: 16th September 2014

2. Introduction
• Odorous emission source - manufacturing, petrochemical, food, solid waste,
sewage treatment and agricultural activities
• Treatment methods - scrubbing, incineration, thermal oxidation, biofiltration and
adsorption
• Air pollution compounds - VOC, sulphurous compounds, ketones, aldehydes, lower
molecular weight fatty acids, ammonia and amines
• Odorous air pollutants - NH3, VOC, sulphur-containing compounds such as H2S, S2-
and mercaptans (R-SH)
• Irritants and some may be hazardous to health at higher exposure
• Modernization of biotechnology - biofiltration systems gaining popularity

3. Introduction to biofiltration
• Biofiltration – biological system, relies on microorganisms to
metabolise/neutralise the malodorous compounds
• Mixed population can develop over time from the indigenous microorganisms
present - natural selection
• Ensure stable environment for microorganisms to proliferate and establish growth
• Controllable parameters - temperature, pH, oxygen and moisture content
• Benefits include:
o economical – does not involve complex chemicals
o controllable system - lower maintenance
o does not produce secondary pollutant
o usually requires ambient temperature and pressure

4. Mechanics of a functional biofilter
• Biofilter filled with packing
material - containing
microorganisms/biofilm
• Odorous air stream into
moist environment
• Transfer of compounds
from gaseous phase into
aqueous phase.
Example of biofilter configuration:
• Increases availability of compounds - serves as alternative energy source for
microorganisms.
• Absorption of the compounds into aqueous phase within the biofilm:
o increases interaction and contact time
o enhance the rate of degradation of odorous compounds

5. Biofilter media
• Availability of suitable media to allow the microorganisms to attach, grow and
develop into a well-established biofilm
• Common choices of packing materials:
o organic : peat, compost, woodchip, agricultural waste materials, seashells
o non-organic : plastics, pumice

6. Biofilter media
• The feasibility of microorganisms to establish a biofilm on the packing material
depends on properties such as:
o high surface area - for microbial cell colonisation
o porosity - increase surface area
o degree of compaction - media degradation
o moisture retention - condition for microbial growth, aqueous phase for reaction
• Commonly used effective biofilter packing material:
o woodchip (organic)
o pumice (non-organic)

7. Woodchip vs. Pumice
Woodchip Pumice
o wide availability - economical prices
o presence of some natural microbial
diversity
o availability of nutrient contents
o biodegradable - prone to loss of
structural stability, microbial
degradation/ chemical degradation
o some may contain antimicrobial
components - natural essential oils,
hinder microbial colonisation
o self odour – e.g. pine wood
o high surface area - promote microbial
colonisation
o lack of natural microbial diversity
o porous structure, light weight
o not biodegradable - no loss of
structural stability
o high silica content (depending on
geography) - chemically inert, hence
less prone to chemical degradation
o odourless

8. Experimental analysis
• Compare properties of woodchip and LavaRok®
o Woodchip - common media used in biofilters
o LavaRok® - pumice, used in OSIL’s high performance hybrid biofilter products
• Analysis of:
o Physical properties
o Moisture uptake / retention
o Rate of colonisation

9. Physical properties: Woodchip vs.
LavaRok®
• Structural condition – scanning electron microscopy (SEM) examination
Photomicrographs of random woodchip samples

10. Physical properties: Woodchip vs.
LavaRok®
• Structural condition – scanning electron microscopy (SEM) examination
Photomicrographs of random LavaRok® samples

11. Moisture: Woodchip vs. LavaRok®
• Percentage moisture uptake
Woodchip LavaRok®
Normal air Moist warm air Normal air Moist warm air
Day 1 134 % 129 % 92 % 52 %
Day 7 188 % 176 % 105 % 57 %
Day 14 197 % 188 % 114 % 61 %
• Percentage moisture retention by media
Woodchip LavaRok®
Normal air Moist warm air Normal air Moist warm air
Day 1 100 % 100 % 100 % 100 %
Day 7 60 % 100 % 67 % 100 %
Day 13 34 % 93 % 43 % 103 %

12. Colonisation: Woodchip vs.
LavaRok®
• Rate of colonisation on woodchip
Day 1
oBubble-like structures - release of plant materials (oils)?
oMay interfere with the availability of oxygen
oMay also contribute to some antimicrobial activity
Day 3
oDense, uncontrolled
colonisation on the surface
of the woodchip
Day 6
oHigh diversity of microbes
present on the woodchip
sample

13. Colonisation: Woodchip vs.
LavaRok®
• Rate of colonisation on LavaRok®
Day 1
oInitial incubation show some bacteria cells
starting to colonize the surface
Day 3
o Dense colonization on
the surface of the
LavaRok®
Day 7
o Very dense microbial colonisation
on the surface of the LavaRok®
o Relatively uniform type of cells
growing on the LavaRok®
o Cells are starting to colonise the
deeper fissures within the
LavaRok® structure.

14. Research outcome
• Woodchip and LavaRok® - suitable biofilter packing material
• Moisture retention properties:
o Woodchip can absorb more moisture compared to LavaRok®
o LavaRok® slightly better at retaining moisture compared to woodchip
• Surface colonisation properties:
o Woodchip - can be “pre-loaded” with microbial diversity, good surface
area for colonisation, possible competition due to fungal hyphae
o LavaRok® - lack of “pre-loaded” microbial diversity, high porosity with
good surface area
• Physical properties:
o Woodchip - prone to degradation (moisture, chemical and microbial
activity), possible compacting of media bed, may contain self-odour
o LavaRok® – inert to chemical reaction, not degradable by microbial
activity, odourless

15. Future research
• Investigate the feasibility of using other materials as biofilter packing
media
• Develop methodology to efficiently adapt biofilter conditions to promote
rapid colonisation
• Collect data to analyse the development/change of microbial population
within a biofilter e.g. changes due to natural selection
• Development of a ready-to-go freeze dried immobilized-cells to be used
as an effective and rapid biofilter re-seeding methodology – OSIL
RescuePack
• Create an adaptable mixed culture of inoculums for the treatment of
more complex odours coming from modern industrial processes

16. Conclusion
• Biofilter performance relies on the healthy population of microorganisms
living within the media bed to degrade the malodourous compounds
• Important to control essential parameters to preserve microbial
population health, hence leading to effective biofilter performance
• There are advantages/disadvantages of using LavaRok® or woodchip
media
• Choice of biofilter packing material will depend on other limiting factors
e.g. cost, maintenance and availability of media
• Colonisation can be promoted by seeding biofilter bed with suitable
inoculums
• Optimum microbiological performance achieved by seeding LavaRok®
• Healthy population of microorganisms = good biofilter performance

17. Collaborators
• OSIL, U.K.
o Matt Wilkes, Dr. Corby Lee, Dr. Wan Li Low
• University of Wolverhampton, U.K.
o Prof. David Hill and Dr. Clive Roberts
• Knowledge Transfer Partnership, U.K.
o Dr. Russ Bromley
Reference
1. Anet, B., Couriol, C., Lendormi, T., Amrane, A., Le Cloirec, P., Cogny, G., & Fillières, R. (2013).
Characterization and Selection of Packing Materials for Biofiltration of Rendering Odourous
Emissions. Water, Air, & Soil Pollution,224(7), 1-13.
2. Frederickson, J., Boardman, C. P., Gladding, T. L., Simpson, A. E., Howell, G., & Sgouridis, F. (2013).
Evidence: Biofilter performance and operation as related to commercial composting.
3. Lebrero, R., Estrada, J. M., Muñoz, R., & Quijano, G. (2014). Deterioration of organic packing materials
commonly used in air biofiltration: Effect of VOC-packing interactions. Journal of environmental
management, 137, 93-100.
4. Low, W. L., Lee, C., Wilkes, M., Roberts, C., & Hill, D. J. (2014). Development of a rapid, effective method
for seeding biofiltration systems using alginate bead-immobilized cells. International Journal of Chemical &
Environmental Engineering, 5(1).

18. Client using OSIL technologies

19. THANK YOU FOR YOUR
TIME
FOR MORE INFO PLEASE VISIT
http://www.osiltd.com
EMAIL US AT info@osiltd.com
OR wanli.low@osiltd.com