Packing material in biofiltration systems: Woodchip vs. pumice

Presenter: Dr. Wan Li Low

Date: 16th September 2014

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

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

Mechanics of a functional biofilter

• 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

• 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:

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

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)

Woodchip vs. PumiceWoodchip 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

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

Physical properties: Woodchip vs. LavaRok®• Structural condition – scanning electron microscopy (SEM) examination

Photomicrographs of random woodchip samples

• Structural condition – scanning electron microscopy (SEM) examination

Photomicrographs of random LavaRok® samples

Physical properties: Woodchip vs. LavaRok®

Moisture: Woodchip vs. LavaRok®

• Percentage moisture uptake

• Percentage moisture retention by media

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 %

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 %

• Rate of colonisation on woodchip

Colonisation: Woodchip vs. LavaRok®

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

• Rate of colonisation on LavaRok®

Day 1

oInitial incubation show some bacteria cells starting to colonize the surface

Colonisation: Woodchip vs. LavaRok®

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.

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 hyphaeo 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-odouro LavaRok® – inert to chemical reaction, not degradable by microbial

activity, odourless

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

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

• 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

Collaborators

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).

Reference

Client using OSIL technologies

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