Anua - Bord na Móna Limited

Biofiltration systems for the treatment of waste gas from industrial plants

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Courtesy of Anua - Bord na Móna Limited

Bord na Móna Environmental Ltd have considerable experience in the field of biological air filtration (600 installations). Initially, the majority of installations were on Municipal and Industrial Wastewater applications. This was quickly followed by Municipal Solid Waste, an application Bord na Móna jointly developed with its Italian partners Air Clean srl. Since 2000, Bord na Móna have concentrated their efforts on VOC, industrial applications and high strength airstreams. New applications include treatment of airstream containing high concentration of H2S, ammonia, VOC or indeed a combination of all three.



In response to increased pressures from stringent environmental legislation, and an increased understanding of the impact of pollutants, there is an increasing requirement for sustainable treatment options for various air emissions to the environment. Success in biofiltration will be shown to be closely linked with in-depth analytical process engineering, accurate characterisation of waste gas streams, control of process conditions for optimisation of biological activity, and the physio-chemical properties of the filter media. Biological technologies have been developed to treat a range of applications from relatively straightforward odour emissions from municipal wastewater treatment plants through to difficult complex industrial emissions.


Biofiltration by definition is the aerobic degradation of pollutants in the presence of a carrier media. The early development work on biofiltration technology concentrated on organic media, such as, peat, compost, wood bark etc. In general terms, organic compounds in air are degraded to carbon dioxide and water, while inorganic compounds, such as, sulphur compounds are oxidised to form oxygenated derivatives.

Initially, Bord na Móna identified the UK municipal wastewater market as a target market for biofiltration systems. A research and development programme was set up to establish the optimum operational conditions for the treatment of sulphur compounds (principally H2S, Mercaptans and Alkyl Sulphides) using peat based biofiltration materials.

The outcome of these results can best be summarised as follows:

(i) Peat/organic media based filtration systems are suitable for municipal applications and can treat H2S levels typically up to a maximum of 50mg/m3.
(ii) Two loading regimes were identified as optimum for airstreams with a maximum of 15mg/m3 H2S and 50mg/m3 H2S.
(iii) The limiting factor for treatment of sulphur compounds in the peat media system was identified as pH. A control system based on the operation of an intermittent irrigation system was developed.
(iv) Various mixes of peat fibre and heather were trialled and optimum media specifications identified.
(v) Optimum operating parameters in terms of gas loading, temperature, pH and operation of irrigation system were identified.
(vi) Requirement for open homogenous media material identified.
Peat fibre/heather mixes limited to one metre in depth.

As part of the study, Bord na Móna trialed a new granular peat media. This media is a fractionalised high density peat media. The media has a high “Air Filled Porosity” (85%) and exhibits excellent physical characteristics. The key potential advantage was that it can be installed up to a depth of 3 metres thus reducing footprint by up to two thirds, of particular relevance to industrial sites. This engineered granulated peat media has been granted a patent and is called MÓNAFIL. Bord na Móna undertook extensive work with its Italian partner Airclean to develop the application of treatment of off-gasses from municipal solid waste treatment facilities, including composting plants with this media from the mid 1990’s onwards. Over twenty such installations have been successfully installed to date.


Field experience on municipal wastewater applications using peat based biofilter media confirmed the R&D findings that pH was indeed the limiting factor. If the system saw high levels (excess of 50 mg/m3) of H2S, it was found that the by-products of H2S oxidation resulted in lowering in pH of the media. At low pH, while H2S removal still remains high, odour removal efficiencies tend to deteriorate particularly if Alkyl Sulphides and Mercaptans are present in the air.

The use of shells in a biotrickling process was identified as offering the following potential advantages:

(i) In-built buffering capability due to the chemical make-up of shells (calcium carbonate)
(ii) High air-filled porosity. (AFP)
(iii) Ability to sustain high irrigation rates and capacity to retain large quantities of water.
(iv) Shape and size of packing is in the correct range for good mass transfer.
(v) Calcium Carbonates are known to be a good media for supporting biological activities.
Media has a high affinity for sulphur compounds.
(vi) Shell media, a natural by-product of shell-fish processing, offer the nutrients required to sustain biological activity.

Laboratory and field trials were carried out on shell-based systems. Early trial results indicated excellent results, so much so that it was decided to develop the process as a stand alone technology. Patents were applied for and the technology was launched in 1995. Since then, over 500 installations have been installed worldwide for airstreams with levels up to and in excess of 500ppm H2S.


In an effort to expand the application of biotechnologies into the region of industrial applications for the treatment of air streams continuous high concentrations of VOC’s, organic sulphur compounds and ammonia an extensive R&D project was initiated in 1997.

From application experience it was known that the main limiting factors when treating VOC’s were as follows:

(i) Limited solubility and volatility of many organic compounds leading to “poor” capture and treatment.

(ii) Excessive biomass production leading to “plugging” of filter media, excessive back pressure and poor treatment.

The project initially concentrated on persistent VOC compounds (Toluene, Benzene and Xylene). The findings of this study has relevance for other groups of compounds and other applications.

These different dynamcis were explored, two of which have significant application to enhance treatment for difficult air streams on Industrial and Municipal applications.

There are:

(i) Air Flow Dynamic
- Recirculation of air
- Multi-Staging

(ii) Utilising of different shell species

(iii) Electromagnetic stimulation of recirculated water to prevent biofouling.

The first commercial installation on an industrial application utilising the outputs from this study was installed in Scotland in 2002. The system is monitored continuously for VOC emissions with analysis validated by local regulatory authority. The system has continuously met the required treatment levels.

One of the main conclusions of the trial was that efficiency can be greatly increased by Multi-Staging with the same overall net contact time. This dynamic can be employed in our standard units for high strength applications on waste water treatment or applicable when high efficiencies are required.

The experience which Bord na Móna has gained over the years has proved that biological technologies can be successfully applied to difficult applications with remarkably predictable performance.

Biological systems need to be engineered such that all critical parameters can be monitored and controlled. Biofiltration is successfully emerging from the shadows as a reliable, low cost option for a broad range of air treatment applications. It is now becoming apparent that biological treatment will play a far more significant role in achieving environmental control on air emissions.

Conclusion with respect to MÓNAFIL

  • Media successfully installed up to 3 metres deep.
  • Media life span in excess of five years.
  • Media can be regraded and re-used at the end of its life.
  • No evidence of media breakdown, proven process performance on installation over prolonged time period in excess of five years.

Conclusion with respect to MÓNASHELL

  • Ability to treat high and variable contaminant levels (up to 1000 ppm H2S).
  • Inbuilt PH control with no additional chemicals.
  • Media consumed in reaction. Predications of media life calculation (based on stoichiometric calculations confirmed).
  • Typical efficiency in excess of 99%.
  • Excellent performance on a broad range of odour components (VOC and nitrogen based compounds).
  • Process proven as effective odour control technology on stand along basis.

Conclusion with respect to MONASHELL EBF

  • Recirculation of air increases removal efficiency from 30 to 80% at the same net contact time on low solubility persistent VOC’s.
  • Eliminates capacity increased from 20g/m3f/h to 60g/m3f/h.
  • Electromagnetic stimulator reduces accumulation of biomass on media preventing build up of pressure.
  • Deployment of different shell types on application by application basis.
  • Development of Multi-Pass system Vs recirculation (reduced power requirements).
  • Optimum operating and control requirements for control of pressure drop through system.
  • Imperative of Co and combined flow configurations.

The above treatments offer superior system performance with the lowest full life cycle and utilities usage costs in Class.

MÓNA Case Studies

Table 1. MÓNAFIL Case Study
Location Milan
Application Treatment of emission from Municipal waste composting
Date of installation 1996
Biofilter size 2 x 1500 m3
Total gas flow rate 300,000 m3/hr
Typical emission Ethanol, Limonene, Acetone, Methyethyl, Ketone, Toluene, Benzene, Xylene
Inlet VOC 100-300 mg/m3
Inlet odour concentration 10-12,000 OU/m3
Outlet odour concentration <200 OU/ m3
Outlet VOC <50 mg/ m3
The above treatments offer superior system performance

Table 2. MÓNAFIL Case Study
Location Rome
Application Treatment of emission from Municipal waste composting
Date of installation 2001
Biofilter size 1500 m3
Total gas flow rate 150,000 m3/hr
Typical emission Ethanol, Limonene, Acetone, Methyethyl, Ketoe, Toluene, Benzene, Xylene
Inlet Odour (average) 50,000 OU/m3
Inlet VOC 100-150 mg/ m3
Outlet odour concentration <200 OU/ m3
Outlet VOC <10 mg/ m3

Table 3. MÓNASHELL Case Study
Location Sewage Treatment Plant, Ireland
Application Treatment of emissions from picket fence thickener
Date of installation April 1998
Biofilter size 3 m3
Total gas flow rate 160 m3/hr
Inlet odour concentration 12,722 ou/m3
Outlet odour concentration 294 ou/m3
Odour removal efficiency 98%*
* Determined by Force Choice Dynamic Olfactometer

Table 4. MÓNASHELL Case Study
Location Industrial Plant, Ireland
Application Treatment of emissions from anaerobic digestor of effluent
Date of installation January 1998
Biofilter size 24 m3
Total gas flow rate 200 m3/hr
Inlet odour concentration 434,531 ou/m3
Outlet odour concentration 508 ou/m3
Odour removal efficiency 99%*
Inlet H2S concentration 1,600 ppm
* Determined by Force Choice Dynamic Olfactometer

Bord na Móna enters the US Air Pollution Market

Bord na Móna Environmental Products U.S. Inc., the American market subsidiary of the State-owned Irish Utility group Bord na Móna recently launched a range of wastewater treatment solutions and new odor/VOC control technologies in the US marketplace at the 81st Annual Water Environment Federation Technical Exhibition and Conference WEFTEC in Chicago. The company’s MÓNASHELL technology suitable for complex low volume, high concentration emissions is complimented by the MÓNAFIL technology which is suitable for high volume, low concentration applications. MÓNAFIL is a patented engineered peat-based organic biofilter media first developed in the early nineties. The media has developed an excellent world wide reputation and has been extensively utilised in large municipal solid waste composting plants. MÓNAFIL is differentiated by its long media life, low energy requirements (low back pressure) and proven process capability. It is one of the few biofilter media’s to meet the strict statuary legal outlet limit in Italy of 300 ou/m3.

The MÓNAFIL technology is currently treating 1,000,000 m3 per hour of air from four of the five large composting installations in Rome (Malagrotto, Viterbo, Albano, and Ama). With hundreds of MÓNASHELL installations worldwide, projects of particular note include: S.I.A.A.P. in Paris which is the largest wastewater treatment plant in Europe, Bransand Northumbrian Water UK, Monza Wastewater Treatment Facility in Italy, and a more recent addition is at Northpoint pumping station in Hong |Kong. (See attached photos)

The first MÓNASHELL installation in the U.S will be at the company’s innovation centre at the Greensboro Municipal Treatment Works where it will be independently monitored and validated by a local university. The Clean Air Solutions range of technologies will deliver low cost, highly effective solutions yielding significant benefits in terms of environment, cost, energy and chemical consumption and long term sustainability.

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