Biological

Scrubbers
The next generation of H2S
odour treatment
 Cost-effective control of odours

Biological Scrubbers, also known as bio- Biological Scrubbers are the next generation of
trickling filters (BTFs) are fast becoming the H2S Odour Control. Historically biofilters, chemical
scrubbers and carbon bed adsorbers have been the
green technology of choice for many H2S main treatment technologies. Biofilters or soil bed
odour removal applications at wastewater filters are widely used for odour control in many
treatment plants and other applications. industrial applications because they are simple,
They efficiently remove objectionable cost effective with low environmental impact. Each
sewage H2S, VOCs and other odours from air technology have their different strengths, weaknesses,
capital and operating costs. For instance biofilters
streams using controlled biological activity. prefer regular, low concentration H2S loadings.

In many situation these systems are now being

Key benefits of Biological Scrubbers are: superseded by biological scrubbers. Biological
Scrubbers have been developed to address the
• Lower operating costs than other limitations of other technologies whilst retaining the
systems and better Life Cycle Cost than economic and environmental advantages of biological
Chemical Scrubbers and Carbon Filters treatment. Biological Scrubbers are now increasingly
at >25 ppm H2S. being used for removal of H2S, VOCs and general
odour control in many applications.
• Compact footprint. Biological
Scrubbers require approximately 10% Biological Scrubbers are used in
of the footprint of equivalent Soil Bed
Filters. • Wastewater treatment plants
• Pumping stations
• Excellent performance. >98% removal
of H2S – better than soil bed filters. • Rendering plants
• Proven performance even at higher • Pulp & Paper plants
H2S concentrations - to over 200ppm. • Food processing plants
• Simple operation No chemicals
needed, just small amounts of
nutrients.
• Consistent performance No
degradation of performance over time
or due to weather.
• Highly controllable as all key
processes are within vessels.
• No hidden operating costs
• Existing system upgrade Able to add
to an existing setup to reduce operating
costs.
• Extensible with the ability to extend the
quality of air discharge with a carbon
bed installation in the future.

April 2014 www.armatec.co.nz 2

How Biological Scrubbers work

Armatec Biological Scrubbers treat gaseous

contaminants in an airstream by passing it
through a bed of microorganisms that feed
on the gaseous molecules, consuming the
H2S and other compounds as food removing
them from the airstream.

These microorganisms (Thiobacillus genus) live on

a high surface inorganic bed inside the dedicated
vessel at a low pH. Because H2S is what they consume,
this eliminates the need for continuous carbon
replacement in carbon bed adsorbers or chemical
consumption in chemical scrubbers.

Biofilters are similar but unique compared to soil bed

filters. Biological Scrubbers use the same microbial 2
activity as soil bed filters to remove H2S and other
contaminants, but require only 10% of footprint of
an equivalent soil bed filter. Additionally the process
is inherently more stable, efficient and independent
of weather conditions as the biological activity is
contained inside the vessel where pH and nutrient
levels can be controlled.

Only small amounts of nutrients are needed

in Armatec Biological Scrubbers for optimizing
microorganism health. No oxidising chemicals are
required, greatly reducing daily operating costs. The
nutrient is typically a multi mineral garden fertilizer
product, and can be minimized or eliminated when
the fresh water stream contains sufficient nutrients.
3
To keep the conditions optimum for the
microorganisms, a small stream of fresh water must
be continuously supplied to the biological scrubber
sump, and excess water at approximately the same
rate overflows to waste. This waste stream contains
spent microorganisms, waste acid and any toxic
byproducts formed. Recycled treated water from
the wastewater treatment plant can be used as the
fresh water source, as long as it does not contain any
chlorine.

Please consult Armatec for more details on the

effective operation of a Biological Scrubber.

1: Armatec Biological Scrubber installed in Fertiliser Plant, 3

Christchurch removing 98% of 300ppm H2S. 2: Biological
action removing pollutants from air 3: Flow diagram of key
process within biological scrubbers.

www.armatec.co.nz 3
 World-class Biological Scrubbers
from Armatec

Armatec provides Biological Scrubbers Easy Startup & Restart

with world-class design, materials and end- As soon as there is a load of H2S in the incoming
to-end service. Our Biological Scrubbers gases, H2S consuming microorganisms start
deliver amongst the highest & most stable establishing. The waste acid they produce lowers the
performance in the industry that is both pH to their favoured range of pH 1 to 2. Startup time
can be reduced by seeding the recirculating liquor.
affordable and simple to operate and Once a population of microorganisms is established,
maintain. they are able to handle fluctuating H2S loads, large
To achieve this, we design our Biological Scrubbers in sudden peaks, and restarts after shutdowns.
conjunction with international expert Marc Deshusses
and use only the highest-grade materials. We provide Performance does not degrade over time, and is not
a full end-to-end service from concept, design, supply, subject to changing weather. If the average weekly H2S
installation, commissioning and support for all our load reduces/increases, then the only change needed
Biological Scrubber installations. Every Biological is a small reduction/increase in the fresh water supply
Scrubber we make is backed with our satisfaction- so that the pH remains in the optimum range.
guaranteed support service, using our extensive on-
site experience in NZ and Australia.

Healthy bugs means reliable performance

The key to good performance in a Biological Scrubber
is a thriving colony of the required species of odour-
eating microorganisms. This is our overarching
design focus in everything we do. The bed of micro-
organisms is continuously wetted to provide both
water and nutrients for their optimum health. Very
small amounts of nutrients (N,P,K+traces) are dosed
to ensure optimum health of the microorganisms.
As the H2S-consuming microorganisms perform
best at pH 1 to 2, the pH of the recirculating liquor is
monitored and the rate of fresh water supply adjusted
so that the pH is kept within this range. Chemical
consumption is eliminated or greatly reduced
compared to a chemical wet scrubber. The only
requirement is an occasional dosing of nutrients.

Corrosion-resistant Fibreglass and high-

grade materials
H2S is extremely corrosive, particularly to concrete
and steel. Armatec biological scrubbers are built in
corrosion resistant fibreglass built to international
standards under ISO 9001 quality assurance at our
own factory. Fibreglass is ideal and proven in this
application and guarantees low maintenance and
long life. Stainless steel and high-grade PVC piping are
used for non fiberglass components. We use proven
inorganic packing media that lasts >10 years to house 4
the army of microorganisms.
4: Armatec Biological Scrubber in Pines II WWTP,
Christchurch removing >99% of 11-42 ppm H2S
5: Inorganic packing media used for microorganisms

April 2014 www.armatec.co.nz 4

Standard models and key features

Optimised designs backed by international

expert Marc Deshusses
We have a range of different Biological Scrubber types
available to suit any application. Our three styles are:
• Vertical towers
• Horizontal crossflow style
• Combination “plug & play” units (see page 7)

As well as standard sizings, we have the design

flexibility to deal with any sized application with
confidence. Below is the table of standard vertical
tower Biological Scrubber sizes available.

5
Model Nom. Dia Typical Airflow
(mm) (m3/s)
Design Considerations
BS-60 1500 0.3 - 1.0
BS-70 1800 0.4 - 1.3 There are many considerations in deciding a
BS-80 2000 0.5 - 1.6 biological scrubber is right for your application,
BS-100 2400 0.7 - 2.3 and the successful implementation of that vision.
We can assist you in the careful selection, design,
BS-110 2800 1.0 - 3.1 commissioning, optimisation and operation of an
BS-120 3000 1.2 - 3.5 Armatec biological scrubber that is ideal for your
BS-140 3500 1.6 - 5.0 project. We are happy to assist with our years of
experience and expertise across all aspects of
Please note choice depends on many factors including this process, and we will work with you to ensure
inlet load and removal performance required. your project is a total success.
Horizontal crossflow styles available on request.
Consult ARMATEC to confirm sizing. The key design considerations to begin the
journey are knowing: H2S load, H2S removal
efficiency required, other odourous compounds,
Key Features of Armatec Biological Scrubbers
scrubber style, design details. Please consult
• Corrosion resistant construction. with one of our highly experienced chemical
engineers at Armatec to help guide you through
• Lower scrubber shell serves as integral sump for this process.
recirculating liquid supply.
• Standard accessories including access doors,
spray headers, piping connections, nozzles,
Not sure? Pilot plants are available
for site trials using a representative
internal structure supports, packing, support
stream of the air to be treated. This
plates and hold-down lugs.
has the advantage of giving actual
• Circulation pump can be mounted on side of performance data allowing for
scrubber to minimise footprint. accurate scale up to the full unit. A
• Nutrient dosing & storage componentry are successful pilot plant trial gives all
optionally included. parties the confidence to proceed
• No complex controlling instrumentation. pH with the full scale unit.
monitored only.

www.armatec.co.nz 5
 Proven performance, guaranteed

Our Biological scrubbers have excellent Fertiliser Plant, Christchurch: Case

credentials – they are proven performers Soil Bed Filter problems resolved Study
and can remove up to 99% of H2S in air
streams and simple to operate. Armatec installed a Biological Scrubber at a fertiliser
Armatec’s Biological Scrubbers are expertly built and plant that removes more than 98% of 300ppm
we have met every agreed performance target. We H2S from the 0.8 m3/s air stream. The previous soil
are so confident in our delivery that we guarantee bed filter was overloaded, and required frequent
the performance of all our Biological Scrubbers, and maintenance. As a result there were many odour
provide complete service to ensure it meets the complaints from neighbours. The ARMATEC Biological
requirements. Below are a cross-section of Biological Scrubber has solved these problems, and been in
Scrubber projects designed and delivered by Armatec, operation for a number of years now. The excellent
performance of this biological scrubber was reported
with associated performance data. in an engineering paper published at a conference in
2007.
Pines II WWTP, Rolleston, Case
Study
Christchurch: >99% performance
Richmond WWTP, West Sydney: Case
Biological Scrubber & Carbon Bed Study
Armatec installed a Biological Scrubber at the WWTP
that removes >99% of 11-42ppm H2S (as shown in the
graphs below) from the 2.0 m3/s air stream. This is the Armatec designed and optimised a Biological
installation featured on the front cover of this booklet. Scrubber with Carbon Bed that removes >97% of
H2S from the 0.6 m3/s air stream measured at 7,765
Odour Units. The Biological Scrubber performance is
>92% H2S removal, and the final odour loading in the
Before scrubber: Carbon Bed outlet is 208 Odour Units.
11-42 ppm H2S
temperature

Biological
Scrubber

temperature

After scrubber: 0 ppm H2S 6: Armatec-designed Biological Scrubber at Richmond WWTP.

7 & 8: Armatec BSCB Plug & Play unit installed in Motueka
WWTP, New Zealand removing >99% of 20-100ppm H2S at
0.2m3/s.

April 2014 www.armatec.co.nz 6

Plug & Play units: simplicity at site
for small air flows

The Biological Scrubber & Carbon Bed (BSCB) Before Biological Scrubber: 20-100 ppm H2S
Plug & Play units are a unique modular
combination style available from Armatec
temperature
that delivers complete odour control from
the first day.

The BSCB Plug & Play units are ideally suited to

>99% remove medium to high odour loads at low air
Biological
volumes of 0.5 m3/s and below. They are compact,
Scrubber
simple to specify, ship, install and operate.

The BSCB Plug & Play units have built-in complete

odour removal and redundancy upon startup for total
assurance. There is low activated carbon usage giving
significant reduction in operating costs. All BSCB Plug temperature
& Play componentry and systems are factory built and
commissioned ready for immediate use.
After Biological Scrubber:
For higher airflows above 0.5 m3/s we provide other 2 ppm H2S average
integrated 2-stage systems to suit your needs.
Carbon
Bed

temperature

After Carbon Bed:

0 ppm H2S
(max <0.1 ppm)

Key features of the Plug & Play BSCB units

• Pre-filter to remove fats, grease

• Biological scrubber bed to remove
95% of H2S and other gases
• Heater to lower humidity
• Fan to drive the air
• Carbon adsorption bed to polish air at
final stage

www.armatec.co.nz 7
Reducing emissions
to the environment

We deliver world-class industrial

fibreglass products and solutions to
reduce emissions to the environment.
We provide full service from quality technical Air Pollution Control
advice at concept through detailed design, Hoods, Covers, Fans, Ducting,
pilot plant trials, fabrication, installation, Scrubbers, Void Towers,
commissioning and optimisation services. Venturis, Strippers, Stacks, &
We combine strong, established solutions more
with leading edge technologies to create the
best outcomes for our customers. We are on Odour Control
the forefront of technological innovation in Carbon Bed Adsorbers,
environmental protection as well as manufacture Biological Scrubbers, Wet
many best-in-class products under international Scrubbers, Green Dome®
licenses. Odour Filters

Our company is made of skilled, passionate and Surface Protection

highly experienced specialist Chemical Engineers Coatings, Linings, Floorings
& Fibreglass Technicians with many years of & Grouts
experience between us. We have established a
reputation as a leading supplier of air pollution Wastewater Management
control equipment and industrial fibreglass Manholes, Pump Stations, DAF
products, with a reputation for highest quality & IAF, Clarifier Components,
products for tough environmental and corrosion Flumes, Vortex Dropper
resistant applications. Formers, Phos/Algae Removal
& more

Chemical Containment
Tanks, Piping, Drainage,
Sump liners & more

Call us today to assist with your project

Armatec Environmental Ltd
P.O. Box 3046 New Plymouth, New Zealand
Ph +64-6-755-0410 | Fax +64-6-755-2346
enquiries@armatec.co.nz
www.armatec.co.nz