Odour
Solution for Sewage Works Looks to Set New Standards
The results of a trial
conducted by a UK company, Probe Industries, looks likely to revolutionise
the control of odours within the water industry. The claims of
success the company made following extensive laboratory tests
have now been replicated in a trial plant using their new product
ProActive.
Pressure from the public and legislation has
raised the profile of odour control within the water industry
and ProActive is being hailed as a major step forward in controlling
odorous compounds in sewage sludge in an effective and safe way.
Encouraged
by the laboratory tests, Probe installed a trial plant at a waste
water treatment works to determine the effectiveness of ProActive
in real life conditions. The trail was monitored closely by Probe’s
Technical Advisor, Bob Fowler. The resulted sludge cake was found
to be odour free and remained so for some time. The level of Hydrogen
Sulphide during the sewage sludge process remained well with the
margins prescribed by legislation for both the working environment
and the wider community.
The details of the trial are as follows:
Waste Water Treatment
Works
Waste water treatment works serving coastal community of 300,000
with long deep interceptor sewers. This modern works has been
designed to minimise fugative odours with all processes within
buildings, extraction and odour scrubbers.
Raw thickened sludge is dewatered by centrifuge,
to a sludge cake at 27%. This sludge cake is then transported
‘off site’ for environmental improvement of derelict
land (the sludge is used as a growing medium for trees).
The centrifuging of thickened sludge to cake
was not included in the original design of the works.
Site Odour Issues
Three management issues resulted from the centrifuging operation
:
- Safety and poor working environment
within the centrifuge area
- Fugitive sludge odours in the vicinity of
the site
- Odours from the sludge cake when delivered
to the environmental improvement area
It was agreed that maintaining H2S
in the working area at or below 1ppm would provide safe and improved
working environment and substantially reduce fugative odour emissions.
It was found impossible to set a measurable target for reduced
cake odours, but agreed that should aim for the ‘ProActive’
dosed sludge cake to be substantially odour free when discharged
from the centrifuge.
Trial Plant Results
A Probe Industries trial plant was installed and H2S
measurements were taken to confirm ‘ProActive’ effectiveness.
Hydrogen sulphide measurements were taken at the two identified
main sources of odours from the sludge dewatering process –
centrifuge air vent and centrate discharge manhole and within
the working area.
Prior to dosing with ‘ProActive’
Centrifuge air vent – H2S always greater than
100ppm
Centrate return manhole – H2S averaged 18ppm
Working area – H2S maximum peak at 4ppm
‘ProActive’
dosed sludge
Centrifugeair vent – H2S always less than 80ppm
Centrate return manhole – H2S always less than
5ppm
Working area – H2S not detected by personal gas
monitors
Sludge cake was substantially odour free when discharged from
the centrifuge. Measurements of H2S in ‘ProActive’
dosed sludge samples demonstrated that there was still a 75% reduction
in cake odours after 24 hours.
How Does ProActive Work?
Probe Industries’ ‘ProActive’ is a chemically
engineered product that destroys odours in all anaerobic liquids,
sludges and sludge cake rather than simply trying to mask them.
The innovative technology used, targets and instantly oxidises
odorous sulphidic compounds in the liquid phase prior to emission
into the atmosphere.
Bob Fowler comments on the results of the trail,
“The trails have confirmed without doubt that ‘ProActive’
provides an effective and easily managed solution to odour problems.
It has also shown ‘ProActive’ has strong safety and
environmental credentials – it does not inhibit biological
activity or restrict the disposal options available for any ‘ProActive’
treated liquids or sludges.”
Bob also points to a further benefit, “The
trial also confirmed that ‘ProActive’ is effective
in eliminating not only hydrogen sulphide but also the ‘cabbage
smelling’ mercaptans and dimethylsulphide.”
The company is now launching ProActive within
the water sector and the interest shown nationally and internationally
may establish ProActive as the standard in controlling odours
in the near future. Details of the trail can be gained from Probe
on 0191 251 1888.
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