Sorry - do I smell?

Written by: Mark Thomas | Published:

Odour and dust suppression is an oft talked about subject in the world of waste and recycling. Mark Thomas asks, do we really understand what the best approach is to deal with it?

If we understand what is available for reducing odour and dust then dealing with the problem should become much easier, while specifying what systems work best should be clearer.

Waste management and recycling processes create odour. Fact.

Waste facilities including landfill sites, waste transfer stations, MRFs, composting, water treatment and AD plants are all regulated by the Environment Agency (EA); and, although most sites are well run, they account for a large proportion of odour complaints received by the EA from members of the public, with landfill sites being one of the main culprits.

Joe public expects the EA to deal with odour (and dust for that matter) when it becomes annoying, a nuisance and unacceptable. This is fairly straightforward when an operator is violating their permit, but not so when odours are from multiple sources.

The operator’s permit is likely to have a clause requiring that appropriate measures be taken to avoid unacceptable impacts, but what constitutes an appropriate measure is sometimes not clear. So, assuming you have an odour issue – i.e. Joe public has been annoyed, considered the odour a nuisance and complained – what do you do about it?

How do you take appropriate action?

In simple terms, planning to manage odour is the best and right answer and should be a major consideration in the planning stages of any waste-handling facility.

Good odour management planning can still be a retrofit solution, working with the right solutions provider. Prevention, however, is always better than cure.

That said, if I smell, what do I do?

These days there are a variety of odour treatment methods which include odour neutralisers, typically pre-diluted and dispersed into the foul airflow using equipment that atomises water and the additive, creating a ‘mist’ which neutralise the odours by removing them, not masking them.

Five solutions

Some of these neutralisers combat odours in five different ways:

- Pairing: additives chemically pair with odorous compounds, changing the properties of the odour molecule, rendering it odourless.

- Oxidation: odour molecules are oxidised to produce an odourless solution. A combination of oxygen, additives and hydrogen ions generates a safe reaction, resulting in odour neutralisation.

- Adsorption: odorous molecules will attach themselves to neutralisers, generating a minute energy charge that partly neutralises their odour and adsorbs them into a larger odourless compound.

- Absorption: odour compounds dissolve into neutraliser, losing their odour in the process.

- Combination: odour neutraliser combines with certain odorous molecules, changing their structure to generate new molecules that are environmentally friendly and odourless.

So how do I use neutralisers?

Commercial odour control systems are predominately rotary atomisers, air nozzle systems and high pressure nozzle systems.

So what’s what? Areas with wide borders and regular impacts such as composting or landfill sites need a high-pressure nozzle line system. These are usually comprised of a high-pressure system that pumps neutraliser or water through a series of installed nozzles one or two metres apart, delivering a ‘misting curtain’, effectively suppressing dust and neutralising odour.

For localised and occasional impacts, trailer-mounted mobile systems can be taken to the source of the problem. Deployed on pig-tail stakes around the problem area, a flexible nozzle line can be adapted to provide a variety of solutions in a range of circumstances.

Rotary atomiser systems are specifically designed to primarily treat localised odour problems in landfill, composting and inside MRFs and WTFs. Rotary atomisers generate a fine mist which can be projected up to 25 metres.

Atomiser systems can be wall- or ceiling-mounted, covering up to 1200m per head. Trailer mounting with its own water and neutraliser supply allow the system to be quickly moved into position to neutralise odour or suppress dust whenever and wherever it occurs.

Odour and dust are part of the process of managing and dealing with waste. The public and the EA each have their demands, and for us in the industry, having a better understanding of the options help to make the right call when it comes to dealing with the issues.

From an EA perspective, the steps from odour formation to odour complaint are as follows:

1. Formation of odorant

2. Transfer to atmosphere

3. Atmospheric dispersion

4. Exposure

5. Perception

6. Appraisal

7. Annoyance

8. Nuisance

9. Complaint

[Adapted from Environment Agency (2002) Assessment of Community Responses to Odorous Emissions. R&D Technical Report P4-095/TR, July 2002]

- Mark Thomas is managing director of odour control & dust suppression systems specialist, Air Spectrum

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