Assessment and control of odour nuisance from waste water treatment: code of practice

ANNEX 3: GUIDANCE ON THE PREPARATION OF AN ODOUR MANAGEMENT PLAN

What is an Odour Management Plan?

An Odour Management Plan is a summary, provided by the operator, of the foreseeable situations which may compromise his ability to prevent and/or minimise odorous releases from the process and the actions he will subsequently take to minimise the impact. This will include operational and control measures for normal as well as abnormal conditions. It is intended to be used as a reference document for operational staff on a day-to-day basis and shows what actions should be taken to minimise the event and who is responsible for authorising or undertaking the action.

The plan is intended primarily to detail operational and control measures appropriate to management and control of odour. It should also document foreseeable events which are outside of the control of the operator, however the operator may wish to include types of failure that are preventable, for example pump failure, biofilter compaction or filter breakthrough in order to highlight the need for the appropriate maintenance work to be undertaken before the failure occurs. It is recommended that the Odour Management Plan becomes the primary odour control document and should therefore include the odour complaints administration procedure.

What is the Format for the Odour Management Plan?

The Odour Management Plan should be a written document which is available on-site and should be available to the local authority and all site personnel.

The operator should address the following issues in the Plan:-

1. the activity which produces the odour and the point of odour release

2. possible process or control failures or abnormal situations

3. potential outcome of a failure in respect of the likely odour impact on local sensitive receptors

4. what actions are to be taken to mitigate the episode, timescales and details of the persons responsible for the actions at the site

5. record keeping.

Examples of the Issues which may be Considered in an Odour Management Plan?

1. Those which have potential to affect the process and the generation of odour

Examples of factors which the operator should normally have made arrangements for are:

• Materials input (seasonal variation in weather may affect odour of influent and intermittent discharge of odorous substances to the sewerage system)
• Process parameters (changes in temperature, aerobic conditions)
• Rate of throughput or increased hours of operation
• Development of anaerobic conditions
• Routine maintenance and inspection.
• 2. Those which affect the ability to abate/minimise odour

Examples of factors which might be considered to be outside of operator's control and best dealt with by management actions:

• Start-up and shut-down of key plant and equipment
• Power failure (although the provision of backup facilities should be considered)
• Poor performance of biofiltration or poisoning (if not the result of poor maintenance or maloperation)
• Flooding of the biofilter due to abnormally high rainfall
• External failure of other utilities, e.g. water supply (This should also be considered where the operator has signed up to an interruptible gas supply).

Examples of factors which the operator should normally have made arrangements for are:

• Mechanical breakdown of abatement equipment such as pumps, fans etc
• Power failure
• Compaction of the biofilter or surface fissures
• Saturation of a carbon filter bed and subsequent breakthrough of odours
• Below optimum temperature of a thermal oxidiser or boiler etc
• Saturation of scrubber liquor, blocked injection nozzles etc.
• Routine maintenance and inspection.

3. Those which affect the ability to contain odour (where releases are not normally permitted)

Examples of factors which might be considered to be outside of the operator's control and best dealt with by management actions:

• Building damage which affects integrity due to for example storms
• Power failure

Examples of factors which the operator should normally have made arrangements for are:

• Failure of automatic doors, i.e. in open position
• Failure in procedures to maintain containment (human error)
• Routine maintenance and inspection.

4. Those affecting dispersion between the source and sensitive receptors (for permitted release points such as vents, stacks or biofilters):

Examples of factors which might be considered to be outside of the operator's control and best dealt with by management actions:

• Short term weather patterns which fall outside of the normal conditions for that area (ie highly unusual, not just the normal meteorological pattern - for example inversions and other conditions unfavourable to dispersion should have been considered in designing the process).

Examples of factors which the operator should normally have made arrangements for are:

• Weather - wind direction, temperature, inversion conditions if these are normal variants of local weather
• Loss of plume buoyancy/temperature

Note: many of the above are design issues to a large extent - the process should be designed to prevent/minimise odour to the required level (a level of acceptability) which takes the range of meteorological conditions into account.