IPC guidance for acid and halogen processes

HM Inspectorate of Pollution (HMIP) has issued the final versions of eight guidance notes dealing with acid and halogen processes and the bulk storage of chemicals.1

The processes covered by the notes come under integrated pollution control (IPC) on 1 November 1993, and applications for authorisation of existing processes will have to be submitted by 31 January 1994. Operators will be expected to upgrade their processes by 1 November 1997 "with the aim of achieving" the standards expected of new plant.

The contents of the notes have not changed greatly since the second drafts (ENDS Report 218, pp 29-31 ). However, a few areas are worthy of note:

  • Ring fencing and process boundaries: This has proved to be a particularly difficult area for the chemical industry, and has become entangled in the current review of the IPC regulations on process definitions (ENDS Report 222, pp 34-35 ). The problem is particularly acute on complex multi-process sites.

    The final versions of the notes reflect the uncertainty, and recommend that the problems should be addressed on a site-specific basis. Guidance on identifying the process boundary is, they say, "readily available to the operator from the Inspector for the site...preferably during the pre-application discussions".

    On complex sites, the Inspector should consider the definition of the various processes covered by the regulations, the potential of the process to cause harm to the environment, and interactions with other installations on the site. Releases of prescribed and other harmful substances will be controlled by numerical limits on discharges to other on-site operations such as shared effluent treatment plant, as well as on direct discharges to the environment. However, the guidance on how such operations should be "ring-fenced", which has been a feature of previous notes, has now been removed.

  • Annual limits: Previous guidance for other sectors has specified that limits should be set on annual mass releases of relevant prescribed substances, including releases to land.

    The latest notes require applicants to submit projections of annual mass releases to all media, and to report regularly on their actual releases. However, no mention is made of annual release limits, and it is no longer clear that HMIP will continue to set them. Many of the appeals against authorisation conditions have focussed on this issue, with some firms complaining that certain annual limits may constrain their output.

  • Release limits: Most of the release limits laid down have remained unchanged since the first drafts.

    As usual, the only limits set for discharges to water are monthly averages of 10µg/l for cadmium and 5µg/l - although where these are present in a raw material HMIP says that "higher concentrations may be appropriate". The main impact of these limits will be on chlorine manufacturers who still use mercury cell technology - principally ICI. In this case, HMIP is likely to seek to apply the 5µg/l limit as the mercury is not a true raw material. This will require considerable investment in further effluent treatment, and will increase the pressure on ICI to switch to membrane technology before the existing target of 2010.

  • Volatile organic compounds: The notes give further explanation of the basis for splitting VOCs into two broad classes. Toluene has been used as a reference material for the less harmful Class B compounds as it is a common solvent, and the 80mg/m3 limit is based on what is "reasonably easy to achieve" using activated carbon adsorption techniques. Expressing limits as total organic carbon (TOC) would have been "too lax", HMIP says, for high molecular weight halogenated compounds.

    Previous versions of the notes have applied this limit to point sources of Class B compounds releasing either more than 5 tonnes per year or 2 kilos per hour. The annual limit has been removed from the final versions, reducing the number of sources covered.

    However, the notes make it clear that the suggested VOC limits are for guidance only, and that "monitoring would be expected to be for individual substances or for TOC."

    HMIP also says that all fugitive releases should be calculated or measured and the results included in the application.

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