First revision of existing air pollution control guides

A guidance note amending and extending official advice given over the past year or so on the local authority air pollution control regime established by the Environmental Protection Act 1990 has been issued by the Department of the Environment (DoE).1 The issues covered range from how local authorities should deal with late applications for authorisation to the control of dioxin emissions from incinerators.

The new guidance is the first in a series of "upgrading guidance" (UG) notes which will modify or add to advice given either in the 78 process guidance (PG) notes or the five general guidance (GG) notes on the air pollution control system.

Part of the new note explains the recent amendments of the statutory definitions of various processes prescribed for local authority control (ENDS Report 207, p 27 ), and gives details of the revised scale of fees payable by operators in 1992/3 (ENDS Report 206, p 33 ).

Among the general issues covered in the guidance note is how local authorities should treat processes for which late applications are submitted by operators. "The fact that the application is late," the DoE says, "does not mean that local authorities should automatically require the new plant standards contained in the relevant process guidance note to be met immediately." Instead, the timetable for upgrading existing processes laid down in each note should normally be applied.

Other general issues covered include procedures for the transfer of processes from central to local authority control, how local authorities should write into authorisations the "residual" condition laid down in the 1990 Act requiring operators to use the best available techniques not entailing excessive cost in any area not covered by a specific condition, and the use of notices requiring extra information from applicants.

The guidance also spells out more clearly how timber processes should be allocated between local and central control. Some operators in this sector have apparently been arguing that, even if they use substances which are prescribed for release to water, they should not be controlled by HM Inspectorate of Pollution on the grounds that, say, their processing equipment and chemical stores are bunded and therefore have no potential to release those substances into water. However, the DoE insists that all such processes have the potential for releases to water as a result of leaching from timber during storage or other stages of production. Indeed, as a number of recent pollution incidents have demonstrated, the mere existence of a bund is no guarantee that water pollution will not occur.

The note goes on to amend or add to several of the process guidance notes. The most important of these changes concern clinical waste and sewage sludge incinerators and crematoria.

The principal changes to the two incineration notes concern the control of dioxin and furan emissions. The DoE consulted on this issue last autumn (ENDS Report 201, p 29), and the new guidance is broadly in line with those proposals.

In essence, operators will be required either to maintain the temperature of combustion gases entering particulate abatement equipment below a specified temperature so as to prevent the formation of dioxins, or keep the temperature of gases entering and leaving such equipment above 450°C. Under the former option the maximum temperatures recom-mended are not consistent across all cases.

On plant where it is not possible to meet the above temperatures due to the design and configuration of equipment, operators will have the option of demonstrating during commissioning that emissions of total dioxins and furans will not exceed 1ng/m3. The sampling protocol for these commissioning tests will have to reflect "typical emissions under all operating conditions." Flue gas temperatures at entry and exit points on particulate arrestment equipment will have to be continuously monitored and recorded.

The dioxin control requirements will apply immediately to new plant, and to existing plant by the upgrading deadlines set in the process guidance notes.

On crematoria, the DoE has relaxed the existing emission limit for hydrogen chloride on the grounds that recent evidence has shown that this cannot be met without the use of acid gas abatement equipment. Crematoria operators will also be able to trade off complying with a tougher limit than that laid down with a lower chimney height.

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