Compliance with Chlor-Alkali Mercury Regulations, 1986-1989: Status Report

• 3.1 Federal Regulations
• 3.2 Integrated Bag Sampling Train

3.1 Federal Regulations

In light of concerns in the late 1960s over widespread contamination of freshwater fish in various locations throughout Canada, it became apparent that federal govemment regulatory intervention would be necessary. Federal intervention initially took the form of the Chlor-Alkali Mercury Liquid Effluent Regulations, promulgated in Match 1972 under the Fisheries Act as amended in 1970. These regulations were revised in July 1977 to define more clearly conditions for monitoring mercury contamination and they have remained in this form to the present.

The effluent regulations

• limit the discharge of mercury in liquid effluents to 2.5 g of mercury per day per tonne of chlorine produced, multiplied by the plant's reference production rate
  
  
• define the reference production rate to clearly establish mercury releases
  
  
• define "effluent" to be all waters leaving the plant site, including storm water runoff
  
  
• require composite sampling of effluent in proportion to the effluent flow rate
  
  
• require accurate daily flow measurements
  
  
• require completion of Schedule I (monthly data to be reported) and Schedule II (daily data to be reported)
  
  
• state the method to be followed to determine total mercury in chlor-alkali effluents (Schedule III)

Mercury cell plants also release mercury as elemental mercury vapour and aerosols, which can be carried off-site by long-distance transport mechanisms or, depending on atmosphere-stability conditions, can be deposited on plant property and subsequently transported off-site as "fugitive trackout" by vehicular and pedestrian traffic, by entrainment mechanisms caused by wind turbulence, and as storm water runoff. Airborne mercury may also present an environmental problem to water bodies either as a result of direct deposition or as a result of uncollected and untreated storm water runoff.

To control mercury emissions from mercury cell plants to the ambient air, the Chlor-Alkali Mercury National Emissions Standards Regulations were promulgated in July 1978. These regulations were subsequently revised in February 1990 and incorporated into the Canadian Environmental Protection Act.

The emission regulations

• limit the release of mercury to 5 g of mercury per day per 1000 kg of rated capacity where the mercury source is ventilation gases exhausted from cell rooms
  
  
• limit the release of mercury to 0.1 g of mercury per day per 1000 kg of rated capacity where the mercury source is the hydrogen gas stream originating front the denuders
  
  
• limit the release of mercury to 0.1 g of mercury per day per 1000 kg of rated capacity where the mercury source is the ventilation gases exhausted from end boxes and tanks
  
  
• limit the release of mercury to 0.1 g of mercury per day per 1000 kg of rated capacity where the mercury source is the gases exhausted from reports
  
  
• limit the total amount of mercury released into the ambient air by a plant from the above-noted sources to 1.68 kg of mercury per day
  
  
• specify the plant operating conditions under which the measurement of mercury releases will be conducted and the duration of sampling (Schedule I)
  
  
• specify the number of measurements for each source
  
  
• specify the standard reference for source testing¹
  
  
• require the submission of written reports in the event that the air pollution control equipment or process equipment malfunctions or breaks down (Schedule II)
  
  
• require the submission of written reports on measures taken to control air pollution at a plant, as required, and if there are changes made to the air pollution control equipment (Schedule III).

Inspections of plants and enforcement of these regulations are carried out by Environment Canada regional offices in conjunction with provincial environmental offices.

3.2 Provincial Regulations

Provinces with mercury cell chlor-alkali plants operating over the period 1986-1989 and the number of plants in each are listed below:

Each province enforces its own effluent and mission regulations or bas adopted appropriate federal regulations. Table 8 summarizes federal and provincial regulations pertaining to effluents, emissions, and solid wastes from the chlor-alkali industry.

¹ Environment Canada, "Reference Method for Source Testing: Measurement of Releases of Mercury from Mercury Cell Chlor-Alkali Plants," Ottawa, Canada, Reference Method EPS 1/RM/5 (June 1990).