Dioxins monitoring under the spotlight
22 Mar 2007
The event provided an overview of current dioxins monitoring procedures including a new MCERTS-approved system to sample dioxins over longer periods and so provide emission levels data. Another feature was the development of a new system by TCR Tecora, based in Italy.
In his presentation, Peter Middleton, business adviser for Scientifics, highlighted how it is not currently possible to measure dioxins emissions continuously real-time due to the extremely small concentrations involved.
Rather, he said, it is necessary to sample over a period of hours and subsequently to analyse the collected sample with a high-resolution gas chromatography mass spectrometer (GC-MS).
According to Middleton, there are over 200 different dioxins and furans, and many of them are considered to be highly toxic. These substances, he said, are unintentionally formed as by-products of chemical processes involving chlorine.
Dioxins accumulate in the fatty tissues and are ingested in trace amounts within contaminated food. The tolerable daily intake has been set at 2 pico grams (two millionths of a millionth of a gram: 10-12 g) per Kg of body mass, noted Middleton.
Emissions monitoring for dioxins is required by the Environment Agency for processes that have the potential to release these compounds and the monitoring requirement is generally to sample for around 8 hours twice yearly, or more often if the process presents a higher level of risk.
Middleton handed over to TCR Tecora director Maurizio Migliore, who explained; “Existing portable dioxins sampling equipment merely provides a ‘snapshot’ of the process from which it is not possible to quantify mass emissions.”
TCR, which specialises in emissions sampling equipment, therefore decided to develop a system that would be permanently installed on a stack and would be able to sample for much longer periods of time.
The new system, known as ‘DECS’ (Dioxins emissions continuous sampling), has received MCERTS and TUV approval and, claimed Migliore: “The launch of DECS has provided regulators all over the world with the facility to require the creation of samples that represent total process Dioxins emissions over much longer periods; up to one month.”
Migliore’s colleague Paulo de Angelis provided a technical description of DECS, explaining that the European Standard EN1948-1 offers the facility to employ one of three methods; filter/condenser, dilution or cooled probe. However, he outlined the weaknesses associated with the latter two methods, describing how this led his development team to choose the filter/condenser method for DECS.
The filter/condenser method is also prescribed in the USEPA 23 standard method. Expanding further on the advantages of the filter/condenser method, de Angelis said: “A heated isokinetic stack sampling probe, in conjunction with the external filter, provides the option to sample for hydrochloric acid, mercury and heavy metals in addition to dioxins and furans.”
The DECS sampling unit is permanently installed on a stack and operates automatically, which means that less labour is involved in the sampling process and the procedure is fully automatic so there is less opportunity for error and operators do not need to be highly trained experts.
TCR Tecora claims that, as a permanently installed fixture, DECS is less costly than occasional sampling. Furthermore, a control unit is installed on-site that can operate up to four samplers and thereby reduce the costs per stack even further.
Summing up, Dominic Duggan, Quantitech director said “Dioxin monitoring is clearly evolving and the launch of the DECS provides process operators and regulators with the ability to produce better quality data. It is interesting to note that visitors to a similar seminar in Paris have recently been required by their regulator to install long-term dioxins sampling equipment, so one suspects that similar circumstances may arise here in the UK.”