The costliest act in town

The implementation of the remaining National Environmental Management: Air Quality Act 39 of 2004, which came into effect in 2010, was a welcome revision to the emission standards. However, writes AVINASH RAMSAYWOK, group national process operations manager at EnviroServ, it seems to have come at a price…

With the poor perception of incinerators as the least desirable technology to treat and dispose of medical waste, when the remaining provisions of the National Environmental Management: Air Quality Act 39 of 2004 (NEMAQA) came into effect on April 1, 2010, the legislation was welcomed.

While the revised air emission standards were intended to clean up the industry and remove the stigma attached to incinerators, it was expected (and found) that the transition from the old Air Pollution Prevention Act (APPA) regulations to NEMAQA would bring challenges around applicability, practicality and interpretation.

The EnviroServ Group has a licensed modern heath-care risk waste (HCRW) incineration facility in Roodepoort. The facility has a valid Air Emission Licence (AEL), which stipulates the minimum emission standards applicable to “new” facilities as per NEMAQA.

Compliance and reporting under NEMAQA has proved to be one of the main challenges experienced by the facility. In addition, the practicality and interpretation of the new legislation and its requirements has added further complexity and costs.

More stringent emission standards mean increased costs of compliance. The frequency, number of reports requiring external consultants, and emission monitoring equipment required to meet these standards have added a significant cost to the incineration of medical waste.

The Roodepoort facility experienced challenges complying with the required emission limit for acid gases using locally available lime for treatment. Trials of various alternative products and studies of overseas markets were conducted to identify more application-specific qualities of lime to effectively treat and optimally neutralise the acid gases in order to meet the new stringent standards.

The back-end gas cleaning systems of the new technologies, now required to meet the regulated emission limits, come with their own challenges. For example, ceramic filters for particulate removal from the gas stream are not available locally and have to be imported at high cost; their lifespan has proved to be much shorter than expected, resulting in more frequent replacement. Speciality gases required for calibration of the equipment to measure pollutants, such as hydrogen chloride (HCl) and hydrogen flouride (HF), are also imported.

Dioxins, formed during incineration, are highly toxic and can cause reproductive and developmental problems, damage the immune system, interfere with hormones and cause cancer. Therefore, the testing for these compounds is included as part of the Air Emission Licence requirements.

The challenge associated with monitoring dioxins is that there are no accredited laboratories available in South Africa to analyse for this species. The costs associated with monitoring and measurement of dioxins and furans are, therefore, high.

One of the pollutants that must be monitored on a frequent (and in some cases continuous) basis is HF. Since the Roodepoort operations commenced in 2011, HF has been monitored regularly.

The results from external Isokinetic sampling have revealed this to be very low, to well below detectable limits in most cases. However, this pollutant must be monitored and measured on a frequent basis ranging from continuously online, to quarterly Isokinetic sampling.

Both monitoring options are not cheap. And, with continuous monitoring, significant capex expenditure will be required to import an online monitor. This raises questions as to why this pollutant should be monitored so frequently (considering that past results have indicated very low concentrations to be present)?

Air pollutant concentrations, as measured or as calculated by air pollution dispersion modelling, must often be converted, or corrected, to be expressed as required by various governmental agencies.

Such regulations involve several different expressions of concentration. Some express the concentrations as ppmv (parts per million by volume); some express the concentrations as mg/m3 (milligrams per cubic metre); while others require adjusting or correcting the concentrations to reference conditions of moisture content, oxygen (O2) content, or carbon dioxide content. The NEMAQA standards for HCRW incinerators use O2 content as the reference condition. A reference of ten percent O2 is used in calculations for O2 correction.

This appears quite simple to implement. However, in an incineration processes the relationship between O2 and carbon monoxide (CO) is a tricky one to manage and with which to comply. It is noticed that during the loading cycles of a typical fixed grate incinerator, the CO spikes (increases) and O2 depletes.

Therefore “excess air” is introduced into the process to ensure that there is enough O2 to completely react with the fuel and waste and reduce the formation of CO, which is a toxic gas associated with incomplete combustion. The management of this balance between O2 and CO in the incineration process has proved to be very challenging.

The challenges are further complicated by the fact that HCRW incinerators in South Africa are typically small incinerators, when compared to similar facilities the United States of America (USA) and Europe, and normally operate at less than one tonne/hour of waste.

The incinerators operational in the USA and Europe are much larger units and run at higher throughputs (typically three tonnes/hour or more). Therefore it becomes easier to manage this relationship between O2 and CO and control the spikes in CO during loading cycles, which leads to the question: Is the O2 reference of ten percent realistic and practical for the HCRW incinerators currently operational in South Africa?

While the implementation of NEMAQA was a welcome revision to the emission standards, since it will certainly clean up the industry and remove the poor perception of incineration as a clean technology, it has come at a price.

The chartering of new territory with regard to revised emission standards has certainly proved over the past few years to be very challenging, and will continue to be an expensive treatment option going into the future.