Fly ash stabilisation ‘key’ to prevent hazards

Friday, August 27, 2010
Issue 1100, Page 3
Word count: 828
Published in: Macau Daily Times

By Poyi (Natalie) Leung

The Macau Ecological Society has stressed that while having a disposal site for fly ash from the solid waste incineration plant in the Coloane hill is “acceptable”, the Government must first ensure that the toxic waste is stabilised with cement before being dumped.

The method of burying the municipal solid waste fly ash is important to ensure it poses no hazard to the environment, said Leong Ut Chong, director of the society’s youth committee yesterday.

The Macau Daily Times reported on Wednesday that the Government is investigating the possibility of using the Coloane hill as a new site to bury fly ash generated from solid waste combustion.

The Infrastructure Development Office (GDI) has also confirmed to the MDT that drilling in the Coloane trail walk is being carried out to “understand the geological data, which is important to better locate a suitable place in the territory for future fly ash disposal”.

Leong, who majored in environmental science, said the Ecological Society cannot be certain about whether the Coloane hill is a suitable location since “we haven’t done any geological monitoring of the area”, but assured to the MDT that fly ash is toxic and generally it has to be stabilised by cement before being disposed, “a way that has been widely adopted” by neighbouring regions.

“The underground water quality also has to be examined. There are actually many things that need to be considered [when choosing a toxic waste disposal site],” Leong said.

“Of course it is a problem if the fly ash is just being dumped there, but if it can be stabilised with cement then generally there will be no problem with it,” he added.

Leong said that while the society is not familiar with the environment and conditions in the Coloane hill he can say that as well as using a safe disposal process, the site must also be far from residential areas.

Landfill location ‘not regulated by law’

Macau currently has three laws on environmental pollution – the Environmental Framework Law, Noise Pollution Law and another one in relation to contamination in maritime jurisdiction.

The Environmental Framework Law regulates the treatment of toxic waste in a general sense but has “no clear requirements, standards or guidelines,” Leong said, adding that that is “why demands have been expressed long time ago that the law needs to be updated.”

In other words, where the Government is going to situate a landfill site is not regulated by law, he admitted to the MDT.

Macau is known for its limited land resources, and finding a place for waste disposal is no easy task.

Leong suggested cooperating with neighbouring regions “where they can bury Macau’s hazardous waste together with theirs in the landfills”. However, he admitted at the same time that this was quite unlikely to occur “not only because Macau has to ask another jurisdiction to take care of the toxic waste that doesn’t belong to itself, there are also international conventions prohibiting the exportation of polluted and hazardous waste”.

Therefore, Leong said that what people can and should do right now is to reduce municipal solid waste, “instead of trying to make it disappear”.

Meanwhile, Leong pointed out that the Government should take the initiative to communicate and discuss with local people about a new fly ash disposal site in Macau.

“If the existing landfill is going to be filled up soon, the Government should let the people know about it and also disclose a schedule and the work progress [of the new site] to the public in order to increase transparency,” he said.

“The Government needs to tell the public how fly ash is treated and whether the disposal process will pose a hazard to surrounding areas, or otherwise people will be worried about whether the new landfill site is to be located near their neighbourhoods,” he added.

A hazard classification

According to Kaimin Shih, assistant professor of the Department of Civil Engineering, the University of Hong Kong, incinerating municipal solid waste (MSW) is not as toxic as incinerating hazardous waste, but is “generally more polluting than burning coal” and “surely more toxic than bottom ash if based on the same source”.

Shih told the MDT that bottom ash is another type of ash that will be generated from burning solid waste.

“The property of fly ash coming from MSW incineration may vary due to the characteristics of local MSW, quality of the burning process, and the equipped air pollution control units,” he said.

“The problem is usually on volatile metals [Hg, As, Cd, Zn, etc] and trace organics [Dioxin, and others if not burning completely],” he added.

In most countries MSW is classified as a “hazardous material”, Shih stressed, which is subject to certain stabilisation processes such as adding cement prior to disposal in a well-controlled landfill.

At present, the ash generated from the solid waste incineration plant is being dumped in a landfill near the Ka-Ho Port by San Meng Fai Construction and Engineering Company.

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