Abstract:

Rock mining and crushing plants are well known as major sources of dust pollution. A large amount of dusts are generated from rock blasting, crushers, belt conveyors, vibrating screens, spreaders, transportation, and re-suspension of road dusts. Nah Pralan, a small district in Saraburi Province with an area only of 66 km2 located about 128 km northeast of Bangkok, has 30 rock mines, 55 crushing plants, and 1 cement plants. The district has been plagued with dust pollution from rock mining and rock crushing plants for more than 15 years. PM10 concentrations during the dry period between December to April of every year constantly violate the daily ambient air quality standard for PM10 of 120 ug/m3. In January 2000 and 2004 the maximum daily concentration of PM10 was 409ug/m3 and 415.7ug/m3 respectively which is about 2.5 times higher than the standard. As a matter of fact, PM10 problem in Nah Pralan District is more serious than in Bangkok.

In August 2004, the National Environment Board designated Nah Pralan District to be Pollution Control Area pursuant to Section 59 of the Enhancement and Conservation of National Environmental Quality Act of 1992 in order to control, reduce, and eliminate dust pollution. Action plan as required by Section 60 was then developed to mitigate and eradicate PM10 problem in Nah Pralan District. Mitigation measures contained in the action plan included intensive inspection and enforcement of emission standards, improvement of road surface, road sweeping and cleaning, roadside black smoke inspection, and plantation. Open-and-cut mining is required for rock mining instead of cliff-hanging explosion and water spray is required to reduce and suppress airborne dust. Rock crushing plants are required to control dust emission from crushers, belt conveyors, vibrating screens, spreaders, and other dust emission sources to have opacity not more than 20%. Water spray and local exhaust system with particulate control equipments such as cyclone and bag filter are normally employed to reduce dust emission. Roads inside the plants are required to be paved with permanent surface such as asphalt or concrete in addition to water spray to reduce and suppress dust re-suspension. Trucks are required to be covered with blanket and go through wheel washing with water before leaving the plants. Stakeholder meeting with public participation was held every month in the first year to follow up on the implementation of the action plan.

Within one year after the designation of the Nah Pralan to be the Pollution Control Area and the implementation of the action plan, PM10 concentrations in Nah Pralan District gradually decline. The maximum concentration of PM10 in 2005 was reduced to 300ug/m3 and percentages of daily PM10 observations which violate the standard was reduced. Nonetheless, continued efforts are still needed to bring down PM10 concentrations in Nah Pralan District to be in compliance with the standard.

Presentation: http://www.cleanairnet.org/baq2006/1757/docs/SW8_2.ppt

Full paper:

Mitigation of Dust Pollution from Aggregate Plants and Quarry Operations [.doc, 2575.8Kb]