The Offensive Odor Control Law
Designation of Regulated Areas
Areas are designated by local governments based on geographical and demographical conditions. Within regulated areas, emissions of offensive odors from business activities are regulated. All kinds of factories and workshops within regulated areas are under regulation of the Law. This applies regardless of type, scale or management organization of business.
Establishment of Regulation Standards
The following 3 types of odor emissions from factories and workshops are regulated. Local governments could establish 3 applicable regulation standards corresponding to those emission types. They are the standard on site boundary, the standard for gas from exhaust pipe, and the standard for effluent from outlet. We are going to introduce the establishment methods of three regulation standards this time. The standard of the site boundary is the basis of the calculations of other two standards.
How to Establish Regulation Standard on Site Boundary
First of all, odor intensity in the regulated area should be established. Local governments can choose environmental preservation level value among 2.5, 3.0, and 3.5, according to the conditions of the land use such as residential or industrial purpose.
How to Establish Regulation Standard for Gas from Exhaust Pipe
As for the regulation standard for gas from exhaust pipe, the equation of air diffusion is applied. The gas which contains odor emitted from the exhaust pipe like chimney and so on gradually diffuses and dilutes and eventually lands onto the surface of the ground. This regulation standard is established to meet the odor emission standard at the exhaust pipe, and the odor index should be under the one at the landing point outside the site boundary.
The emission style applied here covered many kinds of causes such as large-scale plants and low-height chimneys. Therefore we had to consider that the area where buildings close together like big cites, possibly became cause of odor and complaints as a result. In addition to that, odor had to be estimated in a short time. We took these factors, and considered Briggs style (1973) as ascending process, and Huber-Snyder style (1976) as emitting process and after considering the influence of the buildings, we applied it as the air diffusion model.
Then we got a lot of requests from the local government officers for the plain calculation method of the exhaust pipe. Therefore we can clearly calculate the regulated standard of the exhaust gas by taking in new standard called the dilution index. Dilution index means the dilution ratio at the most concentrated point when the gas from exhaust pipe lands on the ground surface diluting. Staff of the companies can calculate the standard of the exhaust gas on the site easily by adding this dilution index and the standard value shown on the graph of the local site boundary. The Ministry of the Environment in Japan and our association made and calculation software called ‘Odor Simulator’ and plain guidebook for ‘Regulation Standard for Gas form Exhaust Pipe’ , which help us to calculate easily, then we have distributed them for free.
In addition, it makes us possible to develop odor control. One of the countermeasures which are often applied for odor control is to put the exhaust pipe at higher place to dilute landing concentration by diffusion. It enables us to calculate the height of the exhaust pipe from the graph after getting necessary dilution index.
How to Establish Regulation Standard for Effluent from Outlet.
We picked 130 business proprietors in Japan among many kinds of business fields and examined effluent from 1997 to 1999. We established the index, which was under the index of the standard on the site boundary, above 1.5 m from water surface to avoid the complaints over effluent downstream. Then we calculated correlation of odor index for gas exhausted from effluent straightly 1.5m above to suppose odor index of effluent and the standard on the site boundary. The odor from the effluent was measured by triangular odor flask method. After consideration of distinction if there were odor complaints and relations with amount of effluent, possibilities for countermeasure realization, we established dilution as 16 evenly. (40-fold dilution) .Therefore the index which is added 16 to the standard on site boundary becomes the standard index effluent from outlet.