Odour Control Methods

Odour Control Methods

Undesirable odours may occur due to the process, as well as the problems that arise in the operation of the facility and the insufficiency of operation. Odour control methods can be discussed under two separate headings.

• By facility type
• According to the precautionary structure

PS: We did not mention the ozone method in this article. There are many articles about the ozone method on our site, you can read them.

By facility type

When the facilities that cause bad odours are examined, it is seen that the source and structure of the odours and the methods that can be applied to prevent them may vary according to the type of these activities. Below are the activities that cause odour formation the most and the prevention methods that can be applied in these areas.

Food industry

• Process Control: Raw materials used in production, their processing, closed or open processes, operating temperatures and times, ventilation conditions, etc.,
• Storage: Storage times and temperatures of organic materials, raw materials and products, warehouse structure, etc.,
• Absorption: Purification of odorous gases and liquids formed by absorption,
• Bio-filter: Purification of the odorous gases and liquids formed in a biological environment by breaking them down by bacteria,
• Oxidation: Fragmentation of odorous gases and liquids formed by oxidation and purification in this way.

Animal Farms

The way of working and the physical structure of these facilities greatly affect the formation of odour. In this respect, the most appropriate way to prevent odour formation is to establish and operate these facilities according to certain standards. There are guides prepared by various institutions and organizations for such facilities, which attach great importance to odour formation.

• VDI (Association of German Engineers) 3471, 3472,
• 2001/88/EC EU Directive (Swine health),
• Appropriate barn/barn conditions and ventilation (DIN 18910),
• Keeping barns clean and dry,
• Using the moisture-proof floor,
• The design of the faecal storage structure should have a storage capacity of at least 6 months. Warehouses must have impermeable concrete floors,
• Applying safety distance: as the last resort, maintaining certain distances between certain facilities and surrounding residential and commercial activities (Germany, Ireland, Spain, etc.),
• Dutch practice: Limiting the capacity according to the distance of the facility from the surrounding units,
• Ongoing research: Reducing odour emission by changing the feeding regime of animals.

Slaughterhouse and Animal By-Products

• Fast processing of materials,
• Storage of by-products for a short time and at low temperatures,
• Combustion of non-condensable steam and gases,
• Separation of process water from non-process water,
• Collecting the process/facility air and burning it in the incineration plant,
• Odour holder backup systems (Active carbon, etc.).

Slaughterhouse and Animal By-Products - Rendering

• Condensation of cooking steam,
• Combustion or biofiltration of non-condensable steam and gases,
• Thermal oxidation and/or biofiltration of steam and gases,
• Closing the entire process line,
• Removal of water from the blood before rendering (by steam coagulation).

Fish meal and oil

• The use of fresh raw materials,
• Combustion of process air.
• Ozone oxidation of extraction air

Wastewater Treatment Plants

• Closed systems: It is the prevention of odorous gases from spreading to the environment by covering units such as pre-clarification pools, and anaerobic treatment pools, which cause odour but where odour formation cannot be prevented due to the process, such as collection and treatment.
• Biofilter all organic operating gases.
• Flare in chimneys: Combustion of odorous gases with a flame flue in various situations. In this context, the ground glow system should be prevented.
• Ozone treatment of water and ozonation of extraction air.

Odour Control Methods By Precautionary Structure

When odour pollution control and removal is approached according to the principles of clean production and prevention of pollution at its source, it is seen that preventing the formation of odour is more effective and preferable than methods such as purification or applying a safety distance. When approached from this point of view, odour prevention methods are stated as follows, in decreasing order of preference according to the nature of the measure:

• Prevention at source,
• Purification,
• Dilution,
• Deactivation / Masking.

Prevention at source

Preventing odour before it occurs will be a more economical and effective method. This can be done by improving the production structure and operating conditions of the facility.

Use of appropriate raw materials: Choosing raw materials that will not cause odour formation among alternatives. The possible cost difference should be evaluated by considering the treatment cost.

Proper raw material and waste storage: Making warehouses and storage conditions at certain standards is one of the methods that most affect the formation of odour. It is especially important in the food and livestock and livestock industries.

Process control.

Prevention of leaks: Performing operations in closed environments as much as possible, preventing leaks in pipes and boilers, collecting and purifying odorous process gases. (Good Housekeeping).

Purification: Purification of odorous gases and liquids from odour-forming compounds. For this, in addition to general purification techniques, original techniques are used.

• Steam condensation
• Adsorption
• Absorption
• Biofilter
• Aqueous filtration
• Incineration
• Thermal oxidation
• Catalytic oxidation
• Ozone oxidation
• Electrostatic filtration

Condensation

Condensation is a technique for separating solvent vapours or other odorous gases from the waste gas by lowering their temperature below their dew point. In odorous gases, the water, which is separated from the water-saturated gas by condensation, acts as an absorber in the odorous gases and in this way the odorous gas is purified.

The application limit for odorous gases is 100,000 odour units/Nm3.

Adsorption

Adsorption is a heterogeneous reaction in which gas molecules are attached to solid surfaces that favour certain compounds over others and are thus separated from the liquid.

Biofiltration

It consists of the breakdown of bacteria as a certain quality of the gas consumed by passing through the odorous gas environment around it. In the continuation of such investments, the design is not as important as ensuring the management and winning. The temperature rise is related to the humidity and temperature condition of the filter medium and the residence time of the gas.

Bio-Wash

Bio washing combines wet scrubbing with biodegradation. Here, the wash water contains populations of bacteria that can oxidize the odorous gas components. For this, the waste gas content must be washable and the washed components must be biodegradable under aerobic conditions.

Bio-Drip

Bio drip works in the same conditions as bio wash. Unlike bio washing, the bacterial population is attached to support elements, i.e. a bedding material. Here, the liquid is circulated through a bed of inert materials.

Thermal Oxidation

Thermal oxidation is the process of oxidation by heating the mixture of odorous gases in the waste gas stream, together with air or oxygen, in a furnace to a temperature above the flash point and maintaining a high temperature for a sufficient time to cause complete combustion to turn into carbon dioxide and water.

Catalytic Oxidation

Catalytic oxidizers work much like thermal oxidizers. The biggest difference is that the gas passing through the flame zone also passes through a catalyst bed. The catalyst increases the rate of the oxidation reaction, allowing it to take place at lower temperatures. This allows the use of smaller oxidizers.

Comparison of Efficiency of Various Treatment Techniques