Odor Development Due to Bacterial Growth

Background
If not properly operated and maintained, drycleaning systems using hydrocarbon or petroleum solvents may develop an objectionable odor. This problem has existed since the beginning of petroleum drycleaning, but can be successfully managed with proper solvent and equipment maintenance. 

Causes
Bacteria may develop in a drycleaning system if several conditions occur simultaneously:

1. Free Water
   The bacteria identified in drycleaning systems thrive with free water. Free standing water in the storage tanks is an excellent breeding ground for bacteria. Free water usually results from ineffective water separation or leaking steam coils and valves that introduce excessive amounts of water into the equipment. 
   
2. Nutrients
   Bacteria, like all living organisms, requires a source of nutrients (food) and water to sustain life and prosper. Some examples of food that bacteria live on are hydrocarbon solvent, soap, oils, and fatty acids. The latter three are more easily biodegraded than the solvent. Inadequate solvent maintenance can lead to excessive levels of these substances in the solvent.  
   
   
3. Source of Bacteria
   Bacteria are present, unavoidable, and often beneficial in everyday life. They are present naturally in the drycleaning plant, and are introduced into the drycleaning system from garments being cleaned.

1. Ensure that the water separator is designed for solvent lighter than water and has adequate capacity to handle all water introduced into the system. The water separator should be large enough to ensure sufficient residence time for the distillate. This ensures that adequate time is allowed for thorough separation of solvent from water.
2. Solvent storage tanks should be sloped to a sump so that water (which will collect on the bottom, if present) can be removed.
3. Follow manufacturer's recommendation for filter change out so that nutrient sources for bacteria that collect on/in filters are consistently removed.
4. Distill a minimum of 7 gallons / 100 lbs. of cleaning. 
5. Use a properly designed detergent at the manufacturer's recommended concentration or use rate per load.  
6. Maintain cleanliness of the water separator. 
7. Maintain a minimal concentration of detergent in distilled tank to avoid accumulation of free water. 
   
   

Technical Assistance

		Technical Data Topics:
		Building Design Considerations
		Stoddard Replacement
		Safe Handling of Solvent
		Odor Development Protection
		Alternative Solvents Comparison Matrix