A: Anaerobic digestion uses both facultative (acid-forming) and anaerobic bacteria to degrade BOD. Anaerobic digestors are either very stable and predictable or very vulnerable. Our BioGas1 formula — with its six essential trace metals necessary for the function of anaerobic bacteria — has proven valuable in many industrial facilities. It’s the solution whether your anaerobic digestor is located at the front of the plant (e.g., in a rendering, meat packing, or bakery) or in the back (e.g., in a municipal plant were sludge is stored for further degradation of volatile solids).

AQUAFIX products are designed to resolve problems with anaerobic digestors. We are also available to consult with you about any problems you are experience. Whether you are starting a digestor and are worried about a smooth transition, or you are experiencing grease mats or upset in your digestor, contact us and we will put our expert team to work for you. We are also available to consult with you about any problems with your system.

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Q: What Are the Stages of Anerobic Digestion?

A: Stage 1: Hydrolysis of proteins, lipids, and carbohydrates to simple compounds such as amino acids, fatty acids, glycerol, and sugar. This stage of digestion involves production of volatile acids and is accomplished by acid-forming, facultative bacteria. The facultative bacteria can live under anaerobic or aerobic conditions

Stage 2: The production of methane gas by methanogenic bacteria. This process converts all the fatty acids (butyric, proprionic, etc.) to acetate and hydrogen, which are converted to methane gas by the methane formers. Too much of a particular fatty acid can have toxic effects on methane formers. In many cases we have data on the effects of fatty acids on methane production. Extremely small concentrations of oxygen will also kill methanogenic bacteria. All these reactions occurred simultaneously and, in a balanced system, in harmony.

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Q: Should I Monitor my Digestor’s pH and alkalinity?

A: Volatile fatty acids levels should be monitored in an anaerobic digestor. Volitale acid/alkalinity ratio is a common anaerobic digestor test. A ratio of 0.1 – 0.5 is recommended.

The solubilization of grease and other solids into an anaerobic digestor increases the presence of the volatile acids, like fatty acids and acetic acid. Acetic acid is often the most predominate acid in anaerobic systems. These volatile acids are a form of soluble BOD. Stage 2 will convert these acids into methane gas.

In plants with high incoming BOD and high levels of grease it is common for the production of volatile acids to precede faster than the production of methane and this causes the pH to drop in the digestor. This is why many operators monitor pH and alkanlity in a digestor. Methane bacteria function in a low temperature and pH, range. When digestors go sour, they will foam. AQUAFIX manufactures our De-Foam 3000 just for this purpose. De-Foam 2000 is one of the only products which will control anaerobic foam.

 

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