Determination of anaerobic biodegradability with a simple continuous fixed-bed reactor

A simple and inexpensive continuous fixed-bed reactor is introduced in order to investigate the anaerobic biodegradability of water-soluble substances and products as well as wastewater. The bioreactor tube is equipped with a polyester fleece that is soaked with anaerobic sludge. The solution of the test substance or wastewater is pumped into the thermostated bioreactor. The biogas evolved is pumped into a glass tube containing a solution of sodium hydroxide to absorb carbon dioxide. The anaerobic biodegradability of the test substance can be determined with the methane volume evolved and the theoretical maximum amount of methane, which is calculated from the chemical oxygen demand (COD) of the test substance. The test system can also be used to enrich refractory compounds. A validation of the test system is shown with glucose and benzoic acid, which have been degraded to about 90%. Sodium lauryl sulfate was only degraded to about 15%. It was shown that the desulfonated test substance (dodecanol) was adsorbed to the sludge.