Purifying waste water of high organic content - first acid anaerobic, then aerobic, then anaerobic methane fermentations

摘要

Process for the purificn. of waste water having a high content of organic material comprises several stages. The first stage is initially anaerobic fermentation by means of a microbial culture at 20-50 degrees C in acid medium for a residue time of 0.1-0.8 d. kg-1.m3 with conversion of the contained oxygen to a mixt. of organic acids; this is followed by aerobic fermentation for a residence time of 0.03 d. kg-1. m3. At the second stage the mixt. is submitted to an anaerobic methane fermentation by an anaerobic microorganism culture for 6-15 days. The resulting mixt. may then if desired be further purified by a second aerobic stage. By present methods involving an anaerobic followed by an anaerobic stage, in the 1st stage, e.g. methane fermentation, the acids formed lower the pH and inhibit the fermentation. Chalk is used to neutralise the acid but this complicates the process. The above process converts the acids to CO2/water resulting in simplification of the process and avoidance of the use of chalk.