Patent ID: 8864992

Claim:
A process for removing phosphates from wastewater containing phosphates during a multi-phase digestion, the process comprising the steps of: feeding at least one of a primary sludge or a waste activated sludge into an organic acid digester, wherein digestible carbohydrates in the sludge undergo acidogenesis and acetogenesis to provide an organic acid digest comprising volatile fatty acids; raising the pH of the organic acid digest to a pH of less than 8, whereby phosphates are precipitated from the organic acid digest; removing the precipitated phosphates from the organic acid digest; and after removing the precipitated phosphates, either: returning the organic acid digest to the organic acid digester, wherein volatile fatty acids in the organic acid digest undergo methanogenesis to produce methane, such that the removal of the precipitated phosphates from the organic acid digest occurs after the organic acid digest has undergone acidogenesis and acetogenesis in the organic acid digester but before the organic acid digest is returned to the organic acid digester where it undergoes methanogenesis; or sending the organic acid digest into a thermophilic digester or a mesophilic digester, wherein volatile fatty acids in the organic acid digest undergoes methanogenesis to produce methane, such that the removal of the precipitated phosphates from the organic acid digest occurs after the organic acid digest has undergone acidogenesis and acetogenesis in the organic acid digester but before the organic acid digest is sent to the thermophilic digester or the mesophilic digester where it undergoes methanogenesis.