Technology Description

Bacteria can gain substantial energy by mediating the transfer of electrons from an electron donor (e.g., acetic acid) to an electron acceptor (e.g., perchlorate). Biological perchlorate treatment processes capitalize on this principle by maintaining an environment that fosters the growth of perchlorate-reducing bacteria (PRB). FXB biological processes utilize a stationary bed of media such as sand, plastic, or granular activated carbons (GAC) on which biofilms containing PRB develop. Water is drawn from a well, amended with an electron donor and phosphorus, and then pumped across the media bed. Bacteria in the bed reduce dissolved oxygen, nitrate, and perchlorate. Contacting virgin media with raw water for about a month provides the necessary perchlorate-reducing biological activity, thereby eliminating the need for a perchlorate-reducing inoculum. Effluent from the FXB bioreactor passes through an aeration tank to remove nitrogen gas and add oxygen to the process stream. A low dose of cationic polymer will be added to the aeration tank effluent (condition sloughed biomass for improved filtration), which will then pass through a dual media filter (turbidity removal, residual acetic acid oxidation, hydrogen sulfide oxidation), prior to final disinfection. The FXB bioreactors and polishing filters will be backwashed approximately every 24-26 hours to remove excess biomass. Backwash wastewater will be treated in a dissolved air flotation process to separate the biomass from process water. The process water could then be returned to the head of the plant or discharged to a local sewer or catch basin.