Behavior of nitrifying and denitrifying bacteria in a sequencing batch reactor for the removal of ammoniacal nitrogen and organic matter

SBR (Sequencing Batch Reactor) treatment systems are made up of an artificial ecosystem where they develop the microorganisms under controlled and limited conditions, in which the pH, organic load and oxygen within the reactor vary spatially and in time. This causes the microbial population to be neither uniform nor constant and therefore reflects the conditions to which they have been exposed during the treatment system. Nitrifying and denitrifying bacteria in a SBR pilot system were monitored over 252 days, using two types of wastewater in the treatment; one with a high amount of organic matter and the other with a high amount of ammonium, both originating from a meat product processing plant. The two types of wastewater were mixed in different proportions with the aim of varying the organic and ammoniacal loading in the influent, thus allowing the most suitable conditions for obtaining high removal efficiencies in the combined treatment of organic matter and ammonia to be determined. The results showed efficiencies of 99%, 98% and 71% in CODF, BOD5 and NH4+–N, respectively, and a microbial density of about 2.35 × 107 MPN/100 mL for nitrifying bacteria and 2.25 × 107 MPN/100 mL for denitrifying bacteria.

Research Highlights
► The maximum density of bacteria was at the time of the highest removal efficiency.
► The SBR is a suitable treatment for the removal of organic matter and ammoniacal.
► The density of nitrifying bacteria is directly related to the dissolved oxygen.
► The relationship between BOD5/NH4+-N is very important for achieve a good removal.