Advanced nitrogen elimination by encapsulated nitrifiers

Abstract

By introducing a mixed population of nitrifiers encapsulated in gel lens beads a more selective nitrification process was found in treatment of settled sewage in lab scale at a hydraulic retention time (HRT) of about 30 to 60 minutes. The reaction rates for oxidation of soluble chemical oxygen demand (SCOD) were found to vary between 25 to 150 mg/L x h while nitrification takes place around 50 mg nitrogen per hour and litre reaction volume. However, based on this SCOD removal in the nitrification step, a consequent post-denitrification process without nitrate recycle and dosage of external carbon sources has been proven to reach substantial nitrate elimination of up to 20 mg nitrogen per litre at COD/N-ratios of approx. 6 in settled sewage. At such COD/N-ratios, suitable nitrogen elimination seems to be possible, because the bioflocs of settled sewage, produced so far by SCOD oxidation and entrapment of particulate COD, are passing through the nitrification process having a substantial contribution to the denitrification rate additionally to the remaining SCOD.

Improvement of NaNO 2 -Oxidizing Activity in Nitrobacter vulgaris by Coentrapment in Polyacrylamide Containing Polydimethylsiloxane Copolymer and DEAE-Sephadex

“…strains used for nitrite analysis (without enhancer), Nitrobacter vulgaris was shown to be most suitable (25). Mixed populations of immobilized nitrifiers have been widely used for cleaning of different types of wastewaters, but nitrification was not found to be enhanced by any additional agents (28), in contrast to our present work. In the Czech Republic, Chemopetrol A.S. Litvinov operates pilot units for nitrogen removal with encapsulated nitrifiers using LentiKats technology, but also without additives, for improving their performance.…”

“…Nitrifiers can be immobilized in a polymer matrix (1, 10, 15, 19, 32-35, 38, 39) or attached to a membrane with a micro-or macroscale (27). The immobilized nitrifiers (28) are already used in continuously operating pilot units for nitrogen removal from different wastewater sources in the Czech Republic, Chemopetrol a.s. Litvinov. The main advantage of immobilized cells is the high concentration of active biocatalyst attainable in the solid phase (10).…”