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Niedokładność porównania kinetyki pierwszego rzędu w modelowaniu usuwania związków azotu w oczyszczalniach hydrofitowych

Marcinkowski M. J.

Zeszyty Naukowe Politechniki Gdańskiej. Inżynieria Lądowa i Wodna

2012

Nr 1 (625)

71--81

Textbook describe nitrification and denitrification process in a simplified way. The nitrification process begins with ammonia nitrogen (NH4) oxidation to nitrites (NO2) followed by oxidation to nitrates (NO3) by Nitrosomonas and Nitrobacter (or Nitrospira) bacteria, respectively. Hydroxylamine (NH2OH) is an important intermediate product between ammonia and nitrite. Next – or afterward – facultative anaerobic bacteria denitrify by oxidizing organic carbon with nitrate or nitrite. This “model” (in terms of precess) has been successfully applied for conventional wastewater technology and design. However, recent developments in technology of wastewater engineering reveal that that “the classic model” of nitrification and denitrification is specific to the treatment technologies that use it, and thus cannot be consider as a general model for treatment wetlands. This paper present weaknesses of first-order kinetics applied to nitrogen removal processes in treatment wetland system. It points out that reaction constants (k and C*) are strongly dependant on several factors, e.g. hydraulic behavior of wetland system or nitrogen fractions present in untreated wastewater. Precision on first-order model provides only information on general conditions found in filter bed (e.g. effluent COD and TN concentration, but its inaccuracy eliminates possibility of predicting effluent concentration of organic nitrogen (N-Org), total suspended solid (TSS), and BOD5. Background concentration C*place an important role here, however its values in literature are found in a wide range. A distinction was made between true and apparent background concentration. Some of the cases show that these two concentrations are equal, however it is still difficult to use one value of C* in modeling process.