Influence factors in the adjustment of parameters of the modified first-order kinetics equation used to model constructed wetland systems

Abstract

The aim of the present work was to evaluate the relationship between the hydraulic retention time power parameter (n) of the modified first-order kinetic mathematical model (MFOKM) with the hydraulic dispersion number (d) and the organic matter degradability, obtained from the ratio of chemical and biochemical oxygen demands (COD/BOD) along the length of horizontal subsurface flow constructed wetlands (HSSF-CWs). For this purpose, unplanted HSSF-CWs prototypes of equal volumes and length/width ratios (L W^-1) of 1.0, 4.0 and 7.3 were used. All HSSF-CWs were filled with gravel # 0 and received sanitary sewage (SW) during a period of 90 days, in which the BOD and COD, in the total and soluble forms, were monitored in the influent and effluents from the system. These units were subject to tracer tests, before and after the HSSF-CWs received the SW, to obtain d. The MFOKM was adjusted to the COD and BOD experimental data. In all cases, an inverse relation was observed between n and the parameters d or with the organic matter decay rate obtained in the initial part of the HSSF-CWs.