The basic idea of in situ substrate uptake rate detection method[5859] is to converse time — variant variables into space-variant variables. First assumption is to consider matrix concentration as a differential function of filter bed height; the second assumption is that under proper conditions, any of the micro-unit taken from the inner-filter bed can achieve stability. Through the total differential method or the law of conservation of mass, the final expression of matrix degradation velocity can be determined, at this point, the law of conservation of mass is applied, for its intuitionism.

As shown in Fig. 25, under a constant living environment for microbe, in situ oxygen uptake rate (ISOUR) can be described as the oxygen consumption of microbe grown on filter materials per unit time and volume (written as R, mg/(L-h)). Consider the filter porosity in filter column as e, mass concentration of DO in inflow and outflow are p(DOi) and p(DOe) respectively, taking wdh as the micro-unit taken from depth of h in bio-filter bed (w is section area of filer column, m2), and the variation in DO caused by the effect of microbe inside the micro-unit can be described as R(1-e)wdh, according to the law of conservation of mass:

(p(DOi) — p(DOe))Q — R (1 — e )®dh = 0

ISOUR can be described as

dC

dt

In this equation: Q stands for the quantity of water through the filter column, m3/h; v stands for the filter velocity, m/h;

dp( DO)
dh

stands for the gradient of DO at a height of h, along the filter variation height curve. As far as the aerobic biological treatment concerned, the biodegradation velocity on organic matrix is in proportion to its ISOUR. With abundant DO in BAC and BCF filter columns, the breeding microbe is mostly aerobic bacteria. Therefore, by calculating the oxygen consumption rate in the process of treating organics by BAC and BCF filter columns, the respective biological activity can be determined to analyze and evaluate the effect of biodegradation of BAC column.