analysis of a pilot-scale anaerobic baffled reactor treating domestic ...

A filter for converting feed SBCOD composition from the carbohydrate-lipid-protein characterisation
to the elemental composition (CXHYOZNA) is presented in Appendix A6.2.
The wastewater characterisation presented in Table 6.3 represents an average composition of
Kingsburgh WWTP and was used as a base case for investigation of effluent characteristics using the
steady-state model.
An input variable, the extent of treatment fE was defined in order that outflow conditions may be
calculated for ranges of treatment efficiency. Table 6.4 presents values used in the kinetics part of the
steady-state model that is used for predicting the apparent sludge yield of the pseudo-steady-state
model.
Table 6.4: Model parameters used in or calculated by the steady-state model
Parameter Unit Value
Volume (V) ℓ 3 000
Flow rate (Q) ℓ/d 1 800
Extent of treatment (fE) mgCOD/mgCOD 0.80
Fraction of average reactor solids concentration
exiting with outflow stream (fX)
mgCOD/mgCOD 0.01
Apparent sludge yield (fraction of removed COD
converted to sludge through microbial growth) (E)
mgCOD/mgCOD 0.016
Endogenous rate constant (bH) d -1 0.041
Acidogen yield (YAD) mgCOD/mgCOD 0.113
6.4.4 Comparison of steady-state model predictions with experimental data
Several of the parameters in Table 6.3 were estimated and may not have been a true reflection of the
wastewater characteristics (VFA, protein, carbohydrate, unbiodegradable COD). Therefore, it was not
expected that the steady-state model would precisely match the measured properties of the
experimental study.
The steady-state model with sludge retention developed in Appendix A6 was used to calculate an
apparent yield, E. This value represents the reduction in sludge yield due to endogenous respiration of
biomass resulting from the long retention of solids in the reactor. The value obtained was
0.016 mgCOD/mgCOD; i.e. of the SBCOD removed from the wastewater stream, approximately 1.6%
is converted to biomass. Since the model is derived assuming that the concentrations of SBCOD and
biomass do not change significantly with time, this value implies that 1.6% of the influent SBCOD
exits the reactor as washed out biomass.
Figure 6.4 shows the agreement between the measured and simulated outlet characteristics for pH
value, alkalinity concentration and free and saline ammonia concentration. Relatively good agreement
is obtained between simulated and measured values for all three categories, with the simulated value
for free and saline ammonia and alkalinity falling within the confidence limits of the means of the
measured values.
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