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

efore this, there were two incidents that may have caused washout of sludge, on day 14 and day 36.
these incidents resulted in reduction of the sludge bed volume and thus data before day 36 were not
included in the regression.) The regression considers 53 days of stable operation from day 53 to day
106. The regression was found to be significant (Table 5.3) and the sludge volume increased at a rate
in the 95% confidence interval from 6.2 to 12.7 ℓ/d.
In Phase III, there were few sludge washout incidents and there was a much less even distribution of
sludge between compartments (Figure 5.16 a). The average sludge bed height was more than double
that observed in Phase II, and the highest sludge bed was usually observed in compartment 1.
5.6.1.3 Phase IV: Solids levels
In Phase IV, the flow rate and applied OLR were reduced. Operation was stable as a result of
improvements in the control algorithm, and few incidents of any kind were observed. There were no
significant sludge washout incidents. The average height of the sludge beds (Figure 5.17 b) increased
at a slower rate than in Phase III, and the shape of the profiles also changed, with higher settled sludge
beds in the earlier compartments (Figure 5.17 a). Figure 5.17 (b) presents the calculated sludge
volume in the upflow compartments of the pilot-scale ABR for Phase IV operation with a linear
regression between time and sludge load. The linear regression was highly significant (Table 5.3) and
the regressed slope of sludge volume accumulation was found to fall in the 95% confidence interval
from 1.6 to 3.3 ℓ/d.
For Phase IV, total solids data were also available for the average concentration in the upflow side of
each compartment.
ABR solids load
[kg dry solids]
60
50
40
30
20
10
0
May04
Jun04
Jul04
0 50 100 150 200
Phase IV: Time [d]
Figure 5.18: Phase IV: Mass of total solids (dry) in the upflow compartments of the pilot-scale
ABR showing linear regression line with 95% confidence interval on the
regression (------).
A total solids load was calculated for the pilot-scale ABR analogous to the total settled sludge volume
according to Eq. 5-4:
TS
t
( C ⋅Y
) ⎞
⋅ ( c/s
area of up - flow compartment)
=
⎛ ( C ⋅Y
) ⎞
⋅ ( w ⋅ l)
=
⎛
⎜
∑
⎝
⎠
⎝
∑ TS , i i,
max ⎟
⎜ TS , i i,
max
i
i
108
Eq. 5-4
Where CTS,i is the average total solids concentration in a mixed core sample from compartment i, Yi,max
is the maximum height of compartment i and w and l are compartment width and length respectively.
Aug04
Sep04
⎟
⎠
Oct04
0.1