Environmental Engineering Reference
In-Depth Information
Treatment
RI
SB
DR
OR
TF
CF
1
8.09
a
8.32
a
7.61
a
7.22
7.30
a
8.26
a
2
7.89
a
8.24
a
7.63
a
3
7.93
a
8.32
a
7.58
a
7.20
7.37
a
8.22
a
4
7.89
a
8.24
a
7.58
a
1
Abbreviations: RI = raw influent, SB = sedimentation basin, DR = denitrification reactor,
OR = ozonation reactor, TF = trickling filter, and CF = chemical flocculation.
Table 5. Dynamics of pH values through the treatment train
1
for all experimental treatments
(unit outlet values). Means in a column with the same superscript are not significantly
different (
p
>0.05).
suggesting that the relatively high-pH water in our study could be disadvantageous. pH
increased again in the trickling filter, which was somewhat surprising considering that
nitrification occurred in this filter and some alkalinity was lost. The effects of large amounts
of organics in the influent and their compositional diversity may have overshadowed the
effects of nitrification of relatively small amounts of ammonia. Additionally, CO
2
stripping
could have contributed to pH increase.
Further decline of pH occurred during chemical flocculation, reaching final values of about
7.60, which is considered safe for fish production.
3.4 Hardness
Hardness enters the BRA systems with replacement spring water and with feed, and
supports biomass development for both fish and for microorganisms in biofilters. Average
hardness concentrations were between 148.4 and 151.5 mg/l as CaCO
3
, characterizing BRA
effluent as a medium-hard wastewater. Table 6 presents the dynamics of hardness as the
water passed through the treatment station.
SB
DR
OR
TF
Total decrease
2
Treatment
mg/l
mg/l (%)
mg/l (%)
mg/l (%)
(%)
1
139.7 (4.1)
a
138.0 (1.2)
a
8.9
a
151.5
a
145.7 (3.8)
a
2
137.4 (5.7)
b
135.9 (1.1)
a
10.3
a
3
130.6 (7.8)
ab
129.5 (0.8)
a
12.7
a
148.4
a
141.7 (4.5)
a
4
134.6 (5.0)
ab
132.6 (1.5)
a
10.6
a
1
Abbreviations: SB = sedimentation basin, DR = denitrification reactor, OR = ozonation reactor, and
TF = trickling filter.
2
Hardness decrease between settling basin and trickling filter effluent concentrations.
Table 6. Dynamics of hardness through the pilot plant
1
for
all experimental treatments (unit
outlet values). Means in a column with the same superscript are not significantly different
(
p
>0.05).
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