Degradation and detoxification of a mixture of persistent compounds (2-chlorophenol, phenol and
m-cresol) were studied by using pure and mixed indigenous cultures in aerobic reactors. Biodegradation ...assays were performed in batch and continuous flow reactors. Biodegradation was evaluated by determining total phenols, ultraviolet spectrophotometry and chemical oxygen demand (COD). Microbial growth was measured by the plate count method. Scanning electronic microscopy was employed to observe the microbial community in the reactor. Detoxification was evaluated by using
Daphnia magna toxicity tests. Individual compounds were degraded by pure bacteria cultures within
27
h
. The mixture of 2-clorophenol
(100
mg
l
−1)
, phenol
(50
mg
l
−1)
and
m-cresol
(50
mg
l
−1)
was degraded by mixed bacteria cultures under batch conditions within
36
h
: 99.8% of total phenols and 92.5% of COD were removed; under continuous flow conditions 99.8% of total phenols and 94.9% of COD were removed. Mineralization of phenolic compounds was assessed by gas chromatography performed at the end of the batch assays and in the effluent of the continuous-flow reactor. Toxicity was not detected in the effluent of the continuous-flow reactor.
This paper presents the conception and discusses the results obtained from the operation of an integrated biological anaerobic/aerobic/anaerobic system composed of horizontal-flow anaerobic and ...radial-flow aerobic reactors for domestic sewage treatment. The performance of a horizontal-flow anaerobic immobilized biomass reactor, with five stages, followed by a radial-flow aerobic immobilized biomass reactor was evaluated along 22 weeks. After the 14
th
week, the last stage of the HAIB reactor was used as a denitrifying unit Polyurethane foam cubic matrices with 1-cm sides were used as support for biomass immobilization in all the units. The influent domestic sewage presented mean chemical oxygen demand of 365 ± 71 mg. l
-1
and the temperature was 23 ± 3°C. The integrated system achieved COD removal efficiency of 90% while the maximum ammonium removal efficiency was 97% in the aerobic post-treatment unit The nitrification process was found to be better represented by first-order reactions in series model. The apparent first-order kinetic coefficient for nitrate formation was about 50 times higher than that estimated for the nitrite formation. The denitrification process was well represented by a Monod-type kinetic model. The maximum specific denitrifying rate and the half-saturation coefficient were 2.9 × 10-4 mg NO
3
-N mg
-1
VSS h
-1
and 19.4 mg NO
3
-
-N l
-1
respectively.
