Dissertação
Influência da saturação de fundo e do carregamento orgânico no desempenho de wetland vertical aplicado ao tratamento de esgoto doméstico bruto
Fecha
2020-04-02Autor
Marchioro, Luis Gustavo
Institución
Resumen
The vertical flow constructed wetlands (VFCW) are natural and low cost systems and that
present relative operational simplicity, making this technology attractive to the treatment of
effluents in a decentralized way, fitting well to the needs of small communities. These systems
have a good removal of carbonaceous organic matter and significant nitrification. However,
total nitrogen removal is limited in these systems. An alternative to this limitation is the
saturation of a layer of the filtering bed aiming the formation of an anoxic environment seeking
to make the denitrification process more efficient. The objective of this study was to evaluate
the performance of pilot scale systems of traditional VFCW and adapted systems with a
saturated bottom in a treatment of raw domestic wastewater. The experiment was operated
for 339 days, monitored for 218 days and consisted of using PVC columns with 0,031 m² of
surface area, filled with gravel, transplanted with Canna sp., fed 5 times a day, for 3,5 days a
week with the same time destined to rest (without feeding). The performance of the columns
was assessed for three hydraulic loading rates - HLR (40, 70 and 100 mm d-¹) with the
respective average organic loads of 49, 86 e 123 g DQO m-² d-¹ in two conditions: free drainage
(DL) and saturated bottom (FS). The saturation layer corresponds to 1/3 of the bed
(25cm/75cm), resulting in six evaluated columns, which were named as DL1 and FS1 (40 mm d-¹), DL2 and FS2 (70 mm d-¹) and DL3 and FS3 (100 mm d-¹). There was a better performance
in COD removal for columns with saturated bottom (96, 95 e 93 % for FS1, FS2 and FS3,
respectively), compared to free drainage columns (86, 84 and 78 % for DL1, DL2 and DL3,
respectively). Better performance in the removal of TN was also observed in the FS columns
(94, 87 and 79% for FS1, FS2 and FS3, respectively), compared to the DL columns (80, 73
and 63 % for DL1, DL2 and DL3, respectively). Increasing the HLR, a limitation was observed
for the saturated bottom columns in the removal of N-NH4
+, with FS3 presenting a performance
lower than DL3 for this parameter. The increase of HLR showed to influence the accumulation
of solid material on the surface and the development of vegetation. At the end of the operation
period, the columns had an average accumulation of sludge on the surface of 0.128, 0.272
and 0,477 kg m-² for pairs DL1/FS1, DL2/FS2 and DL3/FS3, respectively, as well an average
production of vegetable biomass of 1.70, 2.78 and 4.74 kg m-². With the realization of this
experiment, we can conclude that the adaptation of bottom saturation layer plays an important
role in the operation of VFCW, being able to substantially increase the performance of these
systems when applied to the treatment of raw domestic sewage.