carbon and nitrogen removal with SBR treatment may
have increased at the extreme salinity and temperature
levels.
The 10:1 C:N treatment had lower final concentrations
of nitrate-N and nitrite-N than all other C:N treatments
(Table 3). The 5:1 and 10:1 C:N treatments reduced total
ammonia-N more than the 20:1 and 30:1 C:N treatments
by the end of the eight day sequence (Table 3). All variables
tested were reduced by at least 91% for the 10:1 C:N ratio
treatment (Table 3). This result showed that the C:N ratio
of 10:1 is better than higher C:N ratios. By simply doubling
the C:N ratio from 5:1 to 10:1 via the addition of an
inexpensive molasses the performance of SBR could be
improved significantly.
Previous literature suggests that a C:N ratio of 20:1 or
30:1 is better than a 10:1 ratio for various wastewater
treatment such as poultry waste, cow manure, and coffee
waste (DeRenzo, 1977; Sathianathan, 1975; Boopathy
and Mariappan, 1984). However, we found that a 10:1
C:N ratio was the optimal ratio for SBR treatment of
shrimp aquaculture wastewater. The C:N ratio can be
manipulated by the feed offered to the culture animals or
at a later stage before the wastewater is treated. Based in
this study, we suggest that SBR be operated at the salinity
and temperature levels of the culture system and that the
C:N ratio is maintained near 10:1 for the most efficient
treatment of wastewater. This study was conducted at the
benchtop scale with only a single batch per reactor. Future
work will investigate pilot scale SBR.
Acknowledgements
This work was supported by the funds from the US
Department of Agriculture, Cooperative State Research
Service of Marine Shrimp Farming Program. We thank
Heidi Atwood for providing the wastewater for the study.