Assessment of cell retention time and sewage concentration in biological removal of nutrients: removal of nutrients in sequential batch reactors
DOI:
https://doi.org/10.6008/CBPC2179-6858.2021.006.0027Keywords:
Biological removal of nutrients, Sequential batch reactor, Concentrated sewage, Moderate sewageAbstract
The biological removal of nitrogen and phosphorus has been efficiently achieved in sewage treatment using sequential batch reactors (SBR). However, biophosphate and heterotrophic denitrification occur when there is organic carbon available in stoichiometric proportions, among other factors, such as the sludge age and the period time of the aerobic, anaerobic and anoxic phases. In this context, aimed to evaluate the efficiency of two SBR in biological removal of sewage nutrients with different influent concentrations, under different cell retention times (CRT), and cycle times. Therefore, two experimental systems were paralleled operated: system 1 had concentrated sewage as an influent; and in system 2 the influent was moderate sewage. In both experiments, two SBR were used with cycle times of 24 and 8 hours, and the CRT of 12 and 5 days, respectively for R1 and R2. The average removal efficiencies in experimental system 1 for R1 were 60%, 42% and 81%, and for R2 were 83%, 80% and 35%, respectively for total phosphorus, orthophosphate and nitrogen. On the other hand, the average removal efficiencies in experimental system 2 for total phosphorus, orthophosphate and nitrogen were respectively 47%, 43% and 83% (R1), and 56%, 54% and 33% (R2). The influent with higher concentrated sewage, which were operated at experimental system 1, achieved the best performance of biophosphate after R2, and the best efficiency of nitrification/denitrification process after R1. In addition, the COD/P (55 to 65) and COD/N (6 to 9) ratios proved that, in both experiments, there were enough organic matter for removal processes of nitrogen and phosphorus to occur properly in activated sludge systems.
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