Biomedical Engineering Reference
In-Depth Information
causes the poor settlement of activated sludge flocs (Liss et al., 2002). This mechanism can
also be used to explain the results obtained from other studies in which heterotrophs
dominated, or saline wastewater was treated and a low SRT occurred (Wu et al., 2008b; Liss
et al., 2002).
Based on this study, it is recommended that biofilm systems or membrane systems can be
used to nitrify wastewaters with low carbon substrate concentrations. By this means, the
effect of poor settleability of activated sludge flocs can be avoided.
5. Conclusion
Short-term effects of glucose addition on nitrification and sludge settlement were
investigated. High specific nitrification rates were observed in the N-Reactor without the
addition of glucose, while high volumetric nitrification rates occurred in the G-Reactor with
the addition of glucose. Nitrite accumulation was due to low pH caused by the processing of
nitrification in both reactors. In the G-Reactor the biomass concentration remained relatively
stable, while in the N-Reactor the biomass concentration decreased with time. The reason for
the decrease in the biomass concentration in the N-Reactor was due to the high amount of
EPS produced, which caused the poor settlement of activated sludge flocs; consequently,
more activated sludge was washed out from the N-Reactor and a very low SRT occurred; the
low SRT further encouraged poor settlement of activated sludge flocs.
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