participate in nitrogen degradation and assist the removal of
nitrogen. After 2 days, the number of bacteria in RC decreased
dramatically; at the same time, nitrogen concentration began to
increase. Therefore, the death and degradation of bacteria (Fig. 2)
and algae (Fig. 1a) might be the main reason for following increasing
of total nitrogen concentration in the raw centrate medium (Li
et al., 2012). That again indicated that algae and bacteria have a
symbiotic relationship.
4. Conclusions
A mutual compound relationship between algae and centrateborne
bacteria has been demonstrated in this study. Algae can promote
bacterial growth and optimal initial algal concentration may
be more favorable for bacterial growth. Moreover, bacteria could
increase the algal growth rate and nutrients removal rate at the
initial stage of the cultivation, which is very important in the continuous
cultivation process. To obtain the maximum algal biomass,
semi-continuous and/or continuous cultivation and the appropriate
hydraulic retention time of 2 days are recommended. This
result could provide a guideline for efficient microalgae-based
organic-rich wastewater treatment and wastewater energy crop
production.