Bioavailability of wastewater-derived organic nitrogen to the
alga Selenastrum Capricornutum
Elif Pehlivanoglu and David L. Sedlak
Department of Civil and Environmental Engineering
University of California
609 Davis Hall, Berkeley, CA 94720, USA
Abstract
Recent attempts to control cultural eutrophication in nitrogen-limited
systems have focused on the simultaneous control of all forms of
nitrogen with the underlying assumption that inorganic and organic
nitrogen are equally bioavailable. To assess the validity of this
assumption, algal growth bioassays were conducted on denitrified
wastewater effluent samples, in the presence and absence of bacteria
isolated from an effluent-receiving surface water. Bioassay results
indicated that wastewater-derived dissolved organic nitrogen (DON) is
not bioavailable to the algae Selenastrum Capricornutum in the absence
of bacteria. However, approximately half of the wastewater-derived
organic nitrogen was available to the algae in the presence of bacteria
during a 2-week incubation. These results suggest that while it is
inappropriate to assume that wastewater-derived DON cannot cause
cultural eutrophication, it will not cause as much eutrophication as
inorganic nitrogen. Additional research is needed to develop methods of
minimizing the discharge of bioavailable forms of wastewater-derived
organic nitrogen by wastewater treatment plants.