Faculty advisor: Bo HuThis research was supported by the Undergraduate Research Opportunities Program (UROP)

Hu, Bo

Prill, Allison

Rajendran, Aravindan

University of Minnesota Digital Conservancy

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Excess phosphate from first and second-point 
pollution sources easily enters water systems, causing 
serious problems like eutrophication. The consequences 
of excess nutrients in water systems can result in rapid 
decline of many native populations due to lack of oxygen 
and other complications1. 
An effective method of removing excess nutrients 
from wastewater is needed to reduce the impact of 
runoff and other sources of pollution. Recent research 
shows that several species of algae, including 
Phormidium bohneri, can be used at wastewater sites as 
a cost-effective means of removing excess phosphate 
from the wastewater in an industrial setting2. 
To test this, P. bohneri was cultivated in media with 
three different levels of initial phosphate. The phosphate 
levels were measured as a function of time. The results 
of this experiment show the P. bohneri has the ability to 
remove significant amounts of phosphate from a liquid 
media and bind to a mixed-media matrix successfully. 
These results are important in developing a system of 
removing excess phosphate from wastewater. Further 
research is necessary to understand how this species 
performs in a non-synthetic media. 
Conclusions
Photosynthetic biofilm reactor (PBR) for nutrient removal from wastewater
Allison Prill, Dr. Aravindan Rajendran, and Dr. Bo Hu
Department of Bioproducts and Biosystems Engineering
Bibliography
From the data given, it is reasonable to conclude 
that Phormidium bohneri, when cultivated in the 
nutrient-rich BG-11 media with proper lighting and 
agitation, has the ability to drastically reduce the 
phosphate levels in a synthetic media. This result is 
important because it identifies P. bohneri as a 
candidate species for phosphate removal from water 
systems. While most of the flasks displayed a drastic 
reduction in phosphate levels, there were a few 
flasks that did not follow this trend to the same 
extent. The reason for this has yet to be determined, 
but an ion chromatography analysis of the samples 
in the future could reveal some answers. Most likely, 
this is due to bacterial contamination. Regardless, 
the conclusion that phosphate levels are reduced by 
P. bohneri holds true, although the level of reduction 
varies. 
Introduction
Materials and Methods
1. Talbot, P., & Noue, J.D. (1993). Tertiary treatment of wastewater with 
Phormidium bohneri (Schmidle) under various light and temperature 
conditions. Water research, 27(1), 153-159. doi:10.1016/0043-
1354(93)90206-w 
2. Blier, R., Laliberte, G., & Noue, J.D. (1995). Tertiary treatment of cheese 
factory anaerobic effluent with Phormidium bohneri and Micractinum 
pusillum. Bioresource Technology, 52(20, 151-155. doi:10.1016/0960-
8524(95)00014-6
This project was supported by 
the University of Minnesota's 
Undergraduate Research 
Opportunities Program.
Further Studies
Phormidium bohneri was inoculated with the liquid 
BG-11 media in a different concentration for each 
trial. Three flasks were prepared in each trial. 
• The low concentration had 8.5 mg/L of K2HPO4
• as the initial source of phosphate. 
• The medium concentration had 18.5 mg/L of 
K2HPO4 for the initial phosphate source.
• The high concentration had 30 mg/L of K2HPO4 
as the initial source of phosphate. 
The flasks were cultivated under fluorescent 
lighting and were constantly agitated by a shaker. 
Periodically, Hach Reactive Phosphorus tests 
were used to monitor the phosphate levels in each 
flask. 
• The experiments should be repeated in a 
nonsynthetic media, ideally from a nearby 
body of water known to have undesirably 
high levels of phosphates that leads to lower 
water quality. 
• Ion chromatography analysis should be 
performed on all samples to determine any 
key differences between the high-performing 
flasks and the outlying low-performing 
flasks. 
• The same biofilm mats should be cultivated 
in new media to determine their ability to 
continually remove phosphate from a non-
depleting source. 
Results
• The phosphate levels decreased for 
all trials at each of the three 
concentrations
• The largest percent difference in 
phosphate levels was a -80.52% 
decrease, with the average percent 
difference being -50.13%
• Vial 2B showed very little attachment 
or ability to remove phosphate, most 
likely due to a bacterial contaminant. 
Figure 2. The percent difference between the initial 
and final phosphate values is shown above.  Figure 5. The phosphate level as a function of time for 
the highest initial phosphate concentration is shown 
above. 
Figure 4. The phosphate level as a function of time for 
the medium initial phosphate concentration is shown 
above. 
Figure 3. The phosphate level as a function of time 
for the lowest initial phosphate concentration is shown 
above. 
Figure 1. Trial 3B is shown 
after 195 hours to the right. 
P. bohneri shows nearly 
perfect attachment to a 
cotton-polyethylene matrix in 
a nutrient-rich media, BG-11.
Figure 6. The experimental procedure for the reactive 
phosphate level experiment is shown above.   
• 150 rpm
• 27 degrees Celsius 


Photosynthetic biofilm reactor (PBR) for nutrient removal from wastewater

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Photosynthetic biofilm reactor (PBR) for nutrient removal from wastewater

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