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ABSTRACT
Our aim was to study the biomass growth of microalga Chlorella vulgaris using diluted human urine as a sole nutrient source. Batch cultivations (21 days) were conducted in five different urine dilutions (1:25–1:300), in 1:100-diluted urine as such and with added trace elements, and as a reference, in artificial growth medium. The highest biomass density was obtained in 1:100-diluted urine with and without additional trace elements (0.73 and 0.60 g L−1, respectively). Similar biomass growth trends and densities were obtained with 1:25- and 1:300-diluted urine (0.52 vs. 0.48 gVSS L−1) indicating that urine at dilution 1:25 can be used to cultivate microalgal based biomass. Interestingly, even 1:300-diluted urine contained sufficiently nutrients and trace elements to support biomass growth. Biomass production was similar despite pH-variation from < 5 to 9 in different incubations indicating robustness of the biomass growth. Ammonium formation did not inhibit overall biomass growth. At the beginning of cultivation, the majority of the biomass consisted of living algal cells, while towards the end, their share decreased and the estimated share of bacteria and cell debris increased.
Acknowledgements
The authors are grateful to M.Sc. Viljami Kinnunen for the co-operation during the laboratory experiments.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
The financial support provided by TUT Doctoral Programme in Engineering and Natural Sciences, Finnish Doctoral Programme in Environmental Science and Technology (EnSTe) and Maa- ja vesitekniikan tuki ry. are highly appreciated.