OrbHab Paper
Microalgae Cultivation For Nutrient Recovery From Human Urine (2015)
ID: 315 Flag Paper
Title: Microalgae Cultivation For Nutrient Recovery From Human Urine
Authors: K. Tuantet
Journal Name: Thesis
Year of Publication: 2015
Page Number:
Category: biosphere
Availability: pdf
Detail Page: /papers/315
Web Link: https://edepot.wur.nl/337297
BoK Link: [[paper:315]]
Abstract
Nitrogen (N) and phosphorus (P) are key nutrients for all living organisms. At the same time,discharge of wastewaters containing these elements on surface waters has a strong negativeimpact on the environment. Urine is the major nutrient source in domestic wastewater andthese nutrients cover 24% of the N, 20% the P and 32% of the potassium (K) in artificialfertilizers (year 2010). Separation of urine from other household wastewater streams andusing it for nutrient recovery therefore is considered much more efficient and less energyconsuming than treatment of large volumes of highly diluted domestic wastewater. Thisthesis aimed to apply microalgae cultivation as a tool to recover the nutrients from humanurine. Because of the high N:P ratio of microalgae biomass, it was expected that all of the Pand a significant amount of the N could be simultaneously recovered from source-separatedurine.At first, growth of a pre-selected microalga, Chlorella sorokiniana, on urine was tested inbatch at different degrees of urine hydrolysis in order to assess possible limitations formicroalgae growth. Hydrolysis of urea in urine resulted in a changing in urine compositionand a higher pH, and stimulated precipitation of P, magnesium (Mg) and some traceelements, reducing their availability for the microalgae. Supplementation of these compoundstherefore was required to enhance microalgae growth. Next, C.sorokiniana was cultivated ina short light-path photobioreactor under continuous illumination at a high light intensity andat various hydraulic retention times (HRTs) to optimize biomass productivity, biomass yieldon light and nutrient uptake from both synthetic and human urine. The highest biomassproductivity and nutrient recoveries respectively were 1.1 g-dw L-1 h -1 , 123 mg-N L -1 h-1 and13 mg-P L-1 h-1 in synthetic urine, and 0.8 g-dw L-1 h-1 , 82 mg-N L-1 h-1 and 8 mg-P L -1 h-1 inhuman urine. The highest biomass yield on light in synthetic and human urine respectivelywere 0.98 and 0.74 g-dw mol-photons -1 showing high photosynthetic efficiency even at ahigh irradiance level of 1500 μmol-photons m-2 s -1 at the photobioreactor surface. Withhuman urine free ammonia toxicity negatively affected system performances.Experiments under outdoor conditions with simulated day/night cycles, showed thatmicroalgae specific growth rate, biomass productivity and nutrient uptake rates were exertedduring the day period in a short HRT reactor. At night, growth and nutrient removal could notbe demonstrated. Hence, the microalgae reactor should be operated at short HRTs during the day period and at long HRTs or in batch during the night. Model calculation showed that forDutch conditions system optimization may be possible by increasing the ratio betweenilluminated surface and photobioreactor volume and by applying urine dilution. In Dutchsummer conditions with system optimization, <1 m2 of ground surface is needed for aphotobioreactor treating the urine of a single person. However, the combination ofmicroalgae production and treatment of concentrated urine probably is restricted to regionswhere light availability and temperature are higher than in The Netherlands.
Title: Microalgae Cultivation For Nutrient Recovery From Human Urine
Authors: K. Tuantet
Journal Name: Thesis
Year of Publication: 2015
Page Number:
Category: biosphere
Availability: pdf
Detail Page: /papers/315
Web Link: https://edepot.wur.nl/337297
BoK Link: [[paper:315]]
Abstract
Nitrogen (N) and phosphorus (P) are key nutrients for all living organisms. At the same time,discharge of wastewaters containing these elements on surface waters has a strong negativeimpact on the environment. Urine is the major nutrient source in domestic wastewater andthese nutrients cover 24% of the N, 20% the P and 32% of the potassium (K) in artificialfertilizers (year 2010). Separation of urine from other household wastewater streams andusing it for nutrient recovery therefore is considered much more efficient and less energyconsuming than treatment of large volumes of highly diluted domestic wastewater. Thisthesis aimed to apply microalgae cultivation as a tool to recover the nutrients from humanurine. Because of the high N:P ratio of microalgae biomass, it was expected that all of the Pand a significant amount of the N could be simultaneously recovered from source-separatedurine.At first, growth of a pre-selected microalga, Chlorella sorokiniana, on urine was tested inbatch at different degrees of urine hydrolysis in order to assess possible limitations formicroalgae growth. Hydrolysis of urea in urine resulted in a changing in urine compositionand a higher pH, and stimulated precipitation of P, magnesium (Mg) and some traceelements, reducing their availability for the microalgae. Supplementation of these compoundstherefore was required to enhance microalgae growth. Next, C.sorokiniana was cultivated ina short light-path photobioreactor under continuous illumination at a high light intensity andat various hydraulic retention times (HRTs) to optimize biomass productivity, biomass yieldon light and nutrient uptake from both synthetic and human urine. The highest biomassproductivity and nutrient recoveries respectively were 1.1 g-dw L-1 h -1 , 123 mg-N L -1 h-1 and13 mg-P L-1 h-1 in synthetic urine, and 0.8 g-dw L-1 h-1 , 82 mg-N L-1 h-1 and 8 mg-P L -1 h-1 inhuman urine. The highest biomass yield on light in synthetic and human urine respectivelywere 0.98 and 0.74 g-dw mol-photons -1 showing high photosynthetic efficiency even at ahigh irradiance level of 1500 μmol-photons m-2 s -1 at the photobioreactor surface. Withhuman urine free ammonia toxicity negatively affected system performances.Experiments under outdoor conditions with simulated day/night cycles, showed thatmicroalgae specific growth rate, biomass productivity and nutrient uptake rates were exertedduring the day period in a short HRT reactor. At night, growth and nutrient removal could notbe demonstrated. Hence, the microalgae reactor should be operated at short HRTs during the day period and at long HRTs or in batch during the night. Model calculation showed that forDutch conditions system optimization may be possible by increasing the ratio betweenilluminated surface and photobioreactor volume and by applying urine dilution. In Dutchsummer conditions with system optimization, <1 m2 of ground surface is needed for aphotobioreactor treating the urine of a single person. However, the combination ofmicroalgae production and treatment of concentrated urine probably is restricted to regionswhere light availability and temperature are higher than in The Netherlands.