Microalgae cultivation in source seperated human urine

Energy scarcity is getting important day by day due to the population increase and lack of the fossil fuel resources. Today, we are consuming next years fossil resources and there is no any reversible way to gain these resources. Therefore new energy alternatives should be found or renewable energy sources should be used. In that purpose, biomass energy is commonly started to be used and developing topic in the last decades. The most significant advantage of biomass energy is due to its sustainable property and also its close connections with waste management. Nowadays, algae is the one of the significant subject of the biomass energy and sustainable environment. Treating a wastewater consumes high amount of energy and it needs high costs. Also only treating a wastewater is not a major problem with the developing technology. All around world scientists started to enhance a treatment systems that beneficial purposes such as energy production, valuable chemicals and fertilizers. We should find a way to utilize valuable products from waste and wastewater for the sustainable environment. What really makes the use of algae a thriving technology is that these microorganisms have the potential to efficiently remove nutrients from wastewater, and provide a biomass energy source. Additionally, when combined with the conventional activated sludge systems, the algae-bacteria symbiosis can reduce the electrical energy demands from aeration, which can represent more than 50 percent of the total energy of wastewater treatment plants. The positive interactions are clear when microalgae provide, through photosynthesis, the oxygen necessary for aerobic bacteria to biodegrade organic pollutants, consuming in turn the carbon dioxide released from the bacterial activity. Biomass produced in photobioreactors can be used for several purposes, including biogas substrate, biofuels, fertilizers and biopolymers, which can be converted into packaging materials, and have the advantage of being renewable. While the application of by-products derived from algae are technically feasible, their economic feasibility is still under discussion. Microalgae cultivation is significantly increasing from day to day because of their valuable ingredients such as biodiesel, bioethanol, biohydrogen, animal feed, biofertilizer, food suppliment and valuable chemicals. All these valuable purposes are depends on the microalgae species and cultivation media. If the cultivation media is wastewater production of some of these valuable products can be risky therefore, energy production from the wastewater media is easier and more economic than the others. Also multiple valuable product acquire is possible and more logical however in this study only biodiesel potential of microalgae with urine media is studied. Stream segregation/ECOSAN claims that domestic wastewater is not a waste to be discard, however; a source to be revaluated, and is based upon seperating various streams at their point of origin and avoiding mixing of these segregated streams that including storage and processing. In the process of segregation streams which are different in terms of their character as well as their pollution are seperated at the first point that they are generated, stored and processed without mixing to produce products for beneficial end-uses. As such, it is an option which the management process at the household level and is closely related to control at the source. Currently seperation is practiced either as two component (black and grey) or three component (yellow, brown and grey) segregation. In case of two segratation, domestc wastewater is seperated into black water and grey water, where grey water refers to all portions of domestic wastewater exclusion of toilet wastewater and black water to that portion coming from the toilet-bowl. With three component segregation, also and more commonly known ECOSAN seperation, streams are yellow water which is seperately collected human urine and brown water which is seperated collected feces, in addition to grey water as deccribed above. Yellow water (Urine) is the wastewater which includes between 5-30% of total wastewater amount created domestically. Also this portion of wastewater includes 38% of potassium, 88% of nitrogen and 68% of phosphorus in the total amount of domestic wastewater. Therefore, if load that come from this portion of wastewater to domestic wastewater plants is seperated and treated seperately, it will disburden the domestic wastewater treatment plants economically. Also production of the valuable products from yellow water decreases treatment costs, and since it is photoautotraphic treatment, it will decrease the carbon emissions. As a valuable product biodiesel is the best alternative rather than others due to the method of acquire. Production of biodisel from wastewater do not have to be produce in hygienic conditions rather than other valuable products such as some chemicals used in pharmaceutical or food industry. In this purpose, biodiesel production potential of human urine which was one of the most important wastewater type was examined. Mixed culture and pure culture of microalgae species were cultivated in urine in this study. First mixed culture microalgae was taken from the Istanbul Technical University's ponds and it was cultivated in the BG-11 media. After the cultivation in synthetic media mixed cuture microalgae was started to cultivate in urine. Urine was taken from the Istanbul Technical University Environmental Engineering Department's toilet. The stabilized urine used in the study, waited enough for the transformation of organic nitrogen to ammonia and ammonium nitrogen. 1,5% dilution rates were started for the first acclimation to urine and dilution rate and cultivation volume increased with time. Chlorella protothecoides, Gloeotilopsis planctonica and Pandorina morum species were studied as pure culture microalgae species. Originally, these species were cultivated in BBM media. For the adaptation to the urine media it was started with the 1,5% human urine dilution rate and it was cultivated 2 times in 1,5% dilution rate with the 200 mL working volume. Then 1,5% dilution rate was kept same and it was operated with the 400 mL working volume and 5% 600 mL volume was studied. Pure culture microalgae were more sensitive than the mixed culture microalgae therefore, dilution rates did not increase as much as mixed culture. Also original media of the pure culture microalgae were BBM media which include less amount of nitrogen according to BG-11 media. In this study, microalgae is cultivated with the source seperated human urine. 5%, 10%, 20% and 40% dilution rates were studied with the microalgae cultivation in human urine. Best growth was observed in the 5% urine dilution rates and biomass reached to maximum 0,5 g/L. Also 5%, 10%, 20% and 40% dilution rates of human urine was studied with the Chlorella protothecoides, Gloeotilopsis planctonica and Pandorina morum species. Chlorella protothecoides, and Gloeotilopsis planctonica species were grown in 5% urine dilution rates however, Pandorina morum species did not grow as in this rate. According to these studies, it was seen that best growth was still with the 5% dilution rates. It can be said that microalgae were inhibited with the high amount of ammonia higher than the 5% dilutions. Mixed culture microalgae cultivation completed in 30 to 35 days for the %5 human urine dilution rate. On the other hand, growth just completed in a week for the Chlorella protothecoides, Gloeotilopsis planctonica and Pandorina morum species. When the two studies compared according to their growth rate and biomass amount the advantage of each cultures could be realized. Average 0,2 g/L biomass produced in the pure culture studies. When the pure culture and mixed culture microalgae studies were compared, mixed culture microalgae biomass was double in mixed culture. On the other hand, when the growth rate was compared, pure culture had 3 times higher growth rate. These two parameter was very significant for the biodiesel production and according to the results pure culture microalgae had better potential. Also microalgal biomass' lipid content was the fundamental parameter that showed to its biodiesel potential. Lipid content of mixed culture microalgal biomass was found as 23% and Chlorella protothecoides, Gloeotilopsis planctonica and Pandorina morum species had 35%, 32% and 26% lipid contents respectively. According to the lipid contents pure culture microalgae had higher lipid content but their biomass production is half of that of culture. In short, if the production rate and lipid content were evaluated, Chlorella protothecoides species would be the best option for biodiesel production. From the other side, if total biomass production was taken into account, mixed culture microalgae would be a better option. It was suggested that for the open system cultivation mixed culture microalgae was better option because of the contamination of the pure culture microalgae. If the photobioreactor system was operated, Chlorella protothecoides species would have higher potential for the biodiesel production according to high growth rate and high lipid content. Also it was suggested that the pH adjustment studies should be analyzed more deeply by reason of volatile form of NH3-N. Some researchers showed that, pH adjustment was also affecting the production of the biomass, therefore; pH adjustment and biomass production should be modified very well. This study showed that microalgae was a good alternative for the removal and energy production with the separated urine cultivation. For the further researches, it was expected that these study would support and would be basis to other researches.