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RMW - May 2017

SCIENCE, RESEARCH & TECHNOLOGY Several types of wastewater are appli-cable for algae treatment including municipal wastewater, produced water from oil and gas extraction, and dairy and swine farm wastewater. During treatment, nitrates and phosphates are combined with water and carbon diox-ide to grow the algae. Microalgae often is represented by the chemical formula C106H263O110N16P1. It is important to note the phosphorus-to-nitrogen ratio of 1:16 when evaluating the design, as well as looking to add carbon dioxide to bal-ance the carbon:nitrogen:phosphorus ratio and achieve completed nutrient assimilation, according to Ron Sims, who gave the presentation Microalgae-based Approaches to Algae-based Tertiary Waste-water Treatment at the forum. Most of our existing laws and regula-tions that deal with wastewater were designed with conventional treatment systems in mind. How does algae fit into the regulatory environment? Defi-nitions for Class A and Class B biosolids are contained in 40 CFR Part 503. Algae from municipal wastewater (as part of the treatment system) are subject to Part 503. Algae solids from municipal treatment could meet class A or Class A/EQ in a number of ways. Metals are unlikely to be problematic and consis-tent low metals and pathogens may provide basis for reduced monitoring, said Robert Bastian in his presentation, Algae Biotechnology for Wastewater Treat-ment: Regulatory Issues, at the forum. Figure 2. Raceway algae high rate pond. CREDIT: LUNDQUIST ET AL, 2016. Bioproducts and bioenergy A number of bioproducts can be pro-duced 34 | ROCKY MOUNTAIN WATER MAY 2017 from algae biomass. Fertilizers from algae solids generally have about 8 to 10 percent nitrogen content and 1 to 2 percent phosphorus content, Bastian said. The biomass also can be used as feed for aquaculture and agri-culture. Products from phycocyanin include pigments and antioxidants, Sims added. The first techno-economic analysis for algae biofuels integrated with wastewa-ter treatment was performed in 1960, according to Algae Biotechnology for Wastewater Treatment: An Introduction, presented by John Benneman. Using anaerobic digestion, the biomass can produce biogas, especially when mixed with food wastes and municipal waste-water biosolids to generate more meth-ane for combined heat and power. Addi-tional processing, such as hydrothermal liquefaction (pressure cooking) can convert algae to biocrude oil. Other pro-cesses can produce biodiesel, bioplastics, acetone, butanol, and ethanol, Sims said. When evaluating any energy resource recovery opportunity, it is important to calculate the energy return on invest-ment (EROI): Does the system provide more usable energy than it consumes? According to recent work in Europe, algae biofuels have an EROI of 1.9, substantially higher than corn ethanol’s and biodiesel’s value of 1.3. In addition,


RMW - May 2017
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