Microalgae at wastewater treatment in cold climate

Abstract: The thesis concludes that microalgae may improve wastewater treatment in ponds in cold climate, from a treatment perspective as well as a sustainability perspective. A literature review revealed that the microalgae biomass produced may find economic use, depending on what species will come to dominate, since there are many possible products from microalgae biomass. Laboratory experiments showed that microalgae collected in the Mid Sweden region can grow readily in wastewater from the same region also under cold climatic conditions. During spring and autumn conditions - between 5-10 Centigrades - the doubling times of the fastest growing cultures in the experiments were below 2 days. A microalgal treatment plant model were considered having a better position for sustainable development, than a conventional three-step wastewater treatment plant and a mechanical-chemical plant complemented with a constructed wetland, when sustainability was evaluated with a socio- ecological method (Holmberg et al. 1996), and emergy evaluation (Odum 1996).