Microalgae at wastewater pond treatment in cold climate : an ecological engineering approach

• Main Author: Grönlund, Erik
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Luleå tekniska universitet 2004
• Subjects: Water Engineering; Vattenteknik; Subarctic
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16822

Three types of wastewater ponds in subarctic climates were investigated, each of them highly dependent on microalgae. They were fellingsdams, i.e. wastewater stabilization ponds complemented with chemical precipitation, high-rate algal ponds (HRAPs), and a type of aquaculture interface ponds between a wastewater treatment plant and the natural surrounding. From a microalgae taxa perspective green algae and cryptophytes were dominant in the wastewater ponds. Green algae and cryptophytes were also, together with chryso- and haptophytes, dominating the hypereutrophic and eutrophic stages of the natural lakes. Biomasses in the different types of ponds were of very different order of magnitude. From 100-1000 mg/l in the stabilization ponds during summer and 10-100 mg/l in spring and autumn, 70- 90 mg/l in a HRAP in autumn, to 5-30 mg/l in the most hypereutrophic stage in the natural ponds, 1-10 mg/l in the eutrophic stage, and below 1 mg/l in the oligotrophic stage. The connection between wastewater pond treatment and the field of ecological engineering was recognized. Future development of pond technology may benefit from a stronger connection to the theoretical framework of systems ecology developed in collaboration with the field of ecological engineering and ecotechnology. Godkänd; 2004; 20061005 (ysko)