Biomass production and nutrient removal by Chlorella sp. as affected by sludge liquor concentration

• Published in: Journal of environmental management 2014-11, Vol.144, p.118-124
• Main Authors: Åkerström, Anette M., Mortensen, Leiv M., Rusten, Bjørn, Gislerød, Hans Ragnar
• Format: Article
• Language: English
• Subjects: Algae; Anaerobiosis; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Biomass; Chlorella - growth & development; Conservation, protection and management of environment and wildlife; Fundamental and applied biological sciences. Psychology; General aspects; Microalgae; Microalgae - growth & development; Nitrogen; Nitrogen - metabolism; Nutrient removal; Phosphorus; Sewage - analysis; Sludge; Sludge liquor; Waste Disposal, Fluid; Water Pollutants, Chemical - metabolism
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2014.05.015

The use of microalgae for biomass production and nutrient removal from the reject water produced in the dewatering process of anaerobically digested sludge, sludge liquor, was investigated. The sludge liquor was characterized by a high content of total suspended solids (1590 mg L−1), a high nitrogen concentration (1210 mg L−1), and a low phosphorus concentration (28 mg L−1). Chlorella sp. was grown in sludge liquor diluted with wastewater treatment plant effluent water to different concentrations (12, 25, 40, 50, 70, and 100%) using batch mode. The environmental conditions were 25 °C, a continuous lightning of 115 μmol m−2 s−1, and a CO2 concentration of 3.0%. The highest biomass production (0.42–0.45 g dry weight L−1 Day−1) was achieved at 40–50% sludge liquor, which was comparable to the production of the control culture grown with an artificial fertilizer. The biomass production was 0.12 and 0.26 g dry weight L−1 Day−1 at 12% and 100% sludge liquor, respectively. The percentage of nitrogen in the algal biomass increased from 3.6% in 12% sludge liquor and reached a saturation of ∼10% in concentrations with 50% sludge liquor and higher. The phosphorus content in the biomass increased linearly from 0.2 to 1.5% with increasing sludge liquor concentrations. The highest nitrogen removal rates by algal biosynthesis were 33.6–42.6 mg TN L−1 Day−1 at 40–70% sludge liquor, while the highest phosphorus removal rates were 3.1–4.1 mg TP L−1 Day−1 at 50–100% sludge liquor. •Chlorella sp. was grown in reject water from anaerobically digested sludge.•Light transmission was increased by diluting with effluent water.•Cellular nutrient content was dependent on concentration of sludge liquor.•Highest biomass production of was achieved at 40–50% sludge liquor.•At 40–70% sludge liquor the highest nitrogen removal rate was achieved.