Step-wise temperature decreasing cultivates a biofilm with high nitrogen removal rates at 9°C in short-term anammox biofilm tests

• Published in: Environmental technology 2016-08, Vol.37 (15), p.1933-1946
• Main Authors: Zekker, Ivar, Rikmann, Ergo, Mandel, Anni, Kroon, Kristel, Seiman, Andrus, Mihkelson, Jana, Tenno, Taavo, Tenno, Toomas
• Format: Article
• Language: English
• Subjects: Ammonium Compounds - chemistry; Ammonium Compounds - metabolism; Biofilms; Bioreactors; free ammonia; inorganic carbon; low temperature; nitrite inhibition; Nitrogen - analysis; Nitrogen - isolation & purification; Nitrogen - metabolism; redox potential; Reject water; substrate limitation; Temperature; Waste Water - chemistry; Water Purification
• ISSN: 0959-3330; 1479-487X
• DOI: 10.1080/09593330.2015.1135995

The anaerobic ammonium oxidation (anammox) and nitritation-anammox (deammonification) processes are widely used for N-rich wastewater treatment. When deammonification applications move towards low temperature applications (mainstream wastewater has low temperature), temperature effect has to be studied. In current research, in a deammonification moving bed biofilm reactor a maximum total nitrogen removal rate (TNRR) of 1.5 g N m −2  d −1 (0.6 kg N m −3  d −1 ) was achieved. Temperature was gradually lowered by 0.5°C per week, and a similar TNRR was sustained at 15°C during biofilm cultivation. Statistical analysis confirmed that a temperature decrease from 20°C down to 15° did not cause instabilities. Instead, TNRR rose and treatment efficiency remained stable at lower temperatures as well. Quantitative polymerase chain reaction analyses showed an increase in Candidatus Brocadia quantities from 5 × 10 3 to 1 × 10 7 anammox gene copies g −1 total suspended solids (TSS) despite temperature lowered to 15°C. Fluctuations in TNRR were rather related to changes in influent concentration. To study the short-term effect of temperature on the TNRR, a series of batch-scale experiments were performed which showed sufficient TNRRs even at 9-15°C (1.24-3.43 mg N g −1  TSS h −1 , respectively) with anammox temperature constants (Q 10 ) ranging 1.3-1.6. Experiments showed that a biofilm adapted to 15°C can perform N-removal most sufficiently at temperatures down to 9°C as compared with biofilm adapted to higher temperature. After biomass was adapted to 15°C, the decrease in TNRR in batch tests at 9°C was lower (15-20%) than that for biomass adapted to 17-18°C.