Generalized temperature dependence model for anammox process kinetics.

Temperature is a key operational factor influencing the anammox process kinetics. In particular, at temperatures below 15 °C, the specific anammox activity (SAA) considerably decreases. This study aimed to describe the temperature dependence of the anammox process kinetics in the temperature range from 10 to 55 °C, including the specific characteristics of "cold anammox". The commonly used Arrhenius and extended and modified Ratkowsky equations were examined. The Ratkowsky equations yielded a strong correlation (coefficient of determination, R2 = 0.93-0.96) between the measured and predicted data over the analyzed temperature range (10-55 °C). However, these equations could not correctly reflect the anammox temperature dependence at temperatures below 15 °C (R2 = 0.36-0.48). Therefore, a new generalized temperature model was proposed. The generalized temperature equation (GTE) considered the division of the analyzed temperature range into three temperature ranges: 10-15 °C, 15-35 °C and 35-55 °C. The ranges correspond to "cold anammox", "(low) mesophilic anammox" and "thermophilic anammox". The applied approach yielded a strong correlation between the measured and predicted SAA (R2 = 0.97) over the temperature range from 10 to 55 °C and over the low-temperature range from 10 to 15 °C (R2 = 0.99). Overall, the GTE could enhance the predictions of the temperature dependence of the anammox process kinetics. The GTE can help examine anammox-based bioaugmentation systems operating at both high temperatures (sidestream reactors) and low temperatures (mainstream reactors).

Influence of temperature on the activity of anammox granular biomass.

The aim of this study was to determine a short-term and long-term effect of temperature on the anammox rate and determination of temperature coefficients in the Arrhenius and Ratkowsky equations. The short-term effects of temperature on the anammox granular biomass were investigated in batch tests at ten different temperatures in the range of 10-55 °C. The maximum overall nitrogen removal rate of 1.3 gN gVSS(-1)·d(-1) was observed at 40 °C (VSS: volatile suspended solids). The minimum rate, close to 0 gN gVSS(-1)·d(-1), was observed for the limits of the analyzed temperature range (10 and 55 °C). The activity tests carried out at 55 °C showed an irreversible loss of the activity due to the observed biomass lysis. Subsequently to the batch tests, a sequencing batch reactor (SBR) was operated at different temperatures (from 30 to 11 °C) to determine the long-term effects of temperature. The system was successfully operated at 15 °C, but when temperature was decreased to 11 °C, nitrite started to accumulate and the system lost its stability. The temperature coefficient (θ) was 1.07 for the batch tests carried out in the temperature range of 10-40 °C. In contrast, during the long-term SBR operation, substantially different θ had to be estimated for two temperature ranges, 1.07 (T = 15-30 °C) and 1.65 (T = 11-15 °C).

The effects of different aeration modes on ammonia removal from sludge digester liquors in the nitritation-anammox process.

The aim of this study was to determine the impact of continuous and intermittent aeration on the rate of ammonia removal in the combined nitritation-anammox process. This process was run in two parallel sequencing batch reactors (SBRs), with a working volume V = 10 L, treating sludge digester liquors from the Gdansk (Poland) wastewater treatment plant (WWTP). The ammonia oxidizing bacteria were cultivated from activated sludge from the same plant, whereas the anammox bacteria originated from the Zurich WWTP (Switzerland). Both SBRs were operated with 12-h cycles, temperature 30 °C and hydraulic residence time between 1 and 7 days depending on the operating period. The maximum specific ammonium utilization rate (sAUR) was observed in the reactor with intermittent aeration, and varied in the range of 4.4-4.7 g N kg VSS⁻¹ h⁻¹. The sAUR in the reactor with continuous aeration was slightly lower and ranged from 4.39 to 4.41 g N kg VSS⁻¹ h⁻¹. In the case of intermittent aeration, the additional measurement was performed at two different dissolved oxygen concentrations, i.e., 1 and 0.8 mg O2L⁻¹, and the observed nitrogen removal rates were 4.7 and 2.7 g N kg VSS⁻¹ h⁻¹, respectively.