Nitrogen removal in MBBR : Investigating the effect of temperature

Sammanfattning

The project undertaken in this thesis was performed at MittSverige Vatten och Avfall (MSVA) in cooperation with the Swedish Environmental Research Institute (IVL). The effect of temperature on nitrogen removal using moving bed biofilm reactor (MBBR) was controlled using two separate lines by investigating the influence of temperature on nitrification, pre-denitrification, and post- denitrification in a pilot plant scale. By monitoring the process using chemical analysis, batch tests and online systems, it was possible to observe the changes occurring in the different reactors along with different parameter set-ups and react to the undesirable changes in the system. Due to some limitations, the master's thesis couldn’t fully answer the objective of the study. Nonetheless, the processes were investigated and evaluated to better understand the possibilities and limitations of nitrogen removal with MBBR with treating cold wastewater. During the study period, the inflow coming to the pilot plant, recirculation flow, external carbon dosing, set points of dissolved oxygen and temperature values were controlled. By manipulating these different parameters, it was possible to observe their impacts on the processes. The inflow was variable between 0.42 and 0.67 m3/h, recirculation flow was set to 1.2 m3/h at the beginning then changed to function same as the inflow after being reduced to 0.84 m3/h in between. DO level was variable throughout the entire study period with an average concentration of 4.2mg/l in line 1 and 4.43 mg/l in line2 in all the aerated zones for each line. Temperature of incoming water varied between 5.94 and 9.3 oC with an average temperature of 7.73 oC while the average temperature of the water in the system in line 1 was 13.3 oC and 12.62 oC in line 2. During the 5 months study period, the system achieved an average total nitrogen removal efficiency of 46% in line 1 and 60% in line 2.