COD And NH4-G Lab Report

The removal of sCOD and NH4-N reached 71% and 28%, respectively, after the first hour of aeration. This indicates that COD was degraded the fastest in the first hour of aeration after the anoxic phase. The high removal of COD was due to the fact that COD concentration decreased during the first two hours of the anoxic phase because the heterotrophic bacteria used COD as a source of organics for denitrification. In the next 2 hours of aeration, ammonium was oxidized faster than COD and reached 89%. This was a result of the increase in DO concentration that exceeded 6 mg/L. The increase in DO made the oxidation of NH4-N unlimited. The first-order kinetic constants were 0.34 h-1 and 0.24 h-1 (Table 6), with correlation coefficients of 0.94 and
This higher NH4-N removal efficiency could result from the SBR operational conditions. During the aeration phase of the SBR cycle, the temperature and DO values were almost 18ºC and 6-8 mg/L, respectively, for a longer time (Figure 4); pH and sludge age were around 7.5-8.5 and 42 d. These conditions are favorable for the growth of nitrifying bacteria. Because nitrification needs a long aeration period and long sludge age, optimum pH is in the range of 8-9 and DO should be > 4.2 mg/L [33]. Rodrigues et al. [26] operated the SBR for the post-treatment of the brewery wastewater under the anoxic-aeration-anoxic strategy with DO concentration of 2.8 mg/L. Nearly the same results were reported. The first-order kinetics constant k and a specific oxidation rate for NH4-N were 0.42 h-1 and 0.044-0.057 kg/(kg MLVSS∙d), respectively, with the correlation coefficient of 0.89. According to Lateef et al. [8], during dairy wastewater treatment by biological activated sludge system it was found out that the k value was 4.46 d-1, based on sBOD. The authors also noted that the maximum substrate utilization rate value for domestic wastewater and k value for cheese processing is 5 g sCOD/(g VSS∙h) and 9.3 d-1, respectively, showing that k value was lower for dairy wastewater due to the difference in wastewater composition. Therefore, in the present study, k value (0.34 h-1 or 8.16 d-1) neatly fit with that obtained in the cited study. The value of k is an important parameter for wastewater treatment plant as it explains how fast the conversion or removal of contaminants takes place. Furthermore, this value also affects the volume of the reactor. At higher k values, necessary volume of the bioreactors is smaller, which makes the process more economically-efficient. In the present study, the operation strategy had high dissolved oxygen and long aeration period. Aeration