Effect of Organic Loading Rates on Performance of Treating Dairy Wastewater in a Lab-Scale Sequencing Batch Reactor

Abstract

This study aims to investigate, the effect of organic loading rates (OLRs), nutrient ratio addition, and sludge retention time (SRT) on treating dairy wastewater in a sequencing batch reactor (SBR) system. This investigation is verified by experiments conducted in 3 phases at 3 different OLRs (1.8, 1.2, and 0.9 kg/m3d, respectively). Urea ((NH2)2CO) is added to make a suitable (COD:N:P) ratio of (100:5:1) in dairy wastewater. The SRT is adjusted from 50 days to an appropriate value of 18 days. The obtained results show that the COD, TN, and TP removal efficiencies are increased with decreasing OLRs. Sludge concentration in the SBR tank is stable at 1100 mg/L after adding (NH2)2CO. In addition, the SBR operated at a suitable SRT (i.e. 18 days) helps the biomass stably, resulting in enhancement of COD, TN, and TP removal. The results are helpful to the design of SBR for treating dairy wastewater.

Enhancement of SBR’s treatment under organic shock load

“…Pictures of the biofilm were taken during the start-up period with a depth vision camera with ƒ/1.4 aperture, in the beginning, the biofilm community was free-floating individual cells with no interconnection between each other, over time during start-up, microorganisms became attached and stick together until the emerging biofilm community develops a complex, three-dimensional structure compared to the original community as shown in figure 2. This phenomenon was observed in previous studies, and due to the adaptation of microorganisms within the SBR, there has been an observed increase in the quantity of activated sludge and it's color has transitioned from its initial dark brown to a lighter brown and yellow within the SBR system [17]. In addition, the research conducted by Calero et al [30] yielded similar results in terms of biofilm acclimatization.…”

“…Twelve different organic loading rates were applied to evaluate the performance of up-flow anaerobic sludge blanket to treat Cattle slaughterhouse wastewater and the results showed that COD removal efficiency drooped from 90 % to 50 % when OLR increased from 0.4 g/L d −1 to 15 g/L d −1 [13], the same results were obtained and the performance of SBR drooped under a high organic loading rate [14,15]. Furthermore, the performance of an anaerobic SBR was evaluated for organic loading rates of 3000, 6000, and 12000 mg COD/L.day, and at operational load rates of 6000 and 12000 mg COD/L per day, the efficiency of organic matter removal decreased as the fill time increased, this decline was more significant in the operation with an OLR of 12000 mg COD/L day [16] on the other hand, the research conducted by Khac-Uan et al [17] not yielded similar results in terms of COD removals where the OLR was reduced from 1.8 to 0.9 kg/m 3 d, the results showed a decrease in the quantity of activated sludge, consequently, the treatment efficiency for COD also declined.…”