## 3 Results
### Overall Performance of the DEGBR
In another study of the biological treatment of an actual slaughterhouse wastewater (SWW) treated in an anaerobic baffled reactor (ABR), followed by an aerobic activated sludge (AS) reactor in continuous mode at laboratory scale, it was indicated that a gradual growth in the biomass led to a more stabilized TSS removal [33], as the anaerobic bed acted as a biofilter. Moreover, it was also established that an optimum minimum TSS residual is achieved when both the influent total organic carbon (TOC) concentration and feed flow rate are minimum. For this study, having an average TSS removal efficiency of the entire process being 97 \(\pm\) 1.2%, at an operational HRT of 106 h over 18 weeks (126 days), was commendable. This means that the longer the operational time and the lower the volumetric flow rates, the better the TSS removal efficiencies due to an improved biomass growth resulted in an acclimation process which was adequate. Moreover, increased organic loading rates (OLRs) and constant high hydraulic retention times (HRTs) resulted in a well-developed granular sludge bed in the DEGBR, which also led to enhanced TSS removal efficiencies. The high TSS removal efficiency was further attributed to the used inoculum from a brewery-activated sludge system, which had fully \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Inlet Feed (mg/L)** & **DEGBR Product (mg/L)** & **Efficiency (\(\eta\)) (\%)** \\ \hline COD & 5896 & 669 & 92 \(\pm\) 6.3 \\ \hline TSS & 5399 & 185 & 97 \(\pm\) 1.2 \\ \hline FOG & 1765 & 28 & 97 \(\pm\) 0.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Overall performance of the biological pre-treatment coupled with DEGBR. acclimatized and resulted in a well-developed biomass that promoted the filtering of TSS present in the PSW [34]. Further results obtained from this study showed that, by using the EooflushTM, solubilization of some FOG components resulted in the decoupling of TSSs, which resulted in the further filtering efficiency of the PSW in the pre-treatment stage, subsequently yielding better performance in FOG removal in the DEGBR. Comparatively, another study used for long-term PSW treatment, whereby the DAF contributed to the reduction of FOG, COD and TSS prior to the application of an UASB [19], only FOG, COD and TSS removal efficiencies of 63%, 67%, and 61%, respectively, were achieved. In another study, PSW treatment using a pilot SGBR reactor, with organic loading rates between 0.63 to 9.72 kg/m\({}^{3}\)/d and a hydraulic retention time (HRT) of 9 to 48 h, only reported removal efficiencies of COD above 90% and a TSS above 80%, respectively [35], results which were comparatively similar to the ones reported herein using a DEGBR. Therefore, by using EooflushTM as a solubilization agent, it was indicated that the microorganisms present in it aided in the biological hydrolysis of some pollutants present in the PSW. Since the raw PSW was first aerated to invigorate the microorganisms in the EooflushTM, the proliferation of bacteria in the agent resulted, which contributed to the initial degradation of organic material and pollutants. Overall, the microbes partially consumed the organic contaminants and further bound less soluble matter found in the raw PSW, which also reduced the odor of the wastewater. Since the DEGBR ran at a stable VFA/Alkalinity ratio of 0.2, which is below 0.3, it means that there was adequate organic matter digestion in the reactor [7]. It has been established that an acidic digester or reactor is one which is above a 0.8 VFA/Alkalinity ratio; therefore, the consequence of an acidic reactor is that there could be a microbial inhibition of methane gas production [30]. However, it was found that the methanogenetic activity in the DEGBR decreased only after the addition of EooflushTM in the biological pre-treatment stage (i.e., as a preceding step before the DEGBR process), whereby methanogenesis was expected to ensue.