## 3 Results
### The Performance of the Debgr  
The product of the pre-treatment system was continuously fed to the DEGBR with the intention of further reducing the concentration of the contaminants present in the PSW. The fluctuation of the concentration of the COD, TSS and FOG during the experiments for both the inlet and the outlet of the DEGBR, including their corresponding removal efficiencies, are provided in Figure 8. Following the same methodology as the data processed for the pre-treatment system, the evaluation of the presence of outliers was undertaken. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Inlet Feed (mg/L)** & **Product (mg/L)** & **Efficiency (\(\boldsymbol{\boldsymbol{\eta}}\)) (\%)** \\ \hline COD & 9946 & 5896 & 39 \\ TSS & 5399 & 2392 & 56 \\ FOG & 1765 & 269 & 80 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Raw and pre-treated poultry slaughterhouse wastewater (PSW) characteristics average range. From Figure 9a, it can be observed that the distribution of the inlet COD and TSS had an outlier each. These outliers were replaced with the median value of each affected distribution, as depicted in Figure 9b. From the latter, it can be observed that the data processing step addressed the challenges associated with the presence of outliers in the listed distribution and led to a further analysis of the performance of the DEGBR, as illustrated in Figure 10 indicating how the fluctuations varied for the concentration of TSS, FOG and COD at the inlet and outlet of the DEGBR, including their corresponding removal efficiencies. Figure 8: Performance of the DEGBR before outliers replacement. Figure 7: Photographs of the raw PSW in comparison to pre-treated PSW. Overall, the average removal efficiencies were 89 \(\pm\) 2.8% for the FOG, 87 \(\pm\) 9.5% for the COD and 94 \(\pm\) 3.7% for the TSS. The concentration of these contaminants was below the required discharge standards prescribed by City of Cape Town by-laws (2013) [17] and supported the recourse undertaken suggested an efficient process system for the treatment of PSW or a wastewater having similar characteristics. The DEGBR designed for this study performed well in comparison to the EGSB used in another study, whereby it was indicated that the performance was attributed to a rapid start-up of the EGSB, in which brewery wastewater sludge was used in the treatment of slaughterhouse wastewater. It was determined that the sludge could develop faster within a period of 10 days in the EGSB reactor, with few detached sludge granules, achieving removal efficiencies of up to 72.9% of COD at an operational hydraulic retention time (HRT) of 12.1 h [22]. It was also observed that the performance of the DEGBR was high even at the beginning of the process, whereby the sludge micro-organisms were still acclimatizing to the new type of wastewater they were processing (i.e., PSW). This was due to the low organic loading rate used for the system throughout the experiment, which was sustained by the pre-treatment step used prior to the supply of the wastewater to the DEGBR system that  
Figure 10: Performance of DEGBR after outliers replacement. Figure 9: Boxplots of the investigated parameters associated with DEGBR performance. significantly reduced the organic load. The management of this organic load to the DEGBR with respect to the FOG, COD, and TSS is illustrated in Figures 11-13, respectively. From these figures, it can be observed that the removal efficiencies of the DEGBR remained high throughout the experiment despite various fluctuations of the organic loading rate (OLR). This demonstrates the suitability of the DEGBR for the treatment of such wastewater and highlights the importance of a good pre-treatment step prior to feeding the wastewater to the anaerobic reactor.