## 3 Results
### Overall Performance of the DEGBR  
Figure 17 provides an overall performance of the complete system, for the removal of the COD, TSS, and FOG during the experiment, despite a slow start for the removal of COD during the first three weeks. However, the average removal efficiency was 97 \(\pm\) 0.8% for the FOG and, subsequently, improved to 92 \(\pm\) 6.3% for the COD and 97 \(\pm\) 1.2% for the TSS. The robustness of the entire system is demonstrated by the low standard deviation of the TSS and FOG removal efficiencies, as also illustrated in Figure 17. This also demonstrates that such an arrangement can provide similar overall results for the treatment of PSW. Table 2 below illustrates the overall performance of the biological pre-treatment of PSW coupled with the DEGBR. For overall removal efficiency results of the system, the average feed of the pre-treatment and the DEGBR product was used for the calculations. When comparing the overall performance in terms of COD removal, of the UASB and the DEGBR, the results indicated a better performance for the DEGBR in comparison with another similar study in which the treatment of PSW was undertaken, albeit the used  
Figure 16: Biogas production during the operation of the DEGBR. Figure 17: Overall performance of the complete system. UASB was operated for 1228 days, yielding a removal efficiency of up to 85% for COD [14]. Additionally, the overall biological pre-treatment of PSW coupled with DEGBR of this study, performed better when compared to another similar study which ran concurrently with this study under similar conditions using a similar pre-treatment strategy for the PSW (i.e., using Eco-flushTM in the pre-treatment unit). Although, in the other study, an EGSB was used whereby it was reported that low FOG, COD and TSS removal efficiencies of about 80%, 60% and 80% were achieved [24]. An in-Depth Analysis of Pre-Treatment Unit-DEGBR Performance Parameters  
Most PSW treatment technologies normally comprise of the dissolved air floatation (DAF) system coupled with the up-flow anaerobic sludge blanket (UASB) as a primary treatment for PSW [31]. However, in most cases the latter type of anaerobic reactor usually fails to meet discharge standards because of the effluent produced from the UASB that contains high content of ammonia nitrogen and a significant amount of residual COD [32]. Another study of PSW treatment plant for high strength effluent, the DAF pre-treatment system reported FOG and COD removal efficiency of 28.0 \(\pm\) 5.6% and 38.7 \(\pm\) 8.0%, respectively [31]. The second step of biological treatment using the UASB yielded FOG and COD removal efficiencies of about 34.3 \(\pm\) 12.5% and 69.1 \(\pm\) 6.9%, due to the insoluble nature of lipids in the PSW, with some being purported to absorbed onto sludge granules. Since, in this study, the COD removal efficiency was a crucial parameter that was used to evaluate alternative technologies either as single units or in combination, determination of the average COD removal efficiency needed to be much higher (92 \(\pm\) 6.3%) than that reported elsewhere. As such, this study proves that the designed lab-scale plant had a significant effect of reducing COD. This could be attributed by a variety of factors ranging from the use of the EcoflushTM in the pre-treatment stage, the use of sieves/screens which eliminated larger particles in the pre-treatment units, as well as the use of a DEGBR reactor which further promoted biodegradation of organic matter, thus reducing pollutants in the wastewater. A performance attribute of 92 \(\pm\) 6.3% COD removal for this study was slightly higher in comparison with other similar studies whereby the reported COD was 85% [14], refer to Figure 17 and Table 2. Furthermore, it was observed that neither an increase in ORL nor a decrease in HRT had an adverse effect on the process [7]. The TSS removal efficiency was another parameter used in this study to measure the performance of the system used.