## 3 Results  
### MBR Performance Efficiency during acclimatization  
The overall biomass concentration was estimated based on the mixed liquor volatile suspended solids (MLVSS) fraction, a safe indicator of the active biomass in wastewater treatment plants [5]. The initial MLVSS and MLFSS concentration of the MBR was approx. 6.0 g/L and 5.0 g/L, respectively. The temporal evolution of the MLVSS and MLFSS concentration during the operating period is shown in Figure 2. MLVSS varied between 5.2 g/L and 12.0 g/L when no excess sludge was removed (until the 42 nd day); subsequently the MLVSS concentration stabilized at approx. 8.0 g/L. MLFSS exhibited a more stable course as their concentration, quickly stabilized at 2.0-3.0 g/L (Figure 2). The increase of the MLVSS denotes that the bio-community shortly after the start-up started to biodegradable the wastewater organic compounds and multiply, producing new biomass. The pH values of the feed and the mixed liquor remained around neutral values (Figure 2). Interestingly, the mixed liquor, after a short drop of its pH value (around Day10) shifted towards mild alkaline conditions between 8.0 and 8.8, exhibiting a very stable and self-controlled behavior. Mixed liquor pH mean value after day 10 was 8.5, with a standard deviation of 0.22. \begin{table}
\begin{tabular}{c c} \hline
**Component** & **Concentration (g/L)** \\ \hline Crude Sugar & 75.0 \\ Peptone & 8.00 \\ Meat Extract & 5.50 \\ Urea & 1.50 \\ NaHCO\({}_{3}\) & 10.5 \\ K\({}_{2}\)HPO\({}_{4}\) & 1.40 \\ NaCl & 0.35 \\ CaCl\({}_{2}\):2H\({}_{2}\)O & 0.20 \\ Mg\({}_{2}\)SO\({}_{4}\):7H\({}_{2}\)O & 0.10 \\ \hline \end{tabular}
\end{table} 
Table 1: Composition of the CSW used in this study. The TOC concentration of the feed and permeate are shown in Figure 3. Upon inspection, it is obvious that the physicochemical characteristics of the TOPW are not stable; in fact, there are significant fluctuations regarding organic matter (Figure 3) and polyphenolic compounds concentrations (Figure 3). The TOC concentration of the feed fluctuates widely in a range between 500 to 9000 mg/L with a mean value of 3386 mg/L and a high standard deviation of 1897 mg/L, as expected from real wastewater samples. In contrast, the permeate TOC concentration is comparatively more stable. Lower TOC permeate concentration and high fluctuations are observed during the first 20 days of the acclimatization period (49.9 \(\pm\) 35.1 mg/L), when CSW was initially used as a feed to the MBR (Days 0-8), whereas a somehow higher, but less variable, TOC concentration is observed between Days 21 and 100 (144.7 \(\pm\) 38.2 mg/L). Polyphenolic compounds concentration (Figure 3), follows a similar pattern; TPh concentration in the MBR feed varies considerably between 120 and 901 mg/L, while TPh concentration in the MBR permeate has a mean value of 39.7 \(\pm\) 9.6 mg/L. No polyphenolic compounds are measured during the first seven days when no TOPW was used as feed. Adsorption and bioaccumulation of the polyphenolic compounds in the suspended bio-flocs, as well as biodegradation by specific microorganisms are two possible mechanisms of polyphenolic compounds removal. To quantitatively assess the MBR performance in TOC and TPh removal efficiency, the probability plot of the removal ratios of the TOC and TPh during the MBR operation is presented (Figure 4). The TOC removal ratio was greater than 0.85 in all the examined samples, 90% of the TOC removal ratios were over 0.90, and half of the calculated TOC ratios were greater than 0.96. TPh removal ratios were also quite high, though a little lower than those of TOC. The lowest TPh removal ratio was approx. 0.80, whereas 90% of TPh removal ratios were higher than 0.85, and half of TPh removal ratios were over 0.90. Therefore, it is evident that the MBR system exhibited excellent removal performance regarding TOC and polyphenolic compounds. Figure 2: Temporal variation of mixed liquor characteristics.