## Materials and Methods
### Filtration Experiment  
The six different membranes cannot operate at the same pressure. For example, at low pressures, the smaller pore sized membranes like 0.083 kDa and 0.058 kDa pore sized membranes, will not flux. In this case, the osmotic pressure would be higher than the driving force. And in the other end, if higher pressures were used, bigger pore sized membranes, like the micro filters, would not be able to handle this high pressure, and would therefore crush. A membrane housing with six slots was used for this study, as seen in Figure 2. Filters of each type were filled in these slots one at a time. For each two sets of filters, same feed was used (ran in parallel). Figures 3 and 4 show the membrane filtration experiment and post-DAF membrane filtration experiment respectively. During the membrane filtration experiment, the feed from the equilibrium tank went into a 189 L tank, which was then pumped through the membranes in the membrane module. A variable frequency controlled piston pump was used to pump the feed from the tank. The pressure side of the pump had a baffler, temperature and pressure sensors, and a pressure relief valve. The baffler was used to reduce any pulsations caused by the positive displacement pump. The various operating pressures chosen for each set of membranes are listed in Table 3. The permeate comes out of the circumference of the membranes and was collected and sent down to the municipality.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Membrane Type** & **Cleaning chemistry** & **Acid** & **Temperature (\({}^{\circ}\)C)** \\ \hline AFC99 & 0.25\% sodium hydroxide & 0.3\% nitric acid & 50 \\ AFC30 & 0.5\% enzyme & 0.3\% nitric acid & 45 \\ Others & 1\% chlorinated alkaline detergent & 0.3\% nitric acid & 50 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Membrane cleaning characteristics [20].  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Membrane** & **Retention** & **Membrane** & **pH Range** & **Maximum** & **Maximum** \\
**Cmmercial Name** & **Characteristic (kDa)** & **Material** & **pH Range** & **Pressure (bar)** & **Temperature (\({}^{\circ}\)C)** \\ \hline FP200 & 200 & PVDF * & 1.5–12 & 10 & 80 \\ FPA03 & 20 & PVDF * & 1.5–10.5 & 7 & 60 \\ PU608 & 8 & Polysulphone & 1.5–12 & 30 & 80 \\ ES404 & 4 & Polyethylsulphone & 1.5–12 & 30 & 80 \\ AFC30 & 0.083 & Polyamide film & 1.5–9.5 & 60 & 60 \\ AFC99 ** & 0.058 & Polyamide film & 1.5–12 & 64 & 80 \\ \hline \hline \end{tabular}  
* Polyvinylidene fluoride, ** Reverse osmosis.  
\end{table}
Table 1: Membrane characteristics [20].  
The reentate was sent back into the feed tank to concentrate it in order to get more recovery. Once the feed was too concentrated, it would be drained to the municipality during down time of the factory. An automated back-pressure valve was used to achieve very high pressures through feedback control. For all three experiments of membrane filtration experiment, the pump was run at a volumetric flow rate of 1135.62 L/h.  
During the post-DAF membrane filtration experiment, as seen in Figure 4, the feed from the equilibrium tank was added with coagulants and flocculants with pH correction, and then pumped into the bottom of the DAF together with air bubbles. The sludge was skimmed off from the top and the clear effluent was then sent into a tank to be fed to the membrane filtration unit. A piston pump was used to flow this treated water through the membranes and the permeate was sent to the municipality. The reentate was sent back to the start of treatment, just before the addition of coagulants. This was basically two treatments--DAF and membrane filtration in series.