# A Low-Temperature and Low-Pressure Distillation Plant for Dairy Wastewater
## 3 Results and Discussion
### Distillate (Evaporate)  
As discussed above, the effectiveness of the process is analyzed by considering the removal in the distillation fraction of a certain pollutant substance at the end of the purification treatment. The experimental results for the distillate fraction explain the ability of the LTPD process to purify the whey wastewater. Table 7 reports the final distillate characteristics. As the maximum limit for effluent discharge for industrial wastewater is 5.5-9.5 for pH, 50 mg/L for TN, 500 mg/L for COD and 250 mg/L for BOD5, from Table 7 it is evident that the obtained distillate is not suitable to be directly discharged as effluent. This is due to the small volume of treated whey (20 L). However, by increasing the amount of treated \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Slope (RC)** & **Intercept** & **R2** \\ \hline pH & 0.00 (\(-\)0.01,0.01) & 0.94 & 0.03 \\ Conductivity & 0.85 (0.75,0.95) & 0.97 & 0.97 \\ BOD5 & 0.72 (0.37,1.06) & 1.66 & 0.68 \\ COD & 0.72 (0.39,1.04) & 1.86 & 0.70 \\ TN & 0.76 (0.51,1.01) & 1.68 & 0.82 \\ TP & 0.30 (0.13,0.46) & 3.16 & 0.62 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Linear model of pH, conductivity, BOD5, COD, TN and TP vs. SC%. The slope represents the retaining capability (RC) regarding the specific pollutant referred to SC. In round brackets the 95% confidence bounds for the slope are reported. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Coding** & \
\begin{tabular}{c} **Temperature** \\ (°C)** \\ \end{tabular} & **pH** &
\begin{tabular}{c} **Conductivity** \\ **(uS/cm)** \\ \end{tabular} & **BOD5** & **COD** & **TN** \\ \hline P1 & & 5.9 \(\pm\) 0.3 & 180 \(\pm\) 17 & 598 \(\pm\) 133 & 975 \(\pm\) 232 & 31.6 \(\pm\) 1.6 \\ P2 & 60 & 6.5 \(\pm\) 0.5 & 171 \(\pm\) 23 & 280 \(\pm\) 84 & 728 \(\pm\) 217 & 30.3 \(\pm\) 5.5 \\ P3 & & 6.1 \(\pm\) 0.5 & 236 \(\pm\) 40 & 323 \(\pm\) 77 & 682 \(\pm\) 156 & 28.4 \(\pm\) 4.3 \\ \hline P4 & & 6.6 \(\pm\) 0.4 & 324 \(\pm\) 42 & 543 \(\pm\) 112 & 816 \(\pm\) 168 & 19.9 \(\pm\) 3.3 \\ P5 & 53 & 5.5 \(\pm\) 0.7 & 284 \(\pm\) 52 & 308 \(\pm\) 98 & 767 \(\pm\) 213 & 25.3 \(\pm\) 3.6 \\ P6 & & 6.3 \(\pm\) 0.4 & 331 \(\pm\) 61 & 355 \(\pm\) 70 & 634 \(\pm\) 131 & 26.0 \(\pm\) 3.6 \\ \hline P7 & & 6.8 \(\pm\) 0.3 & 323 \(\pm\) 44 & 433 \(\pm\) 131 & 805 \(\pm\) 120 & 31.9 \(\pm\) 3.3 \\ P8 & 46 & 5.9 \(\pm\) 0.4 & 287 \(\pm\) 44 & 362 \(\pm\) 88 & 742 \(\pm\) 153 & 25.3 \(\pm\) 12.7 \\ P9 & & 5.7 \(\pm\) 0.3 & 161 \(\pm\) 31 & 345 \(\pm\) 70 & 709 \(\pm\) 157 & 27.7 \(\pm\) 11.6 \\ \hline P10 & & 5.8 \(\pm\) 0.4 & 317 \(\pm\) 44 & 452 \(\pm\) 88 & 833 \(\pm\) 162 & 48.4 \(\pm\) 10.3 \\ P11 & 39 & 6.5 \(\pm\) 0.3 & 307 \(\pm\) 50 & 370 \(\pm\) 77 & 753 \(\pm\) 142 & 28.9 \(\pm\) 2.8 \\ P12 & & 6.8 \(\pm\) 0.2 & 295 \(\pm\) 50 & 325 \(\pm\) 74 & 646 \(\pm\) 173 & 32.9 \(\pm\) 6.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Final distillate characteristics. The standard deviation is reported after the \(\pm\) character. where, due to the scaling properties of the plant, the distillate polluting load can be reduced to allow for its direct discharge as effluent. It is possible to assess the pollutant removal efficiency during each trial considering:  
* The amount of pollutant in the starting raw whey;
* The volume of the treated raw whey;
* The pollutant in the distilled outflow and the volume of the distillate. Table 8 reports the removal efficiency of each specific pollutant as 100% minus the ratio between the volumetric pollutant amount into distillate and into raw whey expressed as percentage. Unfortunately, due to some problems during the analysis, no measures are available concerning the TP and SC of the distillate fraction. The minimum and maximum value of the removal efficiency (considering the initial (raw whey) and the final (distillate) value of conductivity, BOD5, COD and TN) ranges from 94.6% to 97.7% for conductivity; from 98.3% to 99.5% for BOD5; from 98.7% to 99.6% for COD and from 98.2% to 99.3% for TN.