## 2 Analysis of the Potential for the Increase in Yeast Production and Results  
The research presented in this paper involves the analysis of the influence of the direction of additional wastewater into the ES on an increase in yeast production. The analysis reported in this paper involves the concentration of total nitrogen in wastewater streams (\(S_{i}\)), as it is the main parameter applied to determine the amount of wastewater that can be applied in AF. In addition, this analysis accounts for the use of the AF-ES-WWTP system. The increase in yeast and fertilizer production was achieved by assuming a constant area of AF. Nitrogen is a basic parameter in limiting the amount of wastewater directed to AF. Moreover, the analysis includes also the AF-ES-WWTP. Figure 1 shows the scheme of the yeast production process and the AF-ES-WWTP system. Figure 1A shows the sources of process wastewater in the yeast factory, and Figure 1B shows the paths of the wastewater streams. The \(S_{6}\) stream of process wastewater (Figure 1A) is directed directly to the WWTP (Figure 1B). This stream is not directed to the AF, because it is a domestic wastewater resulting from the washing of the devices. This stream of the wastewater includes detergents, oils, domestic pollutants, chemicals, heavy metals, metal, and rubber filings, among other waste products. However, after treatment of this wastewater (as clean wastewater), it can be directed to the wastewater pumps, in order to dilute the process wastewater stream \(S_{9}\) directed to the AF. The concentration of nitrogen (\(C_{1}\)) in the \(S_{1}\) stream is very high, but the \(S_{1}\) stream has low volume (see Table 1). The concentration of the nitrogen (\(C_{8}\)) in the \(S_{8}\) stream is high, but the \(S_{8}\) stream is negligible. This stream is needed only for microbes for the operation of the WWTP (Figure 1B). Thus, these streams (\(S_{1}\) and \(S_{8}\)) do not have a large effect on the final nitrogen concentration (of the \(S_{9}\) stream). Process wastewater (\(S_{2}\) and \(S_{3}\)) from first and second centrifuges is characterized by the highest concentrations of pollutants. Although the wastewater from clarification of molasses (\(S_{1}\)) is characterized by even higher pollutant concentrations, the volume of this wastewater is very small. The volume of the process wastewater and amount of nitrogen in process wastewater are presented in Table 1. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Streams of Process** & \(S_{1}\) & \(S_{2}\) & \(S_{3}\) & \(S_{4}\) & \(S_{5}\) \\ \hline  & wort & 1 st centrifuge & 2 nd centrifuge & 3 rd centrifuge & vacuum \\  & decantation & separator & separator & separator & filters \\ \hline volume & [m\({}^{3}\)/yr] & 400 & 17,150 & 232,850 & 53,300 \\ \hline \(C_{i}\) **of total N** & [kg/m\({}^{3}\)] & 8.5 & 3.3 & 2.1 & 0.65 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Volume and nitrogen of the process wastewater. \(S_{i}\), stream of wastewater [m3/year];  
\(S_{1}\), stream of process wastewater after molasses clarification;  
\(S_{2}\), stream of process wastewater from the first centrifuge separator;  
\(S_{3}\), stream of process wastewater from the second centrifuge separator;  
\(S_{4}\), stream of process wastewater from the third centrifuge separator;  
\(S_{5}\), stream of process wastewater from the vacuum filters;  
\(S_{6}\), stream of domestic wastewater and after cleaning of the process devices;  
\(S_{7}\), stream of pre-treated process wastewater after the evaporator station (ES);  
\(S_{8}\), little stream of process wastewater directed to the wastewater treatment plant (WWTP);  
\(S_{9}\), stream of process wastewater directed to the agricultural fields (AF) from equalized wastewater;  
\(S_{10}\), stream of cleaned wastewater directed to the AF;  
\(S_{11}\), stream of water from the river;  
Figure 1: Scheme of the wastewater sources (**A**) and the three-stage wastewater treatment system (**B**) in the analyzed yeast factory. \(Y_{p}\), yeast production; \(F_{p}\), fertilizer production.