Analysis of the Potential of an Increase in Yeast Output Resulting from the Application of Additional Process Wastewater in the Evaporator Station  
[PERSON]  
1 Institute of Technical Science, Faculty of Natural Sciences and Technology, University of Opole,  
Dmowskiego str. 7-9, 45-365 Opole, Poland; [EMAIL_ADDRESS]  
1  
[PERSON]  
1 Institute of Technical Science, Faculty of Natural Sciences and Technology, University of Opole,  
Dmowskiego str. 7-9, 45-365 Opole, Poland; [EMAIL_ADDRESS]  
1  
Footnote 1: email: {[EMAIL_ADDRESS]; 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31  
In recent years, the Polish food sector has undergone tremendous changes, both in terms of technology and measures linked to environmental protection. Thanks to the constant technical, engineering, and innovative development, Poland has become one of the leading food producers in Europe. One of the factories belonging to the group of European leaders, in terms of the variety of products on offer, is provided by the yeast factory analyzed in this paper [3; 4]. The yeast industry consumes significant amounts of water for the production of yeast and, consequently, huge amounts of process wastewater (technological wastewater) are produced, which need to be later utilized. Process wastewater from the yeast industry mainly originates from decanting and word thickening. This wastewater is of plant origin and due to the high content of nitrogen, potassium, and organic substances, it can be (and often is) deposited on agricultural fields (AF) to play the role of a fertilizer. Chemical analysis of the level of humus in soils, in which process wastewater from the yeast plant is deposited, does not demonstrate an increase in the accumulation of heavy metals. The values of concentrations of trace elements in soils irrigated with yeast wastes are much lower than the levels that are permitted in soils and plants. The parameters of natural geochemical values in soils are, thus, not exceeded [5]. Research has also been carried out into the treatment of yeast wastewater by application of nano-filtration, electro-coagulation, or in the use of technological yeast wastes for application in the direct generation of electricity using microbial fuel cells [6; 7; 8; 9; 10; 11; 12]. The deposition of process wastewater derived from the yeast industry on agricultural fields (AF) seems to represent the most rational solution [5; 13; 14]. Cultivation on AF fertilized with yeast technological wastewater is characterized by a considerable efficiency. In addition, such wastewater contains organic substances that have a positive effect on the fertilized soils and contributes to the improvement of soil quality in the vicinity of the plant [15]. However, it is possible to irrigate AF using only limited amounts of process wastewater [15; 16]. The main reason that the volume of wastewater directed to AF needs to be limited is associated with the concentration of nitrogen in this wastewater [15; 17]. For this reason, wastewater is often pre-treated in an evaporator station (ES), in order to decrease the nitrogen concentration in wastewater that is applied to AF. Theoretically, when a larger amount of wastewater is routed to process in an ES, the possibility of using larger amounts of process wastewater in AF is feasible, which, in turn, can lead to an increase in the yeast output [18]. Previous studies [18; 19] have shown the necessity of a detailed analysis of the wastewater treatment system in yeast factories. The analyzed factory includes a three-stage wastewater treatment system, comprised of an agricultural field (AF), an evaporator station (ES), and a biological wastewater treatment plant (WWTP). The analysis of the three-stage wastewater treatment system (AF-ES-WWTP) in a yeast factory will provide the development of a solution leading to an increase in production, without the plant exerting additional pressure on the natural environment.