Water quality

The basic element of proper water management in the food industry is to ensure adequate water quality. This is a prerequisite for prevention of incidents arising from security threats. Risk prevention constitutes of detection and identification (recognition). Risk control in both factories is carried out by specially developed programs to monitor the quality of raw water and treated water. Such programs provide appropriate steps throughout the whole chain: supply, production, and distribution of water. The most important, however, insignificant from the point of view of the analysis of sanitary water security threats is a parameter that requires constant monitoring, namely—iron. Iron as a component of water-bearing rocks occurs in waters of almost 80% underground sources. Harmless from the point of view of health, it causes significant trouble in production processes, particularly affecting negatively the quality of dairy products. The most important parameters of the quality of raw water in individual plants with reference to the current standards are presented in Table 2.

Table 2 The most important water quality parameters in DF-1 and DF-2 wells, with reference to the current national and European standards Full size table

Since at both plants the problem of excessive concentration of iron in raw water has been recognized, both analyzed plants are equipped with iron removal system. Iron removal systems operate on the basis of the same unit processes, namely, aeration, which aims to oxidize ferrous iron, as well as rapid filtration, in an attempt to stop the precipitated iron compounds. In order to ensure microbiological safety after the iron removal process, at both plants, the water is being disinfected with the use of chlorine. Analysis of archival data and interviews with employees at the plant lead to the conclusion that the operating treatment system ensures the required security level, both in terms of quantity and quality of water used in the manufacturing process. As previously mentioned, the process water, which may have contact with food, must meet strict quality requirements, which prevents it from being reused.

Nonetheless, the water used for washing machines and halls, especially when used for the first washing, is not the subject of such restrictive preconditions. This case was adopted at DF-2 where the CIP system has been implemented. After the completion of the technological process, clearing machines, and equipment from the product and its detachment from supply tanks, the rinsing is conducted in a closed circuit. The process of cleaning the line begins with pre-wash, which removes the remaining product from washed surfaces. Cleaning agent containing many contaminants is removed from the system. Thereafter, the preliminary heavily contaminated water is transported directly to the treatment plant. The initial washing is followed by proper wash with the use of detergents. The solution remaining from last washing is passed to the pre-wash tank at the washing station. The process ends with rinsing with clean water. Considering that such water may have contact with food production, it must meet the requirements for drinking water.

Other requirements are set for the water used for steam production. In the dairy industry, the technological steam is used not only as a heat carrier, but also, and perhaps primarily as a disinfecting agent in the process of sterilization and pasteurization. Some processes require direct contact of steam with the product (e.g., a direct sterilization process for producing the UHT milk). If in the production process the steam being used has direct contact with food products, the parameters of water used for steam production should correspond to the parameters of drinking water, including the boiler water used for steam boilers. Such water must meet the requirements defined by the manufacturers of boilers, which usually relate to the hardness of water. The requirements depend on the design of a boiler and increase accordingly with its operating pressure.

At both study sites, there are water softener stations which effectively remove hardness to the levels below 0.01 mval/l, supporting the operation of boilers. In addition, water in the boiler system is adjusted through the use of chemicals that do not have toxic, carcinogenic, mutagenic, or harmful properties and are thermostable under normal operating conditions of the boiler. These substances are approved by the National Institute of Health for having contact with food. Both basic ingredients of these formulas and complementarity-stabilizing additives are a category of chemicals listed in food additives. This approach of both companies creates the comfort of safety, both from the point of view of the construction of the boiler and steam quality, and thus the quality of dairy products.

Another problem regarding water management at the company is to ensure the supply of water to maintain greenness in the summer, and the provision of sufficient quantities of water in case of fire. In these cases, the requirements for water quality are not as restrictive, since this part of water management depends on the quantity of water available. At both plants during the summer months, the maintenance of green areas was carried with raw water and additionally with treated wastewater which quality allowed for such use (Zahuta 2015). Regarding the fire objectives, the capacity of the reservoirs of clean water does not guarantee complete safety in the event of a large fire. Therefore, companies should consider the possibility of using treated wastewater as a potential reservoir for fire protection. The quality of treated wastewater allows such a solution; however, it should be noted that the water should contain disinfectant components, so that when sprayed during a water rescue, it does not pose a bacteriological danger for persons conducting work at the company.

Water consumption indicators

Dairy processors are aggressively challenged to conserve water necessitating the need for not only reducing water consumption but also to employ measures for recovery and recycling of process water without compromising on the hygienic quality and safety of the products. In Poland, there are norms of water consumption specified by the Minister of Infrastructure Regulation of 14 January 2002 on determining the average water consumption standards. Specific standards of the average water consumption for dairy products are presented in Table 3.

Table 3 Average water consumption standards in processing plants in dairy industry based on Regulation (2002) Full size table

In the literature, Flemmer (2012), Perry (2011) and Steinhoff-Wrześniewska et al. (2013), Strzelczyk et al. (2010), there is diversified information on the use of water, which typically oscillates between 1 ÷ 10 l of water per liter of processed milk. However, the actual water consumption varies depending on the progress and modernization of production facilities and introduction of new technologies. In the production of milk and dairy products, one can observe a certain itineracy. Just as diverse is the demand market for dairy products during a year, accordingly varied is the demand for water and the volume of wastewater discharged from these processes. This is presented in Fig. 3, which shows the changes in monthly water consumption and wastewater production during a year. As can be seen, the volume of wastewater is equivalent to about 90% of water production, while during the summer, this figure is somehow lower, because a small amount of treated wastewater is used for irrigation of green areas.

Fig. 3 Changes in monthly water consumptions and wastewater production during the year Full size image

Respective processes have been analyzed at the plants in order to evaluate water consumptions. Water consumption indicators broken down by technological processes in both analyzed companies are presented in Tables 4 and 5.

Table 4 Water consumption indicators for DF-1 in 2014 Full size table

Table 5 Water consumption indicators for DF-2 in 2014 Full size table

The diversity of indicators at individual factories was discovered to be resulting from the diversity in the type of production. When comparing the data with the available literature data as presented in the introduction, at Table 1, it can be noted that the situation at the analyzed companies is not drastic, but there is a potential to reduce water consumption from primary sources. The capability for the introduction of innovative technologies can be applied for such operations as automated rinsing of milk receiving tank trucks and cleaning of the tankers at the dairy plant; automated dairy food processing operations processing milk; automated circulation cleaning; and the use of liquid detergents and chemical sanitizing agents on a controlled basis.

The data presented indicate a high potential of this industry to use systems reuse water. According to literature, data recovery of water used can save up to 20–40% of the total costs associated with the production of water (Milani et al. 2011; Kasztelan 2012).

This is an essential fact because Poland is in the process of major legislative changes and the introduction of significant increase in fees for the use of water from primary sources. Therefore, any change will translate into tangible economic savings and improve enterprise competitiveness.

Undoubtedly, water consumption is also influenced by the nature of dairy production. Most water is required at plants that produce milk powder and cheese, a little less is consumed at plants producing drinking milk. In order to compare the levels of water consumption for both of analyzed plants, the average water consumption indicators have been calculated: the average for years 2011–2014 and for 2015 only, after the introduction of water management industry changes. The data are presented in Table 6.

Table 6 Water consumption indicators: average for 2011–2014 and for 2015 Full size table

When taking into account data of the year by year period, we may observe reduction in water consumption per liter of product. These improvements are attributed to developments in process control and cleaning practices. During the research period on presented case studies has been implemented the system of simple changes and lower water consumption in the washing process. Additionally, some percent of wastewater has been used for green area irrigation, and all leaks have been monitored. At DF-1, 10% decrease in water consumption indicator has been achieved. At DF-2, almost 15% presumably because DF-2 uses CIP and only a slight modification to CIP has resulted in high reduction of fresh water use. Significant impact of controlling and optimizing cleaning parameters on water consumption was described also by Wojdalski et al. (2013). Practical solutions for reducing water consumption in dairy plants indicate that the water scarcity footprint at the plants was not only related to total freshwater consumption and production, but also closely related to the scarcity of water resources in the watershed basin or area (Bai et al. 2017).

The above data allows us to draw very optimistic forecasts and conclusions, namely that the existing measures aimed to reduce water consumption from primary sources do bring the expected results.