# Water Consumption, Quantity and Quality of Wastewater and Sewage Sludge from Polish Dairies
## 2 Materials and Methods  
Eighteen Polish dairies took part in this study. The survey included questions on the production profile, amount of milk processed, water consumption, use of closed water circuits within the plant, equipment for wastewater pre-treatment or treatment, disposal of domestic sewage in WWTPs, the quantity of waste water produced, the treatment technology, the equipment of the technological sequence of the treatment or pre-treatment plant and the pollution indicators of wastewater discharged into the dairies' wastewater treatment plants or into the municipal sewage system. The data received from the companies relate to the year 2023. The amount of water consumed was determined on the basis of water meter readings. The volume of wastewater discharged into the wastewater treatment plant was measured using flow meters installed at the entrance to the wastewater treatment plant. For both meters, the readings of both meters on 1 January and 31 December 2023 were used as the basis for calculating the annual water consumption and the annual wastewater volume. Since the plants (dairies) differ greatly in terms of product range and production volume, no average values were determined for the entire sector, neither for water consumption, nor for the quantity and value of the indicators of wastewater pollution nor for the quantity and parameters of sewage sludge.  
The scope of the physico-chemical analysis of the wastewater included BOD\({}_{5}\) (biochemical oxygen demand), COD (chemical oxygen demand), total suspended solids, total nitrogen, total phosphorus and pH. The analyses were carried out in accordance with the Polish standard methods for the examination of water, wastewater and sludge (PN-EN ISO 5815-1:2019-12; PN-EN ISO 15705:2005; PN-EN 872:2007+Ap1:2007; PN-EN 12260: 2004 (A),(W),(NR); PN-EN ISO 11885:2009; PN-EN ISO 10523:2012 (A)) [21; 22; 23; 24; 25; 26]. The pollutant loads in the wastewater were determined in daily composite samples based on 24 h quality monitoring of the wastewater.  
Data on the amount of sewage sludge were provided by 14 dairies. The results of the qualitative studies were submitted by 9 dairies.  
The dairies were asked to state whether domestic sewage is discharged into the WWTP, how much sludge is produced annually, how the sludge is processed and whether it is used for agricultural purposes. They were also asked about the results of the sanitary tests of the sludge (presence of _Ascaris_ sp., _Trichuris_ sp., _Toxocana_ sp. Eggs and presence of Salmonella) and the results of the physicochemical analysis of the sludge (dry matter, organic matter, ammonium nitrogen, TKN, Mg, Ca, TP, Cr, Zn, Cd, Cu, Ni, Pb, Hg and pH value). The sewage sludge analyses were carried out in accordance with the Polish standard methods for the examination of water, wastewater and sludge (PN-EN 15934:2013-02; PN-EN 15935:2022-01; PN-75/C-04576/15(W); PN-EN 13342:2002; PN-EN ISO 11885:2009 PN-EN 16173:2012; PN-EN ISO 11885:2009 PN-EN 16173:2012; PN-EN ISO 11885:2009 PN-EN 16173:2012; PN-EN ISO 11885:2009 PN-EN 16173:2012; PN-EN ISO 11885:2009 PN-EN 16173:2012; PN-EN ISO 11885:2009 PN-EN 16173:2012; PN-EN ISO 11885:2009 PN-EN 16173:2012; PN-EN ISO 11885:2009 PN-EN 16173:2012; PN-EN ISO 11885:2009 PN-EN 16173:2012; PN-EN ISO 11885:2009 PN-EN 16173:2012; PN-EN ISO 11885:2009 PN-EN 16173:2012; PN-EN ISO 11885:2009 PN-EN 16173:2012; PN-EN ISO 11885:2009 PN-EN 16173:2012; PN-EN 15933:2013-02) [25; 27; 28; 29; 30; 31; 32]. Sanitary tests of the sludge were performed in accordance with the following standards: PN-Z-19000-4:2001 and PN-EN ISO 6579-1:2017-04/A1:2020-09 [33; 34].  
Analyses of sludge and wastewater were carried out by accredited laboratories.