REPORT#1

The impacts of two modes of cheesemaking on the qualilty and treatment of factory wastewater

By Brigitta Züst, Switzerland

In cheese factories and the food industry generally, perfect hygiene is a basic requirement. A newly published report (1) shows the influence of two different cleaning procedures on the quality of wastewater in a factory where hard Emmenthal cheese is produced.

Traditionally, milk was poured manually into copper lined open vats. Modern hygiene rules now impose on most cheese factories the "curd master" system. In the curd master system, milk is transported through a closed pipe system to the relevant stages in the production process. The cleaning is different for the two production lines. In the traditional way, the surfaces to be treated are accessible and thus, most of the cleaning can be done by hand with a few appropriate cleaning and disinfection agents. In modern cheese making, milk is circulated in inaccessible pipes, and therefore, the cleaning has to be done purely chemically, which requires much more powerful cleaning agents.

Figure 1:
Cheesemaking (1994) in copper lined open vats ("Kessi"), in Scheimatt cheese factory, Switzerland.
Photo: Peter Kurmann

The transformation of a factory from traditional methods to the curd master process allowed a comparative study on the influence of the cleaning agents of both production types in mostly identical conditions: cheese factory, milk, water quality, quality of cheese, operator and climate. From June 1993-April 1994 settled wastewater from open vat production was analysed (24 samples; ref.2). After the introduction of a curd master, wastewater was again analysed from February 1997 till January 1998 (14 samples). the figure shows that the mean organic load of the wastewater increased to 257% (PO₄-P), 285% (total N; not shown) and 332% (COD₅). As the quality and quantity of the cleaning and disinfection agents represented the only major changes, the increase is attributed to them.

Figure 2a) & b):
Mean concentration of COD₅ and PO₄-P of settled wastewater of open vat and curd master operation and means of the curd master wastewater as percent of the mean of open vat wastewater (open vat = 100%)

Other changes attributed to the change in the mode of cheese making are summarized in the following table. The changes in composition and in components of the cleaning and disinfection agents was not considered.

These changes due to a "simple" change in the mode of operation mostly go unnoticed. Similar changes in operation replacing manual labour with chemical agents occurred in other areas e.g. in laundry and dish washing, most likely with similar results. In view of their magnitude, they are of importance, particularly if only an individual building is considered (e.g. for dimensioning an individual treatment plant).

References (both in German): Both studies can be obtained from the Center of Applied Ecology Schattweid, CH-6114 Steinhuserberg. Pre-payment required (Eurocheque)

1) Züst,B. and Fischer,P. 2001. Chemikalien ersetzen Muskelkraft. Einfluss der Kessi- und der Fertiger Betriebsweise mit automatischer CIP-Reinigung auf das Abwasser und seine Reinigung in einer Hartkäserei. Center of Applied Ecology Schattweid, CH-6114 Steinhuserberg. Price sFr 40.-

2) Züst,B. and Schönborn,A. 1994. Naturnahe Reinigung von Käsereiabwasser. Center of Applied Ecology Schattweid, CH-6114 Steinhuserberg. Price sFr 40.-