ries. The method is cheap, rather easy to perform, does not require highly sophisticated techniques and can be apllied because of the usually low pollutional strength of the produced wastewater [33]. br/>
8. Waste production and its consequences
In the three types of animal-product-processing industries (slaughtering, tanning and milk processing), wastewater problems appear to be the most severe ones. Processing activities inevitably produce wastewater, frequently in large quantities. This wastewater is polluted with biodegradable organic compounds, suspended solids, nutrients and toxic compounds (particularly chromium and tannins from tanneries). Via the reduction of dissolved oxygen this pollution directly or indirectly leads to a decreasing suitability of (surface) water for aquatic life, and drinking, swimming or other purposes [32]. The density of animal product processing is so low that the concentration of pollutants in the receiving water bodies remains low, the production of wastewater does not necessarily lead to environmental problems. However, when from the comparison of the values ​​of Table 26 with the European target values ​​for urban wastewater discharge (eg 25 mg BOD, 10-15 mg N and 1-2 mg P per litre), it becomes clear that, from a wastewater production point of view, that there is a trend towards increasing densities of product processing even at relatively small amounts of processed animal products [15]. heavy metal Chromium, occurring in the waste of tanneries, has caused and will in all likelihood continue to cause , serious environmental problems. It is common practice that most of the chromium is released in wastewater. There are no indications of other heavy metals in the waste of the animal processing industry causing environmental problems.caused by air pollution and solid waste disposal are minor in comparison to those related to wastewater production. The main cause of air pollution is the use of fossil energy, with as major exception the volatile organic compounds in the leather industry [18]. In slaughterhouses solid waste disposal may lead to hygienic problems, but in principle these are relatively easy to solve. An exception is the leather waste that contains chromium. This waste must be dumped on special grounds.a proper discussion of the environmental impact of slaughtering, tanning, and dairy industry, the effects of related activities such as transportation, spoilage by the consumer, durability of the product etc. also have to be taken into account. These activities are especially important for the discussion concerning the advantages and disadvantages of the various production processes and the scale at which processing is undertaken [10]. br/>
8.1 Data availability and reliability
In Table 26 typical values ​​of wastewater production for several processes ...
