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Industrial waste management is nowadays one of the main issues for ensuring a sustainable environment. Dairy waste management in particular, is very crucial in view of the high organic matter and high nutrient levels contained in dairy effluents. Dairy waste can be effectively treated either with aerobic or anaerobic processes. The main advantages of the former consist of low yield, high kinetics, pathogen free product, and high temperature operation whereas the latter is a simple, low budget and conservative technology. Occasionally pre-treatment strategies (i.e. wetlands) are required in order to improve the efficiency of treatment methodology. Wetlands are a promising technology applied in order to remove the greater part of nutrients and minerals contained in milk based products.
Keywords dairy industry waste, aerobic, anaerobic, wetlands, sustainability, bioremediation
INTRODUCTION
The production process of dairy products results in a significant amount of waste mainly in the form of chemically modified liquids. The latter are characterized by high organic load (e.g. fatty acids and lactose), considerable variations in pH (4.2-9.4) as well as increased content of suspended solids (0.4-2 g/1) (Kosseva et al., 2003). Moreover, since the water requirement of a dairy plant for washing and cleaning operations corresponds to 2-5 litres of water per litre of processed milk (Amritkar, 1995), dairy industries produce a large amount of wastewater per day. The dairy wastewater usually contains proteins, salt, fatty substances, lactose as well as residues of chemicals used during cleaning processes (Thassitou and Arvunitoyannis, 2001). The influence of those chemicals and their additives to the COD (Chemical Oxygen Demand) of the dairy wastewater is rather small, compared to the one caused by the presence of other components such as milk cream or whey (Wildbrett, 1988). However, detergents often contain sequestering agents and surfactants (Grasshoff, 1997) shown to strongly affect the river ecosystems due to their high toxicity to aquatic animals (IDF, 1993).
Furthermore, flow and characteristics of the wastewaters vary from one factory to the other, since a great variety of systems, technologies, operational methods but also final products are being used or produced (Rico et al., 1991). The application of the ISO 14000, resulted in compliance with the increasingly demanding standards of environmental management systems for industries with considerable challenges in a number of areas such...