Nowadays, the dairy industry is categorized into two distinct production areas. The primary production of milk is principally on farms, whereby cows and other animals, such as goats, sheep, and among others, are bred for the production of milk for human consumption. The processing of milk has for main objective of extending its saleable life and keeping quality. This can be achieved by a number of food transformation and preservation techniques. Milk can be heat treated, can be prepared variously in a dehydrated form like butter and milk powder, thirdly by freezing, for instance, ice cream and other frozen desserts and finally by fermentation like yoghurt, cheese, ghee, kefir and among others.

1.1.1 Profile of the dairy processing industry in Mauritius

Mauritius has one of the strongest economies in Africa, with a per capita GDP close to U$3,900. Its economy has been heightened greatly over the past 15 years and the main sectors, which have driven the performance, were the textile, tourism and sugar industry. However, studies prepared by the Imani Development Consultants (2004), for the Regional Agricultural Trade Expansion Support Program, have demonstrated that the local dairy is a very small sector with only about 5000 dairy cows, producing about 4 million litres of milk, which represent only 5% of the total requirements. Hence, Mauritius does not have the resources and capacity to produce milk efficiently. About 1 million litres of the milk produced, through reconstitution from powder milk, is marketed as pasteurised milk by the Agricultural Marketing Board and other dairy industries.

Likewise the Imani Development Consultants (2004) added that the consumption trend of most dairy products has considerably increased over the past 5 years from 12,800 tons in 1995 to 22,000 tons in the year 2002. This trend is expected to continue with the rising standard of living of the Mauritian population. There is now a growing market for UHT milk despite the fact that milk powder is widely preferred by the population. Australia and New Zealand remain the principal suppliers of dairy products to Mauritius. There are various renowned dairy products brands in most supermarkets and retail shops.

Although Mauritius is not a milk producing country, it has three main dairy products manufacturers, namely Maurilait Ltd., INNODIS Ltd., and Laiterie de Curepipe, which are producing mainly yoghurt, ice cream, sterilised milk and flavoured milk, using imported raw materials.

1.1.1.1 INNODIS Limited

INNODIS Limited is one of the main food and grocery distributors and producers in Mauritius. It is a large company engaged in different sectors, ranging from poultry, rice milling, consumer goods, frozen foods, dairy production and among others. The company has invested profusely to bring over a high performance in quality and reliability of its products and this has nowadays led to an annual turnover of Rs 2.5 billion (Anon2, 2010).

The dairy Plant of INNODIS Ltd was set up since 1952, with an Ice Cream business activity, manufacturing Nestle products under the brand name Dairymaid. It has nowadays developed close partnerships with South African licenses and has integrated other production lines of yoghurt, nectars, and sterilized milks under the brand name of DairyVale, Ceres, Twin Cows and Ole respectively. Ice Cream production includes 45% of the total production, followed by 30% of yoghurt production and a remaining of 25% for nectars and sterilized milk (pers. comm., 2010).

The dairy plant of INNODIS Ltd has adopted a food safety management system, for instance, the HACCP Codex Alimentarius Standards and adheres to the Nestle and Ceres Standards in order to keep up consistency in quality of products and work within the factory. The installed capacity of the dairy processing plant is 2million Litres of milk per year and is presently being used at 90% of its capacity milk (pers. comm., 2010).

1.2 Dairy Processing Waste

1.2.1 Water consumption

Water is the principal raw material and cleaning constituent in the food processing sector. In the dairy processing industry, substantial volumes of water is used for cleaning equipment and work areas to maintain the hygienic conditions, in cooling departments like in cooling towers and in energy production for example in boilers. Water also accounts for a large proportion as raw material in the reconstitution of milk powders for the production of liquid milk, yoghurt, ice cream, butter, cheese and among others.

Rates of water consumption can vary significantly based on the scale and capacity of the plant and type of processing, whether batch or continuous processes. The type of mix being generated, the methods and cleaning equipments being in use as well as considering the human factor with inference to the practices of the operatives on the production departments can also affect drastically the consumption of water in the dairy processing.

A typical range for water consumption in reasonably efficient plants is 1.3–2.5 Litres water/Kg of milk intake (UNEP, 2000). In most parts of the world, fresh water is becoming scarcer with the evolution of climatic phenomenon like droughts and ‘el lino’ and as such, the cost of water is rising and the true environmental costs of its supply are being taken into consideration. Water has thus become an increasingly valuable commodity and its efficient use is being now emphasized on drastically.

There can be effective water management strategies for reducing water consumption and this can involve technological solutions or equipment upgrading. Moreover, a dairy plant waste load can be curbed down considerably by monitoring the amount of water used and reducing the amount of product lost into the effluent. This control will all depends upon the machine set-up and the operator’s practices. Stopping wastage at its source will therefore be less costly and more practical than end-of-pipe waste treatment. By doing so, the water expenditure can be declined up to 0.8–1.0 Litres water/kg of milk intake (UNEP, 2000). Techniques described in the publication made by the UNEP in 2000 are well defined accordingly:

• Continuous rather than batch processing is better to be introduced as it prevents frequent cleaning.
• Automated cleaning-in-place (CIP) systems allow less dismantling of equipments and therefore less use of water.
• Flow meters are placed at different spots of the processing line to control and monitor the flow of water for manual cleaning procedures.
• High pressure rather than high volume is preferred for cleaning surfaces. Compressed air can be used also.
• Re-circulating or re-using clean water which may have been used for rinsing to other activities which is not a commodity for cleaning and processing.

1.2.2 Waste water discharge

Water discharges are produced mainly in the dairy industry by processing operations but also by clean water which are released from cooling water and steam and evaporator condensates. This discharge ultimately becomes the effluent, which contains predominantly milk and milk constituents which have been lost from the process. According to studies made by the UNEP (2004), milk loss can be as high as 3–4% with the main source of loss being residues which remain on the internal surfaces of vessels and pipes, draining of mix from machines before filling, spills during emptying tanks and overflowing of vats or hoppers. Likewise, the organic load of the effluent varies greatly with the type of cleaning practices being applied. Batch processes will normally require a greater and frequent cleaning. Thus, the COD level can reach up to about 8 Kg/m3 milk intake.

1.2.2.1 Characteristics of waste water and their impacts on the environment

The characteristics of the waste water generally vary from different types of dairy products owing to their different constituents and ways of processing.