Sustainable water management in industry

Jacques J.M. van de Worp

1.1 THE SUSTAINABILITY CONCEPT

The past decades have witnessed an increasing awareness that human activities, in particular intensive agriculture and industrial technologies, must be brought in harmony with the global material cycles in the biosphere. In other words, a transition will have to be made from exploitation of our natural resources towards a partnership with the global ecosystem (Harder 1995).

At the end of the 80s, after the publication of the Brundtland report Our Common Future (1987), sustainable development became a key issue. Sustainable development was defined as "economic, social and environmental development that meets the needs of the present without compromising the ability of future generations to meet their own needs" (Brundtland 1987). In the years following the publication of this report, several attempts have been made to translate its basic philosophy and recommendations into an operational approach for the immediate future (Jansen and Vergragt 1995). The problem of the Brundtland definition, which is formulated in abstract terms, is that sustainable development cannot be scientifically unequivocally defined. The Netherlands Scientific Council for Government Policy (WRR) and the Social and Economic Council (SER) - two of the main advisory bodies of the Dutch Government - have observed that sustainable development is the result of a process of weighing up political options. In this process not only environmental aspects (planet) have a part to play, but also economic (profit) and social aspects (people) such as welfare and employment. It is therefore up to the society to establish the standards that will be decisive in determining a sustainable development policy in the medium term (VNO-NCW 2001).

A growing number of companies have developed, or are developing, a business strategy based on the concept of sustainability. This development which is taking place all over the world - is universally seen as something that is highly desirable. The Dutch Government is therefore working on a national sustainability strategy (VNO-NCW 2001).

In Gothenburg in mid-June 2001, the European Commission proposed a European Union Strategy for Sustainable Development as a spin-off from the UNCED Summit in Rio de Janeiro in 1992. This strategy is part of the EU preparations for the 2002 World Summit on Sustainable Development in Johannesburg (VNO-NCW 2001).

In the case of industrial technologies, a working group of the World Business Council for Sustainable Development (WBCSD 1995) considered the following elements to be essential:

• Dematerialise: reduce the amount of raw materials used

• Increase the energy efficiency

• Eliminate the negative environmental impact of processes and products

• Close material cycles: design for recyclability, but not at any cost

• Borrow from natural cycles, particularly where renewable resources and recycling are concerned

• Extend the durability and service life of products.

Entrepreneurial activity based on the principles of prevention and precaution, make use exclusively of renewable energy and raw materials (including fuels and other materials), thus involving no discharge of waste in any form whatsoever into the environment (zero emission) and impose only a responsible burden on the available space. Thus, the entrepreneurial activity does not give rise to any adverse effects on water, air, soil or biodiversity either at home or abroad. This definition however, has a number of disadvantages:

• it is intended as a reference point for a process with a timescale generally spanning 20 or 30 years

• it is difficult for the average company to give substance to a frame of reference so far in the future

• the definition does not take into account the balance between the three pillars of sustainable development (planet - people - profit)

• the definition offers a static description, whereas sustainable development and hence sustainable enterprise is a dynamic process

Water is an essential resource in three of the six elements mentioned in the WBCSD-list above, but so far it has not been identified as a key issue by decision-makers. In 2000 at the 2nd World Water Forum in The Hague the world water problems were addressed to the politicians. A number of multinationals, such as Unilever, Heineken and Nestlé presented a companies corporate Sustainable Water Use statement. The driving force behind these statements is that sustainability is seen by companies as a condition for continuity (World Water Forum 2000).

1.2 WATER RESOURCES

1.2.1 General

Water is a most important natural resource. On a global scale, there is no shortage of water, since more than 70% of our planet is covered with it (see Figure 1.1). Since there is essentially no exchange of materials between earth and outer space, the total amount of water on the planet is constant. On earth, water is only found in a thin layer of approximately 60 km at the outer surface (Donkers 1994).

Liquid water is essential for life. Many organisms consist for more than 90% water. The human body contains some 65% water, and man can only survive for approximately 3 days without drinking. The problem with regard to the requirement for water by terrestrial ecosystems (including humans) is not only related to its availability, but more in particular to its quality, notably its chemical and bacteriological composition.

On earth, there is a relationship between water quality and the type and composition of ecosystems that it can support. Thus, water quality always has to be related to the required purpose for use. Water fulfils many different functions, such as:

• Essential reactant for organisms

• Environment for aquatic organisms

• Drinking water for animals and human beings

• Utility in household and industry

• Power supply (steam and waterpower; coolant).

In order to fulfil the different functions, water has to be 'fit for use'.

1.2.2 Water cycles

1.2.2.1 The global water cycle

According to the latest calculations, the earth contains some 1386 million km3 (1.4 * 1018 m3) of water. However, 97.5% of this water amount is salty seawater (see Figure 1.1). From the total freshwater reserves on earth, only 0.26% (93,000 km3) is available to terrestrial lifeforms (humans, animals, vegetation, lower organisms) (Shiklomanov 1993 in: Donkers 1994).

The water on earth is not static, but participates in a cycle maintained by solar energy and the rotation of the earth (see Figure 1.2). At sea, the evaporation exceeds precipitation, which leads to the building up of clouds. The clouds are transported from the oceans to the continent by wind, and since the temperature over continents is higher than over sea, the airmass is forced to rise. The resulting drop in temperature causes the vapour in the clouds to condense, and precipitation occurs. The precipitation meets the land surface. In humid areas there is a surplus situation (precipitation exceeds evaporation). The surplus water flows to rivers and aquifers, or directly to the sea. In arid areas however, there is no flow of surplus water, since evaporation equals precipitation. The residence time of the water in the atmosphere mostly is short, some 10 days. In aquifers, the residence time on average is 600 years (range <1->>10,000 years). In rivers, the residence time amounts to 10 to 20 days (average), and in oceans 3000 years (average) (Donkers 1994).

The amount of water available for terrestrial activities on an annual basis depends on the precipitation on the continents. Over two-thirds of the precipitation eventually evaporates, while the rest (47,000 km3) is supplied to the groundwater stocks, rivers and lakes (see Figure 1.3). Man is not capable of using all the water before it flows back into the oceans. From the available 47,000 km3, man can only use 9,000 km3, which translates to some 1,600 m3 per person. However, this amount of water is not equally divided over the world: in some parts it never or seldom rains, in other parts it rains excessively (see Figures 1.4 and 1.5). Unfortunately, in the dry areas, more water evaporates, and agriculture is only possible when the land is irrigated. In some cases, nature offers some help by transporting water from wet to dry areas. Where nature fails man intervenes and transports water in an artificial manner (World Resources Institute 1994 in: Donkers 1994).

Water is not only unequally divided geographically, but also in time. In some regions, it rains very intensively in a short period of time. In other regions, precipitation is more or less equally divided over the year (World Resources Institute 1994 in: Donkers 1994). The annual amount also can change from year to year, as in the Southeast of Spain. Moreover, the water consumers are unequally divided over the continents. In some regions (Africa, the Middle East) relatively many people have very little water available, while in other regions (Canada, Iceland, the Amazon, the Congo Delta) few people have access to excessive amounts of water (World Resources Institute 1994 in: Donkers 1994).

The local water situation not only depends on the water supply, but also on the water demand. The latter is usually subdivided into domestic, industrial and agricultural demand. Because of the growth of both the domestic demand per capita and the world population, the domestic water demand increased from 100 billion m3 in 1977 to 260 billion m3 in 1987. The predicted figure for the year 2000 is 920 billion m3, whereas Gleick predicts a figure of 340 billion m3 in the year 2025 (Donkers 1994; Gleick 2001). The industrial demand increased over the same period (1977-1987) from 445 to 745 billion m3 (Gleick: in the year 2025: 1000 billion m3) (Donkers 1994; Gleick 2001). The fastest growing sector, however, is agriculture (Gleick: in the year 2025: 2930 billion m3), due to extensive irrigation programmes, necessary to support the food production of the exponentally increasing world population (Gleick 2001). Between 1960 and 1990, the earth's irrigated area increased from 90 to 234 million hectares (Gleick: in the year 2000: 270 million hectares) (Donkers 1994 and Gleick 2001). In Israel, 65% of the water supply is used for agriculture. Figures for Egypt (88%), Iraq (92%) and Sudan (99%) are even higher (Donkers 1994).

1.2.2.2 Urban water cycles

It is not a coincidence that the first settlements and industries were erected on the shores of brooks, rivers and lakes, since in these areas fertile soil, water for consumption and water for use in various production processes is found. After use, when the water quality has decreased, it can be disposed of readily by discharge into the surface water. In our modern age, a city has a very complex water cycle and infrastructure (see Figure 1.6).

Even in the Netherlands for instance, where most of the urban and industrial waste water is treated continuously, it is necessary to draw attention to the prevention of pollution and the purification of waste water. This is the case because the urban and industrial water cycles have a significant impact on the greater water cycle, both in quantitative and qualitative terms. Some recent issues are listed below (DTO 1995; van der Graaf et al. 1995):

• modern urban society urges non-disturbed functioning, this requires sufficient drainage

• due to ageing, many sewer systems show leakage's, leading to groundwater pollution

• due to water extraction, groundwater levels have dropped, leading to withering

• due to human activities including agriculture and industry, ground and surface water have become polluted with various substances, both from natural and manmade origin.

Table 1.1 presents the contribution from natural and domestic, agricultural plus industrial sources to the pollution of the river Rhine. The figure shows clearly that over a 12-year period quite an effort has been made, but that manmade pollution by far still exceeds natural contribution levels.

1.2.2.3 Industrial water cycles

In current practice, an industrial water cycle is generally not closed. The industry draws water from aquifers, from surface water or the public drinking water net. Used water is disposed of. In industry, water is often seen as a utility and is used for various purposes, such as (Assink et al. 1996):

Table 1.2. The functions – including examples – of water use in industrial processes

Function of process water Examples
Product, reactant Production of beverages, hydrolysis
Solvent, absorption Gasscrubber, pickling
Washing, adsorption Textile finishing
(Energy) Transport Cooling, steam circuits, solid wastes,
sugar canes
Washing and rinsing Cleaning of equipment, installation and
piping

In the first application (product and reactant), water is a raw material which cannot be replaced by any other component. In the other applications, however, water is a utility. In these cases, water is qualified as irreplaceable, due to the absence of adequate alternatives. Water is an attractive substance because of its physico–chemical properties, its relatively low price and its abundant availability in many industrialised parts of the world (Assink and Weenk 1996).

Especially for cooling, washing and rinsing purposes, industry uses relatively large quantities of water. Cooling accounts for some 90% of the total industrial water consumption. The main water pollution occurs by extensive conditioning and cleaning activities, and in processes where water is in direct contact with water-soluble components (Assink and Weenk 1996).

Groundwater, surface water and even potable water cannot always be used without pre-treatment, in order to satisfy the quality requirements. Examples are the removal of suspended solids (SS), water softening (removal of Ca, Mg) and removal of iron (Fe) and manganese (Mn). More specific examples are water demineralisation and sterilisation (Assink and Weenk 1996).

After the use in a process, water generally contains components which deteriorate its quality in such a way that the water cannot be re-used in the process without treatment, because it would lead to negative effects on product quality or production costs. For these reasons, in many cases, water is used only once, and after use it is discharged in a sewer system for treatment on-site or off-site or disposal (Assink and Weenk 1996).

The amount of water required strongly depends on the current production process. To produce 1 l of beer, 12–16 l of water are required overall, according state-of-the-art technology in the brewing process and the growing of the crop. The production of 1 kg of cotton, however, requires 10,000 l of water, including the growing of cotton (overall requirement). To produce the metal of one car requires 450 m3 of water, four tyres for the car another 760 m3 of water. In the production of paper, the water use has decreased from 30 to 10–15 m3 of water different product than cardboard (6–9 m3/tonne), white paper (15–20 m3/tonne) and money-bills (100–150 m3/tonne) (see Tables 1.3–1.5).