Water Recycling In Other Parts Of The World

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Water recycling is an obvious choice in water-stressed regions where it is the only option to grow or even to survive. Many of these regions can be often found in less developed regions in Africa, Asia, and Latin America.

In Africa, the Goreangab reclamation plant in Windhoek, Namibia, is the typical example. Namibia has ca. 1.8 million inhabitants and has an average annual rainfall of 285 mm. There are large differences in rainfall. In the south, bordering South Africa, the Oranje River is an important water source. In the north, the Kunene River from Angola can be used; this part of Namibia has plenty of water as it is within the catchment area of the Zambezi and Okavango rivers (with even direct access to the Zambezi through the Caprivi Strip). In the west, the coastal plain quickly transforms to the Namib Desert, where rainfall is virtually zero. The Namib Desert has been hyperarid for 17 million years; local people, the Topnaar, survive by making use of temporary rivers and vegetation adapted to extreme conditions such as a plant called Inara. These conditions are barely sufficient for a very small number of people; growing pressure from tourism in this extraordinary region poses a severe threat. In the east of Namibia, the

Kalahari Desert is also dry. Windhoek is located in between these deserts, too far away from the rivers in north and south (750 and 900 km, respectively). It has ca. 250 000 inhabitants and relied originally on groundwater. When the city grew, other sources had to be found by constructing dams catching water from ephemeral rivers. The Avis Dam was constructed in 1933 (2.4 Mm3), the Goreangab Dam in 1958 (3.6 Mm3). Potable water was produced in a conventional treatment plant. From 1969 on, the effluent from the Gammams Wastewater Treatment Plant was also treated in this plant. This was the start of the first, and to date still the only water recycling plant for direct potable reuse [23]. The initial capacity was 4300 m3/day; after a number of upgrades this became 7500 m3/day. The effluent used for reclamation originates from domestic and business wastewater; industrial effluents are treated in a separate plant. Treatment occurred by coagulation/flocculation with FeCl3, dissolved air flotation, rapid sand filtration, adsorption on granular activated carbon, chlorination, and pH correction.

In 2002, a new plant was started, with a capacity of 21,000 m3/day. This plant was based on thirty years of experience, but the previously applied scheme was extended with ozonation and ultrafiltration Fig. 7). The policy is to blend the wastewater with other water sources, so that the final drinking water has a maximum of 35% reclaimed water. Monitoring of the quality ofraw water, intermediate water, and drinking water is obviously of extreme importance; communication and public perception is another main point of attention [23]. Safety measures can be taken, ranging from diversion of raw water to addition of powdered activated carbon.

The Goreangab Water Reclamation Plant was (and still is) a pioneer in water recycling. Elsewhere in Africa, water recycling is not at all developed, with a few exceptions: Zambia and South Africa reused up to 16% of their wastewater in the late 1980s [12], and this was even up to 75% in Tunisia's capital Tunis. Bixio et al. [10] identified a total of 20 recycling sites in sub-Saharan Africa, which is a remarkably low number.

In Latin America, the overall picture is similar to Africa. The number of sites identified by Bixio et al. [10] is 50, and this low number says all. According to the Pan-American Health Organization, less than 14% of the wastewater in Latin America receives any sort of treatment before discharge to rivers or the sea. The situation is roughly the same in all Latin American countries, with dramatic numbers such as 1% sewage treatment in Suriname, 5% in Venezuela, and 13% in Mexico [12]. It is understood that in these circumstances, water reuse is not feasible, at least not in the sense that recycled water should be a safe and reliable water source.

Raw water inlet -

Raw water inlet -

Reverse Recycling

Drinking water out

Figure 7 Water reclamation scheme used in the Goreangab Water Reclamation Plant, Windhoek, Namibia.

Drinking water out

Figure 7 Water reclamation scheme used in the Goreangab Water Reclamation Plant, Windhoek, Namibia.

Irrigation with raw wastewater, however, is common practice; more than 500,000 ha of agricultural land in Latin America is irrigated with untreated wastewater.

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