WATER RECLAMATION IN SOUTH AFRICA: THE ANSWER FOR THE INCREASING WATER DEMAND IN THE GAUTENG REGION? S. Vandaele*, C. Thoeye*, K. Snyman** * Aquafin NV, Dijkstraat 8, B-2640 Aartselaar, Belgium; [email protected] ** Water & Environment Department Pretoria, PO Box 1409, Pretoria 0001, South-Africa ABSTRACT South Africa, and especially the Gauteng area, is known as a water stressed region. The total available water resources in South Africa amount to 28 470 × 106 m3 per year, which corresponds to less than 1 700 m3 per capita per year. In this paper some case studies from Pretoria are presented. For example, at the Zeekoegat STP the use of a membrane bioreactor to produce a very high quality effluent that can be used for the production of drinking water is studied. At the STP of Sunderland Ridge recharge of the underlying dolomite layer can be an option. At the STP of Rooiwal about 10,2 × 106 m³/a of the effluent is reclaimed for irrigation applications and circa 2 000 m³/d of the effluent is used as cooling water in the nearby power station. Furthermore, the new policy of South Africa with regards to reclamation is discussed such as the role of Integrated water resources management, water pricing and Catchment Management Agencies in the implementation of reclamation. Some points of attention such as risks for public health, social aversion towards reclamation and managing risk and liability are discussed. KEYWORDS: Sources (of water), reclamation, re-use, water consumption, sustainable water management, water treatment. WATER, A PRECIOUS RESOURCE We often take water for granted; believing it is abundant and inexhaustible because it falls freely from the sky. Although water is a renewable resource, it is a finite one. Earth is the "blue planet", but 97% of the planet’s water is seawater, 2% is locked in icecaps and a large proportion of the remaining 1% lies too far underground to exploit. 10.000 8.000 6.000 4.000 2.000 0 Bangladesh Botswana France Belgium South Egypt Africa Renewable water per capita 2000 [m³] Figure 1. Renewable water resources per capita per year for different countries Especially in South Africa water is a scarce commodity. The total available water resources in South Africa amount to 28 470 × 106 m³/a which corresponds to less than 1 230 m³ of water per capita per year (Figure 1). South Africa will move into the water-scarcity category of less than 1 000 m³ per capita per year by 2025. The Food and Agriculture Organisation (FAO) of the United Nations (UN) regard water as a potentially serious constraint on socio-economic development and environmental protection at levels of internal renewable water availability of less than 2 000 m³ per capita per year. Particularly in drought years major problems may arise (DWAF, 1997a). South Africa has an average annual rainfall of 497 mm (compared to a world average of 860 mm), that is poorly distributed in time and space. There is a gradual change in climatic conditions from the sub-humid eastern regions to arid western coastal belt along the Atlantic Ocean (Figure 2). Besides, due to the high evaporation losses (1 100 mm/a in the east - 3 000 mm/a in the west) South Africa has a mean annual runoff to mean annual precipitation ratio of 8,6%, that is, only 8,6% of the rainfall is available as surface water. This is one of the lowest conversion ratios in the world. Figure 2. Variation in precipitation throughout South Africa Because of the spatial variability of water resources and the scarcity of water throughout the country, in many catchments the need for water exceeds the supply. The Gauteng Province, in particular, has to deal with a restricted availability of water resources since it is the only highly populated industrial centre in the world situated on a watershed. THE SEARCH FOR A SUSTAINABLE WATER PRODUCTION The figures mentioned above stress the importance of an integrated water resource management system to ensure a sustainable water production that supports not only economical expansion but also daily comfort and health of its population. In the past the Lesotho Highland Water scheme program - that has as objective the transfer of bulk water from wetter regions to dryer, but more highly populated centres - fulfilled a large part of the water demand of the Gauteng province. It seems although that this is rapidly becoming less feasible as the discrepancies between water requirements and availability in other water-scarce catchments increase. At the projected population growth and economic development rates, it is unlikely that the projected demand on water resources in South Africa will be sustainable. CLOSING THE WATER LOOP As the pressure on scarce water resources is growing, reclamation of water could lead to a sustainable use of the available resources and should be an integrated part of water management. In cities, almost 70% of all water used is treated in a sewage treatment plant (STP) and could be seen as a new constant resource of water. There are an estimated 1 400 STP’s in South Africa. These discharge approximately 321 × 106 m3/a to the oceans, while 715 × 106 m3/a is returned into inland rivers and dams (Grobicki, 1999). The estimated flow from major point sources therefore amounts to 1 036 × 106 m3/a. In the total Gauteng area, about 60% of the water extracted by Rand Water is returned to the Vaal and Crocodile rivers as treated sewage effluent (TSE). Until now, wastewater was always re-introduced in the hydrological cycle, disregarding whether it was treated or not. Without really taking notice, water has been reclaimed for years. During winter, almost all the water extracted out of the Rietvleidam, which is used as drinking water for the city of Pretoria, consists already of TSE coming from the STP of Kemptonpark. The closing of the cycle is seen as a “win-win” strategy, offering a solution to the increasing water demand, but also providing a sustainable and environmentally friendly solution. Reclaimed water, a ‘new’ water resource located right on the doorstep of the urban areas Nowadays the technology to treat water is such that any water quality required can be produced out of TSE. In most cases this can even take place at a very competitive price and reclamation of such amounts of TSE can play a significant role in water management. Faced with the need to expand some STP’s, and to provide a higher level of treatment for the expanded facilities, Pretoria wants to evaluate prudently a variety of effluent reclamation alternatives. The focus is on the treatment of TSE to acceptable quality so that it may be used safely for any purpose. Therefore a compilation of a technology matrix for the reclamation of effluent for the Pretoria Metropolitan area has been initiated. This matrix includes an overview of all possible applications of recycled water and their required quality standards on one hand and the most suited technology to obtain these quality standards on the other hand. For the different STP’s several applications for water reclamation have been identified. Amongst a wide variety of applications, this includes irrigation of crops and golf courts, industrial applications, recharge of groundwater and production of drinking water. Case STP Zeekoegat The Zeekoegat STP is located adjacent to the west of Roodeplaat Dam. The TSE flows into Roodeplaat Dam via a short earth canal that passes through the Roodeplaat Dam Nature Reserve. An important reason for the Zeekoegat STP being constructed in the Roodeplaat Dam catchment is that the Department of Waters and Forestry (DWAF) had specifically requested that the treated sewage effluent (TSE) from the Zeekoegat STP remains in the catchment due to expected increases in the water demand from this impoundment. Magalies Water uses the Roodeplaat dam as primary water resource for its drinking water production. Recently, the Greater Pretoria Metropolitan Council (GPMC: after the local election known as the Tshwane Metropolitan Municipality) has applied for a permit at DWAF to abstract water from Roodeplaat dam for drinking water production in a new purification plant for a total capacity of 60 MLD, which is still to be built. Because the high indirect reclamation activities it was specified that the STP outflow would have to meet the Special Standard for phosphate, as promulgated in the Water Act (Act 54 of 1956). The TSE is therefore of very high quality and exceeds the quality of Roodeplaat Dam. The actual STP of Zeekoegat can possibly treat about 60 MLD. The implementation of a membrane bioreactor to produce a very high quality effluent that can be used for the production of drinking water is studied. Indirect reclamation of the treated sewage effluent of the STP of Zeekoegat is thus the currently followed strategy. Indirect reclamation, as it was applied here, has some strong disadvantages e.g. · Eutrophication and algae bloom in Roodeplaat Dam causing extra treatment costs, · Cost implications due to double treatment (double sand filtration, disinfection), · Increase of salt content due to double disinfection, · Extra energy consumption (extra pumping, double installations), · Extra O&M and personnel costs, · Extra costs due to charges on pumping of water out of Roodeplaat Dam · In the future charges will be imposed on the discharged water if it does not meet the required quality standard. KLIPVOOR Moretele NYLSTROOM DAM Pienaars River PROPOSED KLIPVOOR STP MORETELE 1 TEMBA STP River LEEUKRAAL DAM Pienaars MATHANJANA ROOIWAL STP WALLMANNSTHAL WATER WORKS Apies River Kaalplaasspruit ROSSLYN PROPOSED NEW WW BON ACCORD PROPOSED DAM DOORNPOORT RESERVOIR ROODEPLAAT DAM ZEEKOEGAT STP BAVIAANSPOORT STP MONTANA Apies River RESERVOIR WONDERBOOM SINOVILLE RESERVOIR RESERVOIR WAVERLEY Skinnerspruit RESERVOIR DASPOORT STP From Bigen Africa Figure 3: Overview of the municipal drinking water and sanitation infrastructure in Pretoria Direct reclamation of the TSE could engender a list of advantages.