WATER RECLAMATION IN SOUTH AFRICA: THE ANSWER FOR THE INCREASING WATER DEMAND IN THE GAUTENG REGION?

Transcription

1 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; Stefaan.Vandaele@aquafin.be ** 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 m 3 per year, which corresponds to less than m 3 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, m³/a of the effluent is reclaimed for irrigation applications and circa 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. Renewable water per capita 2000 [m³] Bangladesh Botswana France Belgium South Africa 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 m³/a which corresponds to less than m³ of water Egypt

2 per capita per year (Figure 1). South Africa will move into the water-scarcity category of less than m³ per capita per year by 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 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 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.

3 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 STP s in South Africa. These discharge approximately m 3 /a to the oceans, while m 3 /a is returned into inland rivers and dams (Grobicki, 1999). The estimated flow from major point sources therefore amounts to m 3 /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

4 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 DAM Moretele Pienaars River NYLSTROOM PROPOSED KLIPVOOR STP MORETELE 1 TEMBA STP LEEUKRAAL DAM Pienaars River ROOIWAL STP Kaalplaasspruit Apies River WALLMANNSTHAL WATER WORKS MATHANJANA ROSSLYN Skinnerspruit Apies River BON ACCORD DAM DASPOORT STP WONDERBOOM PROPOSED DOORNPOORT SINOVILLE PROPOSED NEW WW MONTANA WAVERLEY ZEEKOEGAT STP ROODEPLAAT DAM BAVIAANSPOORT 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. Direct reclamation could combine ao. a more efficient water and energy use. Since the technologies (e.g. membrane technology) of wastewater treatment and drinking water production are converging strongly, an integration of both plants could bring along optimisations as well from an investment as from an operational point of view. Besides, the plans exist to transfer water from the Pienaars river to the Apies river to create a better water balance. If water of Zeekoegat would be reclaimed for the production of potable water, this water would, after use, drain to the Rooiwal STP and thus to the Apies river. This

5 has the additional advantage that no concentration effects of undesirable components can occur. Case STP Sunderland Ridge In the South of Pretoria a large dolomite extension is present. To date more than 7,7 x 10 6 m³/a of water is extracted out of this dolomite layer. This water is the cheapest water source for Pretoria since it has a relative stable and good quality. At present the production capacity is limited in view of the fact that the stability of the dolomite becomes problematic if the ground water table decreases. The TSE of the STP of Sunderland Ridge could, as a means of storage, storage be injected after treatment in the underlying dolomite extension. Recharge of this dolomite extension to augment the production capacity should seriously be taken into account. Besides TSE, storm water could form a valuable source of water. However, since the dolomite formation may have subterranean canals of preferential flow and since the distance between the actual extraction wells and the STP of Sunderland Ridge is approximately 10 kilometres the recovery can be expected to be relatively low. Special attention has to be paid to the quality of the infiltrating water to prevent an irreversible contamination of the aquifer. On the other hand, if recharge of TSE is done in a controlled way, it can be considered as the safest and cheapest sustainable way of reclamation. The population growth in that region is at present not such that this project has to be implemented in short term. It is nevertheless recommended to start investigating this option to anticipate the growth of the demand in the near future. Case STP of Rooiwal The STP Rooiwal produces m³ TSE/a. It is the largest STP of the Pretorian area and treats about 37% of the total flow treated by the GPMC. Because of the scale effects it is well suited to reclamation the effluent. Agriculture: Roughly 10, m³/a or 25% of the effluent of the STP of Rooiwal is reclaimed for irrigation purposes. The treated and disinfected effluent is delivered to the surrounding fields. Till 1986 the STP used its TSE to irrigate a poplar plantation. The surrounding farmers used the remaining runoff. Since 1986 the TSE is distributed directly to the farmers via open distribution canals. At present no charge is asked for this water but negotiations have started to involve the farmers financially in the upgrading and the operation and maintenance of the system. Currently, no special quality control is effectuated to evaluate the presence and the effects of pathogens in the TSE. Although the reclaimed water does not have to comply with any specific legal standards, it is in general treated to the discharge quality standards and disinfected prior to use. Most of the crops irrigated consist of luzern for stock feeding but vegetables for human consumption are irrigated as well. Up to 12 different vegetables, amongst which lettuce, are cultivated in this area. Irrigation of lettuce with the non-disinfected effluent can form a threat for public health since this vegetable is eaten raw. Measures to secure the quality and control steps to assess and minimise all the risks are important. Industry: The GPMC uses about m³/d or m³/a of the TSE of Rooiwal as cooling water at their power station next to the STP. The location of the STP has specially been chosen nearby the power station for this purpose.

6 Urban applications: The neighbouring urban development of Rooiwal is equipped with a second reticulation system, used for irrigating the gardens, washing the car and other urban applications. Cross-connection inspections are advised right after the initial construction or re-construction with distribution system modifications, however, in general, no periodic cross-connection inspections have been carried out. There is an assumption that no cross-connection would occur in the dual reticulation systems, thus, no annual cross-connection inspections would be required after the initial inspection (Asano et al, 2000). Pretoria is an expanding city. Different new developments are planned. The GPMC should coordinate with the responsible planning department if new dual reticulations should be installed. A feasibility study of reclamation of TSE should be a prerequisite for approvals of new major developments. Since the cost of the investment in general lies with the developer and the benefit goes to the user and the community, the installation of a dual reticulation system has to be enforced via permits or adequate financial incentives. However, it should be stressed that the costs of a dual reticulation system are relative high and may not countervail against purification to drinking water quality. Moreover, safety aspects of urban applications have to be surveyed. A systematic quality control is extremely important. HACCP might be an adequate protocol to assess the risks and critical points. POLICY IN SOUTH AFRICA Integrated water resources management (IWRM) Undoubtly, raw water is recognised as a scarce commodity in the Gauteng area and has to be managed accordingly. Reclamation should be based on IWRM, with planning and management of water resources taking account of social, economic and environmental factors. IWRM depends on collaboration at all levels, based on a political commitment to the need for water security and the sustainable management of water resources. The local councils, as service provider, have to play a prominent role in the achievement of a good IWRM in this region. There are four general approaches that may be used to intervene, and all should be adopted to support IWRM at a catchment scale. The four approaches may be summarised as (Pegram, 1997): 1. Direct intervention: through water resource development. 2. Co-operative government: for land use planning & management (agriculture, rural & urban). 3. Influence: of other authorities and stakeholders for economic, social and spatial planning. 4. Control and enforcement: through regulations and licensing. Among these, levy policy and licensing will become some of the most important policy instruments of DWAF. A system of licensing has traditionally been applied to try to achieve the required balance between the different demands on the water environment. The riparian system of allocation, in which the right to use water is tied to the ownership of land along rivers, will effectively be abolished. Previous agreements and licences will be reviewed and adapted to the demands of sustainable development and should take reclamation into account. Water pricing

7 In South Africa, economic instruments are increasingly being applied to complement the licensing system. Water pricing to promote conservation is becoming an important consideration in the development of water policy and is of great consequence for the promotion of reclamation. The DWAF Head Office circular Minute C 20 comprises the charges for water supplied from government water works. These levies are charged to industrial users and producers of drinking water. Nevertheless, prices today do not cover the full cost of water services. For example, at this stage the charges for water used for irrigation tend to be very low (or none at all). Water services, irrigation water, municipal water supply, and wastewater treatment are heavily subsidised. Users do not value water, and so waste it. To be effective in promoting the efficient (re)use of water, taxation on raw water use has to be set at a rate which influences the extent of the abstraction and which reflects the real cost of this resource. In addition the use of rivers and other water resources to dispose of wastes will be made subject to a catchment management charge, which covers actual costs. Early in 1999, DWAF began a three-year project aimed at developing a Waste Discharge Charge System (WDCS). The system will provide a framework for charging people who dispose of their waste into water. This total approach of DWAF, called Cost Recovery Principle (CRP) wants to reflect the real value of water, and the need for efficient management of water resources (Gleick). The use of CRP will make reclamation of water also more necessary on a cost basis. Cost incentives for reclamation will thus be formally implemented within tariff structures (Grobicki, 2000). Catchment Management Agencies Since water does not recognise political boundaries, its management has to be carried out in catchment water management areas (CMA). These CMA s coincide either with natural river catchments, groups of catchments, sub-catchments or areas with linked supply systems with common socio-economic interests) (DWAF, 1997). Allocation of water and arbitration of claims among competing users should be done in CMA s instead of the narrow views of sector users or the artificial boundaries of administrative and political units. As set out in the National Water Act of 1998, the power of the CMA s has been mandated to a number of national, provincial and local government departments and authorities. As indicated in the Water Policy, effective catchment management requires that the agency "responsible for water resource protection must be able to influence or prevent land use planning decisions which could lead to unacceptable impacts on water resources, " as well as "control over other activities which can have serious impacts on water resources (Görgens et al. 1998). The move towards the establishment of CMA s should facilitate water reclamation. Since the CMA s are required to frame targets for water reclamation in their catchment area, the local service providers will need to negotiate with the relevant CMA, in order to determine volumes of discharge, as well as water abstraction. Water reclamation projects would then form part of such negotiations. POINTS OF ATTENTION Risks for Public health

8 The main problem with TSE reclamation is the threat to public health, if reclamation is not done carefully. To provide maximum protection against disease transfer, TSE reclamation guidelines are developed. These typically cover 4 areas for each application: chemical standards, microbiological standards, wastewater treatment processes and applications. The World Health Organisation (WHO) has developed in 1989 quality guidelines for the reclamation of TSE for irrigation. In 1995 the Developing human health-related chemical guidelines for reclaimed TSE and sewage sludge applications in Agriculture and the Effect of human viruses on public health associated with the use of TSE and sewage sludge in agriculture were added. In addition to identifying a combination of treatment and application restrictions, the WHO guidelines also outline safe waste application methods and control of human exposure. Currently, there are discussions regarding the applicable microbiological quality standards. While industrialised countries (led by California) and providers of technology usually promote a stringent water quality, developing countries call for studies to defend existing less stringent WHO quality guidelines. Pathogens are difficult to monitor, therefore, the WHO guidelines only prescribe a limit for faecal coliforms and intestinal nematodes. As a consequence, the whole argument revolves around the validity of such limits as a sufficient guarantee of safety. While there appears to be a wide agreement that the WHO guidelines are insufficient, there is so far no general consensus on the best approach to follow. The California approach on the contrary has as advantage is its safety first philosophy but it is the most expensive (2,5 times the WHO guidelines) and disregards established traditional practices and local socioeconomic conditions. As a result, there are a number of experts in favour of a Third Way, somewhere in between the California and the WHO approaches (Angelakis, 2000). This third approach is followed in the South African Water Quality Guidelines elaborated by the DWAF. Although 8 volumes of guidelines haven been established in function of the different applications most of them are only guidelines and are not enforced by law. Managing risk & liabilities About the legal issues, such as risk and liability, associated with reclamation is little known. Historically, adherence to water quality standards has been used to minimise health and safety risks to both users and producers of reclaimed water. Contractual agreements between the retailer and the user could be the primary means of limiting liability as they relate to quality and/or quantity of reclaimed water, public health issues, and personal injury and property damage claims. Water reclamation agencies have also used pilot studies to assess their risk and limit liability, particularly in instances of innovative reclaimed water uses (Metcalf & Eddy and Groupe Générale des Eaux, 1999). To date, the liability and risk associated with the production and use of reclaimed water has not manifested itself. Development of conservative water quality standards and the diligence of the reclamation agencies are the two primary reasons for this. Social aversion Public awareness and knowledge of the different aspects with regard to wastewater and reclamation are in general very limited, which may result in a negative attitude towards the different applications of reclamation. The major reasons for this are concern for public health, psychological aversion and religion. Experience in the USA and Flanders (Belgium) demonstrates that an early and open public awareness effort is effective in diminishing the

9 fears and suspicions frequently encountered when considering the use of reclaimed water (Vandaele, 2000). Compared to overall program costs, public outreach initiatives are inexpensive. They do however generate greater public acceptance, and usually overcome the instinctive aversion of the public towards reclaimed water. TSE reclamation should be promoted as a positive image of environmental protection resulting from the construction of sewerage and wastewater treatment infrastructure. Water reclamation can be viewed as new water resources located right on the doorstep of the urban areas. REFERENCES Angelakis A. N. and Asano I. (2000). Wastewater reclamation in Eureau countries: Necessity of Establishing EU-guidelines. Union of Municipal Enterprises for Water Supply and Sewerage, Larissa, Greece: Dept. of Civil Engineering, Univ. of Calif. Davis, CA 95616, USA Asano T., Ogoshi M., Suzuki Y. (2000). Lessons learned from the Japanese water reclamation experiences. Water Reuse Conference 30/01/2000 2/2/2000 San Antonio, Texas (USA) DWAF (1997a). Overview of water resources availability and utilisation in South Africa. DWAF report P RSA/00/0197 DWAF. (1997b). White Paper on Water Policy South Africa. Pretoria EEA/WHO. (1998). Water resources and human health in Europe. Environmental Issues Nov Gleick P.H. (2000). The changing water paradigm. A look at twenty-first water resources development. Water International. 25, 1, Görgens A., Pegram G., Uys M., Grobicki A, Loots L., Tanner A. & Bengu R. (1998). Guidelines for Catchment Management to Achieve Integrated Water Resources Management in South Africa. Water Research Commission, Pretoria. Report No. KV 108/ pp. Grobicki A. & Cohen B (1999). A flow balance approach to scenarios for water reclamation Water SA, October 1999, 25, 4, 473. Grobicki A. (2000). Water Reclamation in South Africa. Water Water Reuse Conference 30/01/2000 2/2/2000 San Antonio, Texas (USA) Metcalf & Eddy and Groupe Générale des Eaux (1999). Study of Nonpotable Water Reuse Practices for the Water Environment Research Foundation in US and internationally (Alexandria, VA, USA). Pegram G.C., Day S. & Howard L. (1997). Towards integrated catchment management: linking the needs of economic and social development with water resources management through spatial planning. 8th South African National Hydrology Symposium 17-19/11/1997 Sanlam Conference Centre, University of Pretoria, South Africa Vandaele S., Geenens D. & Thoeye C. (2000). Integrated management of water recourses in Flanders (Belgium): Re-use of biologically treated wastewater effluent. CIWEMconference: Standards & Technology to meet the challenges of the 21th century. April 2000.