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Ecosystem Protection, Integrated Management and Infrastructure are Vital for Improving Water Quality in Africa Hongtao Wang,*,† Isaiah Bosire Omosa,†,‡ Arturo A. Keller,§ and Fengting Li†,* †
UNEP-TONGJI Institute of Environment for Sustainable Development, College of Environmental Sciences and Engineering, State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai, China 200092 ‡ Department of Civil Engineering, Kenyatta University, P.O Box 43844-00100 Nairobi, Kenya § Bren School of Environmental Science and Management, University of California, Santa Barbara, California, United States for coagulation, but to protect, restore, and rehabilitate the ecosystem in the upstream regions. Water quantity and quality are affected directly by waste streams and solids from industry, agriculture, and many other aspects. Therefore, a comprehensive and integrated management framework must be adopted to ensure effective water and wastewater treatment. For example, excessive algae are significantly threatening waterworks in Africa, due mainly to the increasing discharge of nutrients from agricultural runoff. In Kenya, oxidants and activated carbon adsorbents are being considered to control algae, but it is still too early to determine whether these approaches will be cost-effective and safe. In addition, pesticides in raw water are also a concern for many waterworks in Africa. One main source of pesticides is commercial agriculture. For example, millions of roses are exported from Kenya to Europe every year. Rose cultivation in greenhouses produces a large volume of runoff containing pesticides. To address the problems of algae and pesticides in Africa, we should rely on effective management of agricultural runoff instead of “advanced technologies” to remove pollutants ccess to safe water and sanitation is an important from water. component of the Millennium Development Goals In addition to agricultural runoff, management of industrial (MDGs). It was expected that 86% of the developing world effluent and hospital wastes is of great importance for water and 1 would have gained access to safe drinking water by 2015. wastewater treatment. With increasing economic activity, more Unfortunately, at present only 65% of Africans use improved and more factories in Africa discharge pollutants. Typical 2 drinking water sources. Rapid population growth and activities causing contamination include rubber plantations in urbanization make meeting water and wastewater treatment Liberia, mining in Zambia, oil production in Equatorial Guinea, goals more challenging. From 2005 to 2010, Africa’s population and logging in Gabon.2 However, most industrial wastewater is growth rate was 2.3%, the highest in the world; the growth rate discharged devoid of proper pretreatment, imposing a heavy of the African urban population was 3.4%.3 burden on the municipal wastewater treatment plants Increasing population and urbanization deteriorate the (WWTPs). Stabilization ponds are widely used in Africa surrounding ecosystems, which contribute to ecosystem (Figure 1). The influent concentration is high due to services such as clean water. While the goal is to provide insufficient pretreatment. For example, the influent COD and clean drinking water and wastewater treatment, it is also very BOD5 in the Dandora WWTP in Kenya is around 2030 mg/L important to consider ecosystem protection to conserve and and 1500 mg/L, respectively. Such concentrations are too high for the WWTPs, so the effluent cannot reach the discharge preserve water quality.4 One case in point is the treatment of standard. In addition, hospital sewage is a main source of higher drinking water in Nairobi, where the turbidity of raw water concentration to WWTPs. In most hospitals in Africa, there are varies widely from 3 NTU in the dry season to 5000 NTU in minimal or no on-site treatment and/or pretreatment facilities, the rainy season. This is a major challenge for coagulation and sewage from these hospitals enters directly WWTPs, rivers, treatment, because it is difficult to determine the dose of and lakes. Thus, the most important task at the present is not to coagulants that should be applied. While endless efforts have replace the stabilization ponds with secondary treatment been directed to optimizing coagulation, the fundamental systems, e.g. activated sludge (which is energy intensive), but solution is to protect the upstream ecosystem. High turbidity is due to soil erosion, ascribed to construction of dams and roads, Received: April 10, 2012 overcultivation, and fuel wood harvesting activities. Thus, the Accepted: April 11, 2012 Published: April 19, 2012 best solution for the waterworks is not to use more chemicals
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© 2012 American Chemical Society
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Figure 1. Stabilization pond for wastewater treatment in Nairobi, Kenya.
protect water quality. Energy supply, including electricity and biogas production, is an important part of the infrastructure for water and wastewater treatment. Efforts in these three areas will contribute to better water quality in Africa.
to require that industries and hospitals pretreat their wastewater ahead of discharge. The mismanagement of solid wastes is another threat to water quality. In many African countries, there are practically no collection systems for solid wastes. A huge amount of municipal, industrial, and hospital solid waste is dumped in wetlands, rivers, and lakes. Waste dumping is a common practice in Africa. In Kibera, the largest slum in Kenya, flyingtoilets (plastic bags used for defecation and thrown away outside door) are flushed into rivers along with other municipal solid waste when it rains. In addition, leachates from solid waste cause severe pollution to groundwater. Thus, strict regulation and management of solid wastes is necessary to protect water quality. Infrastructure is a bottleneck for water and wastewater treatment in Africa. Consider power supply, for instance. In 2010, during the 15th African Water Association (AfWA) International Congress and Exhibition at Kampala, Uganda’s President Yoweri Museveni said that one of his priorities is to get enough energy to exploit water resources. However, many treatment plants cannot operate properly due to insufficient power supply. In Nairobi, local experts are considering the possibility of harvesting energy from wastewater to run the mechanized treatment unit; even in Libya, where energy seems to be abundant, local experts are considering a desalination system with solar energy because of the unreliable power system. Furthermore, the lack of reliable energy and transportation systems affects the use of aerobic treatment of wastewater and the distribution of chemicals to treatment plants. In conclusion, ecosystem protection, integrated management and infrastructure are of vital importance for improving water quality in Africa. Ecosystem restoration and rehabilitation can reduce the consumption of chemicals and cost for water treatment. Management of agricultural runoff, industrial and hospital effluents, and solid wastes should be integrated to
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AUTHOR INFORMATION
Corresponding Author
*Phone: +86(0)21-65980567. E-mail:
[email protected] (F. L.);
[email protected] (H. W.). Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported in part by the China International Science and Technology Cooperation Fund No.2010DFA92800 and 2010DFA92820. We thank Dr. Chao Wang and Dr. Wei Zhang for their constructive comments and suggestions.
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REFERENCES
(1) Schnoor, J. L. The Most important promise ever made. Environ. Sci. Technol. 2010, 45 (1), 1−1. (2) UNEP. Africa Water Atlas; UNEP: Nairobi, 2010. (3) UNEP, Green Hills, Blue Cities: An Ecosystems Approach to Water Resources Management for African Cities. A Rapid Response Assessment; UNEP: Nairobi, 2011. (4) Cheng, H. F.; Hu, Y. A.; Hao, J. F. Meeting China’s water shortage crisis: Current practices and challenges. Environ. Sci. Technol. 2009, 43 (2), 240−244.
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