Phương pháp tiếp cận để kiểm soát ô nhiễm nguồn nước ban đầu tập trung vào phương pháp tiếp cận phát thải cố định (xem Chương 3) và các tiêu chuẩn chất lượng nước và phương pháp tiếp cận mục tiêu. Nhấn mạnh được chuyển sang phương pháp tiếp cận tích hợp. | Approaches to water pollution control initially focused on the fixed emissions approach see Chapter 3 and the water quality criteria and objectives approach. Emphasis is now shifting to integrated approaches. The introduction of holistic concepts of water management including the ecosystem approach has led to the recognition that the use of water quality objectives the setting of emission limits on the basis of best available technology and the use of best available practices are integral instruments of prevention control and reduction of water pollution iCwE 1992 UNcEd 1992 UNECE 1993 . These approaches should be applied in an action-orientated way Enderlein 1995 . A further development in environmental management is the integrated approach to air soil food and water pollution control using multimedia assessments of human exposure pathways. Why water quality criteria and objectives Water quality criteria are developed by scientists and provide basic scientific information about the effects of water pollutants on a specific water use see Box . They also describe water quality requirements for protecting and maintaining an individual use. Water quality criteria are based on variables that characterise the quality of water and or the quality of the suspended particulate matter the bottom sediment and the biota. Many water quality criteria set a maximum level for the concentration of a substance in a particular medium . water sediment or biota which will not be harmful when the specific medium is used continuously for a single specific purpose. For some other water quality variables such as dissolved oxygen water quality criteria are set at the minimum acceptable concentration to ensure the maintenance of biological functions. Most industrial processes pose less demanding requirements on the quality of freshwater and therefore criteria are usually developed for raw water in relation to its use as a source of water for drinking-water supply agriculture and .
