Wastewater discharge and water quality standards in Brazil--implications for the selection of wastewater treatment technologies.

The paper describes and comments the Brazilian standards for water quality and effluent discharge (CONAMA Directive No. 20, 1986). The emphasis of the paper is on the conventional parameters which characterise domestic wastewater (BOD, SS, NH4+, N, P and coliforms). The wastewater treatment systems for achieving compliance are analysed with two perspectives: requirements for the discharge standards and requirements for the receiving water standards. The main treatment technologies available are listed, together with their capability to remove the major pollutants included in the Brazilian legislation. The analysis for the receiving water standards are given for different dilution ratios (river/discharge flows): 1/10, 1/1, 10/1 and 100/1. The difficulty in complying with the receiving water standards for BOD, phosphate and coliforms is highlighted and the cost implications for the adoption of more sophisticated technologies in order to achieve compliance are also provided. Although the specific quantitative values cited in the paper are associated with the Brazilian legislation, it is believed that the major conceptual issues are applicable to a large number of urban areas in other countries.