Brazilian law and the state define the responsibilities for wastewater treatment, as well as the financing system of treatment. They also set standards of water quality where the treated effluent should be posted.

1988 Federal Constitution: Article 225. Everyone is entitled to an ecologically balanced environment and the common use and essential to a healthy quality of life, imposing upon the State and society the duty to defend and preserve it for present and future generations.
Law 10,406 of 2002 - Civil Code: Article 1291. The possessor of the property above can not pollute the waters essential to the first necessities of life for owners of buildings below and the others who pollute should recover, compensating the damages they suffer, if unable to recover or diverting the course artificial waters.
Decree 24643 of 1934 - Water Code
Law 9433/97, the Water Law of 1997
CONAMA 357/2005: Parameters for discharge of effluents into water bodies

Source: Pesquisa Nascente