Aspectos sanitários e físico-químicos da autodepuração do rio Bodocongó (Paraíba).

Abstract

The catchment area of Bodocongo River comprises a total area of409 km2 located at Southeast Region of Paraiba State (34°45'54" - 38°45'45" W e 6°02'12" - 8°19'18" S), (34°45'54" - 38°45'45" W e 6o02'12" - 8°19'18B S), Northeast Brazil. The river head, at 691 m above sea level, is located in Pocinhos municipality. With a total length of 75 km the river crosses several municipalities in a north-south direction ending in the Paraiba River, at 350 m above sea level Bodocongo drains the West Region of Campina Grande city (300.000 inhabitants) when receives raw sewage. In the Southeast Region receives the Depuradora stream (responsible for the drainage of Campina Grande city's Central and East Region). Downstream receives 0.26 m3/s of find effluent of Campina Grande Sewage Treatment Plant. This volume represent two times the river flow during dry season (0.11 m3/s). The river water is used by agricultural activities for irrigation of several cultures (green vegetables, forage grass) and by the population for clothes and plate washing, bathing and animal use. This work aimed to study the sanitary and physical-chemical aspects of Bodocongo River contamination to evaluate its actual pollution level and their capacity of self depuration. The study used dissolved oxygen balance of Streeter and Phelps equation for a river segment (48 km) from the Sewage Treatment Plant to the river mouth at Paraiba River, during dry and wet season. Six sampling station were monthly monitored from october/96 to october/97. The results showed a good self depuration capacity related to dissolved oxygen and BOD concentrations. Despite the reduction of fecal bacteria the river water presented high concentration of fecal conforms being not suitable for recreation and for irrestricted irrigation (CONAMA Standard 20/86 and WHO 1989 < 1000 UFC/100 mL). Due to its multiple uses, river water would be recommended the elimination of all sewage discharges of raw sewage and to improve the Sewage Treatment Plant efficiency, since and increase of organic load would bring severe consequences to the body ecology. A dissolved oxygen simulation showed a good correlation among field data and those from Streeter e Phelps.