Caracterização do esgoto bruto e avaliação da eficiência de redução de matéria orgânica e de bactérias entéricas, em diferentes processos de tratamento de esgotos domésticos, empregados na cidade de Salvador-Bahia.

Abstract

This research had the following objetíves: a) To characterize the afluent sewage from the city of Salvador, studing four differents local stations for waste treatment, so called: Trobogy, Muriçoca, Pituaçú and Cajazeiras X. b) To study how capable those different local station for waste treatment were for : reducing Organic Matéria (COD, BOD5) and enterical bactéria (Faecal Coliform and Faecal Streptococcus) in each of those differents kinds of treatment : I o Aered ponds, facultative in serie; T Oxidation ditch; 3o Imhoff Tank; 4o Facultative Stabilization pond. The affluent sewage in Salvador was caracterized as the media of each parameter in each of the local stations studied.We found: a) Temperature: 26,72°C; b) pH : 7,22; c) Ammonium: 49,52 mg N/l; d) Nitrite: 0,03 mg N/l; e) Nitrate: 0,12 mg N/l; f) Total phosphorus: 10,63 mg P/l; g) Soluble ortophosphato: 5,73 mg N/l; h) COD : 941,58 mg 0 2 / l ; i) BOD5 : 425,69 mg 0 2 li; j) Faecal coliforms (CF) 2,0*108 CF/100 ml ;1) S. faecalis (EF) 1,42*107 EF/100 ml; m) Total solid : 1081,83 mg/l; n) Total solid volatile : 559,15 mg/l; o) Total solid fixed : 522,38 mg/l. For the avaliation of the performance of each kind of waste treatment we studíed at the fínd effluent: Temperature, pH, COD, BOD5, Faecal Coliforms (CF) Faecal Streptococcus (EF). The organic matéria decreced, media expressed by COD and BOD5 in the four stations in the following range : COD 45,88% to 82,34%; BOD5 39,98% to 89,90%. The percentage of removal (media) for Faecal coliforms and Streptococcus faecalis in the four station was: Faecal coliforms from 89,81% to 99,40% and S. faecalis from 91,76% to 99,56%. The media for temperature and pH at the effluent of each station were: a) Aered pond, facultative, in serie; 26,59°C and p 6,88. b) Oxidation ditch: 25,92°C and pH 6,99. c) Imhoff Tank: 26,32°C and pH 6,99. d) Facultative stabilization ponds: 26,12°C and pH 7,38. Aered pond, facultative in serie was the sistem more efficient for removal of organic matéria and enteric bactéria than the other. For organic matéria aered pond, facultative, in serie showed COD and BOD5 of 82,34% and 89,80% with concentration media, at the and of 167,42 mg/l and 32,33 mg/l; and for Faecal coliforms and S. faecalis, shawed efficience of 99,92% and 99,56%, with a concentration media of bactéria at the final effluent of 1,55*105 EF/100 ml and 4,35*104 EF/100 ml.