Rediseño del sistema de tratamiento de aguas residuales para la tenería Núñez ubicada en la ciudad de Ambato

Abstract

The wastewater treatment system from the vegetable tanning stage at the Núñez tannery was redesigned to comply with current environmental regulations, so the wastewater was characterized, and it was determined that the following parameters were outside the permissible limits: oils and fats 72,333 mg/L, sulfides 16.6 mg/L, pH 4.307, total suspended solids 1047 mg/L, total solids 1,757 mg/L, COD 19,467 mg/L and BOD 1,833 mg/L. The type of treatment was defined on the basis of the value obtained from the biodegradability index, which was 0.042, and establishes that the treatment is physicochemical; therefore, it began with aeration of the wastewater for 3 hours, which helped to reduce sulfides, obtaining a removal percentage of 80.72%; the treatability was also carried out to precipitate the sludge, using 3 grams of lime P-24. The coagulation and flocculation were performed to the supernatant; 15 mL of aluminum sulfate (1 %) was used as coagulant at 100 rpm, while 2 mL of anionic polyelectrolyte (1 %) was used as flocculant at 30 revolutions for 15 minutes; it was left to settle for 3 hours and the effluent passed through a filter composed of sand, granulated activated carbon, fine and coarse gravel. The wastewater obtained in this last step underwent physicochemical and microbiological characterization and it was verified that all the parameters were within the permissible limits. The redesign consists of a manual cleaning grid system, an aeration tank, a cylindrical settling tank with a truncated cone bottom and a filter composed of sand, granulated activated carbon, fine gravel and coarse gravel.