Date

10-2009

Degree

Bachelor of Science in Chemical Engineering

College

College of Engineering and Agro-Industrial Technology (CEAT)

Adviser/Committee Chair

Monet Concepcion C. Maguyon

Co-adviser

Veronica P. Migo

Committee Member

Marilyn C. Del Bario, John Meynard Tengco

Abstract

The technical feasibility of sodium sulfite reduction coupled with alkali precipitation for the removal of chromium for a local chrome-tannery effluent was evaluated. Initially, the combined reduction-precipitation process was tried using a synthetic solution of pure hexavalent chromium. Independent effects of operating variables (reaction time, pH and sulfite dose) for chromium removal were explored. Results showed that 20 minute-reaction time was needed to attain maximum reduction efficiency. In addition, Cr(VI) reduction efficiency increases with sulfite dose but decreases with pH. Maximum Cr(VI) reduction efficiency (100% Cr(VI) reduction) was attained at pH 1.0 and 2 g/L, sulfite dose. For alkali precipitation, maximum residual total chromium (1.6 ppm) and minimum residual Cr(VI) (0.023 ppm) concentrations were attained at a pH range of 8 to 12. The treated synthetic solution completed with the DAO 35 limit of 0.1ppm for Cr(VI), however, the total chromium concentration was still above the 0.5ppm standard. Using actual chrome-tannery effluent, results of sulfite reduction experiments showed that a maximum of 50% Cr(VI) reduction efficiency was attained at pH 0.5 and sulfite dose of 15mg/L. alkali precipitation results showed that 100% removal of Cr(VI) (or 0ppm residual Cr(VI)) can be attained at pH 8 whether the actual chrome wastewater underwent sulfite reduction prior to alkali precipitation or not. Respective residual total chromium of 12ppm and 14ppm were attained for combined reduction-precipitation process and for alkali precipitation process only. The treated actual chrome wastewater complied with the DAO 35 limit of 0.1ppm for Cr(VI), however, the total chromium concentration was still above the 0.5ppm standard. The treatment cost per cubic meter of wastewater was estimated at Php 36.50 and Php 334.50 for sulfite reduction and alkali precipitation respectively.

Language

English

LC Subject

Chromium removal, Precipitation, Land treatment of wastewater

Call Number

LG 993.5 2009 E62 D46

Document Type

Thesis

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