Dissolved oxygen balance in polishing ponds treating UASB reactor effluent

ABSTRACT

Polishing ponds are post-treatment units for anaerobic effluents that act to remove residual organic matter as well as pathogens and nutrients. The intermittent operation of these lagoons favors the removal efficiency of these constituents. The oxygen balance was investigated in experimental polishing lagoons (0.4 m deep and 1.5 m² surface area), operated under sequential batch regime with HDT of 10 days, fed by UASB reactor effluent, without initial microalgae inoculation. The experimental system was installed in Campina Grande, Paraíba, and operated during the summer period (high levels of radiation and temperature). The results obtained showed that an aerobic environment was established in these lagoons, and the production of DO by the photosynthesis of microalgae is sufficient to meet the demand for DO consumption for oxidation of organic matter, respiration of microalgae, and atmospheric escape by desorption.

Keywords:
sequential batch polishing ponds; microalgae; oxygen production rate; oxygen consumption rate; atmospheric oxygen exchanges