Reduction of Odor Emission by Alkaline Treatment for Stabilization of Undigested Sludge from Wasterwater in Arequipa - Peru

Authors

Valverde Ortiz, José Luis

Guzmán Monje, José

Gutiérrez Calderón, Gretel

Aliaga Sánchez, Holman

Chávez Velando Rodriguez, Piero

Estay Ahumada, Aliro

Gutiérrez Calderón, Gretel

Abstract

Odor emissions in wastewater treatment facilities are one of the most relevant issues to address in order to protect the image and acceptance of the plant in areas that may cause annoyance to passers-by or nearby neighborhoods. The waste from the treatment process consists of sludge, which is generally treated in the plant through stabilization procedures with anaerobic, aerobic, thermal drying or other systems. In the event that the sludge is not digested (stabilized), the emanation of odors from the sludge can become extremely high and aggressive for the receivers and workers of the Plant. In the present study, the solution for the undigested sludge is proposed, which is transported to an external facility to the wastewater treatment plant for drying in the sun and after reaching 40% humidity, they are disposed in a storage cell (monofill) as a final disposal. The undigested sludge, generated at the Wastewater Treatment Plant in Arequipa, Peru, is transferred with a humidity of 80 to 82% to a solar drying platform where, with continuous turning procedures, the desired dryness condition is achieved in an average time of 30 days. Being an undigested sludge, in its drying process, it eventually generated gas emissions with annoying odors for workers and drivers of vehicles that travel along the road surrounding the area. To determine odor levels, both at emission points and at receptors in areas surrounding the facility, a dynamic olfactometry tasks have been carried out using the European standard UNE-EN 13725 for protocols for measuring and modeling the dispersion of odors, this information was contrasted to determine the intensity of odors under the scale of the VDI 3882 standard. The present study proposed an alkaline treatment of sludge with the addition of quicklime (CaO) useful at 85% for the stabilization of undigested sludge and the consequent decrease in odor generation. Pulverized lime dosing tests were carried out in the laboratory and the appropriate dose was determined to control odors. Large-scale pilot tests were carried out on the drying platform, controlling at all times that the pH levels in the treated sludge are maintained for above 12 up to 72 hours, to inhibit the emission of gases resulting from microbial activity. The dosage of lime at the beginning of the drying process gave the expected result, generating a stabilization of the sludge and reducing the period of solar drying, which drastically reduced the emission of odoriferous gases. The odor control objective was endorsed by the reduction in odor perception from level 5 (very strong) to level 2 (weak), inside and outside the facility. The gas microsensors recorded a considerable difference between the concentration of gases in the sludge treatment platform, the monofill and the surrounding areas, the latter being much smaller and less perceptible to internal and external users of the plant