☆ 4.8 Article

Aerobic and two-stage anaerobic-aerobic sludge digestion with pure oxygen and air aeration

BIORESOURCE TECHNOLOGY (2008)

Journal

BIORESOURCE TECHNOLOGY

Volume 99, Issue 1, Pages 100-109

Publisher

ELSEVIER SCI LTD

DOI: 10.1016/j.biortech.2006.11.054

Keywords

aerobic digestion; anaerobic digestion; pure oxygen digestion; nitrification; ammonium nitrogen removal

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Abstract

The degradation using either air or pure oxygen at different temperatures. Sludge treated with pure oxygen was degraded at temperatures from 22 degrees C to 50 degrees C while samples treated with air were degraded between 32 degrees C and 65 degrees C. Using air, sludge is efficiently degraded at 37 degrees C and at 50-55 degrees C. With oxygen, sludge was most effectively degraded at 38 degrees C or at 25-30 degrees C. Two-stage anaerobic-aerobic processes were studied. The first anaerobic stage was always operated for 5 days HRT, and the second stage involved aeration with pure oxygen and an HRT between 5 and 10 days. Under these conditions, there is 53.5% VSS removal and 55.4% COD degradation at 15 days HRT - 5 days anaerobic, 10 days aerobic. Sludge digested with pure oxygen at 25 degrees C in a batch reactor converted 48% of sludge total Kjeldahl nitrogen to nitrate. Addition of an aerobic stage with pure oxygen aeration to the anaerobic digestion enhances ammonium nitrogen removal. In a two-stage anaerobic-aerobic sludge digestion process within 8 days HRT of the aerobic stage, the removal of ammonium nitrogen was 85%. (C) 2006 Elsevier Ltd. All rights reserved.

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Anoxic-Aerobic-Anoxic sequencing batch reactor for enhanced nitrogen removal

Susan N. James, Arya Vijayanandan

Summary: An anoxic-aerobic-anoxic process was established in a sequencing batch reactor to simultaneously remove organic carbon and nitrogen from wastewater. The study found that the optimum conditions for the process were achieved with a dissolved oxygen level of 1.5 mg/L and 1 hour pre-anoxic and post-anoxic periods. Under these conditions, the removal efficiencies of TOC, NH4+-N, and TN were 98.76%, 98.52%, and 88.23% respectively. Breakpoints in the pH, DO, and ORP curves provided insights into the biochemical reactions occurring in the reactor. Inhibition studies revealed that nitrogen removal pathways such as heterotrophic nitrification or direct conversion contributed to the removal of 27.69% of NH4+-N, while aerobic denitrification accounted for the removal of 20.55% of TN. Microbial community analysis confirmed the presence of heterotrophic nitrifiers and aerobic denitrifiers. The study emphasized the benefits of the varied redox conditions provided by limited aeration for nitrogen removal, leading to reduced energy usage and operating costs.

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