Factors Affecting Anaerobic Stabilization During Biological Phosphorus Removal

Anaerobic stabilization (AnS) is denned as difference between actual and theoretical oxygen use in activated sludge systems with anaerobic selectors. AnSrelated oxygen savings translate into po tentially lower aeration power costs. A comprehensive electron balance approach was developed for more accurate determination of AnS, along with procedures forzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA in-situ oxygen uptake rate (OUR) measurement and analysis of dissolved gases by vacuum stripping.Labscale anaerobic/oxic (A/O) and anaerobic/anoxic/oxic (A2/ O) systems operated under various conditions yielded AnS values of 1555% of the theoretical oxygen requirement. Hydrogen and methane production together explained less than 1% of AnS, except when the A/ O feed was supplemented with formate, in which case methane pro duction explained about 19% of AnS. Stripping of reduced volatiles ex plained less than 1% of AnS in both systems. Kinetic limitations of the chemical oxygen demand (COD) test were not found to be significant in explaining AnS, but thermodynamic limitations were identified as potentially capable of explaining a significant fraction of AnS. Mecha nisms are hypothesized that can partially explain AnS based on the results of this study. Water Environ. Res., 66, 161 (1994).

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 93%

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Investigation of hypothesized anaerobic stabilization mechanisms in biological nutrient removal systems

Wable¹,

Randall²

1994

“…zyxwvutsrqponmlkjihgfedcbaZYXWV Study 2-laboratory-scale BPR system with nitrification/denitrification. Further investigation of the fate of COD in a BPR system was accomplished in a second set of experiments involving a six-reactor completely mixed laboratory-scale BPR system (Randall, 1987;Randall et al, 1985;. The primary purpose of the study was to establish whether oxygen requirements may be reduced by anaerobic stabilization in addition to the oxygen credit associated with denitrification, as postulated in the first study (Lan et al, 1983, and.…”

Section: Experimental Studiesmentioning

confidence: 99%

The case for anaerobic reduction of oxygen requirements in biological phosphorus removal systems

Randall¹,

Brannan²,

McClintock³

et al. 1992

zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Laboratory and pilot-plant scale studies were conducted to investigate the occurrence of anaerobic reduction of oxygen requirements in excess biological phosphorus removal (BPR) systems. The investigation was accomplished through application of chemical oxygen demand (COD)/oxygen-utilization mass balance techniques. Reductions of 0 to approximately 50% in the oxygen required for organic stabilization were achieved during treatment of synthetic and raw wastewaters. The reductions were attributed to stabilization occurring in the anaerobic reactors and represent a potential aeration energy savings that could be realized with BPR systems in addition to any savings associated with denitrification. Factors which influence the occurrence and magnitude of anaerobic stabilization include the composition of the influent wastewater, and the strength of the influent wastewater. It was concluded that substantial reduction of oxygen requirements can occur as a result of anaerobic stabilization and that the principal mechanism is probably metabolism by bacteria, such as fermenters, that do not accumulate phosphorus.zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Water Environ. Res., 64, 824 (1992).

“…Consequently, the slower decay of the poly-P bacteria will result in an additional organic sludge production, which was calculated by Wentzel et al (1990) to some 10% at a sludge age of 20 days. (3) Depending on the wastewater characteristics and the operating conditions (e.g., anaerobic hydraulic retention time), a so-called anaerobic stabilization (Randall et al. 1987) can occur that describes the substrate utilization under anaerobic conditions by means of fermentative processes.…”

mentioning

confidence: 99%

Waste activated sludge production of the enhanced biological phosphorus removal process

Jardin¹,

Pöpel²

1997

The effect of the enhanced biological phosphorus removal process (EBPR) on waste activated sludge (WAS) production and the type of phosphorus storage were investigated in two continuous‐flow activated‐sludge systems in a semitechnical scale. One of the plants was operated with the A/O® process, whereas the other plant was operated in a conventional, fully aerobic mode and served as a control. By monitoring the elementary composition of the activated‐sludge solids in plant II and by using phosphorus fractionations, it was found that nearly all of the enhanced phosphorus removal was due to storage as polyphosphate (poly‐P). The additional uptake of phosphorus resulted in an increase of the inorganic sludge mass, which was determined to be 3.05 g suspended solids (SS)/g P using the results of the measurements of the nonvolatile solid fraction. This value was confirmed experimentally by the measurement of the difference between the WAS production of plant I and plant II. Based on the specific WAS production, an additional dry solids production of 3.14 g SS/g P was calculated. No indications for a significant difference of the organic sludge production between both plants were found, although the organic WAS production was slightly higher in experimental periods with a relatively high phosphorus content of the activated‐sludge solids of plant II.