Two-phase, two-stage, and single-stage anaerobic process comparison

In this research, three anaerobic process configurations-namely, two-phase dual sludge (TPDS), two-stage single sludge (TSSS), and single-stage-were e valuated for effluent COD concentration. The same temperature, SRT, and glu cose substrate were used in all experiments. In every case, TPDS and TSSS c onfigurations significantly outperformed the single stage. All experiments were carried out at a temperature of 35 degreesC, end all reactors were ope rated as daily fill-and-draw with HRT = SRT. The following ranges for each design parameter were studied: pH (4.5, 5.5, and 6.5); first stage HRT (3, 8, and 24 h); and flee load (3, 9, and 27 gCOD/gVSS). The overall HRT/SRT o f all systems was 30 days, and a pH-Stat system was used to control the pH in the acidification reactors at the desired value. Statistical evaluation of the results indicated that a flee load of 3 in the first reactor of TPDS yielded the lowest effluent COD concentrations under the studied range of parameters, while fur the TSSS reactor configuration the staging of the sys tem itself was the controlling phenomena responsible for reduced effluent G OD.