با استفاده از سوبستره سنتتيك )uASB( و راكتور بستر لجن بي هوازي با جريان رو به بالا )HAIS( مقايسه ي عملكرد راكتور جريان افقي با بستر ثابت بي هوازي

PERFORMANCE COMPARISON OF HORIZONTAL-FLOW ANAEROBIC IMMOBILIZED SLUDGE (HAIS) AND UASB REACTORS USING A SYNTHETIC SUBSTRATE

Performance of fixed-bed and suspended-growth high-rate anaerobic reactors has been investigated in this study. Two 2-L and 3.3-L Horizontal-flow anaerobic immobilized sludge (HAIS) reactors were filled with polyurethane (PU) and polyethylene (PE) beds with surface to volume ratios of 1100 and 1250 m-1 density of 700 and 12 kgm-3 and bed porosities of 0.42 and 0.28,respectively. The 3.3-L upflow anaerobic sludge blanket (UASB) reactor was filled with granular sludge with a VSS concentration of 45 g/l and both sets of reactors were operated at 30±2°C. Synthetic glucose-based substrate was the main carbon source (COD of 1750 ± 250 mg/L) feeding both sets of reactors. The concept of quantitative CT number in terms of Hounsfield units (H),which is approximately linearly related to the mass density of the attenuating tissue and materials in objects in Computed Tomography Scanning (CT-Scan) technology, was used to characterize HAIS reactor contents including biofilm, media, and biogas. The results confirmed satifactory performance of HAIS in providing suitable environmental conditions for biomass growth and retention during the short startup period of 25 days. At the optimum period of operation, the loading rates of reactors were: organic loading rate (OLR) of 13±6g COD/L.d and F/M: 1.34±0.82g COD/g VSS.d in UASB;surface loading rate (SLR) of 28±12g COD /m2.d and F/M: 1.72±0.77g COD/g VSS.d for HAIS-PU; and SLR of 23±14g COD/m2.d and F/M of 1.52±0.99g COD/g VSS.d for HAIS-PE. For these loadings, the observed COD removal efficiencies and biogas productions were:64.3±15.2 % and 1771 ±704 mL/d for UASB; 63.5±17.5 % and 1160±400mL/d for HAIS-PU; and 61.6±18.6 % and 1018±645 mL/d for HAIS-PE. It was found that UASB operation with granular sludge and more efficient gas-liquid-separator (GLS) has a better performance than both HAIS reactors containing immobilized sludge and two gas collectors in different shapes: perforated tube (HAIS-PU) and sheet (HAIS-PE). Performance of HAIS-PU was better than PE possibly due to higher bed porosity (e) of HAIS-PU (f=0.42) compared to HAIS-PE (e=0.28). Channeling effects for low bed porosity reactors can be the main factor responsible for such performance.