Start‐up and steady‐state results of a UASB reactor treating high pH baker's yeast molasses wastewater for methane production

Abstract

BACKGROUND The baker's yeast industry is a major market and due to the intensified production large quantities of waste are generated. Wastewater from the baker's yeast industry with high content of molasses was treated anaerobically in an upflow anaerobic sludge blanket (UASB) reactor for the production of methane (CH4). RESULTS The molasses wastewater obtained from industry had a high pH value around 8.0 ± 0.5, which remained constant during the experimental period. The system was operated at an organic loading rate (OLR) of 2.4–7.65 g of volatile solids per liter per day (g VS L−1 d−1) and the best results were observed at 4 g VS L−1 d−1, where methane production exceeded 350 L CH4 kg−1 VS. Anaerobic chemical oxygen demand removal was also examined and it was found that for the latter conditions of optimum OLR, it was more than 35%. VFA analysis revealed that acetic acid concentration in the reactor was more than 25 mmol L−1 even under optimum conditions. CONCLUSIONS The tested hydraulic retention time (HRT) values did not affect methane production, unlike the OLR. The increased acetic acid concentration in the UASB reactor and the high pH were credited to the inhibition of aceticlastic microorganisms. © 2016 Society of Chemical Industry

Performance study on enlarged‐clarifier hybrid upflow anaerobic sludge blanket reactor for treating the slaughterhouse wastewater

“…At lower HRT, methanogenic microorganisms do not have the time to complete digestion of high VFA concentration and thereafter to convert them into methane gas. But in the case of higher HRT, microorganisms were having sufficient time to digest high acetic acid concentration and to increase the methane percentage simultaneously (Mischopoulou et al , 2017). Therefore, it was evident that the initial operating conditions of the reactor also have a role in the performance of EC‐HUASB reactor.…”

The feedstock microbiome selectively steers process stability during the anaerobic digestion of waste activated sludge

“…Because of the rather low organic loading rate and limited biodegradability of the 388 WAS, the VFA accumulation potential was low, and residual VFA increase and pH decrease 389 remained limited in both cases. Therefore, based on the results of both disturbances, i.e., 390 glycerol and NaCl, it could be hypothesized that long-term inhibition in AD is not caused by 391 the cations themselves, which only temporarily inhibit methanogenesis, but rather by the 392 subsequent accumulation of VFA that permanently inhibit methanogenesis at higher organic 393 loading rates (Mischopoulou et al 2017;Zhang et al 2017a). The similarity of both treatments 394 demonstrates that the microorganisms in the feedstock apparently did not have an influence on 395 the inhibition caused by salts.…”

Feedstock thermal pretreatment selectively steers process stability during the anaerobic digestion of waste activated sludge

“…Because of the rather low organic loading rate and limited biodegradability of the WAS, the VFA accumulation potential was low, and residual VFA increase and pH decrease remained limited in both cases. Therefore, based on the results of both disturbances, i.e., glycerol and NaCl, it could be hypothesized that long-term inhibition in AD is not caused by the cations themselves, which only temporarily inhibit methanogenesis, but rather by the subsequent accumulation of VFA that permanently inhibit methanogenesis at higher organic loading rates (Mischopoulou et al 2017;Zhang et al 2017a). The similarity of both treatments proves that the microorganisms present in the feedstock and the increased soluble COD content due to the thermal pretreatment did not influence salts inhibition.…”