Effect of Organic Loading Rate on Anaerobic Digestion Performance of Mesophilic (UASB) Reactor Using Cattle Slaughterhouse Wastewater as Substrate

Abstract

In this study, the performance of a laboratory scale upflow anaerobic sludge blanket (UASB) reactor operating at mesophilic temperature (35 °C) was examined. Cattle slaughterhouse wastewater (CSWW) was used as the main substrate. The total and effective volumes of the reactor were 8 L and 6 L, respectively. Twelve different organic loading rates (OLR) were applied and the performance was evaluated. The chemical oxygen demand (COD) removal efficiency was more than 90% during batch study. In the continuous study, COD removal was also approximately 90% at OLR 0.4 g/L d−1 which subsequently dropped to below 50% when the loading rate increased to 15 g/L d−1. Approximately 5 L/d of biogas was obtained with high methane concentration at stages VI and XI corresponding to OLR of 2 and 10 g/L d−1, respectively. It was observed that the concentration of volatile fatty acids was low and that the alkalinity of the wastewater was sufficient to avoid acidification. Specific methane yields of 0.36 and 0.38 LCH4/g COD added were achieved at OLR 7 and 10 g/L d−1. A hydraulic retention time (HRT) of 1 day was sufficient to remove greater than 70% of COD which correspond to 89% methane concentration. Parameters like soluble COD, NH3-N, pH, alkalinity, total suspended solid (TSS), fats, oil, and grease were also investigated. The results show that the UASB reactor could serve as a good alternative for anaerobic treatment of CSWW and methane production.

Chemically Stressed Bacterial Communities in Anaerobic Digesters Exhibit Resilience and Ecological Flexibility

“…Compared with the acidosis events in the aforementioned works from Goux et al (2015) and Musa et al (2018), it appears that the OLR in the present study (max. 2.72 gVS L −1 d −1 ) was still too small to cause acidosis.…”

“…In an experiment by Goux et al (2015), where the OLR was gradually increased, acidosis took place approximately at 4 gVS L −1 d −1 . In a recent study by Musa et al (2018), an UASB reactor showed an even higher stability compared with that of Goux et al (2015), as the OLR was increased until 15 gCOD L −1 d −1 before acidosis took place. In the study presented here, the loading rate in the reactor receiving sodium phosphate was based on the works from Goux et al and Musa et al, and an OLR of 1.29 gVS L −1 d −1 , not close to a range that could cause acidosis.…”

A Comparative Study of Biogas Production from Cattle Slaughterhouse Wastewater Using Conventional and Modified Upflow Anaerobic Sludge Blanket (UASB) Reactors

“…It includes chemical coagulation, lagoon pond systems, sedimentation and filtration, adsorption, chlorination, and high rate oxidation ditches [14]. These methods produce high-quality effluent, however, the large area space requirement for plant installation, huge sludge production, high energy demand, offensive odor, lack of energy recovery, and the overall cost of operation and maintenance have been reported as the major drawback [19]. Due to pressure from environmentally aware consumers, various guidelines and water quality criteria have been set by both local and international committees.…”

Performance Comparison of Conventional and Modified Upflow Anaerobic Sludge Blanket (UASB) Reactors Treating High-Strength Cattle Slaughterhouse Wastewater

“…A functional anaerobic digestion system depends on the buffering capacity and the degree of adaptation of the microorganisms [19]. The high protein and lipid content of slaughterhouse wastewater makes it a challenging substrate for degradation by the microbial consortium.…”

“…Moreover, the condition at which the UASB reactor operates plays a vital role in the performance of the bioreactor. For instance, the study of Musa et al [19] on SWW treatment under mesophilic temperature (35 • C) revealed a COD removal efficiency of 70% at an organic loading rate of 10 g L −1 day −1 . Similarly, Mittal et al [20] reported a UASB reactor with an average COD removal efficiency of 80-85% and is very much efficient when operated at an organic loading rate (OLR) of 2.7-10.8 kg COD m −3 day −1 .…”