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

Mohammed Musa,Nik Daud,Che Hasfalina,Syazwani Idrus

doi:10.3390/ijerph15102220

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.

Highlights

The use of biodegradable waste materials to generate energy in the form of biogas has gained more popularity due to climate change [1,2]
The chemical oxygen demand (COD) and biological oxygen demand (BOD) are normally found to be tens of thousands mg/L [4]. This range varies from 18,000 mg/L to 43,000 mg/L [5], but the strength differs from one industry to another depending on the number of animals slaughtered
They were immediately transported to a public health laboratory situated at the Faculty of Engineering, Universiti Putra Malaysia

Summary

Introduction

The use of biodegradable waste materials to generate energy in the form of biogas has gained more popularity due to climate change [1,2]. Cattle slaughterhouses are among the many food industries that consume a considerable amount of freshwater and generate large volumes of wastewater rich in organic contaminants and nutrients [3]. The water produced during and after the operation is considered as high-strength wastewater, because of the presence of protein, fats, oil, and grease (FOG) with a high tendency for rapid acidification. The chemical oxygen demand (COD) and biological oxygen demand (BOD) are normally found to be tens of thousands mg/L [4]. This range varies from 18,000 mg/L to 43,000 mg/L [5], but the strength differs from one industry to another depending on the number of animals slaughtered.

Objectives

Methods

Results