Enhancement of Anaerobic Digestion of Waste-Activated Sludge by Conductive Materials under High Volatile Fatty Acids-to-Alkalinity Ratios

Anaerobic digestion (AD) represents a suitable option for the management of the waste-activated sludge (WAS) produced in municipal wastewater treatment plants. Nevertheless, due to its complex characteristics, WAS is often barely degradable under conventional anaerobic processes. The use of conductive materials during AD provides a promising route for enhancing WAS digestion, through the effects of direct inter-species electron transfer (DIET). The present paper aims to evaluate the effects of the addition of four different materials—granular activated carbon (GAC), granular iron, and aluminium and steel scrap powders—in semi-continuous lab-scale reactors under very high volatile fatty acids-to-alkalinity ratios. In particular, the use of metallic aluminium in WAS digestion was investigated for the first time and compared to the other materials. The AD of WAS without the addition of conductive materials was impossible, while the use of steel powder and zero-valent iron is shown not to improve the digestion process in a satisfactory way. On the contrary, both GAC and Al allow for effective WAS degradation. At stable conditions, methane yields of about 230 NmLCH4/gVS and 212 NmLCH4/gVS are recorded for GAC- and Al-amended reactors, respectively. These two materials are the most promising in sustaining WAS AD through DIET also in case of unbalanced volatile fatty acids-to-alkalinity ratios.

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Performance and Microbial Community Dynamics in Anaerobic Digestion of Waste Activated Sludge: Impact of Immigration

Energies ◽

10.3390/en12030573 ◽

2019 ◽

Vol 12 (3) ◽

pp. 573 ◽

Cited By ~ 10

Author(s):

Juhee Shin ◽

Si-Kyung Cho ◽

Joonyeob Lee ◽

Kwanghyun Hwang ◽

Jae Chung ◽

...

Keyword(s):

Anaerobic Digestion ◽

Activated Sludge ◽

Growth Rates ◽

Municipal Wastewater ◽

Community Dynamics ◽

Oxygen Demand ◽

Waste Activated Sludge ◽

Municipal Wastewater Treatment ◽

Microbial Community Dynamics ◽

Ch4 Production

Waste activated sludge (WAS) is a byproduct of municipal wastewater treatment. WAS contains a large proportion of inactive microbes, so when it is used as a substrate for anaerobic digestion (AD), their presence can interfere with monitoring of active microbial populations. To investigate how influent cells affect the active and inactive microbial communities during digestion of WAS, we operated model mesophilic bioreactors with conventional conditions. Under six different hydraulic retention times (HRTs; 25, 23, 20, 17, 14, and 11.5 d), the chemical oxygen demand (COD) removal and CH4 production of the AD were within a typical range for mesophilic sludge digesters. In the main bacteria were proteobacteria, bacteroidetes, and firmicutes in both the WAS and the bioreactors, while in main archaeal methanogen group was Methanosarcinales in the WAS and methanomicrobiales in the bioreactors. Of the 106 genera identified, the estimated net growth rates were negative in 72 and positive in 34. The genera with negative growth included many aerobic taxa. The genera with positive growth rates included methanogens and syntrophs. In some taxa, the net growth rate could be positive or negative, depending on HRT, so their abundance was also affected by HRT. This study gives insights into the microbial dynamics of a conventional sludge anaerobic digester by distinguishing potentially active (growing) and inactive (non-growing, dormant) microbes and by correlating population dynamics with process parameters.

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Synergistic pretreatment of CaO and freezing/thawing to enhance volatile fatty acids recycling and dewaterability of waste activated sludge via anaerobic fermentation

Chemosphere ◽

10.1016/j.chemosphere.2021.130939 ◽

2021 ◽

pp. 130939

Author(s):

Yuecheng She ◽

Wenxuan Wei ◽

Xiaodong Xin ◽

Junming Hong ◽

Xiaohuan Ai

Keyword(s):

Fatty Acids ◽

Activated Sludge ◽

Volatile Fatty Acids ◽

Anaerobic Fermentation ◽

Waste Activated Sludge

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Polysorbate-80 Pretreatment Contributing to Volatile Fatty Acids Production Associated Microbial Interactions Via Acidogenic Fermentation of Waste Activated Sludge

SSRN Electronic Journal ◽

10.2139/ssrn.3947634 ◽

2021 ◽

Author(s):

Xiaohuan Ai ◽

Xiaodong Xin ◽

Wenxuan Wei ◽

JiaQian Xie ◽

Junming Hong

Keyword(s):

Fatty Acids ◽

Activated Sludge ◽

Volatile Fatty Acids ◽

Microbial Interactions ◽

Waste Activated Sludge ◽

Polysorbate 80 ◽

Acidogenic Fermentation

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Synergistic effects of iron and persulfate on the efficient production of volatile fatty acids from waste activated sludge: Understanding the roles of bioavailable substrates, microbial community & activities, and environmental factors

Biochemical Engineering Journal ◽

10.1016/j.bej.2018.10.010 ◽

2019 ◽

Vol 141 ◽

pp. 71-79 ◽

Cited By ~ 12

Author(s):

Jingyang Luo ◽

Lijuan Wu ◽

Qian Feng ◽

Fang Fang ◽

Jiashun Cao ◽

...

Keyword(s):

Fatty Acids ◽

Microbial Community ◽

Environmental Factors ◽

Activated Sludge ◽

Volatile Fatty Acids ◽

Synergistic Effects ◽

Waste Activated Sludge ◽

Efficient Production ◽

Community Activities

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Mesophilic and Thermophilic Digestion of Thickened Waste Activated Sludge: A Comparative Study

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.113-116.450 ◽

2010 ◽

Vol 113-116 ◽

pp. 450-458 ◽

Cited By ~ 2

Author(s):

Yong Zhi Chi ◽

Yu You Li ◽

Min Ji ◽

Hong Qiang ◽

Heng Wei Deng ◽

...

Keyword(s):

Anaerobic Digestion ◽

Activated Sludge ◽

Municipal Wastewater ◽

Treatment Plant ◽

Methane Content ◽

Waste Activated Sludge ◽

Digested Sludge ◽

Anaerobic Digestion Process ◽

Digestion Process ◽

Significant Difference

This paper presents an experimental study over 204 days on anaerobic degradation of thickened waste activated sludge (TWAS) from a municipal wastewater treatment plant (WWTP). The experiments were conducted under thermophilic (55°C) and mesophilic (35°C) condition, respectively, by using the semi-continuous flow completely mixed reactors. The influent total solids (TS), hydraulic retention time (HRT) and chemical oxygen demand (COD) loading levels were around 4%, 30 days and 1.67 kg-CODCr•m-3•d-1 , respectively. During the opration period, the thermophilic anaerobic digestion process (TADP) and the mesophilic anaerobic digestion process (MADP) were stable and well-functioned without ammonia inhibition. Particulate organic matters reduction of TADP was superior to that of MADP. This result implies that TADP has higher sludge reduction efficiency than MADP. According to the simulated chemical formula of TWAS, C5.85H9.75O3.96N, and the stoichiometric equation, the methane content and the ammonia yield in the anaerobic process could be calculated, which were consistent with the experimental results. The methane yield of TADP was a little higher than that of MADP. The statistical mean values of methane content for TADP and MADP were 60.97% and 62.38%, respectively.According to paired t-test, there was a significant difference in methane content between TADP and MADP(α=0.01, n=62). Compared with the mesophilic digested sludge, the dewaterability of thermophilic digested sludge was lower.

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Improved energy balance at a municipal Wastewater Treatment Plant through waste activated sludge low-temperature alkaline pretreatment

Journal of Environmental Chemical Engineering ◽

10.1016/j.jece.2021.106366 ◽

2021 ◽

pp. 106366

Author(s):

Magdalena Budych-Gorzna ◽

Lukasz Jaroszynski ◽

Piotr Oleskowicz-Popiel

Keyword(s):

Wastewater Treatment ◽

Energy Balance ◽

Low Temperature ◽

Activated Sludge ◽

Wastewater Treatment Plant ◽

Municipal Wastewater ◽

Treatment Plant ◽

Alkaline Pretreatment ◽

Waste Activated Sludge ◽

Municipal Wastewater Treatment

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Volatile Fatty Acids and Biomethane Recovery from Thickened Waste Activated Sludge: Hydrothermal Pretreatment’s Retention Time Impact

Processes ◽

10.3390/pr8121580 ◽

2020 ◽

Vol 8 (12) ◽

pp. 1580

Author(s):

Farokh laqa Kakar ◽

Ahmed El Sayed ◽

Neha Purohit ◽

Elsayed Elbeshbishy

Keyword(s):

Fatty Acids ◽

Activated Sludge ◽

Retention Time ◽

Volatile Fatty Acids ◽

Oxygen Demand ◽

Hydrothermal Pretreatment ◽

Waste Activated Sludge ◽

Optimum Conditions ◽

Pretreatment Temperature ◽

Biomethane Production

The main objective of this study was to evaluate the hydrothermal pretreatment’s retention time influence on the volatile fatty acids and biomethane production from thickened waste activated sludge under mesophilic conditions. Six different retention times of 10, 20, 30, 40, 50, and 60 min were investigated while the hydrothermal pretreatment temperature was kept at 170 °C. The results showed that the chemical oxygen demand (COD) solubilization increased by increasing the hydrothermal pretreatment retention time up to 30 min and stabilized afterwards. The highest COD solubilization of 48% was observed for the sample pretreated at 170 °C for 30 min. Similarly, the sample pretreated at 170 °C for 30 min demonstrated the highest volatile fatty acids yield of 14.5 g COD/Lsubstrate added and a methane yield of 225 mL CH4/g TCODadded compared to 4.3 g COD/Lsubstrate added and 163 mL CH4/g TCODadded for the raw sample, respectively. The outcome of this study revealed that the optimum conditions for solubilization are not necessarily associated with the best fermentation and/or digestion performance.

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