Two-stage anaerobic digestion harnesses more energy from the co-digestion of end-of-life dairy products with agro-industrial waste compared to the single-stage process

Anaerobic digestion offers a good alternative for human waste treatment. However, the fate of enteric bacterial pathogens present in human night soil (HNS) remains a major concern for hygienic safety of the process. A two-stage anaerobic digestion process, consisting of separate acidogenic and methanogenic digesters, was designed and its efficacy in the inactivation of Salmonella typhi was compared to a single-stage digestion process. In a single-stage digestion, complete pathogen inactivation was achieved only in the digesters with high levels of volatile fatty acids (VFA ≅18,000 mg/l) and acidic pH (≅6.0). These digesters, however, showed drastic reduction in methane yield. In the two-stage digestion process, S. typhi was completely inactivated in the acidogenic digester and the methanogenic digester was free from the pathogen even after receiving a daily dose of the pathogen. The process also achieved complete inactivation of other enteric pathogens, viz., Shigella dysenteriae and Vibrio cholerae. The two-stage process was efficient in biogas generation from HNS. Thus, the two-stage process ensures complete hygienic safety in anaerobic digestion of human night soil.

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Characterization and anaerobic digestion of highly concentrated Mexican wine by-products and effluents

Water Science & Technology ◽

10.2166/wst.2020.102 ◽

2020 ◽

Vol 81 (1) ◽

pp. 190-198 ◽

Cited By ~ 1

Author(s):

M. Vital-Jacome ◽

M. Cazares-Granillo ◽

J. Carrillo-Reyes ◽

G. Buitron

Keyword(s):

Anaerobic Digestion ◽

Oxygen Demand ◽

Anaerobic Treatment ◽

Single Stage ◽

Organic Load ◽

Organic Loading Rate ◽

Two Stage ◽

Wine Production ◽

Stage Process ◽

By Products

Abstract Wine production has increased in recent years, especially in developing countries such as Mexico. This increase is followed by an increase of winery effluents that must be treated to avoid environmental risks. However, little information is available about the characteristics of these effluents and the possible treatments. This paper aimed to characterize the effluents and by-products generated by the Mexican winery industry and to evaluate the performance and stability of the anaerobic treatment using a single-stage and a two-stage process. Results showed that the winery effluents had a high content of biodegradable organic matter, with chemical oxygen demand (COD) values ranging from 221 to 436 g COD/L. The single-stage anaerobic process was able to treat an organic loading rate of 9.6 kg COD/(m3 d); however, it was unstable and highly dependent on the addition of bicarbonate alkalinity (0.31 g NaHCO3/g COD removed). The two-stage process was more stable working at a higher organic load (12.1 kg COD/(m3 d)) and was less dependent on the addition of bicarbonate (0.17 g NaHCO3/g COD removed). The results highlight the potential of the winery effluents to produce methane through anaerobic digestion in a two-stage process, making wine production more sustainable.

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Assessment of Single- vs. Two-Stage Process for the Anaerobic Digestion of Liquid Cow Manure and Cheese Whey

Energies ◽

10.3390/en14175423 ◽

2021 ◽

Vol 14 (17) ◽

pp. 5423

Author(s):

Margarita Andreas Dareioti ◽

Aikaterini Ioannis Vavouraki ◽

Konstantina Tsigkou ◽

Michael Kornaros

Keyword(s):

Anaerobic Digestion ◽

Production Rate ◽

Methane Production ◽

Cheese Whey ◽

Biogas Production ◽

Single Stage ◽

Cow Manure ◽

Two Stage ◽

Methane Production Rate ◽

Stage Process

The growing interest in processes that involve biomass conversion to renewable energy, such as anaerobic digestion, has stimulated research in this field in order to assess the optimum conditions for biogas production from abundant feedstocks, like agro-industrial wastes. Anaerobic digestion is an attractive process for the decomposition of organic wastes via a complex microbial consortium and subsequent conversion of metabolic intermediates to hydrogen and methane. The present study focused on the exploitation of liquid cow manure (LCM) and cheese whey (CW) as noneasily and easily biodegradable sources, respectively, using continuous stirred-tank reactors for biogas production, and a comparison was presented between single- and two-stage anaerobic digestion systems. No significant differences were found concerning LCM treatment, in a two-stage system compared to a single one, concluding that LCM can be treated by implementing a single-stage process, as a recalcitrant substrate, with the greatest methane production rate of 0.67 L CH4/(LR·d) at an HRT of 16 d. On the other hand, using the easily biodegradable CW as a monosubstrate, the two-stage process was considered a better treatment system compared to a single one. During the single-stage process, operational problems were observed due to the limited buffering capacity of CW. However, the two-stage anaerobic digestion of CW produced a stable methane production rate of 0.68 L CH4/(LR·d) or 13.7 L CH4/Lfeed, while the total COD was removed by 76%.

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Enhancement of Biogas Production by Using a Two-Stage Process for the Anaerobic Digestion of Cheese Whey

Linnaeus Eco-Tech ◽

10.15626/eco-tech.2010.013 ◽

2017 ◽

pp. 130 ◽

Cited By ~ 1

Author(s):

Margarita A. Dareioti ◽

Spyros N. Dokianakis ◽

Constantina Zafiri ◽

Michael Kornaros

Keyword(s):

Anaerobic Digestion ◽

Cheese Whey ◽

Biogas Production ◽

Organic Content ◽

Single Stage ◽

Total Carbon ◽

Municipal Sewage ◽

Two Stage ◽

Specific Product ◽

Stage Process

Cheese making companies have a specific product that is seasonally produced and, like most other agro-industries, generate wastewaters characterized by a high organic loading. Cheese whey is the most important waste stream produced having a high organic content (up to 70 g COD/L), which is highly biodegradable, and low alkalinity (50 meq/L). Cheese production industries worldwide generate more than 145 million tones of liquid whey per year. Because of these characteristics, cheese whey may cause serious environmental problems on the local municipal sewage treatment systems or water receptors if disposed untreated. Anaerobic digestion is a particularly attractive treatment solution for high strength wastewaters due to the operational economy and generation of biogas and therefore is considered as a promising solution for energy production from cheese whey, in this case. In this work, a comparative study between single and two-stage anaerobic treatment of cheese whey was conducted in order to enhance biogas production. Our experiments were carried out using one reactor for the single-stage process (operated at a HRT of 20 d), and two reactors connected in series, from which the first one was used for acidogenesis (operated at a HRT of 3 d) and the other for methanogenesis (operated at a HRT of 20 d). The single-stage process presented many operational problems, as a result of little or no buffering capacity of whey, which caused the pH of the anaerobic digester to drop drastically and the process being inhibited. This kind of inhibition proved to be irreversible and the digester was not able to recover even though it was operated batchwise and the value of the pH was restored to 7.0. On the contrary, the two-stage process exhibited a stable biogas production rate of 1.57 L/Lreactor/d with the composition of methane in the biogas reaching 54.3%. The dissolved COD and total carbon concentration removal was 70.5% and 77.2% respectively.

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