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Effect of Biological Pretreatment on Anaerobic Sewage Sludge Digestion: Using Growth Media for Methanogenic Bacteria and Kinetic Studies for Biogas Yield

Lihi Khadija, Auajjar Nabila, Hamdi Inass, Echchayeb Kaouatar, Attarassi Benaissa

Journal of Ecological Engineering

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2023

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Vol. 24, nr 12

178--186

EN

The valorization of sewage sludge, a by-product of wastewater treatment by anaerobic digestion (AD), is getting more attention as a result of the advantages it provides for the environment and economy. The current investigation is an experiment performed in a lab setting using a batch-operated anaerobic digestion reactor with a mesophilic temperature of 35°C. This study examined the generation of experimental biogas and biodegradability .The effect of pretreatment by methanogenic bacteria growth medium on anaerobic digestion of sewage sludge was studied on three different concentrations of growth media, a control, and a low, medium and high concentration of culture medium, with cumulative biogas production of 610N ml /gVS added, 750 N ml /gVS added, 900 N ml /gVS added, 10 N ml /gVS added, respectively, with biodegradability rate of 52.16%, 56.5%, 74.04%, 28.70% respectively. Biogas production was enhanced at a medium concentration of culture medium and inhibited at a high concentration during anaerobic digestion of sewage sludge. Additionally, a theoretical biogas estimate was evaluated using four kinetic models (Logistic function, Modified Gompertz, Transference function, and First order); which were utilized to match the experimental biogas generation process involving the anaerobic digestion of untreated and pretreated sewage sludge by various concentrations of growth media of methanogenic bacteria . The kinetic findings demonstrated that both models, Modified Gompertz and Logistic function, were useful for predicting biogas output and matched experimental biogas production.

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Survival of Bacterial Pathogen Isolated from Urine in Surface Water in Sebou River Estuary (Morocco)

Ech-Chayeb Kaouatar, Auajjar Nabila, Lihi Khadija, Attarassi Benaissa

Ecological Engineering & Environmental Technology

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2023

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Vol. 24, iss. 3

71--78

EN

Hospital effluents are one of the main sources of contamination of groundwater and rivers if they are collected by urban networks and sent to wastewater treatment plants (WWTP), without prior treatment. These effluents are potential vectors of resistant pathogenic bacteria and could contribute to the spread of these strains in the environment. The Sebou River is used as a receptacle for domestic water treatment from the city of Kenitra. The main of the study is to analyze the effect of pH (8.2, 7.5, and 6.5) at a temperature of 22°C on the behavior of three pathogenic bacteria isolated from urine in filtered and sterilized water Sebou River. The water of Sebou River was inoculated with the three bacterial strains tested by a concentration that varied from 106–108 CFU/mL, then incubated for 30 days. The results of the obtained analyses showed that the pH affects the survival of the tested bacterial strains. For some strains, the alkaline pH at 22°C is a beneficial effect that prolongs survival. The main finding from the study was that the three strains of Escherichia coli at a pH of 8.2 have a better survival that reaches the 7th day and then declines. On the other hand, with a strain of Klebsiella pneumoni and Staphylococcus aureus at pH 7.5, the action effects are harmful; it limits survival to 72 hours and causes a rapid decrease in the number of bacteria. We have shown in our experiments that bacteria survive much better at low temperatures and basic pH.

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Kinetic Modeling of Methane Production from the Anaerobic Digestion of Wastewater Sludge from a Treatment Plant in Kenitra, Morocco

Lihi Khadija, Auajjar Nabila, Nizar Youness, Attarassi Benaissa

Ecological Engineering & Environmental Technology

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2023

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Vol. 24, iss. 1

165--174

EN

It is necessary to understand the process of anaerobic digestion (AD) of sewage sludge and to find an adequate strategy to improve the efficiency of methane production. In this work, the production of methane and detailed properties of sludge are determined. The physico-chemical parameters of the digester 1 'D1' and the digester 2 'D2' remain in the optimal range of AD stability with a median value of pH (7.82; 7.93); Temperature (36.70; 37.10°C); alkalinity (3.52; 3.58 g/L); and volatile fatty acids (0.47; 0.52 g/L), respectively. This paper focuses on the performance optimization of the methane production by kinetic models of two continuous digesters in a wastewater treatment plant in Kenitra City, Morocco. Mathematical models used in anaerobic digestion are: Modified Gompertz, transference functions, and logistics functions. These kinetic models have benefitted experimental methane production for both digesters. Results show that all the models used are appropriate to optimize the kinetic parameters for producing methane, showing that the transference function is the most suitable model for predicting kinetic results.

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Comparative Evaluation of Biogas Yield and Physicochemical Properties of Three-Phase and Traditional Olive Oil Mill Wastes – The Most Suitable Choice for Efficient Anaerobic Digestion

Hamdi Inass, El Asri Ouahid, Lihi Khadija, Hamdaoui Hajar, Auajjar Nabila, Chafi Abdelhafid, Attarassi Benaissa

Ecological Engineering & Environmental Technology

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2023

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Vol. 24, iss. 5

76--83

EN

Olive oil mill waste is characterized by its high organic matter content, especially fatty acids, polyphenols, sugars, and proteins. These nutrients can be used as a source of energy for biogas production. However, olive oil mill waste can also contain heavy metals such as lead, cadmium, copper, and zinc that can be absorbed by plants. In addition, very high concentrations of heavy metals can also inhibit the anaerobic digestion process by affecting the methanogenic bacteria involved in biogas production The aim of this research is to determine the composition of solid and liquid rejections from traditional and continuous three-phase crushing systems, by analyzing samples from different oil mills in the eastern region of Morocco. We also applied the technology of anaerobic digestion of solid and liquid waste forms of oil mills, to make a link between the biogas yield and the physicochemical characteristics of these wastes. The results suggest that traditional oil mill wastewater (Discontinuous OMWW) has high organic matter, nutrients, and heavy metals content and a low concentration of phenolic compounds, which can increase its biogas production potential with a production of 10.02 Nml/g VS, while three-phase wastewater (Continuous OMWW) has limited biogas production potential (3.83 Nml/g VS) due to the low organic matter and nutrients content, and high concentration of phenolic compounds. Three-phase olive pomace (Continuous OMSW) has a higher biogas production (9.28 Nml/ g VS) than traditional olive pomace (Discontinuous OMSW) with 5.91 Nml/g VS. In fact, the lower content of phenolic compounds and volatile fatty acids favors their anaerobic digestion and improves their biogas production. In conclusion, the selection of the type of waste adapted for biogas production must be based on the physicochemical and microbiological characteristics of these wastes.