Effect of pretreatments and catalytic route in the quality and productivity of biodiesel obtained from secondary sludge

The treatment characteristics of municipal sludge were investigated by the anaerobic activated sludge digestion (AASD) system. This study used the suspended growth system and mesophilic temperature in the digestors and separators; the system achieves a more stable and improved process; such a process configuration offers the possibility of a substantial reduction in the total volume necessary for efficient stabilization. This study presents data indicating that the AASS system is feasible. In general, with an applied solids concentration of TS= 2%, the nonbiodegradable portion of the substrate concentration contained in the primary and secondary sludge was found to be 40.6% and 35.1% on the basis or TVS and COD, respectively. This study also provides evidence that the reactions at a recycling ratio of R=1 and R=3 are considerably more stable than those achieved in conventional or other recycling ratio digestors with a HRT of 9 days or longer. The gas production and bioactivity is also higher than that normally produced by the conventional single-stage digestion system. The experimental results also indicate that the dilution rate exceeds the maximum specific growth rate as the HRT is decreased from 9 days to 6 days. The significant saving in reactor volume and enhanced methane generation should offset the energy required for digested sludge recycling.

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The influence of fibres on the structure of thermally dried sludge product

Water Science & Technology ◽

10.2166/wst.1996.0465 ◽

1996 ◽

Vol 34 (3-4) ◽

pp. 469-473

Author(s):

Paul Lowe ◽

Michael Brown ◽

Kathleen Hudson

Keyword(s):

Bulk Density ◽

Fibre Content ◽

High Concentration ◽

Secondary Sludge ◽

Limited Experience ◽

Apparent Reason ◽

Drying Technology ◽

Dried Sludge ◽

Lower Bulk Density ◽

The Relationship

There appears to be a limited experience world-wide in the application of thermal drying technology to processing raw undigested sludge. This limited experience has shown that the products from raw sludge processing have a much lower bulk density than those from digested sludge. The apparent reason for this phenomenon demonstrated by this work, is the high concentration of fibres in the raw undigested sludge. Different sludges show varying degrees of fibre concentration with a decrease in fibre content as the proportion of secondary sludge increases. The relationship between the bulk density of the product and the fibre content are given and this shows that as the fibre content increases the bulk density of the product will fall. It is recommended that a compaction/pelletisation stage is included in the process stream for high fibre sludges.

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Microbiome of Seven Full-Scale Anaerobic Digestion Plants in South Korea: Effect of Feedstock and Operational Parameters

Energies ◽

10.3390/en14030665 ◽

2021 ◽

Vol 14 (3) ◽

pp. 665

Author(s):

Michal Sposob ◽

Hee-Sung Moon ◽

Dongjin Lee ◽

Yeo-Myeong Yun

Keyword(s):

Microbial Population ◽

Ammonium Nitrogen ◽

H2 Production ◽

Full Scale ◽

Organic Loading Rate ◽

Operational Parameters ◽

Sludge Digestion ◽

Secondary Sludge ◽

Potential Activity ◽

Total Ammonium

In this study, the microbiomes linked with the operational parameters in seven mesophilic full-scale AD plants mainly treating food waste (four plants) and sewage sludge (three plants) were analyzed. The results obtained indicated lower diversity and evenness of the microbial population in sludge digestion (SD) plants compared to food digestion (FD) plants. Candidatus Accumulibacter dominated (up to 42.1%) in SD plants due to microbial immigration from fed secondary sludge (up to 89%). Its potential activity in SD plants was correlated to H2 production, which was related to the dominance of hydrogenotrophic methanogens (Methanococcus). In FD plants, a balance between the hydrogenotrophic and methylotrophic pathways was found, while Flavobacterium and Levilinea played an important role during acidogenesis. Levilinea also expressed sensitivity to ammonia in FD plants. The substantial differences in hydraulic retention time (HRT), organic loading rate (OLR), and total ammonium nitrogen (TAN) among the studied FD plants did not influence the archaeal methane production pathway. In addition, the bacterial genera responsible for acetate production through syntrophy and homoacetogenesis (Smithella, Treponema) were present in all the plants studied.

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Anammox brings WWTP closer to energy autarky due to increased biogas production and reduced aeration energy for N-removal

Water Science & Technology ◽

10.2166/wst.2008.048 ◽

2008 ◽

Vol 57 (3) ◽

pp. 383-388 ◽

Cited By ~ 209

Author(s):

H. Siegrist ◽

D. Salzgeber ◽

J. Eugster ◽

A. Joss

Keyword(s):

Hydraulic Retention Time ◽

Biogas Production ◽

Sludge Treatment ◽

N Removal ◽

Secondary Sludge ◽

Organic Carbon Source ◽

Anammox Process ◽

Dry Weather Flow ◽

Heterotrophic Denitrification ◽

Bod Removal

Fifty years ago when only BOD was removed at municipal WWTPs primary clarifiers were designed with 2–3 hours hydraulic retention time (HRT). This changed with the introduction of nitrogen removal in activated sludge treatment that needed more BOD for denitrification. The HRT of primary clarification was reduced to less than one hour for dry weather flow with the consequence that secondary sludge had to be separately thickened and biogas production was reduced. Only recently the ammonia rich digester liquid (15–20% of the inlet ammonia load) could be treated with the very economic autotrophic nitritation/anammox process requiring half of the aeration energy and no organic carbon source compared to nitrification and heterotrophic denitrification. With the introduction of this new innovative digester liquid treatment the situation reverts, allowing us to increase HRT of the primary clarifier to improve biogas production and reduce aeration energy for BOD removal and nitrification at similar overall N-removal.

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Investigation of Some Qualitative Characteristics of Sludge Produced in Hamadan Wastewater Treatment Plant and Its Application in Agricultural Lands

Avicenna Journal of Environmental Health Engineering ◽

10.34172/ajehe.2019.01 ◽

2019 ◽

Vol 6 (1) ◽

pp. 1-7

Author(s):

Reza Shokoohi ◽

Samira Moradi ◽

Zhila Ghavami ◽

Azam Nadali ◽

Raheleh Amiri

Keyword(s):

Heavy Metals ◽

Wastewater Treatment ◽

Wastewater Treatment Plant ◽

Environmental Protection Agency ◽

Treatment Plant ◽

The United States ◽

Average Concentration ◽

Agricultural Lands ◽

Secondary Sludge ◽

Qualitative Characteristics

In this study, qualitative characteristics of the sludge produced in Hamadan wastewater treatment plant and the feasibility of its application in agricultural lands were investigated. Samples were taken from the primary and secondary sludge and indices such as VS/TS, PH, TKN, COD, TKN, SOUR, Na, Ca, SAR, heavy metals and biological properties (the mean fecal coliform count and the number of parasitic eggs) were measured. The results were compared with the United States Environmental Protection Agency (US EPA) standards (40 FCR-503). The results showed that the VS/TS ratio of the raw sludge was 0.8, 0.55, and 0.55 and that of the secondary sludge was 0.65, 0.28, and 0.32 for fall, winter, and summer, respectively. The average concentration of COD, TKN, SOUR, Na, and Ca for the initial sludge was 51283, 107, 0.50, 609, and 952 and for secondary sludge, it was 35595, 81, 4.90, 306, and 493 mg/L, respectively. The MPN for primary and secondary sludge was determined to be 19.83 × 106 and 186 × 106 , respectively and the average number of parasite eggs in primary and secondary sludge was 7.05 and 7.2 in 4 g of dry solids. Entamoeba coli had the highest number of parasite. The results of this study showed that the highest concentration of heavy metals in the sludge was 21396 mg/kg. The values obtained for the above-mentioned indices and heavy metals were in standards range. The results of this study show that none of the primary and secondary sludge samples has been properly stabilized. The values obtained for biological characteristics of sludge were not in the standard range. Therefore, it was revealed that the use of sludge for agriculture needed more stabilization.

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Beneficial effects of treating waste secondary sludge with thermally activated persulfate

Journal of Chemical Technology & Biotechnology ◽

10.1002/jctb.5108 ◽

2016 ◽

Vol 92 (6) ◽

pp. 1192-1202 ◽

Cited By ~ 13

Author(s):

Isil Akmehmet Balcioglu ◽

Nalan Bilgin Oncu ◽

Nazire Mercan

Keyword(s):

Beneficial Effects ◽

Thermally Activated ◽

Secondary Sludge ◽

Activated Persulfate

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Free ammonia pre-treatment of secondary sludge significantly increases anaerobic methane production

Water Research ◽

10.1016/j.watres.2017.04.015 ◽

2017 ◽

Vol 118 ◽

pp. 12-19 ◽

Cited By ~ 63

Author(s):

Wei Wei ◽

Xu Zhou ◽

Dongbo Wang ◽

Jing Sun ◽

Qilin Wang

Keyword(s):

Methane Production ◽

Free Ammonia ◽

Secondary Sludge ◽

Pre Treatment

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Evaluation of Feasibility of Using the Bacteriophage T4 Lysozyme to Improve the Hydrolysis and Biochemical Methane Potential of Secondary Sludge

Energies ◽

10.3390/en12193644 ◽

2019 ◽

Vol 12 (19) ◽

pp. 3644

Author(s):

Sangmin Kim ◽

Seung-Gyun Woo ◽

Joonyeob Lee ◽

Dae-Hee Lee ◽

Seokhwan Hwang

Keyword(s):

Cell Wall ◽

Bacterial Cell ◽

Wastewater Treatment Plants ◽

Biogas Production ◽

Bacteriophage T4 ◽

Suspended Solid ◽

T4 Lysozyme ◽

Biochemical Methane Potential ◽

Secondary Sludge ◽

Methane Potential

Anaerobic digestion (AD) of secondary sludge is a rate-limiting step due to the bacterial cell wall. In this study, experiments were performed to characterize secondary sludges from three wastewater treatment plants (WWTPs), and to investigate the feasibility of using bacteriophage lysozymes to speed up AD by accelerating the degradation of bacterial cell walls. Protein was the main organic material (67.7% of volatile solids in the sludge). The bacteriophage T4 lysozyme (T4L) was tested for hydrolysis and biochemical methane potential. Variations in the volatile suspended solid (VSS) concentration and biogas production were monitored. The VSS reduction efficiencies by hydrolysis using T4L for 72 h increased and ranged from 17.8% to 26.4%. Biogas production using T4L treated sludges increased and biogas production was increased by as much as 82.4%. Biogas production rate also increased, and the average reaction rate coefficient of first-order kinetics was 0.56 ± 0.02/d, which was up to 47.5% higher compared to the untreated samples at the maximum. Alphaproteobacteria, Betaproteobacteria, Flavobacteriia, Gammaproteobacteria, and Sphingobacteriia were major microbial classes in all sludges. The interpretation of the microbial community structure indicated that T4L treatment is likely to increase the rate of cell wall digestion.

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Genetically Encoded Biosensor-Based Screening for Directed Bacteriophage T4 Lysozyme Evolution

International Journal of Molecular Sciences ◽

10.3390/ijms21228668 ◽

2020 ◽

Vol 21 (22) ◽

pp. 8668

Author(s):

Seung-Gyun Woo ◽

Seong Keun Kim ◽

Baek-Rock Oh ◽

Seung-Goo Lee ◽

Dae-Hee Lee

Keyword(s):

High Throughput Screening ◽

Bacteriophage T4 ◽

T4 Lysozyme ◽

Screening System ◽

Random Mutation ◽

Secondary Sludge ◽

Enzyme Screening ◽

Model Protein ◽

Genetically Encoded Biosensor ◽

Lysozyme Evolution

Lysozyme is widely used as a model protein in studies of structure–function relationships. Recently, lysozyme has gained attention for use in accelerating the degradation of secondary sludge, which mainly consists of bacteria. However, a high-throughput screening system for lysozyme engineering has not been reported. Here, we present a lysozyme screening system using a genetically encoded biosensor. We first cloned bacteriophage T4 lysozyme (T4L) into a plasmid under control of the araBAD promoter. The plasmid was expressed in Escherichia coli with no toxic effects on growth. Next, we observed that increased soluble T4L expression decreased the fluorescence produced by the genetic enzyme screening system. To investigate T4L evolution based on this finding, we generated a T4L random mutation library, which was screened using the genetic enzyme screening system. Finally, we identified two T4L variants showing 1.4-fold enhanced lytic activity compared to native T4L. To our knowledge, this is the first report describing the use of a genetically encoded biosensor to investigate bacteriophage T4L evolution. Our approach can be used to investigate the evolution of other lysozymes, which will expand the applications of lysozyme.

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Preliminary evaluation of biosolids characteristics for anaerobic membrane reactors treating municipal wastewaters

Water Science & Technology ◽

10.2166/wst.2015.356 ◽

2015 ◽

Vol 72 (8) ◽

pp. 1446-1454 ◽

Cited By ~ 1

Author(s):

Qirong Dong ◽

Martha Dagnew ◽

Jeff Cumin ◽

Wayne Parker

Keyword(s):

Suspended Solids ◽

Municipal Wastewater ◽

Nutrient Content ◽

Pilot Scale ◽

Land Application ◽

Membrane Reactors ◽

Preliminary Evaluation ◽

Secondary Sludge ◽

Volatile Solids ◽

Class B

This study assessed the characteristics of biosolids of a pilot-scale anaerobic membrane bioreactor (AnMBR) treating municipal wastewater. The production of total solids (TS) and volatile solids (VS) was comparable to that reported for the extended aeration system at solids residence time (SRT) longer than 40 days. The yields of TS and VS were reduced as SRT increased from 40 to 100 days and increased with the addition of 26 mg/L of FeCl3. The AnMBR destroyed 60–82% of the VS loading in feed wastewater and hence it was concluded the biosolids met the requirements for vector attraction reduction for land application. The concentrations of volatile suspended solids and total suspended solids in the sludge were less than those reported after anaerobic digestion of conventional primary and secondary sludge mixtures, and hence dewatering of the waste stream may be required for some applications. The nutrient content in terms of total Kjeldahl nitrogen and total phosphorus was similar to that of anaerobically digested municipal sludges. The dewaterability of the biosolids was poorer than that reported for sludges from aerobic treatment and anaerobically digested sludges. Dewaterability was improved by addition of FeCl3 and reduced SRT. The biosolids met standards for land application with regards to the concentration of heavy metals but would need further treatment to meet Class B pathogen indicator criteria.

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