Inactivation of pathogenic bacteria under mesophilic and thermophilic conditions

1997 ◽  
Vol 36 (6-7) ◽  
pp. 25-32 ◽  
Author(s):  
Haruki Watanabe ◽  
Tomokazu Kitamura ◽  
Shuichi Ochi ◽  
Masaaki Ozaki
Keyword(s):  
Anaerobic Digestion ◽  
Fecal Coliform ◽  
Pathogenic Bacteria ◽  
Anaerobic Treatment ◽  
Digested Sludge ◽  
Primary Sludge ◽  
Digestion Process ◽  
Mesophilic Digestion ◽  
Thermophilic Digestion ◽  
Number Of Bacteria

This paper concerns field survey and laboratory experiment on the inactivation of pathogenic bacteria during sludge treatment processes with particular emphasis on anaerobic digestion process. We surveyed the inactivation of pathogenic bacteria processes by sampling various types of sludges from 17 wastewater treatment plants located in Japan and counting the number of bacteria in the sampled sludges. The bacteria we counted included fecal coliform groups, enterococcus and salmonella. The median number of fecal coliform groups in primary sludge was found to be 105 MPN/g, while the number of fecal coliform groups in digested sludge decreased to 103 MPN/g. We also confirmed that the treatments of dewatering using inorganic coagulant, drying and composting are also effective in inactivating pathogenic bacteria. In addition, we studied the performance conditions of anaerobic digestion and the degree of inactivation of pathogenic bacteria in the experiment of anaerobic treatment of the primary sludge. This study showed that the number of fecal coliform groups in mesophilic digestion sludge was in the range of 102 to 104 MPN/g regardless of the HRT, whereas the number of bacteria in thermophilic digestion sludge was of the order of 100 MPN/g, clearly indicating that the number of bacteria substantially decreases when the sludge is digested at thermophilic temperature. The number of enterococcus in digested sludge was in the range of 102 to 105 MPN/g after the sludge was subjected to mesophilic digestion while the number decreased to 100 MPN/g after the sludge was digested at thermophilic temperature. The number of salmonella in digested sludge was in the range of 1.8 to 30 MPN/4g after the sludge was digested at mesophilic temperature, but the number decreased to less than 1.8 MPN/4g after the sludge went through thermophilic digestion process. The thermophilic digestion is thus effective in inactivating pathogenic bacteria.

scholarly journals THE EFFECT OF IRON SALT ON ANAEROBIC DIGESTION AND PHOSPHATE RELEASE TO SLUDGE LIQUOR / GELEŽIES DRUSKOS ĮTAKA ANAEROBINIO DUMBLO PŪDYMO PROCESUI IR FOSFATŲ IŠSISKYRIMUI Į DUMBLO VANDENĮ

2011 ◽  
Vol 3 (5) ◽  
pp. 123-126
Author(s):  
Svetlana Ofverstrom ◽  
Regimantas Dauknys ◽  
Ieva Sapkaitė
Keyword(s):  
Anaerobic Digestion ◽  
Phosphorus Content ◽  
Wastewater Treatment Plants ◽  
Biogas Production ◽  
Iron Salt ◽  
Digested Sludge ◽  
Sludge Treatment ◽  
Primary Sludge ◽  
Digestion Process ◽  
Iron Salts

Iron salts are used at wastewater treatment plants (WWTPs) for several reasons: for removing chemical phosphorus, preventing from struvite formation and reducing the content of hydrogen sulfide (H2S) in biogas. Anaerobic digestion is a common scheme for sludge treatment due to producing biogas that could be used as biofuel. Laboratory analysis has been carried out using anaerobic digestion model W8 (Armfield Ltd, UK) to investigate any possible effect of adding FeCl3 on the anaerobic digestion of primary sludge (PS) and waste activated sludge (WAS) mixture as well as on releasing phosphates to digested sludge liquor. The obtained results showed that FeCl3 negatively impacted the anaerobic digestion process by reducing the volume of produced biogas. Fe-dosed sludge (max) produced 30% less biogas. Biogas production from un-dosed and Fe-dosed sludge (min) was similar to the average of 1.20 L/gVSfed. Biogas composition was not measured during the conducted experiments. Phosphorus content in sludge liquor increased at an average of 38% when digesting sludge without ferric chloride dosing. On the contrary, phosphate content in sludge liquor from digested Fe-dosed sludge decreased by approx. 80%. Santrauka Nuotekų valymo įrenginiuose geležies druskos naudojamos cheminiam fosforui šalinti, sieros vandeniliui biodujose mažinti ir struvito nuogulų formavimosi prevencijai. Tyrimai atlikti laboratorinėmis sąlygomis naudojant anaerobinio pūdymo modelį W8 (Armfield Ltd., Didžioji Britanija) ir pūdant pirminio perteklinio dumblo mišinį, į kurį buvo dedama geležies druskos, siekiant nustatyti geležies druskos naudojimo efektą anarobinio pūdymo procesui ir fosfatų išsiskyrimui į dumblo vandenį. Rezultatai parodė, kad pūdant dumblą be geležies druskos ir dedant geležies druskos minimalią dozę, susidarė vidutiniškai vienodi kiekiai biodujų (mL/gBSMtiekiam.), bet į pūdomą dumblą dedant maksimalią geležies dozę, biodujų išeiga vidutiniškai sumažėjo 30 %. Į pūdomą dumblą nededant geležies chlorido, fosfatų koncentracija dumblo vandenyje vidutiniškai padidėjo 38 %. Ir priešingai, geležies chlorido dozės fosfatų koncentraciją pūdyto dumblo vandenyje sumažino 80 %.

scholarly journals Two-Stage Anaerobic Digestion Process Combining Pre-digestion with Methanization

2015 ◽  
Vol 9 (2) ◽  
pp. 55-60
Author(s):  
Mohammed Mohaibes
Keyword(s):  
Anaerobic Digestion ◽  
Detectable Level ◽  
Process Efficiency ◽  
Two Stage ◽  
Biogas Yield ◽  
Digestion Process ◽  
Vs Removal ◽  
Mesophilic Digestion ◽  
Thermophilic Digestion ◽  
Biogas Process

Anaerobic digestion of a mixture of manure and sewage sludge by combination of the biological predigestion at 73°C with methanization at 55°C was studied with regard to the biogas process efficiency,energy balance and sanitation effect. Performance of the two-stage digestion was compared with theconventional, one-stage moderate thermophilic digestion at 55°C and mesophilic digestion at 37°C,respectively. The best performance was achieved by the two-stage treatment both in terms of VolatileSolids (VS) removal and biogas yield. Up to 60% of VS was removed and a specific methane yield of 300ml CH4 gVS-1 was achieved. Sanitation effect was measured as inactivation of the indicators of bacterialpathogens - the faecal enterococci and spores of Clostridium perfringens. Elimination of faecal enterococcito non-detectable level occurred only during treatments at 73°C and 55°C. Numbers of Clostridiumperfringens spores were reduced solely by the combined 73°C/55°C treatment.

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

2010 ◽  
Vol 113-116 ◽  
pp. 450-458 ◽  
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.

Initial examination of microwave pretreatment on primary, secondary and mixed sludges before and after anaerobic digestion

2008 ◽  
Vol 57 (3) ◽  
pp. 311-317 ◽  
Author(s):  
C. Eskicioglu ◽  
K. J. Kennedy ◽  
R. L. Droste
Keyword(s):  
Anaerobic Digestion ◽  
Sequencing Batch Reactor ◽  
Batch Reactor ◽  
Waste Activated Sludge ◽  
Initial Examination ◽  
Primary Sludge ◽  
Sludge Characteristics ◽  
Microwave Pretreatment ◽  
Before And After ◽  
Mesophilic Digestion

The effects of microwave pretreatment on disintegration and mesophilic digestion of waste activated sludge (WAS), primary sludge (PS), combined (PS + WAS) sequencing batch reactor (SBR) sludge and anaerobically digested biocake were investigated by both household and bench scale industrial types microwaves at temperatures below and above boiling point. Pretreatment variables, temperature, intensity (cooking rate) and sludge concentration had statistically significant effects on solubilization. The microwave pretreatment also increased the bioavailability of sludge components under batch anaerobic digestion and enhanced the dewaterability of pretreated sludges after digestion. However, the level of improvements in solubilization and biodegradation from different waste sludges were different. While the largest improvement in ultimate biodegradation was observed in WAS, microwave irradiation only affected the rate of biodegradation of pretreated PS samples. Similarly, relatively lower solubilization ratios achieved for combined - SBR sludge was attributed to high sludge age of extended aeration SBR unit. It is possible that initial sludge characteristics may influence final pretreatment outcomes so that general statements of performance cannot always be made.

Microbiology of Anaerobic Digestion

1986 ◽  
Vol 18 (12) ◽  
pp. 1-14 ◽  
Author(s):  
R F. V. Novaes
Keyword(s):  
Anaerobic Digestion ◽  
Anaerobic Treatment ◽  
Anaerobic Digestion Process ◽  
Digestion Process ◽  
General Overview ◽  
And Control

This paper presents a general overview of studies conducted with microorganisms involved in the anaerobic digestion process, and also some ways of applying these studies as fundamental tools in the understanding, improvement and control of the anaerobic treatment of residuals.

Feasibility of the on-site treatment of sewage and swill in large buildings

2000 ◽  
Vol 41 (1) ◽  
pp. 9-16 ◽  
Author(s):  
Grietje Zeeman ◽  
Wendy Sanders ◽  
Gatze Lettinga
Keyword(s):  
Storage Time ◽  
Anaerobic Treatment ◽  
Primary Sludge ◽  
Ambient Temperatures ◽  
Reactor Volume ◽  
Accumulation System ◽  
Storage Volume ◽  
Mesophilic Digestion ◽  
Completely Stirred Tank Reactor ◽  
Cstr System

Three concepts are proposed for the on-site treatment of sewage and swill in large buildings, like hospitals. The production and anaerobic treatment of night soil in combination with swill in a slurry digestion system and separate production and treatment of grey water is the most attractive concept. The slurry digestion could either be carried out in a CSTR-system at mesophilic conditions or in an Accumulation-system at ambient temperatures. The reactor volume needed for the digestion of a mixture of swill and night soil (or primary sludge) in an Accumulation (AC)- and Completely Stirred Tank Reactor (CSTR)-system at different process temperatures is calculated based on literature values. From the results it should be concluded that mesophilic digestion (30°C) and a SRT of 20–30 days is to be recommended for the digestion of a mixture of night soil and swill in a CSTR system. The latter coincides with the installation of 40–60 l reactor volume per person. Depending on the applied temperature and therefore the minimum storage time and percentage inoculation, a r eactor/storage volume of 431 or 951 litres per person should be installed at 20 and 15°C, respectively when an Accumulation system is applied. An Accumulation-system has the advantage that storage and digestion are combined, implying a completely closed system, also for the storage. The latter is of highest importance for the indoor treatment, as proposed in the paper.

Full-scale application of anaerobic digestion process with partial ozonation of digested sludge

2005 ◽  
Vol 52 (1-2) ◽  
pp. 245-252 ◽  
Author(s):  
H. Yasui ◽  
K. Komatsu ◽  
R. Goel ◽  
Y. Y. Li ◽  
T. Noike
Keyword(s):  
Anaerobic Digestion ◽  
Full Scale ◽  
Digested Sludge ◽  
Anaerobic Digestion Process ◽  
Digestion Process ◽  
New Process ◽  
Sludge Cake ◽  
Dewatered Sludge ◽  
Solid Liquid ◽  
Solid Liquid Separation

For improving sludge digestion and biogas recovery, a new anaerobic digestion process combined with ozonation was tested at a full-scale unit for 2 years and its performance was compared with a simultaneously operated conventional anaerobic digestion process. The new process requires two essential modifications, which includes ozonation for enhancing the biological degradability of sludge organics and concentrating of solids in the digester through a solid/liquid separation for extension of SRT. These modifications resulted in high VSS degradation efficiency of ca. 88%, as much as 1.3 times of methane production and more than 70% reduction in dewatered sludge cake production. Owing to accumulation of inorganic solids in the digested sludge, water content of the dewatered sludge cake also reduced from 80% to 68%. An energy analysis suggested that no supplemental fuel was necessary for the subsequent incineration of the cake from the new process scheme. The process is suitable to apply to a low-loaded anaerobic digestion tank, where power production is used.

scholarly journals The Utilization of Pineapples Waste Enzyme for the Improvement of Hydrolysis Solubility in Aquaculture Sludge

2019 ◽  
Vol 1 (2-2) ◽  
Author(s):  
M. Fatma Syahirah ◽  
R. Nazaitulshila
Keyword(s):  
Anaerobic Digestion ◽  
Treatment Time ◽  
Oxygen Demand ◽  
Anaerobic Treatment ◽  
Ammonia Nitrogen ◽  
Plastic Container ◽  
Anaerobic Digestion Process ◽  
Digestion Process ◽  
Total Ammonia

High volumes of sludge discharge from the aquaculture industry have relatively high pollutant content that may lead to severe local environmental problems. Anaerobic digestion is one of the technologies for sludge treatment that might be an efficient method to reduce salty aquaculture sludge production load. However, hydrolysis solubility is becoming a limitation step during the anaerobic digestion process when the occurrence of intermediate accumulation resulted from the conversion of non-soluble biopolymers to soluble organic compounds. Thus, pretreatment is required to increase the solubilization of pollutant parameters from aquaculture sludge before it is further treated in the anaerobic treatment. Therefore, this study focuses on the production of biocatalytic enzyme from the fermentation of pre-consumer supermarket waste such as pineapple dregs to increase the solubility of aquaculture sludge. The fermentation of the pineapples waste was produced via a three-month fermentation of the mixture of molasses, pineapple dregs and water, with the ratio of 1:3:10 in a tight plastic container. Apart from that, analyses showed that the enzyme possessed lipase, amylase and protease activity. The sludge solubilization pretreatment was performed at different pH values, with treatment time for 120 hours and the solubilization was evaluated by determination of Chemical Oxygen Demand (COD) and Total Ammonia Nitrogen (TAN) solubilization; the solubilization of COD and TAN increased by 80% and 50%, respectively. This finding showed that the pineapple enzyme has the capability to solubilize organic compound, which has the potential to improve hydrolysis in further anaerobic digestion process.

scholarly journals Inactivation of Clostridium difficile in sewage sludge by anaerobic thermophilic digestion

2016 ◽  
Vol 62 (1) ◽  
pp. 16-23 ◽  
Author(s):  
Changyun Xu ◽  
Hamidreza Salsali ◽  
Scott Weese ◽  
Keith Warriner
Keyword(s):  
Acetic Acid ◽  
Clostridium Difficile ◽  
Sewage Sludge ◽  
Digested Sludge ◽  
Sludge Digestion ◽  
Final Density ◽  
Potential Source ◽  
Mesophilic Digestion ◽  
Thermophilic Digestion ◽  
Ribotype 078

There has been an increase in community-associated Clostridium difficile infections with biosolids derived from wastewater treatment being identified as one potential source. The current study evaluated the efficacy of thermophilic digestion in decreasing levels of C. difficile ribotype 078 associated with sewage sludge. Five isolates of C. difficile 078 were introduced (final density of 5 log CFU/g) into digested sludge and subjected to anaerobic digestion at mesophilic (36 or 42 °C) or thermophilic (55 °C) temperatures for up to 60 days. It was found that mesophilic digestion at 36 °C did not result in a significant reduction in C. difficile spore levels. In contrast, thermophilic sludge digestion reduced endospore levels at a rate of 0.19–2.68 log CFU/day, depending on the strain tested. The mechanism of lethality was indirect — by stimulating germination then inactivating the resultant vegetative cells. Acidification of sludge by adding acetic acid (6 g/L) inhibited the germination of spores regardless of the sludge digestion temperature. In conclusion, thermophilic digestion can be applied to reduce C. difficile in biosolids, thereby reducing the environmental burden of the enteric pathogen.

Influence of Pretreatment on Anaerobic Stabilisation of Sewage Sludge

1984 ◽  
Vol 16 (12) ◽  
pp. 365-373 ◽  
Author(s):  
F Wechs
Keyword(s):  
Anaerobic Digestion ◽  
Sewage Sludge ◽  
Short Term ◽  
Digested Sludge ◽  
Digestion Process ◽  
Reference Process ◽  
Stage Process ◽  
Rate Limiting ◽  
Hydrolysis Of ◽  
Pretreatment Processes

In order to intensify anaerobic stabilisation of sewage sludge, several pretreatment processes have been tested. Pretreatment processes investigated are: prepasteurisation, separate acidification, short-term anaerobic digestion. Anaerobic stabilisation was performed in 500 1 digestors. All experiments were performed in parallel to a process operated with untreated raw sludge, the later serving as a reference process. Prepasteurisation turned out to improve solids degradation and dewaterability of the digested sludge, whereas acidification was found to be a rather slow and uncomplete process due to the rate limiting function of hydrolysis of sludge particulates. Using a short-term anaerobic digestion process before anaerobic stabilisation, the easily degradable organics were readily converted to methane. It was shown that this two-stage process improves stabilisation efficiency in comparison to a 20 day one-stage process very significantly.

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