A pilot study of anaerobic membrane digesters for concurrent thickening and digestion of waste activated sludge (WAS)

2010 ◽  
Vol 61 (6) ◽  
pp. 1451-1458 ◽  
Author(s):  
Martha Dagnew ◽  
Wayne J. Parker ◽  
Peter Seto
Keyword(s):  
Activated Sludge ◽  
Retention Time ◽  
Substantial Reduction ◽  
Biomass Energy ◽  
Supernatant Fraction ◽  
Waste Activated Sludge ◽  
Short Term ◽  
Solids Concentration ◽  
Volatile Solids ◽  
Anaerobic Membrane Bioreactors

The increased interest in biomass energy provides incentive for the development of efficient and high throughput digesters such as anaerobic membrane bioreactors (AnMBRs) to stabilize waste activated sludge (WAS). This paper presents the results of a pilot and short term filtration study that was conducted to assess the performance of AnMBRs when treating WAS at a 15 day hydraulic retention time (HRT) and 30 day sludge retention time (SRT) in comparison to two conventional digesters running at 15 (BSR-15) and 30 days (BSR-30) HRT/SRT. At steady state, the AnMBR digester showed a slightly higher volatile solids (VS) destruction of 48% in comparison to 44% and 35.3% for BSR-30 and BSR-15, respectively. The corresponding values of specific methane production were 0.32, 0.28 and 0.21 m3 CH4/kg of VS fed. Stable membrane operation at an average flux of 40 ± 3.6 LM−2 H−1 (LMH) was observed when the digester was fed with a polymer-dosed thickened waste activated sludge (TWAS) and digester total suspended solids (TSS) concentrations were less than 15 gL−1. Above this solids concentration a flux decline to 24.1 ± 2.0 LM−2 H−1 was observed. Short term filtration tests conducted using sludge fractions of a 9.7 and 17.1 gL−1 TSS sludge indicated 84 and 70% decline in filtration performance to be associated with the supernatant fraction of the sludge. At a higher sludge concentration, the introduction of unique fouling control strategy to tubular membranes, a relaxed mode of operation (i.e. 5 minutes permeation and 1 minute relaxation by) significantly increased the flux from 23.8 ± 1.1 to 37.8 ± 2.3 LMH for a neutral membrane and from 25.7 ± 1.1 to 44.9 ± 2.9 LMH for a negatively charged membrane. The study clearly indicates that it is technically feasible to employ AnMBRs to achieve a substantial reduction in digester volumes.

A mechanical pretreatment of waste activated sludge for improvement of anaerobic digestion system

1997 ◽  
Vol 36 (12) ◽  
pp. 111-116 ◽  
Author(s):  
Kyung-Yub Hwang ◽  
Eung-Bai Shin ◽  
Hong-Bok Choi
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Protein Concentration ◽  
Waste Activated Sludge ◽  
Cell Rupture ◽  
Mechanical Pretreatment ◽  
Solids Concentration ◽  
Sludge Pretreatment ◽  
Volatile Solids ◽  
Before And After

This study evaluated the effectiveness of sewage pretreatment as it affected the subsequent anaerobic digestion of waste activated sludge (WAS). The key to this sludge pretreatment process was that microorganism cells within WAS were ruptured by mechanical jet and smash under pressurized conditions, 5–50 bar pressure. Cell rupture was estimated by soluble protein concentration (SPC) because the cytoplasm of microorganisms is mainly composed of protein. The SPC in the WAS varied significantly before and after pretreatment. In particular, cell rupture increased from 6% to 43% with the increase of the pretreated pressure (5–30bar), volatile solids concentration and thickening time of WAS. In the WAS pretreatment with long-thickening time (12h < thickening time ≤ 48h), cell rupture was monitored 5–10 % higher than short-thickening time (Oh <thickening time ≤ 12h). Generally, it was observed that higher anaerobic digestion efficiencies of WAS could be obtained according to the increase of microorganism cell rupture through mechanical pretreatment of WAS.

Comparison of Aerobic and Anoxic-Aerobic Digestion of Waste Activated Sludge

1985 ◽  
Vol 17 (8) ◽  
pp. 1475-1478 ◽  
Author(s):  
A P. C. Warner ◽  
G. A. Ekama ◽  
G v. R. Marais
Keyword(s):  
Experimental Data ◽  
Activated Sludge ◽  
Waste Activated Sludge ◽  
Activated Sludge Process ◽  
Cycle Times ◽  
Waste Sludge ◽  
Volatile Solids ◽  
In Series ◽  
Flow Through ◽  
Theoretical Simulations

The laboratory scale experimental investigation comprised a 6 day sludge age activated sludge process, the waste sludge of which was fed to a number of digesters operated as follows: single reactor flow through digesters at 4 or 6 days sludge age, under aerobic and anoxic-aerobic conditions (with 1,5 and 4 h cycle times) and 3-in-series flow through aerobic digesters each at 4 days sludge age; all digesters were fed draw-and-fill wise once per day. The general kinetic model for the aerobic activated sludge process set out by Dold et al., (1980) and extended to the anoxic-aerobic process by van Haandel et al., (1981) simulated accurately all the experimental data (Figs 1 to 4) without the need for adjusting the kinetic constants. Both theoretical simulations and experimental data indicate that (i) the rate of volatile solids destruction is not affected by the incorporation of anoxic cycles and (ii) the specific denitrification rate is independent of sludge age and is K4T = 0,046(l,029)(T-20) mgNO3-N/(mg active VSS. d) i.e. about 2/3 of that in the secondary anoxic of the single sludge activated sludge stystem. An important consequence of (i) and (ii) above is that denitrification can be integrated easily in the steady state digester model of Marais and Ekama (1976) and used for design (Warner et al., 1983).

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

Processes ◽  
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.

Long and short term impacts of CuO, Ag and CeO2nanoparticles on anaerobic digestion of municipal waste activated sludge

2016 ◽  
Vol 18 (2) ◽  
pp. 277-288 ◽  
Author(s):  
E. Kökdemir Ünşar ◽  
A. S. Çığgın ◽  
A. Erdem ◽  
N. A. Perendeci
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Municipal Waste ◽  
Waste Activated Sludge ◽  
Short Term

In this study, long and short term inhibition impacts of Ag, CuO and CeO2nanoparticles (NPs) on anaerobic digestion (AD) of waste activated sludge (WAS) were investigated.

scholarly journals Methanosarcinaceae and Acetate-Oxidizing Pathways Dominate in High-Rate Thermophilic Anaerobic Digestion of Waste-Activated Sludge

2013 ◽  
Vol 79 (20) ◽  
pp. 6491-6500 ◽  
Author(s):  
Dang P. Ho ◽  
Paul D. Jensen ◽  
Damien J. Batstone
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Retention Time ◽  
Elevated Temperatures ◽  
Stable Carbon Isotope ◽  
High Rate ◽  
Continuous Reactor ◽  
Waste Activated Sludge ◽  
Acetate Oxidation ◽  
Syntrophic Acetate Oxidation

ABSTRACTThis study investigated the process of high-rate, high-temperature methanogenesis to enable very-high-volume loading during anaerobic digestion of waste-activated sludge. Reducing the hydraulic retention time (HRT) from 15 to 20 days in mesophilic digestion down to 3 days was achievable at a thermophilic temperature (55°C) with stable digester performance and methanogenic activity. A volatile solids (VS) destruction efficiency of 33 to 35% was achieved on waste-activated sludge, comparable to that obtained via mesophilic processes with low organic acid levels (<200 mg/liter chemical oxygen demand [COD]). Methane yield (VS basis) was 150 to 180 liters of CH4/kg of VSadded. According to 16S rRNA pyrotag sequencing and fluorescence in situ hybridization (FISH), the methanogenic community was dominated by members of theMethanosarcinaceae, which have a high level of metabolic capability, including acetoclastic and hydrogenotrophic methanogenesis. Loss of function at an HRT of 2 days was accompanied by a loss of the methanogens, according to pyrotag sequencing. The two acetate conversion pathways, namely, acetoclastic methanogenesis and syntrophic acetate oxidation, were quantified by stable carbon isotope ratio mass spectrometry. The results showed that the majority of methane was generated by nonacetoclastic pathways, both in the reactors and in off-line batch tests, confirming that syntrophic acetate oxidation is a key pathway at elevated temperatures. The proportion of methane due to acetate cleavage increased later in the batch, and it is likely that stable oxidation in the continuous reactor was maintained by application of the consistently low retention time.

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