scholarly journals Comparison of the impacts of thermal pretreatment on waste activated sludge using aerobic and anaerobic digestion

2018 ◽  
Vol 78 (8) ◽  
pp. 1772-1781 ◽  
Author(s):  
Hyungjun (Brian) Jo ◽  
Wayne Parker ◽  
Peiman Kianmehr
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Oxygen Demand ◽  
Waste Activated Sludge ◽  
Thermal Pretreatment ◽  
Decay Products ◽  
Anaerobic Biodegradability ◽  
Pretreatment Conditions ◽  
The Impact ◽  
Aerobic And Anaerobic

Abstract A range of thermal pretreatment conditions were used to evaluate the impact of high pressure thermal hydrolysis on the biodegradability of waste activated sludge (WAS) under aerobic and anaerobic conditions. It was found that pretreatment did not increase the overall extent to which WAS could be aerobically biodegraded. Thermal pretreatment transformed the biodegradable fraction of WAS (XH) to readily biodegradable chemical oxygen demand (COD) (SB) (16.5–34.6%) and slowly biodegradable COD (XB) (45.8–63.6%). The impact of pretreatment temperature and duration on WAS COD fractionation did not follow a consistent pattern as changes in COD solubilization did not correspond to the observed generation of SB through pretreatment. The pretreated WAS (PWAS) COD fractionations determined from aerobic respirometry were employed in anaerobic modeling and it was concluded that the aerobic and anaerobic biodegradability of PWAS differed. It was found that thermal pretreatment resulted in as much as 50% of the endogenous decay products becoming biodegradable in anaerobic digestion. Overall, it was concluded that the COD fractionation that was developed based upon the aerobic respirometry was valid. However, it was necessary to implement a first-order decay process that reflected changes in the anaerobic biodegradability of the endogenous products through pretreatment.

Characterization of sludges for predicting anaerobic digester performance

2008 ◽  
Vol 57 (5) ◽  
pp. 721-726 ◽  
Author(s):  
R. Jones ◽  
W. Parker ◽  
Z. Khan ◽  
S. Murthy ◽  
M. Rupke
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Waste Activated Sludge ◽  
Anaerobic Conditions ◽  
Modified Model ◽  
Primary Sludge ◽  
First Order ◽  
Decay Products ◽  
Aerobic And Anaerobic

Batch anaerobic digestion tests of primary sludge and waste activated sludge were conducted for a duration of 123 days to determine the ultimate degradability of the sludges. For primary sludges the inert fraction of the particulate COD that was predicted by the wastewater models could be employed to predict their biodegradability under anaerobic conditions. The degradation of waste activated sludge was adequately characterized for the first 60 days of digestion using a model that assumed equivalent biodegradability of particulate COD components under aerobic and anaerobic conditions. However after 60 days of anaerobic digestion it appeared that decay of the endogenous products was occurring. This could be described with a first order decay function with a coefficient of 0.0075 d−1. For continuous flow digesters operating at SRTs of 30–60 days, the predicted VSS destruction with the modified model was approximately 10% higher than that predicted on the basis of inert endogenous decay products.

scholarly journals Enhancement of waste activated sludge anaerobic digestion by a novel chemical free acid/alkaline pretreatment using electrolysis

2013 ◽  
Vol 67 (12) ◽  
pp. 2827-2831 ◽  
Author(s):  
W. Charles ◽  
B. Ng ◽  
R. Cord-Ruwisch ◽  
L. Cheng ◽  
G. Ho ◽  
...  
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Energy Savings ◽  
Treatment Time ◽  
Free Acid ◽  
Oxygen Demand ◽  
Waste Activated Sludge ◽  
Anode Chamber ◽  
Cathode Chamber ◽  
Exchange Membrane

Anaerobic digestion of waste activated sludge (WAS) is relatively poor due to hydrolysis limitations. Acid and alkaline pretreatments are effective in enhancing hydrolysis leading to higher methane yields. However, chemical costs often prohibit full-scale application. In this study, 12 V two-chamber electrolysis using an anion exchange membrane alters sludge pH without chemical dosing. pH dropped from 6.9 to 2.5 in the anode chamber and increased to 10.1 in the cathode chamber within 15 h. The volatile suspended solids solubilisation of WAS was 31.1% in the anode chamber and 34.0% in the cathode chamber. As a result, dissolved chemical oxygen demand increased from 164 to 1,787 mg/L and 1,256 mg/L in the anode and cathode chambers, respectively. Remixing of sludge from the two chambers brought the pH back to 6.5, hence no chemical neutralisation was required prior to anaerobic digestion. Methane yield during anaerobic digestion at 20 d retention time was 31% higher than that of untreated sludge. An energy balance assessment indicated that the non-optimised process could approximately recover the energy (electricity) expended in the electrolysis process. With suitable optimisation of treatment time and voltages, significant energy savings would be expected in addition to the benefit of decreased sludge volume.

scholarly journals Mathematical modelling of waste activated sludge thermal disintegration

2018 ◽  
Vol 23 ◽  
pp. 00027
Author(s):  
Sylwia Myszograj ◽  
Magdalena Wojciech
Keyword(s):  
Activated Sludge ◽  
Mixed Models ◽  
Treatment Time ◽  
Oxygen Demand ◽  
Repeated Measurements ◽  
Waste Activated Sludge ◽  
Disintegration Time ◽  
Random Factor ◽  
Factor Measurement ◽  
The Impact

Chemical Oxygen Demand (COD) solubilisation was used to evaluate the impact of thermal pretreatment on the transfer of sewage sludge from particulate to soluble phase. It was gathering the experimental data needed for building of empirical mathematical model describing the relation between applied temperature and time and rate of COD solubilisation and degradation. In view of repeated measurements, in order to describe the relationship between changes in the fraction of dissolved COD and the time and temperature, mixed models have been adopted where by fixed factor measurement conditions have been adopted: time and temperature, while the random factor changes the characteristics of waste activated sludge. Linear and logistic nonlinear mixed models were analyzed. The tests demonstrated that all variables are statistically significant in assessing their impact on the efficiency of liquefaction of sludge. On the basis of the estimated model, the temperature rise of 10°C increases degree of disintegration 1.7% above the average treatment time for 0.5h, by 2.6% for 1 hour, and by 3.9% for 2h. COD values decrease between 3 to 23% at temperatures in the range of 55 to 115°C. At higher temperatures COD was reduced in the range of 32 to 44%. Disintegration time did not have the significant impact on the degradation effect.

scholarly journals Performance and Microbial Community Dynamics in Anaerobic Digestion of Waste Activated Sludge: Impact of Immigration

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 573 ◽  
Author(s):  
Juhee Shin ◽  
Si-Kyung Cho ◽  
Joonyeob Lee ◽  
Kwanghyun Hwang ◽  
Jae Chung ◽  
...  
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Growth Rates ◽  
Municipal Wastewater ◽  
Community Dynamics ◽  
Oxygen Demand ◽  
Waste Activated Sludge ◽  
Municipal Wastewater Treatment ◽  
Microbial Community Dynamics ◽  
Ch4 Production

Waste activated sludge (WAS) is a byproduct of municipal wastewater treatment. WAS contains a large proportion of inactive microbes, so when it is used as a substrate for anaerobic digestion (AD), their presence can interfere with monitoring of active microbial populations. To investigate how influent cells affect the active and inactive microbial communities during digestion of WAS, we operated model mesophilic bioreactors with conventional conditions. Under six different hydraulic retention times (HRTs; 25, 23, 20, 17, 14, and 11.5 d), the chemical oxygen demand (COD) removal and CH4 production of the AD were within a typical range for mesophilic sludge digesters. In the main bacteria were proteobacteria, bacteroidetes, and firmicutes in both the WAS and the bioreactors, while in main archaeal methanogen group was Methanosarcinales in the WAS and methanomicrobiales in the bioreactors. Of the 106 genera identified, the estimated net growth rates were negative in 72 and positive in 34. The genera with negative growth included many aerobic taxa. The genera with positive growth rates included methanogens and syntrophs. In some taxa, the net growth rate could be positive or negative, depending on HRT, so their abundance was also affected by HRT. This study gives insights into the microbial dynamics of a conventional sludge anaerobic digester by distinguishing potentially active (growing) and inactive (non-growing, dormant) microbes and by correlating population dynamics with process parameters.

scholarly journals Alkaline and acid solubilisation of waste activated sludge

2021 ◽  
Author(s):  
Tales Abreu Tavares de Sousa ◽  
Fernanda Patrício do Monte ◽  
José Vanderley do Nascimento Silva ◽  
Wilton Silva Lopes ◽  
Valderi Duarte Leite ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Soluble Fraction ◽  
Total Dissolved Solids ◽  
Waste Activated Sludge ◽  
Anaerobic Biodegradability ◽  
Consumption Rates ◽  
Alkaline Conditions ◽  
Pre Treatment ◽  
Physical And Chemical ◽  
Aerobic And Anaerobic

Abstract The influence of acidic and alkaline conditions on the solubilisation process of waste activated sludge (WAS) was investigated using HCl and NaOH at pH 2, 10, 11 and 12. The rise in concentration of solubilised compounds, the influence of reaction time, and the influence of the concentration of total solids (TS) during the solubilisation process were determined. Physical and chemical tests demonstrated that pre-treatment provided a release of compounds from the sludge floc matrix into the soluble fraction, characterising the solubilisation process. The highest degree of WAS solubilisation was observed when a pH of 12 was applied. Although largest effects were already attained after 0.25 h, WAS solubilisation continued reaching an increase in total dissolved solids by a factor 10.4 after 720 hrs. Under these conditions, the dissolved organic carbon (DOC), proteins, and carbohydrates resulted in releases up to 15, 40 and 41 times, respectively; and phosphorus increased 5.7 times. Results indicate that by applying alkaline pre-treatment, higher TS concentrations can be treated per reactor volume compared to non-pre-treated WAS. Aerobic and anaerobic biodegradability tests showed increased bioconversion potentials in full-scale treatment plants. The respirometry tests ratify the improvement in solubilisation, with O2 consumption rates increasing 1.4 times, concomitant with an additional 261 mg·L−1 of the COD used, which represents 90% bioconversion of waste activated sludge. Biomethanisation test indicated an increase of 3.6 times relative to the blank.

Effects of mixed alkali-thermal pretreatment on anaerobic digestion performance of waste activated sludge

2020 ◽  
Vol 259 ◽  
pp. 120940 ◽  
Author(s):  
Xuemei Zou ◽  
Ruijie Yang ◽  
Xu Zhou ◽  
Gang Cao ◽  
Rongshu Zhu ◽  
...  
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Waste Activated Sludge ◽  
Thermal Pretreatment ◽  
Mixed Alkali

Prediction of thermal hydrolysis pretreatment on anaerobic digestion of waste activated sludge

2008 ◽  
Vol 58 (7) ◽  
pp. 1467-1473 ◽  
Author(s):  
P. Phothilangka ◽  
M. A. Schoen ◽  
M. Huber ◽  
P. Luchetta ◽  
T. Winkler ◽  
...  
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Cell Mass ◽  
Waste Activated Sludge ◽  
Sufficient Information ◽  
Thermal Hydrolysis ◽  
Systematic Analysis ◽  
Complete Degradation ◽  
Ammonia Release ◽  
Decay Products

Thermal hydrolysis is known for an efficient sludge disintegration capability to enhance biogas potential—but to which extent? Obviously, residual VSS concentration in digested sludge gives not sufficient information to predict additional biogas potential. In this paper, different types of waste activated sludge (WAS) were pre-hydrolysed by a full-scale Thermo-Pressure-Hydrolysis Process (Thermo-Druck-Hydrolyse, TDH) and break-down mechanisms on specific organic compounds were investigated. The IWA Anaerobic Digestion Model No.1 (ADM1) has been used for a systematic analysis of monitoring data gained from experimental work. The TDH process combined with anaerobic digestion can be well described by a modified ADM1 model that includes an XP-fraction (inactivated aerobic biomass and their decay products). More rapid and more complete degradation of TDH-treated sludge is represented by calibrated disintegration rate and disintegration factors, while biokinetic parameters of acetogenesis and methanogenesis show no sensitivity. TDH process impacts mainly biomass and decay products while inerts Xi already contained in the raw wastewater are hardly converted. Final concentration of soluble inerts in digestion effluent has been increased from 2% to 9% of influent COD due to thermal hydrolysis. An increase in biogas generation (ca. +80%) and in ammonia release (ca. +75%) can be explained by complete degradation of cell mass.

The effect of iron and aluminium for phosphorus removal on anaerobic digestion and organic sulfur generation

2010 ◽  
Vol 62 (2) ◽  
pp. 419-426 ◽  
Author(s):  
John T. Novak ◽  
Chang Min Park
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Phosphorus Removal ◽  
Organic Sulfur ◽  
Waste Activated Sludge ◽  
Odor Control ◽  
Digestion Process ◽  
Volatile Solids ◽  
Aluminium Addition ◽  
The Impact

The addition of iron or aluminium into activated sludge basins for phosphorus removal is likely to impact both the efficiency of the anaerobic digestion process and the generation of odor-causing compounds following digestion and dewatering. In this study, the impact of iron and aluminium addition on digestion and odor-causing compounds was investigated by using batch digestion of combined primary and waste activated sludge. It was found that aluminium addition resulted in a decrease in volatile solids destruction by anaerobic digestion of approximately 2%. Of the 7 sludges tested, 5 showed a small increase in volatile solids destruction after iron addition. With regard to the generation of organic sulfur odors from the dewatered sludge cakes, both iron and aluminium reduced odor-causing gases except for one sludge that had already received iron for phosphorus control in the full-scale process. It appears that iron and aluminium addition will benefit odor control.

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