Ultrasound pre-treatment of waste activated sludge

2006 ◽  
Vol 6 (6) ◽  
pp. 35-42 ◽  
Author(s):  
J (Hans) van Leeuwen ◽  
Beril Akin ◽  
Samir Kumar Khanal ◽  
Shihwu Sung ◽  
David Grewell ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Specific Energy ◽  
Energy Input ◽  
Oxygen Demand ◽  
Protein Release ◽  
Waste Activated Sludge ◽  
Bacterial Cells ◽  
Particle Size Reduction ◽  
Specific Energy Input ◽  
Power Ultrasound

Waste activated sludge (WAS) is more difficult to digest than primary sludge due to rate limiting cell hydrolysis. High-power ultrasound can effectively disintegrate the bacterial cells and thus enhance the subsequent digestion. This research examines the effectiveness of ultrasound pretreatment on WAS disintegration at different specific energy inputs, ultrasonic densities and total solids (TS) contents. The results show that the cut diameter (d50) for WAS with 2% TS content declined nearly 6.5-fold at an ultrasonic density of 0.67 W/ml. For higher TS contents of 4 and 6%, higher densities of 1.03 and 0.86 W/ml, respectively, were needed to achieve the same degree of particle size reduction. The efficacy of ultrasonic disintegration measured as soluble chemical oxygen demand (SCOD) release was primarily governed by ultrasonic density (W/ml); whereas ultrasonic density did not show a significant effect on protein release at all TS levels. SCOD release of about 320 mg SCOD/g TS was obtained at a TS content of 2% and specific energy input of 5 kWs/gTS. The SCOD release, however, decreased to 160 and 90 mgSCOD/gTS at 4 and 6% TS contents, respectively. The highest protein release of 73 mg/gTS was obtained at a TS content of 2% and specific energy input of 10 kWs/gTS. The sludge disintegration efficiency declined significantly at higher TS content. Thus, there is a limiting TS concentration that could be effectively disintegrated by ultrasound, and this is governed by the capability of an ultrasonic unit in producing cavitation. The degree of disintegration also depends on types of ultrasonic unit used.

scholarly journals Improving biogas production performance of dairy activated sludge via ultrasound disruption prior to microwave disintegration

2020 ◽  
Vol 81 (6) ◽  
pp. 1231-1241
Author(s):  
M. Al Ramahi ◽  
G. Keszthelyi-Szabó ◽  
S. Beszédes
Keyword(s):  
Activated Sludge ◽  
Specific Energy ◽  
Energy Input ◽  
Suspended Solids ◽  
Biogas Production ◽  
Production Performance ◽  
Specific Energy Input ◽  
Net Production ◽  
Energy Assessment ◽  
Dairy Sludge

Abstract In this study, ultrasound disruption was employed to enhance the efficiency of microwave disintegration of dairy sludge. Results revealed that ultrasound specific energy input of 1,500 kJ/kg TS was found to be optimum with limited cell lysis at the end of the disruption phase. Biodegradability study suggested an enhancement in suspended solids reduction (16%) and biogas production (180 mL/gVS) in floc disrupted (deflocculated) samples when compared to sole microwave pretreatment (8.3% and 140 mL/gVS, respectively). Energy assessment to attain the 15% optimum solubilization revealed a positive net production of 26 kWh per kg sludge in deflocculated samples compared to 18 kWh in flocculated (sole microwave) samples. Thus, ultrasound disruption prior to microwave disintegration of dairy sludge was considered to be a feasible pretreatment technique.

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.

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.

Anaerobic co-digestion of winery waste and waste activated sludge: assessment of process feasibility

2013 ◽  
Vol 69 (2) ◽  
pp. 269-277 ◽  
Author(s):  
C. Da Ros ◽  
C. Cavinato ◽  
F. Cecchi ◽  
D. Bolzonella
Keyword(s):  
Activated Sludge ◽  
Biogas Production ◽  
Oxygen Demand ◽  
Pilot Scale ◽  
Waste Activated Sludge ◽  
Organic Loading ◽  
Operational Conditions ◽  
Loading Rates ◽  
Thermophilic Conditions ◽  
Soluble Chemical Oxygen Demand

In this study the anaerobic co-digestion of wine lees together with waste activated sludge in mesophilic and thermophilic conditions was tested at pilot scale. Three organic loading rates (OLRs 2.8, 3.3 and 4.5 kgCOD/m3d) and hydraulic retention times (HRTs 21, 19 and 16 days) were applied to the reactors, in order to evaluate the best operational conditions for the maximization of the biogas yields. The addition of lee to sludge determined a higher biogas production: the best yield obtained was 0.40 Nm3biogas/kgCODfed. Because of the high presence of soluble chemical oxygen demand (COD) and polyphenols in wine lees, the best results in terms of yields and process stability were obtained when applying the lowest of the three organic loading rates tested together with mesophilic conditions.

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 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.

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 Reaction rate coefficient k20 and temperature coefficient Θ in organic waste thermal disintegration

2018 ◽  
Vol 23 ◽  
pp. 00026
Author(s):  
Sylwia Myszograj
Keyword(s):  
Activated Sludge ◽  
Mixed Model ◽  
Heating Temperature ◽  
Treatment Plant ◽  
Oxygen Demand ◽  
Rate Of Change ◽  
Waste Activated Sludge ◽  
Nonlinear Mixed Model ◽  
The Difference ◽  
Reaction Speed

It was described the test of sewage sludge and organic fraction of municipal mixed solid waste thermal disintegration process. The waste activated sludge used during the tests was collected from the secondary settlement tank in a mechanical-biological wastewater treatment plant. The biowaste used in the studies was collected from an area of new buildings. It was noticed from means values of Soluble Chemical Oxygen Demand (SCOD) plot that both heating temperature and time, influence the amount of dissolved COD. The observations indicate that changes of SCOD can be described by an increasing, differentiable function of time and the rate of change of the soluble COD in the hydrolysates, in time is proportional to the difference of the maximum values of SCOD and its value in time, which leads to the relationship of the first-order ordinary differential equation. The process effectiveness depending on the temperature was described with the mathematical model including Van't Hoff-Arrhenius equation. Inspection of the data and some preliminary fits indicates, that for the description of changes in SCOD terms of time and temperature were adopted the form of nonlinear mixed model. Values of k20 indicator and Θ parameter depend on the substrate type. For waste activated sludge thermal disintegration, value of reaction speed indicator k20 was 0.028 h-1 (0,67 d-1), and value of temperature indicator equalled Θ = 1.024. For thermal disintegration of biological waste, value of reaction speed indicator k20 was 0.016 h-1 (0,38 d-1), and value of temperature indicator equalled Θ = 1.016.

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