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Journal articles on the topic 'Thickened waste activated sludge (TWAS)'

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Author: Grafiati

Published: 10 December 2022

Last updated: 28 January 2023

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1

Chi, Yong Zhi, Yu You Li, Min Ji, Hong Qiang, Heng Wei Deng, and Ya Peng Wu. "Use of Combined NaOH-Microwave Pretreatment for Enhancing Mesophilic Anaerobic Digestibility of Thickened Waste Activated Sludge." Advanced Materials Research 113-116 (June 2010): 459–68. http://dx.doi.org/10.4028/www.scientific.net/amr.113-116.459.

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A combined NaOH-microwave (MW) pretreatment process was studied in order to investigate the effects of NaOH-MW pretreated thickened waste activated sludge (TWAS) on anaerobic digestion. In the NaOH-MW pretreatment studies, Uniform design was successfully applied to determine the relationship of TWAS solubilization to environmental conditions (NaOH dose, target temperature, and MW holding time) and to establish the mathematical model describing the solubilization degree to changes in these variables. The maximum solubilization ratio (85.1%) of volatile suspended solids (VSS) could be achieved at 210°C with 0.2 g-NaOH/g-SS and 35 min holding time. The biochemical methane potential (BMP) tests showed that all digesters fed with pretreated TWAS improved the methane production compared to control system, and the optimal conditions, at 170°C with 0.05 g-NaOH/g-SS and 1 min holding time, were suggested for NaOH-MW pretreatment of TWAS. In spite of the increase in the soluble chemical oxygen demand concentration and decrease in the dewaterability of digested sludge, the semi-continuous reacter fed with the pretreated TWAS without neutralization was stable and gave higher organics reductions and methane yields compared to the control.

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2

Chi, Yong Zhi, Yu You Li, Min Ji, Hong Qiang, Heng Wei Deng, and Ya Peng Wu. "Mesophilic and Thermophilic Digestion of Thickened Waste Activated Sludge: A Comparative Study." Advanced Materials Research 113-116 (June 2010): 450–58. http://dx.doi.org/10.4028/www.scientific.net/amr.113-116.450.

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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.

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3

Hogan, F., S. Mormede, P. Clark, and M. Crane. "Ultrasonic sludge treatment for enhanced anaerobic digestion." Water Science and Technology 50, no. 9 (November 1, 2004): 25–32. http://dx.doi.org/10.2166/wst.2004.0526.

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Ultrasound is the term used to describe sound energy at frequencies above 20 kHz. Highpowered ultrasound can be applied to a waste stream via purpose-designed tools in order to induce cavitation. This effect results in the rupture of cellular material and reduction of particle size in the waste stream, making the cells more amenable to downstream processing. sonixTM is a new technology utilising high-powered, concentrated ultrasound for conditioning sludges prior to further treatment. This paper presents recent results from a number of demonstration and full-scale plants treating thickened waste activated sludge (TWAS) prior to anaerobic digestion, therefore enhancing the process. The present studies have proved that the use of ultrasound to enhance anaerobic digestion can be achieved at full scale and effectively result in the TWAS (typically difficult to digest) behaving, after sonication, as if it were a “primary” sludge. The technology presents benefits in terms of increased biogas production, better solids reduction, improved dewatering characteristics of the digested sludge mixture and relatively short payback periods of two years or less subject to the site conditions and practices applicable at that time.

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4

Young, Bradley, Kevin Kennedy, Robert Delatolla, and Ranya Sherif. "Semi-continuous mesophilic anaerobic co-digestion of thermally pretreated scum." Water Quality Research Journal 51, no. 2 (February 25, 2016): 117–27. http://dx.doi.org/10.2166/wqrjc.2016.024.

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The objective of this study is to investigate the mesophilic, anaerobic, co-digestion of scum with thickened waste activated sludge (TWAS) and primary sludge (PS). Observations of the reactor waste show that higher pretreatment temperatures assist in scum integration and appear to limit coagulation and separation effects associated with digesting fats, oils and greases. The 0.40 kg VS/m3 · d scum loaded reactor with scum pretreated at 70 °C achieved the greatest improvement in biogas production over PS and TWAS co-digestion without scum addition. Based on cell viability analysis of the reactor waste, scum-containing reactors were shown to produce 48 and 39% more biogas per m3 of live cells; signifying that scum addition increased the activity of the microbial population embedded in the waste or caused a microbial shift in the waste towards more active communities.

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5

Suhartini, Sri, Lynsey Melville, and Tony Amato. "Pre-treatment of thickened waste activated sludge (TWAS) for enhanced biogas production via the application of a novel radial horn sonication technology." Water Science and Technology 75, no. 9 (February 22, 2017): 2179–93. http://dx.doi.org/10.2166/wst.2017.069.

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The efficacy of sonication as a pre-treatment to anaerobic digestion (AD) was assessed using thickened waste activated sludge (TWAS). Efficiency was measured in relation to solubilisation, dewaterability, and AD performance. Eighteen experimental conditions were evaluated at low frequency (20 kHz), duration (2–10 s), amplitude (∼8–12 μm) and applied pressure (0.5–3.0 barg), using a sonix™ patented titanium sonoprobe capable of delivering an instantaneous power of ∼6 kW provided by Doosan Enpure Ltd (DEL). An optimised experimental protocol was used as a pre-treatment for biochemical methane potential (BMP) testing and semi-continuous trials. Four digesters, with a 2-L working volume were operated mesophilically (37 ± 0.5 °C) over 22 days. The results showed that the sonix™ technology delivers effective sonication at very short retention times compared to conventional system. Results demonstrate that the technology effectively disrupts the floc structures and filaments within the TWAS, causing an increase in solubilisation and fine readily digestible material. Both BMP tests and semi-continuous trials demonstrated that sonicated TWAS gave higher biodegradability and methane potential compared to untreated TWAS. Partial-stream sonication (30:70 sonicated to untreated TWAS) resulted in a proportionate increase in biogas production illustrating the benefits of full-stream sonication.

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6

Kakar, Farokh Laqa, Frew Tadesse, and Elsayed Elbeshbishy. "Comprehensive Review of Hydrothermal Pretreatment Parameters Affecting Fermentation and Anaerobic Digestion of Municipal Sludge." Processes 10, no. 12 (November 28, 2022): 2518. http://dx.doi.org/10.3390/pr10122518.

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Municipal solid waste treatment and disposal have become one of the major concerns in waste management due to the excessive production of waste and higher levels of pollution. To address these challenges and protect the environment in sustainable ways, the hydrothermal pretreatment (HTP) technique coupled with anaerobic digestion (AD) becomes a preferred alternative technology that can be used for municipal solid waste stabilization and the production of renewable energy. However, the impact of HTP parameters such as temperature, retention time, pH, and solid content on the fermentation of TWAS is yet to be well studied and analyzed. Hence this study was conducted to review the effect of hydrothermal pretreatment of thickened waste-activated sludge (TWAS) on fermentation and anaerobic digestion processes. Many studies reported that fermentation of TWAS at pretreatment temperature ranges from 160 °C to 180 °C resulted in a 50% increase in volatile fatty acid (VFA) yields compared to no pretreatment. However, for the AD process, HTP in the range of 175 °C to 200 °C with a 30–60 min retention time was considered the optimal condition for higher biogas production, with 30% increase in biodegradability and greater than 55% increase in biogas production. Even though there is a direct relationship between increased HTP temperature and the hydrolysis of TWAS, a pretreatment temperature range beyond 200 °C alters the biogas production. The solid content (SC) of sludge plays a crucial role in HTP, where in practice up to 16% SC has been utilized for HTP. Further, a combined alkaline-HTP enhances the process performance.

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7

Dagnew, Martha, Wayne J. Parker, and Peter Seto. "A pilot study of anaerobic membrane digesters for concurrent thickening and digestion of waste activated sludge (WAS)." Water Science and Technology 61, no. 6 (March 1, 2010): 1451–58. http://dx.doi.org/10.2166/wst.2010.028.

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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.

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8

Abudi, Zaidun Naji, Zhiquan Hu, Na Sun, Bo Xiao, Nagham Rajaa, Cuixia Liu, and Dabin Guo. "Batch anaerobic co-digestion of OFMSW (organic fraction of municipal solid waste), TWAS (thickened waste activated sludge) and RS (rice straw): Influence of TWAS and RS pretreatment and mixing ratio." Energy 107 (July 2016): 131–40. http://dx.doi.org/10.1016/j.energy.2016.03.141.

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9

Alqaralleh, Rania Mona, Kevin Kennedy, and Robert Delatolla. "Improving biogas production from anaerobic co-digestion of Thickened Waste Activated Sludge (TWAS) and fat, oil and grease (FOG) using a dual-stage hyper-thermophilic/thermophilic semi-continuous reactor." Journal of Environmental Management 217 (July 2018): 416–28. http://dx.doi.org/10.1016/j.jenvman.2018.03.123.

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10

Hamzawi, N., K. J. Kennedy, and D. D. McLean. "Anaerobic digestion of co-mingled municipal solid waste and sewage sludge." Water Science and Technology 38, no. 2 (July 1, 1998): 127–32. http://dx.doi.org/10.2166/wst.1998.0121.

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This study evaluated the technical feasibility of the anaerobic co-digestion process in the context of typical North American solid waste. Using biological activity tests, an optimal mixture was identified with 25% organic fraction of municipal solid waste (OFMSW) and 75% sewage sludge (65% raw primary sludge (RAW), 35% thickened WAS (TWAS)) based on biogas production. Also, based on the rate of biogas production, the most anaerobically biodegradable components of the OFMSW were paper and grass. The TWAS and the newspaper were found to be the least biodegradable components. Lab-scale testing indicated that alkaline pretreatment increased the biodegradability of the sewage sludge/OFMSW mixture the most, as compared to the untreated control. Thermochemically pretreated feedstocks inhibited anaerobic biodegradability as compared to the control, whereas the anaerobic biodegradability of thermally pretreated feed was not found to be significantly different from that of the control. Empirical models were developed based on alkaline dose, feed total solids concentration and particle size for biogas production and removal of TS and VS. All three experimental factors were found to be significant with respect to the response variables studied.

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11

MacDonald, Allan J., and Onita D. Basu. "Influence of Polymer Selection on Nutrient Phase Separation for Waste Activated Sludge Thickening at Bench Scale." Water Quality Research Journal 43, no. 4 (November 1, 2008): 305–12. http://dx.doi.org/10.2166/wqrj.2008.034.

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Abstract The use of polymers to condition waste activated sludge prior to thickening is a common practice at domestic wastewater treatment plants. In this study, the performance of various commercially available granular polymers was observed. Thickening by gravity belt thickener was simulated at the bench scale, and the thickened sludge and filtrate produced were examined. Laboratory analysis was used to determine the differences in nutrient chemical concentration in the thickened solids and filtrate produced by different polymers. By examining the content of nutrient chemicals such as total Kjeldahl nitrogen (TKN), ammonia nitrogen, and total phosphorous, this research showed that polymer choice could affect the chemical composition of thickened sludge and filtrate with respect to nutrients. Results showed that the total phosphorous and TKN concentrations in the thickened sludge and filtrate were affected by polymer selection, which suggested that the chemical loading on the plant due to filtrate recycle, and the nutrient content of thickened sludge delivered to the digester are affected by polymer choice. Polymer optimization studies that examine nutrient properties of filtrate and thickened sludge beyond the basic total suspended solids analysis may be advantageous to minimize recycling of these compounds into the filtrate phase.

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12

Elbeshbishy, Elsayed, Bipro Ranjan Dhar, and George Nakhla. "Assessing the Nonbiodegradable Fraction of the Thickened Waste Activated Sludge." Water Environment Research 87, no. 8 (August 1, 2015): 707–11. http://dx.doi.org/10.2175/106143015x14338845156821.

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13

Chowdhury, Mohammad M. I., George Nakhla, and J. Zhu. "Estimation of the Unbiodegradable Fraction of Thickened Waste Activated Sludge." Water Environment Research 90, no. 9 (September 1, 2018): 819–25. http://dx.doi.org/10.2175/106143017x15131012187962.

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14

Ara, E., M. Sartaj, and K. Kennedy. "Effect of microwave pre-treatment of thickened waste activated sludge on biogas production from co-digestion of organic fraction of municipal solid waste, thickened waste activated sludge and municipal sludge." Waste Management & Research 32, no. 12 (November 14, 2014): 1200–1209. http://dx.doi.org/10.1177/0734242x14554641.

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15

Czerwionka, K., and J. Makinia. "Dissolved and colloidal organic nitrogen removal from wastewater treatment plants effluents and reject waters using physical–chemical processes." Water Science and Technology 70, no. 3 (June 11, 2014): 561–68. http://dx.doi.org/10.2166/wst.2014.267.

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Four physical–chemical processes were compared in terms of the efficiencies of dissolved and colloidal organic nitrogen (DON and CON) removal from the secondary effluents (SE) and reject water from full-scale biological nutrient removal activated sludge systems. Adsorption on activated carbon was most efficient and allowed removal from the SE of up to 80% and 100% of DON and CON, respectively. High efficiencies of DON removal from SE (up to 55%) were also obtained when using coagulation with iron(III) chloride and calcium hydroxide at final pH = 11.0–11.5. The efficiency of DON removal from thickening waste activated sludge (TWAS) reject water, obtained using coagulation with iron(III) chloride, was comparable with the efficiency for the SE. The efficiency of this process with regard to the sludge digester liquors (SDL) was significantly higher, i.e., 65–70% for both DON and CON. The ion exchange process with strongly acidic cation exchange resin (without pH correction) resulted in a relatively small efficiency of DON removal (<15%), and negligible efficiency of CON removal (<10%). Furthermore, ultrafiltration (0.015 μm) of SE and TWAS reject water resulted in a relatively low efficiency of DON removal (10–13% and 10–20% respectively). Ultrafiltration was found to be more effective for DON removal from SDL (41–68%).

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16

Gary, Dan, James Barry, Robert Morton, Chi-Chung Tang, Robert Horvath, and James F. Stahl. "TESTING OF TWO ULTRASONIC SLUDGE TREATMENT SYSTEMS FOR CONDITIONING OF THICKENED WASTE ACTIVATED SLUDGE." Proceedings of the Water Environment Federation 2005, no. 13 (January 1, 2005): 2803–17. http://dx.doi.org/10.2175/193864705783865541.

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17

Elbeshbishy, Elsayed, Frances Okoye, Dang Ho, Siva Sarathy, and Wayne Parker. "Free Nitrous Acid Pretreatment of Thickened Waste Activated Sludge Improves Anaerobic Degradability." Proceedings of the Water Environment Federation 2017, no. 1 (January 1, 2017): 75–84. http://dx.doi.org/10.2175/193864717821495591.

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18

Zikakis, D., J. Chauzy, I. Droubogianni, and A. Georgakopoulos. "Why applying THP on waste activated sludge makes sense: Psyttalia – Athens case study." Water Practice and Technology 14, no. 4 (November 14, 2019): 921–30. http://dx.doi.org/10.2166/wpt.2019.078.

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Abstract In order to improve the energy footprint of Psyttalia wastewater treatment plant (WWTP) in Athens, the application of a thermal hydrolysis process (THP) was preferred to the option of constructing additional digesters. Since August 2015, approximately half of the generated waste activated sludge (WAS) has been treated by a Cambi B6-4 system, while the thickened primary sludge (PS) is by-passing the THP and is mixed with the hydrolysed WAS before entering the 4 digesters. The 4 other conventional digesters have treated the remaining sludge. The dewaterability of the mixed digested sludge has significantly been improved from 22% dry solids (DS) before THP installation, up to 31% DS after THP installation. This is providing substantial reduction of energy use and cost savings at the sludge drying plant of Psyttalia. In addition, biogas generation and digester efficiency (VSR) have been increased.

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19

Zurzolo, Francesco, Damian J. Kruk, and Jan A. Oleszkiewicz. "Phosphorus Recovery and VFA Generation from Waste Activated Sludge Alone and Co-thickened with Primary Sludge." Proceedings of the Water Environment Federation 2013, no. 19 (January 1, 2013): 204–13. http://dx.doi.org/10.2175/193864713813667656.

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20

Zhang, Liguo, Haoran Duan, Liu Ye, Lei Liu, Damien J. Batstone, and Zhiguo Yuan. "Increasing capacity of an anaerobic sludge digester through FNA pre-treatment of thickened waste activated sludge." Water Research 149 (February 2019): 406–13. http://dx.doi.org/10.1016/j.watres.2018.11.008.

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21

Toreci, Isil, Kevin J. Kennedy, and Ronald L. Droste. "Effect of High-Temperature Microwave Irradiation on Municipal Thickened Waste Activated Sludge Solubilization." Heat Transfer Engineering 31, no. 9 (August 2010): 766–73. http://dx.doi.org/10.1080/01457630903501039.

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22

Wang, Qunhui, Kazuhiro Fujisaki, Yukihide Ohsumi, and Hiroaki I. Ogawa. "ENHANCEMENT OF DEWATERABILITY OF THICKENED WASTE ACTIVATED SLUDGE BY FREEZING AND THAWING TREATMENT." Journal of Environmental Science and Health, Part A 36, no. 7 (July 31, 2001): 1361–71. http://dx.doi.org/10.1081/ese-100104884.

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23

Chowdhury, M. M. I., G. Nakhla, and J. Zhu. "Ultrasonically enhanced anaerobic digestion of thickened waste activated sludge using fluidized bed reactors." Applied Energy 204 (October 2017): 807–18. http://dx.doi.org/10.1016/j.apenergy.2017.07.057.

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24

Scaglione, D., S. Caffaz, E. Ficara, F. Malpei, and C. Lubello. "A simple method to evaluate the short-term biogas yield in anaerobic codigestion of WAS and organic wastes." Water Science and Technology 58, no. 8 (October 1, 2008): 1615–22. http://dx.doi.org/10.2166/wst.2008.502.

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The present study was aimed at setting and applying a procedure to measure the anaerobic degradability of different organic substrates by short-term tests (2–7 days) carried out at lab-scale with a low food to biomass (F/M) ratio. All tests were carried out using an acclimated sludge taken from a pilot-plant anaerobic digester (200 L). Trials were performed with a manometric system. The experimental reliability of the device in measuring the anaerobic degradability was assessed by several preliminary tests carried out using acetate and glucose as reference substrates. The average conversion to methane was 99% for acetate and of 83% for glucose. The results of tests in triplicate showed the high repeatability of the method with an average coefficient of variation lower than 2%. Then, the lab-scale procedure was applied to study the short-term anaerobic degradability of complex organic substrates: thickened waste activated sludge, two kinds of organic fraction of municipal solid waste (a kitchen waste and a fruit and vegetable waste collected at the wholesale market of Florence), olive mill wastewater and freshly harvested grass. Results indicated that organic fraction of municipal solid waste, olive mill wastewater and grass were characterized by a much higher anaerobic degradability if compared to the thickened activated sludge, well in agreement with literature data.

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25

Zubrowska-Sudol, Monika, Katarzyna Sytek-Szmeichel, Piotr Krawczyk, and Agnieszka Bisak. "Energy-Positive Disintegration of Waste Activated Sludge—Full Scale Study." Energies 15, no. 2 (January 13, 2022): 555. http://dx.doi.org/10.3390/en15020555.

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This study aimed to evaluate the effects of mechanical disintegration of waste activated sludge (WAS) on full scale anaerobic digestion, considering the possibility of obtaining a positive energy balance. The results showed that an increase in energy density (εL) used in disintegration was accompanied by an increase in the release of organic compounds from sludge (SCOD increased from 211 ± 125 mg O2/L for εL = 0 kJ/L to 6292 ± 2860 mgO2/L for εL = 180 kJ/L). Some of them were volatile fatty acids. The percentage share of WAS subject to disintegration was also documented as a crucial parameter affecting the efficiency of biogas production. An increase in the value of this parameter from 25% to 100%, even at much lower εL used in disintegration (therefore with much smaller amounts of organic compounds released from sludge flocs) resulted in an increase in biogas production. Conducting disintegration of the entire stream of WAS directed to the fermentation tank at εL 30 kJ/L resulted in an increase in biogas production by 14.1%. Such a surplus would allow production of approximately 360 kWh/d net electricity. Mechanical disintegration of thickened WAS therefore may be an economically justifiable strategy for the intensification of anaerobic sludge stabilisation.

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26

Athanasoulia, E., P. Melidis, and A. Aivasidis. "Anaerobic waste activated sludge co-digestion with olive mill wastewater." Water Science and Technology 65, no. 12 (June 1, 2012): 2251–57. http://dx.doi.org/10.2166/wst.2012.139.

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Co-digestion of waste activated sludge (WAS) with agro-industrial organic wastewaters is a technology that is increasingly being applied in order to produce increased gas yield from the biomass. In this study, the effect of olive mill wastewater (OMW) on the performance of a cascade of two anaerobic continuous stirred tank (CSTR) reactors treating thickened WAS at mesophilic conditions was investigated. The objectives of this work were (a) to evaluate the use of OMW as a co-substrate to improve biogas production, (b) to determine the optimum hydraulic retention time that provides an optimised biodegradation rate or methane production, and (c) to study the system stability after OMW addition in sewage sludge. The biogas production rate at steady state conditions reached 0.73, 0.63, 0.56 and 0.46 lbiogas/lreactor/d for hydraulic retention times (HRTs) of 12.3, 14, 16.4 and 19.7 d. The average removal of soluble chemical oxygen demand (sCOD) ranged between 64 and 72% for organic loading rates between 0.49 and 0.75 g sCOD/l/d. Reduction in the volatile suspended solids ranged between 27 and 30%. In terms of biogas selectivity, values of 0.6 lbiogas/g tCOD removed and 1.1 lbiogas/g TVS removed were measured.

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27

Wang, Ling, Tarek N. Aziz, and Francis L. de los Reyes. "Determining the limits of anaerobic co-digestion of thickened waste activated sludge with grease interceptor waste." Water Research 47, no. 11 (July 2013): 3835–44. http://dx.doi.org/10.1016/j.watres.2013.04.003.

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28

Merzari, Fabio, Jillian Goldfarb, Gianni Andreottola, Tanja Mimmo, Maurizio Volpe, and Luca Fiori. "Hydrothermal Carbonization as a Strategy for Sewage Sludge Management: Influence of Process Withdrawal Point on Hydrochar Properties." Energies 13, no. 11 (June 5, 2020): 2890. http://dx.doi.org/10.3390/en13112890.

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Conventional activated sludge systems, still widely used to treat wastewater, produce large amounts of solid waste that is commonly landfilled or incinerated. This study addresses the potential use of Hydrothermal Carbonization (HTC) to valorize sewage sludge residues examining the properties of hydrochars depending on HTC process conditions and sewage sludge withdrawal point. With increasing HTC severity (process residence time and temperature), solid yield, total Chemical Oxygen Demand (COD) and solid pH decrease while ash content increases. Hydrochars produced from primary (thickened) and secondary (digested and dewatered) sludge show peculiar distinct properties. Hydrochars produced from thickened sludge show good fuel properties in terms of Higher Heating Value (HHV) and reduced ash content. However, relatively high volatile matter and O:C and H:C ratios result in thermal reactivity significantly higher than typical coals. Both series of carbonized secondary sludges show neutral pH, low COD, enhanced phosphorous content and low heavy metals concentration: as a whole, they show properties compatible with their use as soil amendments.

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29

Kakar, Farokh laqa, Ehssan Hosseini Koupaie, Ahmed Shabir Razavi, Hisham Hafez, and Elsayed Elbeshbishy. "Effect of Hydrothermal Pretreatment on Volatile Fatty Acids Production from Thickened Waste Activated Sludge." BioEnergy Research 13, no. 2 (October 23, 2019): 591–604. http://dx.doi.org/10.1007/s12155-019-10056-z.

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30

Alqaralleh, Rania Mona, Kevin Kennedy, and Robert Delatolla. "Molecular weight distribution of pretreated thickened waste activated sludge and fat, oil, and grease." Environmental Science and Pollution Research 27, no. 12 (February 3, 2020): 13227–36. http://dx.doi.org/10.1007/s11356-020-07906-1.

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31

Zurzolo, Francesco, Damian J. Kruk, and Jan A. Oleszkiewicz. "Phosphorus recovery and VFA generation from waste activated sludge alone (WAS) and co-thickened with primary sludge (PS)." Proceedings of the Water Environment Federation 2013, no. 4 (January 1, 2013): 597–604. http://dx.doi.org/10.2175/193864713813525842.

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32

Patroescu, Ion Viorel, Razvan Laurentiu Dinu, Mihai Stefanescu, Valeriu Robert Badescu, Nicolae Ionut Cristea, and Coline Martin. "Application of ultrasonic disintegration to waste activated sludge for increasing of biogas production by anaerobic digestion." Romanian Journal of Ecology & Environmental Chemistry 2, no. 2 (October 14, 2020): 17–21. http://dx.doi.org/10.21698/rjeec.2020.202.

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The municipal wastewater treatment is the source of significant amounts of primary and secondary sludge which is under the present legislation referring to quality and management aspects. It is estimated that a half of wastewater treatment plant costs are due to the sludge management. Anaerobically sludge stabilization, capitalization as energy source, in order to diminish the costs and sludge volume decreasing, are the aims of the main operational steps of sludge treatment, as a part of wastewater treatment plant. The improvement of sludge anaerobically stabilization process must be possible by acting in the rate limiting step - hydrolysis in order to rise the organic carbon solubilization. The increase of soluble carbon can be possible by adding a pretreatment step of waste biological sludge, ultrasonic disintegration being one option. This paper emphasized the experimental results regarding anaerobically stabilization of the thickened waste biological sludge by ultrasonication taking into account the results of blank test, without ultrasonication. Experimental tests show that ultrasonic disintegration of the sludge having initial dried substances content (d.w) 2.72% and soluble organic load COD of 598 mg O2/L led to soluble COD concentration of 4950-6710 mg O2/L after sonication with specific energy in the range of 3.06 - 14.24 kWh/kg d.w. Anaerobically stabilization during 25 test days at 36 0C of the mixture 40% disintegrated biological sludge and 60% digested sludge (inoculum) mixture led to 30-38.6% increase of biogas production comparing with parallel test with non-sonicated sludge.

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Snyman, H. G., P. Forssman, A. Kafaar, and M. Smollen. "The feasibility of electro-osmotic belt filter dewatering technology at pilot scale." Water Science and Technology 41, no. 8 (April 1, 2000): 137–44. http://dx.doi.org/10.2166/wst.2000.0153.

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Sewage sludge is typically dewatered using drying beds, belt filter presses or centrifuges. Mechanical dewatering of sludge is costly in terms of capital and running costs, especially the flocculent. In an attempt to address the need for more cost-effective dewatering technologies, electro-osmotic belt filtering was developed by Smollen and Kafaar in 1995. Themechanical equipment resembles a belt filter press but the belts are stainless steel, woven belts, which act as the electrodes. In this study, thefeasibility of the technology was tested at pilot scale using wasteactivated-, anaerobically digested- and dissolved air flotation sludge. The parameters which were investigated includes the applied voltage, polyelectrolyteusage and sludge feed rate. Applied voltage of between 15 and 25 volts increased the dewatering significantly in the waste activated- and anaerobically digested sludge. Applying a voltage in dissolved air flotation sludge could not enhance the efficiency of dewatering, unless stored to de-air. The technology was found as sensitive to polyelectrolyte dosages as belt presses. The performance of the electro-osmotic belt filter was sensitive to feed rate, but performed well with non-thickened waste activated sludge (0.61% solids), resulting in cake solids above 20%.

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Saunamäki, R. "Sludge Handling and Disposal at Finnish Activated Sludge Plants." Water Science and Technology 20, no. 1 (January 1, 1988): 171–82. http://dx.doi.org/10.2166/wst.1988.0020.

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Between 1984 and 1986 a total of 13 activated sludge treatment plants were built in Finland to handle waste waters from the pulp and paper mills. With just a few exceptions these plants have come up to expectations, achieving BOD7 reductions of 80-95 %. These plants produce around 94,000 tonnes (dry weight) of sludge a year, of which some 27,000 tonnes is biosludge. On a mill basis, biosludge accounts for 10-50 % of total sludge. Generally speaking, the higher the loading at the plant, the more biosludge is produced. The yields of biosludge were 0.3-1.2 kgTS/(kgBOD removed) for a sludge load of 0.1-1.2 kgBOD7/(kgMLVSS*d). The biosludge is separated by sedimentation in clarifiers and thickened in round sedimentation basins to a consistency of 3-5 %. At one mill anaerobic sludge from an oversized thickener is returned to the aeration basin. The aim of this is to minimize the need for nutrient addition. Belt filter presses are normally used for sludge dewatering, the solids contents achieved being about 25-37 %. The difficulty of handling biosludge and the low solids contents achieved were considered by many mills to be the main problems of sludge handling. At one mill a drum press is used to press a pretreated mixture of sludge and bark to around 42 % consistency for burning. Six mills burn all or part of their sludge in a bark-fired boiler. On a dry weight basis the sludge burned normally accounts for 5-10 % of total fuel consumption. Burning sludge has been associated with a reduction in steam generation and an increase in running problems. The other method of disposing of sludge is landfilling. Sludge is not used as a fertilizer or soil improvement agent in Finland.

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35

Francisco, R., J. Scheleuderer, S. S. Venturelli, and G. C. da Rocha. "Alternatives for Soil Disposal of Excess Activated Sludge from the Industrial Waste Treatment Plant at Companhia Alcoolquímica Nacional." Water Science and Technology 19, no. 8 (August 1, 1987): 127–37. http://dx.doi.org/10.2166/wst.1987.0051.

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The industrial wastewater treatment plant at Companhia Alcoolquímica Nacional in Cabo, PE, with operation start-up expected in the second semester of 1986, is composed of: hydraulic and organic load equalization, pH correction and an extended aeration activated sludge plant. For the purpose of disposing of 995 kg solids/day (dry solids) excess biological sludge, a study was undertaken with the intention of using land disposal, after preliminary comparison with other conventional methods. For the disposal of this sludge, which was thickened to 4% suspended solids by dissolved air flotation, two alternatives were proposed:Land disposal by subsurface injection (10 t dry solids per hectare per pass every 60 days).Land disposal by the trench fill system, in an available area of 3 ha. In the case of subsurface injection, grass would be used for the vegetation cover. In the case of the trench fill system, corn and/or manioc tillages would be used. The crops obtained from these tillages may be used for animal feed. After analysing several factors, such as available area, implementation and operating costs, handling facilities and climatic conditions, the trench fill disposal system was chosen. This has the following features:(a)Trenches with 50 cm base, distance from one trench to the next of 100 cm, (i.e., 10 trenches per 15 m), 35 cm depth;(b)0.3% trench slopes;(c)Conveyance of thickened sludge through a main chute with 0.1% slope;(d)120 t dry solids/ha/yr application, on a 3 ha total area;(e)Addition accomplished at a rate of 1/5 ha/day (5 days per week), the whole cycle being completed every three weeks.

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Liu, Yu-Chen, and Johng-Hwa Ahn. "Effect of Combination of Ozone and Microwave Pretreatments on Solubilization of Thickened Waste Activated Sludge." Journal of Korea Society of Waste Management 31, no. 7 (October 31, 2014): 734–39. http://dx.doi.org/10.9786/kswm.2014.31.7.734.

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37

Rabii, Anahita, Yaser Dahman, and Elsayed Elbeshbishy. "Mesophilic Anaerobic Co-digestion of Manure and Thickened Waste Activated Sludge at Different Mixture Ratios." Proceedings of the Water Environment Federation 2018, no. 4 (January 1, 2018): 166–73. http://dx.doi.org/10.2175/193864718824829000.

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38

Wan, Caixia, Quancheng Zhou, Guiming Fu, and Yebo Li. "Semi-continuous anaerobic co-digestion of thickened waste activated sludge and fat, oil and grease." Waste Management 31, no. 8 (August 2011): 1752–58. http://dx.doi.org/10.1016/j.wasman.2011.03.025.

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39

Sarwar, Rubaiya, Elsayed Elbeshbishy, and Wayne Parker. "Effect of thermal pretreatment on digestability of thickened waste activated sludge and primary sludge in two-stage anaerobic digestion." Proceedings of the Water Environment Federation 2015, no. 10 (January 1, 2015): 1562–70. http://dx.doi.org/10.2175/193864715819542377.

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Sarwar, Rubaiya, Elsayed Elbeshbishy, and Wayne J. Parker. "Codigestion of high pressure thermal hydrolysis-treated thickened waste activated sludge with primary sludge in two-stage anaerobic digestion." Environmental Progress & Sustainable Energy 37, no. 1 (September 28, 2017): 425–33. http://dx.doi.org/10.1002/ep.12700.

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41

Jenicek, P., J. Kutil, O. Benes, V. Todt, J. Zabranska, and M. Dohanyos. "Energy self-sufficient sewage wastewater treatment plants: is optimized anaerobic sludge digestion the key?" Water Science and Technology 68, no. 8 (October 1, 2013): 1739–44. http://dx.doi.org/10.2166/wst.2013.423.

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The anaerobic digestion of primary and waste activated sludge generates biogas that can be converted into energy to power the operation of a sewage wastewater treatment plant (WWTP). But can the biogas generated by anaerobic sludge digestion ever completely satisfy the electricity requirements of a WWTP with ‘standard’ energy consumption (i.e. industrial pollution not treated, no external organic substrate added)? With this question in mind, we optimized biogas production at Prague's Central Wastewater Treatment Plant in the following ways: enhanced primary sludge separation; thickened waste activated sludge; implemented a lysate centrifuge; increased operational temperature; improved digester mixing. With these optimizations, biogas production increased significantly to 12.5 m3 per population equivalent per year. In turn, this led to an equally significant increase in specific energy production from approximately 15 to 23.5 kWh per population equivalent per year. We compared these full-scale results with those obtained from WWTPs that are already energy self-sufficient, but have exceptionally low energy consumption. Both our results and our analysis suggest that, with the correct optimization of anaerobic digestion technology, even WWTPs with ‘standard’ energy consumption can either attain or come close to attaining energy self-sufficiency.

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Li, Zhongtian, Melissa Arnot, Joseph Hughes, Hiroko Yoshida, Peiyu Tan, and Michael K. Stenstrom. "Reducing Viscosity of Thickened Waste Activated Sludge, Improving Dewaterability of Digested Sludge, and Increasing Biogas Production through Thermochemical Hydrolysis Process." Proceedings of the Water Environment Federation 2017, no. 5 (January 1, 2017): 5062–69. http://dx.doi.org/10.2175/193864717822156785.

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Okoye, Frances, Elsayed Elbeshbishy, Dang Ho, Wayne Parker, and Siva Sarathy. "The Effect of Free Nitrous Acid Pretreatment on The Anaerobic Digestibility of Thickened Waste Activated Sludge." Proceedings of the Water Environment Federation 2018, no. 4 (January 1, 2018): 766–74. http://dx.doi.org/10.2175/193864718824828434.

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44

Yu, Najiaowa, Anqi Mou, Huijuan Sun, and Yang Liu. "Anaerobic digestion of thickened waste activated sludge under calcium hypochlorite stress: Performance stability and microbial communities." Environmental Research 212 (September 2022): 113441. http://dx.doi.org/10.1016/j.envres.2022.113441.

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45

Kakar, Farokh laqa, Ahmed El Sayed, Neha Purohit, and Elsayed Elbeshbishy. "Volatile Fatty Acids and Biomethane Recovery from Thickened Waste Activated Sludge: Hydrothermal Pretreatment’s Retention Time Impact." Processes 8, no. 12 (November 30, 2020): 1580. http://dx.doi.org/10.3390/pr8121580.

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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.

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Bobade, Veena, Geoffery Evans, and Nicky Eshtiaghi. "Bubble rise velocity and bubble size in thickened waste activated sludge: Utilising electrical resistance tomography (ERT)." Chemical Engineering Research and Design 148 (August 2019): 119–28. http://dx.doi.org/10.1016/j.cherd.2019.05.021.

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Chi, Yongzhi, Yuyou Li, Xuening Fei, Shaopo Wang, and Hongying Yuan. "Enhancement of thermophilic anaerobic digestion of thickened waste activated sludge by combined microwave and alkaline pretreatment." Journal of Environmental Sciences 23, no. 8 (August 2011): 1257–65. http://dx.doi.org/10.1016/s1001-0742(10)60561-x.

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Bruus, Jacob H., Jimmy R. Christensen, and Hanne Rasmussen. "Anaerobic Storage of Activated Sludge: Effects on Conditioning and Dewatering Performance." Water Science and Technology 28, no. 1 (July 1, 1993): 109–16. http://dx.doi.org/10.2166/wst.1993.0028.

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Since dewatering equipment is commonly operated only during normal working hours, activated sludge must often be stored in an anaerobic condition prior to conditioning. It is the objective of this study to investigate the influence of anaerobic storage on conditioning requirements and dewatering performance on a laboratory scale. Sludges were collected at two large treatment plants (removal of organic matter, nitrogen and phosphorus) and one small treatment plant (removal of organic matter). Thickened activated sludges from the three wastewater treatment plants were stored anaerobically in the laboratory and analyzed frequently during fourteen days of storage. Both organic and inorganic conditioning was used. Turbidity and Dissolved Organic Carbon (DOC) in the sludge bulk water increased as a result of the anaerobic storage. These parameters indicated a release of colloids, dissolved exopolymers and fermentation waste products such as fatty acids to the bulk water. These constituents consumed additional cationic polyelectrolyte. Filterability at the optimal dosage of polyelectrolyte was not affected by anaerobic storage. Therefore, polyelectrolyte requirements are governed by the bulk water constituents, whereas filterability of the sludge is determined by the degree of sludge floc conditioning. Iron requirements seemed unaffected by anaerobic storage, but lime requirements to obtain good filterability increased with anaerobic storage time.

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Park, Nathan D., Steve S. Helle, and Ronald W. Thring. "Combined alkaline and ultrasound pre-treatment of thickened pulp mill waste activated sludge for improved anaerobic digestion." Biomass and Bioenergy 46 (November 2012): 750–56. http://dx.doi.org/10.1016/j.biombioe.2012.05.014.

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Abudi, Zaidun Naji, Zhiquan Hu, Bo Xiao, Alkhafaji R. Abood, Nagham Rajaa, and Mahmood Laghari. "Effects of pretreatments on thickened waste activated sludge and rice straw co-digestion: Experimental and modeling study." Journal of Environmental Management 177 (July 2016): 213–22. http://dx.doi.org/10.1016/j.jenvman.2016.04.028.

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