• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.613-619
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• 2018

In this study, various influent sludge pre-treatment methods and the internal recirculation of thickened sludge from effluents using a liquid/solid separation unit were adopted to investigate their effects on the sludge digestion and methane production in a combined mesophilic anaerobic and thermophilic aerobic sludge digestion process. A lab-scale combined sludge digestion process was operated during 5 phases using different feed sludge pre-treatment strategies. In phase 1, the feed sludge was pre-treated with a thermal-alkaline method. In contrast, in phases 2, 3 and 4, the internal recirculation of thickened sludge from the effluent and thermal-alkaline, thermal, and alkaline pre-treatment (7 days) were applied to the combined process. In phase 5, the raw sludge without any pre-treatment was used to the combined process. With the feed sludge pre-treatment and internal recirculation, the experimental results indicated that the volatile suspended solid (VSS) removal was drastically increased from phases 1 to 4. Also, the methane production rate with the thermal-alkaline pre-treatment and internal recirculation was significantly improved, showing an increment to 285 mL/L/day in phase 2. Meanwhile, the VSS removal and methane production in phase 5 were greatly decreased when the raw sludge without any pre-treatment was applied to the combined process. Considering all together, it was concluded that the combined process with the thickened sludge recirculation and thermal-alkaline pre-treatment can be successfully employed for the highly efficient sewage sludge reduction and methane gas production.

• Korean Chemical Engineering Research
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• v.48 no.1
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• pp.103-109
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• 2010

Anaerobic digestion has been widely used for the treatment of sludge, which is generated from the municipal and industrial wastewater treatment, for its volume reduction and methane production. Many researches on sludge pre-treatment have been carried out in order to enhance the performance of anaerobic digestion by increasing the hydrolysis of sludge which is the rate limiting step of anaerobic digestion. In this study, the effect of pre-treatment on sludge hydrolysis(solubilization), methane production and sludge reduction by anaerobic digestion after thermal, ultrasonic, and thermal-alkali sludge treatment were compared. Thermal-alkali treatment showed 67 and 70% solubilization with municipal and industrial wastewater sludge, respectively, while ultrasonic treatment and thermal treatment gave similar solubilization efficiency of 40% or more. Methane content of the anaerobic digestion gas reached 45~70% and pretreated sludge gave higher methane content than the control sludge. Methane production of thermal, ultrasonic, and thermal-alkali pre-treatment gave 2.6, 2.7, 3.5 times of municipal control sludge and 3.5, 4.1, 4.2 times of industrial control sludge, respectively. Sludge reduction of pre-treated sludge after anaerobic digestion gave 5~19% point higher than that of control sludge, and thermal-alkali treatment showed higher reduction efficiency than thermal and ultrasonic treatment. The results proved that pre-treatment contributed significantly not only for the methane production but also for the cost reduction of sludge treatment and disposal, and thermal-alkali treatment gave the best performance for the sludge treatment.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.526-531
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• 2009

This paper suggests the dehydration and RDF(Refuse Derived Fuel) production of organic sludge, livestock manure and sewerage sludge causing environmental problems, with hydrothermal pre-treatment process. The renewable technology from the organic wastes must involve short treatment time required, reusable energy source, anti-odor and viruses, low cost for the treatment, and well-fertilization. The hydrothermal pre-treatment process promotes to evaporate moisture in the sludge after being shortly treated in a reactor, which is supplied steam and heat by an external boiler, due to the pressure with steam breaks the cell walls of the sludge, so this process removes the internal moisture of the cell. Then, the treated sludge(solid-state) is mixed with waste vinyls called RDF(6,706kcal/kg).

• Journal of the Korea Organic Resources Recycling Association
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• v.21 no.3
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• pp.43-52
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• 2013

In this study, various influent sludge pre-treatment methods were adopted to investigate their effects on the sludge digestion and methane production in combined mesophilic anaerobic and thermophilic aerobic sludge digestion process. A lab-scale sewage sludge digestion process was operated during 4 phases using different feed sludge pre-treatment strategies. In phase 1, feed sludge was supplied without any pre-treatment. In contrast, in phases 2, 3 and 4, thermal, thermal-alkaline and long time alkaline treatment (7 days) were applied to influent sludge, respectively. With sludge pre-treatment, TCOD removal was drastically increased from 44% to 76% from phases 1 to 4, respectively. Also, pre-treatment of feed sludge significantly improved the methane production rate of MAD, showing an increment from 101 to 165-256mL/L/day. Meanwhile, TCOD removal and methane production at phase 4 were not increased, compared to those at phase 3. Based on the experimental results, it was concluded that pre-treatment of feed sludge significantly increases the efficiency of sludge digestion and thermal-alkaline method was the most effective method among the pre-treatment methods examined.

• Advances in environmental research
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• v.5 no.4
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• pp.251-262
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• 2016

The biodegradability and decomposition efficiencies increase with the pre-treatment of sludge in a digestion process. In this study, the feasibility of ultrasound coupled with potassium permanganate oxidation as a disintegration method and digestibility of aerobic reactor fed with disintegrated sludge with ultrasound coupled potassium permanganate were investigated. The first stage of the study focused on determining the optimum condition for ultrasonic pre-treatment for achieving better destruction efficiency of sludge. The second part of the study, the aerobic digestibility of sludge disintegrated with ultrasound and potassium permanganate oxidation alone and combined were examined comparatively. The results showed that when 20 min of ultrasonic pre-treatment applied, the specific energy output was 49384 kJ/kgTS with disintegration degree of 58.84%. During the operation of aerobic digester, VS/TS ratios of digesters fed with disintegrated sludge decreased indicating that disintegration methods could obviously enhance aerobic digestion performance. The highest reduction in volatile solids was 75% in the digester fed with ultrasound+potassium permanganate disintegrated sludge at the end of the operation compared to digester fed with raw sludge. Total Nitrogen (TN) and Total Phosphorus (TP) levels in sludge supernatant increased with this combined method significantly. Besides, it promoted the production of ${\bullet}OH$, thus enhancing the release of Carbon (C), Nitrogen (N) and Phosphorus (P) from the sludge. Disintegration with all methods used in this study could not improve Capillary Suction Time (CST) reduction in disintegrated digesters during the operation. The results demonstrated that the combined ultrasound treatment and potassium permanganate oxidation method improves the biodegradability compared to control reactor or their single application.

• Environmental Engineering Research
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• v.19 no.1
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• pp.59-66
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• 2014

The aim of this study was to assess the effect of pre-aeration on sludge solubilization and the behaviors of nitrogen, dissolved sulfide, sulfate, and siloxane. The results of this study showed that soluble chemical oxygen demand in sewage sludge could be increased through pre-aeration. The pre-aeration process resulted in a higher methane yield compared to the anaerobic condition (blank). The pre-aeration of sewage sludge, therefore, was shown to be an effective method for enhancing the digestibility of the sewage sludge. In addition, this result confirms that the pre-aeration of sewage sludge prior to its anaerobic digestion accelerates the growth of methanogenic bacteria. Removal rates for $NH_3$-N and T-N increased simultaneously during pre-aeration, indicating simultaneous nitrification and denitrification. The siloxane concentration in sewage sludge decreased by 40% after 96 hr of pre-aeration; in contrast, the sulfide concentration in sewage sludge did not change. Therefore, pre-aeration can be employed as an efficient treatment option to achieve higher methane yield and lower siloxane concentration in sewage sludge. In addition, reduction of nitrogen loading by pre-aeration can reduce operating costs to achieve better effluent water quality in wastewater treatment plant and benefit the anaerobic process by minimizing the toxic effect of ammonia.

• Journal of the Korea Organic Resources Recycling Association
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• v.19 no.3
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• pp.35-43
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• 2011

In this study, anaerobic biological decomposition were attempted after solubilization treatment of sewage sludge with the complex pre-treatment (acid/base treatment with ultrasonic radiation). Solubilization ratios were compared for ultrasonic treatment at acid or base condition. Solubilization effect of the complex pre-treatment was more effective at higher pH. Biological decomposition of complex pre-treated sludge was faster than non treated (raw) sludge, showing 10 times higher total gas production. Biological digestion of the sludge shows more biogas production. B/A ratio. which indicates hydrogen production potential, was 50% higher with complex pre-treated sludge than raw sludge but lactic acid or propionic acid were also detected during anaerobic decomposition process.

• Journal of Korean Society on Water Environment
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• v.26 no.5
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• pp.810-815
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• 2010

Ultrasonic sludge pre-treatment has been studied to enhance the performance of anaerobic digestion by increasing sludge hydrolysis which is regarded as the rate-limiting-step of anaerobic digestion. In this study, the effect of ultrasonic pre-treatment on sludge hydrolysis (solubilization) and methane production was investigated. Sludge solubilization efficiency increased with ultrasonic energy input. However, it is uneconomical to apply more than 720 kJ/L as the solubilization efficiency per energy input declines afterwards. Volatile fatty acids concentration increased after the ultrasonic sludge hydrolysis. Anaerobic batch digestion showed that methane volume reached 64.7 and 84.5 mL after 18 days of incubation with the control sludge and ultrasonically hydrolyzed sludge, respectively. Methane production potential, maximum methane production rate, and the lag time of modified Gompertz equation were changed from 70 mL, 6.4 mL/day, and 1.2 days to 89 mL, 9.6 mL/day, and 0.5 day, respectively, after the ultrasonic sludge treatment. The results proved that ultrasonic pre-treatment contributed significantly not only for the methane production but also for the reduction of anaerobic digestion time which is critical for the performance of anaerobic sludge digestion.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.413-424
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• 2014

The potential of using the biogas as energy source has long been widely recognised and current techniques are being developed to upgrade the technical quality and to enhance energy efficiency. The objective of this paper is to present efficient and effective pre-treatment methods of increasing the amount of produced biogas in anaerobic digestion of activated sludge treatment process. The paper also presents a review of the effect on biogas production between pre-treated and raw sludge, and also put forward the advantages and disadvantages of each pre-treatment method.

• Journal of the Korea Organic Resources Recycling Association
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• v.11 no.1
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• pp.84-89
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• 2003

The purpose of this study was to evaluate and improve the pre-treatment facility for foodwaste and sewage sludge mixture treatment. The process of foodwaste pre-treatment consists of storage, classification with crushing, and thickening. The effluent of sewage treatment facility was used as the diluting and washing water. The panicle size of foodwaste after pre-treatment was almost under 2mm, the mixture of foodwastes and sewage sludge showed an advantage to the anaerobic digestion. The amount of gas production increased from 0.8ton/day ($CH_4$ : 0.5ton/day) to 3.5ton/day ($CH_4$ : 2.3ton/day) after the anaerobic digestion of the foodwastes and sewage sludge mixture. The amount of sludge cake increased from 11.2ton/day to 21.2ton/day. Therefore, the proper operation of the foodwaste pre-treatment facility was contributed to the efficient anaerobic digestion of foodwaste and sewage sludge mixture treatment.