Organic material solubilization of domestic primary sludge in anaerobic digestion at controlled pH

2003 ◽  
Vol 48 (4) ◽  
pp. 195-198 ◽  
Author(s):  
C. Yangin Gomec ◽  
R.E. Speece
Keyword(s):  
Anaerobic Digestion ◽  
Volatile Fatty Acids ◽  
Oxygen Demand ◽  
Primary Sludge ◽  
Anaerobic Reactors ◽  
Ph Influence ◽  
Soluble Organic Carbon ◽  
Soluble Chemical Oxygen Demand ◽  
Ph Controlled

The role of the pH in the anaerobic digestion of domestic primary sludge at mesophilic temperature was evaluated. Since solubilization of organic materials is seriously affected by pH, much research has been performed for the evaluation of significant pH influence on the production of soluble organic carbon in the acid phase. In this study, the performance of continuously stirred anaerobic reactors for the production of soluble chemical oxygen demand (SCOD) and volatile fatty acids (VFAs) in domestic primary sludge was investigated. In the first anaerobic reactor, the pH was not controlled (pH-uncontrolled) whereas the pH was fixed at 6.5 (pH-controlled) in the second reactor. Two sets were performed. Results of both sets indicated that, VSS was removed with a corresponding production of VFAs and SCOD in both reactors. However, production of VFAs and SCOD stopped earlier in the pH-controlled reactors. Methanogenic phase started to operate at earlier times whereas hydrolysis and fermentation were still operating in the pH-uncontrolled reactors. The process stability and efficiency of anaerobic digestion of substrates such as domestic primary sludge can be improved by anaerobic digestion elutriated phased treatment (ADEPT) in which the acid elutriation reactor and methanogenic reactor are separated. In this respect, ADEPT was introduced.

The role of pH in the organic material solubilization of domestic sludge in anaerobic digestion

2003 ◽  
Vol 48 (3) ◽  
pp. 143-150 ◽  
Author(s):  
C. Yangin Gomec ◽  
R.E. Speece
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Chemical Oxygen Demand ◽  
Suspended Solids ◽  
Oxygen Demand ◽  
Ph Control ◽  
Primary Sludge ◽  
Anaerobic Reactors ◽  
Soluble Chemical Oxygen Demand ◽  
Ph Controlled

The effect of pH on anaerobic solubilization of domestic primary sludge and activated sludge was investigated and compared. Anaerobic solubilization was carried out in continuously stirred anaerobic reactors at mesophilic temperature (35°C) and pH was fixed at 6.5 (pH-controlled). Many researches reported the serious effects of pH on the solubilization of organic materials. Thus, the aim of pH control in the reactors consisting of domestic primary and activated sludges, was the evaluation of retardation in hydrolysis/acidogenesis at low pH values. Since primary and activated sludges have different biodegradation characteristics, results were compared. Results indicated that the destruction of Total Suspended Solids (TSS) and Volatile Suspended Solids (VSS) were better in the pH-controlled reactors. In both sludges, acetic acid was the main Volatile Fatty Acid (VFA) produced. In the pH-controlled reactors, VSS reduction was found to be 72% in about 20 days in the anaerobic digestion of activated sludge, whereas for the same interval VSS reduction could only be achieved by 32% in primary sludge at 35°C. When primary sludge was used as substrate, the pH-uncontrolled and the pH-controlled reactors removed VSS with a corresponding production of VFAs and Soluble Chemical Oxygen Demand (SCOD). However, production of VFAs and SCOD was ceased after 5 days in the pH-controlled reactor whereas VFAs and SCOD production continued after 5 days in the pH-uncontrolled reactor, which indicated that hydrolysis and fermentation did not complete and continued longer. On the other hand; in either the pH-uncontrolled or the pH-controlled reactor of activated sludge, VSS was not removed with a corresponding production of VFAs and Soluble Chemical Oxygen Demand (SCOD). It was apparent that solubilization was occurring, however this solubilization was not observed as VFA production. When total methane production and total COD (CODtot) removal were estimated using VSS removal in both types of sludges, results indicated that pH control enhanced biogas productions as well as CODtot removals.

Effect of Ultrasonic Pretreatment for the Anaerobic Digestion of Sewage Sludge

2012 ◽  
Vol 531 ◽  
pp. 528-531 ◽  
Author(s):  
Na Wei
Keyword(s):  
Anaerobic Digestion ◽  
Sewage Sludge ◽  
Volatile Fatty Acids ◽  
Biogas Production ◽  
Oxygen Demand ◽  
High Concentration ◽  
Ultrasonic Pretreatment ◽  
Soluble Chemical Oxygen Demand ◽  
Pre Treatment ◽  
Settling Characteristics

Anaerobic digestion is an economic and environmentally friendly technology for treating the biomass material-sewage sludge, but has some limitations, such as the low efficient biogass production. In this paper ultrasound was proposed as pre-treatment for effective sludge anaerobic digestion. Sludge anaerobic digestion experiments with ultrasonic pretreatment was investigated. It can be seen that this treatment effectively leaded to the increase of soluble chemical oxygen demand(SCOD) and volatile fatty acids(VFA)concentration. High concentration of VFA leaded to a increase in biogas production. Besides, the SV of sludge was reduced and the settling characteristics of sludge was improved after ultrasonic pretreatment. It can be concluded that sludge anaerobic digestion with ultrasonic pretreatment is an effective method for biomass material transformation.

scholarly journals Evaluation of acidogenic sludge from anaerobic reactors running at low solids retention times to reduce sludge generation and enhance biogas production

Water SA ◽  
2019 ◽  
Vol 45 (4 October) ◽  
Author(s):  
Wilza Da Silva Lopes ◽  
Ysa Helena Diniz Morais de Luna ◽  
Jose Tavares de Sousa ◽  
Wilton Silva Lopes ◽  
Valderi Duarte Leite
Keyword(s):  
Anaerobic Digestion ◽  
Biogas Production ◽  
Kinetic Constant ◽  
Oxygen Demand ◽  
Gas Production ◽  
Primary Sludge ◽  
Anaerobic Reactors ◽  
Solids Retention ◽  
Improved Performance ◽  
Pre Treatment

ABSTRACT   Sludges generated in the biological processing of sewage are complex mixtures, the constituents of which pose risks to public health and the environment. Anaerobic digestion is considered the most sustainable option for treating sludge because it offers the possibility of generating biogas. The aim of this study was to compare the quantities, properties, biodegradabilities and biochemical methane potentials (BMP) of primary sludge (PS) generated by a primary decanter with acidogenic sludges produced by upflow anaerobic (UA) reactors operating at solids retention times (SRTs) of 2, 4, 6 and 8 days (Samples S2, S4, S6 and S8, respectively). Sludges from both pre-treatments were submitted to alkaline solubilization in order to determine the efficiency of the process in disrupting extracellular complexes. Based on the levels of total solids (TS) present, the primary decanter was found to generate higher quantities of excess sludge (yield of 3.1 gTS∙d-1) than UA reactors operating at low SRTs (yields in the range 1.69 to 0.64 gTS∙d-1). The concentrations of dissolved materials in PS and Samples S2 and S8 were considerably higher after alkaline solubilization, with respective increases of 8, 14 and 28-fold in dissolved organic carbon, 12, 20 and 40-fold in chemical oxygen demand, 25, 31 and 59-fold in proteins, and 17, 21 and 63-fold in carbohydrates. In addition, the BMP value for S8 was some 13% higher than that recorded for PS while the kinetic constant for gas production by S8 was 1.8-fold greater than that of PS. It is concluded that a pre-treatment combining anaerobic digestion at low SRT and alkaline solubilisation would lead to improved performance in subsequent stages of anaerobic digestion and, consequently, increased efficiency in biogas production.

scholarly journals Temperature-Phased Biological Hydrolysis and Thermal Hydrolysis Pretreatment for Anaerobic Digestion Performance Enhancement

Water ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 1812 ◽  
Author(s):  
Beraki Bahre Mehari ◽  
Sheng Chang ◽  
Youngseck Hong ◽  
Han Chen
Keyword(s):  
Anaerobic Digestion ◽  
Volatile Fatty Acids ◽  
Municipal Wastewater ◽  
Performance Enhancement ◽  
Treatment Plant ◽  
Oxygen Demand ◽  
Wastewater Sludge ◽  
Thermal Hydrolysis ◽  
Soluble Chemical Oxygen Demand ◽  
Effects Of Temperature

Thermal hydrolysis (TH) and biological hydrolysis (BH) are two main and growing anaerobic digestion pretreatment technologies. In this study, municipal wastewater sludge samples were collected from the Guelph Wastewater Treatment Plant (WWTP) in Ontario, Canada. The effects of temperature on BH treatment, including BH at 42 °C (BH42), 42 °C followed by 55 °C (BH42+55), 55 °C followed by 42 °C (BH55+42), and 55 °C (BH55) were evaluated for anaerobic digestion performance enhancement and compared with TH treatment at 165 °C. The TH, BH42, BH42+55, BH55+42, and BH55 treatments caused the reduction of volatile suspended solids (VSS) by 22.6%, 17.5%, 24.6%, 23.1%, and 25.9%, respectively. The soluble chemical oxygen demand (sCOD) content of the sludge increased by 377.5%, 323.8%, 301.3%, 286.9%, and 221.7% by the TH, BH55, BH42+55, BH55+42, and BH42 treatments, respectively. Volatile fatty acids (VFA) constituted around 40% of the sCOD in the BH-treated sludge and 6% in the TH-treated sludge. The cumulative methane yields (NmLCH4/g COD fed) of sludge treated by BH55+42 and TH were respectively 23% and 20% higher than that of the untreated sludge. For BH pretreatment, sludge treated by BH55+42 produced more methane than those treated by BH42+55, BH55, and BH42. The methane yields of the combined sludge treated by the TH and BH55+42 treatments were in the ranges of 248.9 NmLCH4/g COD to 266.1 NmLCH4/g COD fed, and 255.3 NmLCH4/g COD to 282.2 NmLCH4/g COD fed, respectively.

Investigation of Sewage Sludge Anaerobic Digestion Performance Using Peracetic Acid as a Pretreatment

2014 ◽  
Vol 989-994 ◽  
pp. 138-141 ◽  
Author(s):  
Na Wei
Keyword(s):  
Anaerobic Digestion ◽  
Sewage Sludge ◽  
Peracetic Acid ◽  
Volatile Fatty Acids ◽  
Biogas Production ◽  
Oxygen Demand ◽  
Paper Sludge ◽  
Acid Pretreatment ◽  
Speed Up ◽  
Soluble Chemical Oxygen Demand

Sewage sludge is difficult to degrade in anaerobic digestion systems and pretreatments have been shown to speed up the hydrolysis stage. In this paper sludge anaerobic digestion experiments with peracetic acid as a pretreatment were carried out and the effects of acid pretreatment using peracetic acid on subsequent digestion were investigated. It has been proved that this treatment effectively leads to a solubilisation of organic material and thus leads to a increase of soluble chemical oxygen demand (SCOD) and volatile fatty acids (VFA) concentration. Besides, the SV of sludge was reduced and the settling characteristics of sludge were improved. But high dosage of peracetic acid lead to a decrease in biogas production and the proper dosage was 20 g/kg DS. It can be concluded that sludge anaerobic digestion with peracetic acid pretreatment is an effective method for biomass material transformation.

Alkali pre-treatment of Sorghum Moench for biogas production

2013 ◽  
Vol 67 (9) ◽  
Author(s):  
Karina Michalska ◽  
Stanisław Ledakowicz
Keyword(s):  
Anaerobic Digestion ◽  
Chemical Oxygen Demand ◽  
Volatile Fatty Acids ◽  
Biogas Production ◽  
Oxygen Demand ◽  
Total Phenolic ◽  
Methane Generation ◽  
Pre Treatment ◽  
Alkali Hydrolysis ◽  
Almost All

AbstractThis work studies the influence of the alkali pre-treatment of Sorghum Moench — a representative of energy crops used in biogas production. Solutions containing various concentrations of sodium hydroxide were used to achieve the highest degradation of lignocellulosic structures. The results obtained after chemical pre-treatment indicate that the use of NaOH leads to the removal of almost all lignin (over 99 % in the case of 5 mass % NaOH) from the biomass, which is a prerequisite for efficient anaerobic digestion. Several parameters, such as chemical oxygen demand, total organic carbon, total phenolic content, volatile fatty acids, and general nitrogen were determined in the hydrolysates thus obtained in order to define the most favourable conditions. The best results were obtained for the Sorghum treated with 5 mass % NaOH at 121°C for 30 min The hydrolysate thus achieved consisted of high total phenolic compounds concentration (ca. 4.7 g L−1) and chemical oxygen demand value (ca. 45 g L−1). Although single alkali hydrolysis causes total degradation of glucose, a combined chemical and enzymatic pre-treatment of Sorghum leads to the release of large amounts of this monosaccharide into the supernatant. This indicates that alkali pre-treatment does not lead to complete cellulose destruction. The high degradation of lignin structure in the first step of the pre-treatment rendered the remainder of the biomass available for enzymatic action. A comparison of the efficiency of biogas production from untreated Sorghum and Sorghum treated with the use of NaOH and enzymes shows that chemical hydrolysis improves the anaerobic digestion effectiveness and the combined pre-treatment could have great potential for methane generation.

scholarly journals Improved sludge dewaterability and hydrolysis performance after pretreatment with Fenton's reagent

2017 ◽  
Vol 77 (1) ◽  
pp. 204-210 ◽  
Author(s):  
Hongying Yuan ◽  
Yuping Yang ◽  
Jian Yuan ◽  
Yanning Wang ◽  
Yameng Song ◽  
...  
Keyword(s):  
Volatile Fatty Acids ◽  
Oxygen Demand ◽  
Ammonia Nitrogen ◽  
Fenton’S Reagent ◽  
Excess Sludge ◽  
Reaction Conditions ◽  
Fenton's Reagent ◽  
Soluble Polysaccharide ◽  
Soluble Chemical Oxygen Demand ◽  
Sludge Dewaterability

Abstract The dewaterability of excess sludge significantly improved upon pretreatment with Fenton's reagent in this study. After 0.9 g/L of Fe2+ and 5.0 g/L of H2O2 were added to the sludge, and reacted for 2 h at pH = 4, the specific resistance to filtration (SRF) of the excess sludge decreased from an initial value of 29.74 × 1012 m/kg to 6.49 × 1012 m/kg. The factors that affected this improvement in sludge dewaterability as evaluated by SRF reduction showed the following order: H2O2 > pH > Fe2+ > reaction time. Furthermore, the hydrolysis performance of the sludge under the optimal reaction conditions was investigated. The results indicated that the concentration of soluble chemical oxygen demand in the supernatant increased almost 14 times compared to raw sludge, and the contents of soluble protein and soluble polysaccharide were more than 8 and 17 times higher, respectively, than for the untreated situation. However, the amounts of ammonia nitrogen (NH4+-N) and phosphate (PO43−-P) released from the sludge showed different trends: NH4+-N increased by 200%, while PO43−-P decreased by 82%. The production of volatile fatty acids (VFAs) from the treated sludge showed that total VFAs increased by 66%, and iso-butylacetic acid was the dominant product among the total VFAs.

Temperature effects on the trophic stages of perennial rye grass anaerobic digestion

2011 ◽  
Vol 64 (1) ◽  
pp. 70-76 ◽  
Author(s):  
D. Cysneiros ◽  
A. Thuillier ◽  
R. Villemont ◽  
A. Littlestone ◽  
T. Mahony ◽  
...  
Keyword(s):  
Anaerobic Digestion ◽  
Low Temperature ◽  
Methane Production ◽  
Volatile Fatty Acids ◽  
Oxygen Demand ◽  
Production Performance ◽  
Batch Mode ◽  
Rye Grass ◽  
Long Term Experiment ◽  
Rate Limiting

Continuous Stirred Tank Reactors (CSTRs), operated in batch mode, were used to evaluate the feasibility of psychrophilic (low temperature) digestion of perennial rye grass in a long term experiment (150 days) for the first time. The reactors were operated in parallel at 3 different temperatures, 10, 15 and 37 °C. Hydrolysis, acidification and methanogenesis were assessed by VS degradation, by soluble chemical oxygen demand (SCOD) and volatile fatty acids (VFA) production, and by methane production, respectively. Hydrolysis was the rate-limiting step at all temperatures and the rates and extent of hydrolysis were considerably lower at 15 and 10 °C, than at 37 °C. The total VS degradation was 53%, 34% and 19% at 37, 15 and 10 °C, respectively. Acidification was not affected by temperature and VFA production and consumption was balanced in all cases, except at 10 °C. Methane yields were 0.215 m3 CH4 kg−1 VS−1 added, 0.160 m3 CH4 kg−1 VS−1 added and 0.125 m3 CH4 kg−1 VS−1 added at 37, 15 and 10 °C, respectively. Methanogenesis was not strongly affected at 15 °C but it became rate-limiting at 10 °C. Overall, the solid degradation and methane production performance under psychrophilic conditions was encouraging and greater than previously reported. Considering the non-acclimated, mesophilic nature of the inoculum, there are grounds to believe that low-temperature anaerobic digestion of grass could be feasible if coupled to efficient hydrolysis of the biomass.

Volatile fatty acid production in aerobic thermophilic pre-treatment of primary sludge

1997 ◽  
Vol 36 (11) ◽  
pp. 189-196 ◽  
Author(s):  
K. B. McIntosh ◽  
J. A. Oleszkiewicz
Keyword(s):  
Fatty Acid ◽  
Flow Rate ◽  
Volatile Fatty Acid ◽  
Volatile Fatty Acids ◽  
Final Concentration ◽  
Anoxic Condition ◽  
Fatty Acid Production ◽  
Primary Sludge ◽  
Soluble Organic Carbon ◽  
Pre Treatment

The efficiency of volatile fatty acid (VFA) production in a thermophilic aerobic digester (TAD) process using primary sludge was studied under two oxygenation states and detentions times ranging from 12 to 24 hours. The highest VFA concentration increase occurred in the 18 hour anaerobic aerated digester (O2 flow rate: 0.025 m3/m3·h; ORP: less than -300 mV) from 0.047 mg HAc/mg VSS in the feed to 0.106 mg HAc/mg VSS in the effluent. The anoxic condition (O2 flow rate: 0.14 m3/m3·h; ORP: between 0 to -225 mV) resulted in VFA utilisation and a final concentration of only 0.001 mg HAc/mg VSS. Under the anaerobic aerated condition, acetic acid constituted the largest fraction of short chain volatile fatty acids at an average of 60.4% and propionic trailed at 19.3%. The fraction of butyric and valeric acids were 12.2% and 8.1% respectively. It was found that with a decreasing oxygen supply and a decreasing detention time (HRT), the soluble organic carbon to ammonia ratio (SOC:NH3) increased.

Sludge electrooxidation as pre-treatment for anaerobic digestion

2016 ◽  
Vol 75 (4) ◽  
pp. 775-781 ◽  
Author(s):  
J. A. Barrios ◽  
U. Duran ◽  
A. Cano ◽  
M. Cisneros-Ortiz ◽  
S. Hernández
Keyword(s):  
Anaerobic Digestion ◽  
Volatile Fatty Acids ◽  
Biogas Production ◽  
Oxygen Demand ◽  
Wastewater Sludge ◽  
Boron Doped Diamond ◽  
Boron Doped ◽  
Treatment Conditions ◽  
Volatile Solids ◽  
Pre Treatment

Anaerobic digestion of wastewater sludge is the preferred method for sludge treatment as it produces energy in the form of biogas as well as a stabilised product that may be land applied. Different pre-treatments have been proposed to solubilise organic matter and increase biogas production. Sludge electrooxidation with boron-doped diamond electrodes was used as pre-treatment for waste activated sludge (WAS) and its effect on physicochemical properties and biomethane potential (BMP) was evaluated. WAS with 2 and 3% total solids (TS) achieved 2.1 and 2.8% solubilisation, respectively, with higher solids requiring more energy. After pre-treatment, biodegradable chemical oxygen demand values were close to the maximum theoretical BMP, which makes sludge suitable for energy production. Anaerobic digestion reduced volatile solids (VS) by more than 30% in pre-treated sludge with a food to microorganism ratio of 0.15 g VSfed g−1 VSbiomass. Volatile fatty acids were lower than those for sludge without pre-treatment. Best pre-treatment conditions were 3% TS and 28.6 mA cm−2.

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