Influence of HRT (hydraulic retention time) and SRT (solid retention time) on the hydrolytic pre-treatment of urban wastewater

2001 ◽  
Vol 44 (4) ◽  
pp. 7-14 ◽  
Author(s):  
P. Ligero ◽  
A. De Vega ◽  
M. Soto
Keyword(s):  
Retention Time ◽  
Volatile Fatty Acids ◽  
Oxygen Demand ◽  
Phase Iii ◽  
Urban Wastewater ◽  
Solid Retention Time ◽  
Start Up ◽  
Pre Treatment ◽  
Two Parameters ◽  
Hydrolysis Of

This work presents the results obtained from a study on the pretreatment of urban wastewater using a digester that acted as a system for the retention of solids (sedimentation-filtration), hydrolysis of the retained solids and acidification of the dissolved substances. After start-up (Phase I), the digester was operated at hydraulic retention times (HRT) of 4.4, 3.4 and 2.2 h and at solid retention times (SRT) of 24, 16 and 14 d, during Phases II, III and IV, respectively. The retention and removal of suspended solids (SS) was maintained slightly above 60%, independently of HRT and SRT. Conversely, eliminated chemical oxygen demand (COD) decreased slightly upon reducing HRT and SRT. The influence of these two parameters on the generation of volatile fatty acids (VFA) is more notable, reaching effluent VFA concentration of 29 (Phase II), 96 (Phase III), and 107 (Phase IV) mg COD/l. VFA to SS generation ratios were 0.13 (II), 0.35 (III), and 0.48 (IV) g VFACOD/g SS added. Optimum values were reached at an HRT of 2.2 h. Taking 100 kg influent COD as a base, the conversion of different kinds of COD was as follows (in kg influent:kg effluent): VFACOD (4:17), non-VFA soluble COD (45:23), VSSCOD (51:23). Simultaneously to these conversions, 2 kg VSSCOD are generated as purge stream and 35 kg COD are eliminated during the process.

scholarly journals Effect of the solid retention time in the obtention of polyhydroxyalkanoates

F1000Research ◽  
2021 ◽  
Vol 10 ◽  
pp. 864
Author(s):  
Rolando Calero ◽  
Manuel Martínez
Keyword(s):  
Fatty Acids ◽  
Retention Time ◽  
Volatile Fatty Acids ◽  
Batch Reactor ◽  
Oxygen Demand ◽  
Solid Retention Time ◽  
Dry Cell Weight ◽  
Acidogenic Reactor ◽  
Mixed Microbial Cultures ◽  
Dry Cell

Background: The effect of solid retention time (SRT) over cheese whey substrates in a fermentation process drives changes in the composition of polyhydroxyalkanoates (PHAs) obtained. Volatile fatty acids produced in the first step of an anaerobic sequencing batch reactor were used as substrates to produce PHA using mixed microbial cultures under aerobic dynamic feeding conditions. Methods: Analytical methods were used for the standard analysis of parameters of interest including measuring the amount of ammonium and phosphate, chemical oxygen demand, among others. Results: The SRT increasing from 4 to 6 and 10 days produced changes in the distribution of volatile fatty acids produced. The polyhydroxybutyrate-hydroxyvalerate copolymers formed in the accumulation stage gave the following results: 58:42, 68:32 and 81:19 (%), referred to SRTs of 10, 6 and 4 days, respectively. The maximum PHA accumulation obtained at 10 days of SRT was 52% of the dry cell weight within 7 h, reaching a PHA productivity of 0.62 g L−1 h−1 and a storage yield of 0.37. Conclusion: The SRT variation impact on the distribution of volatile fatty acids in the acidogenic reactor and consequently on the PHA production and composition formed in the accumulation stage.

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 Microbial Structure and Energy Generation in Microbial Fuel Cells Powered with Waste Anaerobic Digestate

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4712
Author(s):  
Dawid Nosek ◽  
Agnieszka Cydzik-Kwiatkowska
Keyword(s):  
Fuel Cells ◽  
Microbial Fuel Cells ◽  
Volatile Fatty Acids ◽  
Current Knowledge ◽  
Oxygen Demand ◽  
Electricity Production ◽  
Stable Operation ◽  
Microbial Structure ◽  
Microbial Composition ◽  
Start Up

Development of economical and environment-friendly Microbial Fuel Cells (MFCs) technology should be associated with waste management. However, current knowledge regarding microbiological bases of electricity production from complex waste substrates is insufficient. In the following study, microbial composition and electricity generation were investigated in MFCs powered with waste volatile fatty acids (VFAs) from anaerobic digestion of primary sludge. Two anode sizes were tested, resulting in organic loading rates (OLRs) of 69.12 and 36.21 mg chemical oxygen demand (COD)/(g MLSS∙d) in MFC1 and MFC2, respectively. Time of MFC operation affected the microbial structure and the use of waste VFAs promoted microbial diversity. High abundance of Deftia sp. and Methanobacterium sp. characterized start-up period in MFCs. During stable operation, higher OLR in MFC1 favored growth of exoelectrogens from Rhodopseudomonas sp. (13.2%) resulting in a higher and more stable electricity production in comparison with MFC2. At a lower OLR in MFC2, the percentage of exoelectrogens in biomass decreased, while the abundance of genera Leucobacter, Frigoribacterium and Phenylobacterium increased. In turn, this efficiently decomposed complex organic substances, favoring high and stable COD removal (over 85%). Independent of the anode size, Clostridium sp. and exoelectrogens belonging to genera Desulfobulbus and Acinetobacter were abundant in MFCs powered with waste VFAs.

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.

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 Effect of Hydrothermal Pretreatment on Volatile Fatty Acids Production from Source-Separated Organics

Processes ◽  
2019 ◽  
Vol 7 (9) ◽  
pp. 576 ◽  
Author(s):  
Farokh laqa Kakar ◽  
Ehssan Hosseini Koupaie ◽  
Hisham Hafez ◽  
Elsayed Elbeshbishy
Keyword(s):  
Fatty Acids ◽  
Chemical Oxygen Demand ◽  
Retention Time ◽  
Volatile Fatty Acids ◽  
Oxygen Demand ◽  
Hydrothermal Pretreatment ◽  
Soluble Substance ◽  
Pretreatment Temperature

The current study investigates the effect of hydrothermal pretreatment (HTP) on acidification of source-separated organics (SSO) in terms of volatile fatty acids (VFAs) production and solubilization. Temperature and retention time for HTP of SSO ranged from 150 to 240 °C and 5 to 30 min, respectively. The soluble substance after hydrothermal pretreatment initially increased, reaching its peak at 210 °C and then declined gradually. The highest overall chemical oxygen demand (COD) solubilization of 63% was observed at “210 °C-20 min” compared to 17% for raw SSO. The highest VFAs yield of 1536 mg VFAs/g VSS added was observed at “210 °C-20 min” compared to 768 mg VFAs/g VSS for raw SSO. Intensification of hydrothermal pretreatment temperature beyond 210 °C resulted in the mineralization of the organics and adversely affected the process.

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.

Influence of Hydraulic Retention Time on Start-Up and Process Stability of Polyurethane Carrier Reactions

1992 ◽  
Vol 25 (1) ◽  
pp. 99-106 ◽  
Author(s):  
M. S. T. Rubindamayugi ◽  
H. J. M. Op Den Camp ◽  
H. J. Lubberding ◽  
H. J. Gijzen ◽  
G. D. Vogels
Keyword(s):  
Retention Time ◽  
Volatile Fatty Acids ◽  
Hydraulic Retention Time ◽  
Organic Loading Rate ◽  
Process Stability ◽  
Reactor Performance ◽  
Steady State Condition ◽  
Start Up ◽  
Reactor Operating ◽  
Startup Period

Influence of hydraulic retention time (HRT) on start-up of Polyurethane Carrier Reactors treating Volatile Fatty Acids (VFA) based wastewater, at constant organic loading rate (OLR) was investigated. OLR was increased stepwise after start-up to evaluate the influence of HRT on process stability. Four parallel experiements were conducted at HRTs of 48, 24, 18 and 12 hours. Results indicate an influence of HRT on duration of start-up period, and process stability after start-up. The reactor operating at HRT of 24 hours required only a relatively stort start-up period and showed higher process stability under steady-state condition. Analysis of individual VFA degradation indicated that butyrate and propionate consuming acetogenic bacteria increased in sigmoid fashion during start-up. Changes in acetate degradation do not show the true increase of acetoclastic population. Instead they reflect concomitant activity of VFA catabolizing acetogens and aceloclastic methanogens . Immobilized biomass increased exponentially during the first three weeks of start-up. The differences in start-up periods between reactors was probably due to differences in quality and activity of biomass immobilized at different HRTs. The HRT of 24 hours was most optimal to obtain stable reactor performance within a short startup period.

Start-Up Operation and Hydraulic Retention Time Selectivity for Palm Oil Mill Wastewater at Mesophilic Temperature in Anaerobic Suspended Growth Closed Bioreactor

2014 ◽  
Vol 955-959 ◽  
pp. 1330-1334
Author(s):  
Yee Shian Wong ◽  
Tjoon Tow Teng ◽  
Soon An Ong ◽  
Morad Norhashimah ◽  
Mohd Rafatullah
Keyword(s):  
Palm Oil ◽  
Retention Time ◽  
Anaerobic Degradation ◽  
Hydraulic Retention Time ◽  
Biogas Production ◽  
Oxygen Demand ◽  
Anaerobic Bioreactor ◽  
Start Up ◽  
Palm Oil Mill ◽  
Pome Wastewater

The start-up operation and hydraulic retention time (HRT) selectivity of anaerobic degradation for palm oil mill effluent (POME) wastewater was carried out in an anaerobic bioreactor. HRT between 35 and 5 days were investigated. The start-up process for the anaerobic degradation of POME wastewater was found to be completed after 40 days of operation. This study also recommended that the anaerobic degradation of POME wastewater should be operated at the HRT between 35 and 10 days without acid risk. The performance of anaerobic bioreactor could reach 90.55% - 87.55% chemical oxygen demand (COD) reduction, 0.06 - 0.40 ratio between volatile fatty acid (VFA) and alkalinity (Alk), -368.2 mV to-445.80 mV of oxygen reduction potential (ORP) and 9.08 - 37.2 liters of biogas production, respectively.

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