Advanced

Pulse Electric Field as a Pre-treatment Method of Wastewater Sludge prior to Anaerobic Digestion

Matilde, Milton LU (2020) VVAM01 20201
Chemical Engineering (M.Sc.Eng.)
Abstract
This work analyzed the impact caused by different intensities of Pulsed Electric Fields (PEF) pre-treatment on the biogas production from small-scale anaerobic digesters of wastewater sludge under thermophilic conditions. PEF technology consists of passing the substrate through an electric field which generates a potential difference across the cells, resulting in electroporation.
Mixed sludge from Källby wastewater treatment plant was used and the biogas yield (Nm3/kg VS) obtained from the semi-continuous lab digesters with untreated sludge was similar to the yield registered by the plant’s full-scale version. Substrate submitted to higher intensities exhibited higher biogas yield improvements. The digestion of PEF-treated sludge reached... (More)
This work analyzed the impact caused by different intensities of Pulsed Electric Fields (PEF) pre-treatment on the biogas production from small-scale anaerobic digesters of wastewater sludge under thermophilic conditions. PEF technology consists of passing the substrate through an electric field which generates a potential difference across the cells, resulting in electroporation.
Mixed sludge from Källby wastewater treatment plant was used and the biogas yield (Nm3/kg VS) obtained from the semi-continuous lab digesters with untreated sludge was similar to the yield registered by the plant’s full-scale version. Substrate submitted to higher intensities exhibited higher biogas yield improvements. The digestion of PEF-treated sludge reached values of biogas production up to 7.4% higher than values obtained from the digestion of untreated sludge with the same solids content. No relevant difference was seen in the methane content of the biogas produced by treated and untreated substrate.
PEF treatment causes an increase in temperature in the substrate. That energy can be used to reduce the external heating requirements of the digester, contributing to offset the energy input required from the treatment. In this study, treatments with intensity around 70 kJ/kg were shown to increase the temperature of the sludge by around 18°C.
Higher cumulative biogas production and VS degradation were achieved by increasing treatment intensity. Increases of 7.3% in cumulative biogas production and 7% in VS reduction were obtained from the anaerobic digestion of mixed primary and secondary sludge pre-treated with intensity of 95 kJ/kg. The increase in substrate temperature caused by the pre-treatment can decrease the energy required for heating the subsequent anaerobic digester and contribute to offsetting the energy required from the pre-treatment.
The treatments conducted in this work only differed in treatment intensity. However, PEF treatment design consists of many other parameters. Thus, the relationship between these parameters and anaerobic digestion should be further investigated so that the true impact of Pulsed Electric Fields can be determined. Additionally, the performance of PEF varies from substrate to substrate, so methods to determine optimal parameters based on sludge type should be developed. (Less)
Popular Abstract
Use of Pulse Electric Field as a method to increase biogas production from wastewater sludge.
The process of treating wastewater generates sludge that needs to be disposed according to governmental legislations. Generally, the sludge needs to be further treated to ensure a number of parameters are below the allowed threshold values. One important parameter is the amount of organic material present in the sludge and degrading that material is also called sludge stabilization. The treatment and disposal of sludge can be the single most expensive step on wastewater treatment systems, for that reason, possibilities, methods and techniques that can help reducing that cost are constantly being pursued.
Anaerobic digestion (AD) degrades organic... (More)
Use of Pulse Electric Field as a method to increase biogas production from wastewater sludge.
The process of treating wastewater generates sludge that needs to be disposed according to governmental legislations. Generally, the sludge needs to be further treated to ensure a number of parameters are below the allowed threshold values. One important parameter is the amount of organic material present in the sludge and degrading that material is also called sludge stabilization. The treatment and disposal of sludge can be the single most expensive step on wastewater treatment systems, for that reason, possibilities, methods and techniques that can help reducing that cost are constantly being pursued.
Anaerobic digestion (AD) degrades organic material generating biogas and it is one of the most common methods used within the European Union (EU) to stabilize wastewater sludge. This method transforms solid organic material (biomass) into biogas, decreasing the amount of organic material present in the sludge while producing clean energy. This process typically takes place in a digester, where sludge is submitted to a heated anaerobic environment (without oxygen). Pre-treatments are often used in order to optimize the anaerobic digestion maximizing biomass degradation and biogas production.
Pulsed Electric Fields (PEF) is a commonly used technology in the food industry to increase juice and olive oil extract, however, studies show that it also has the potential to be used as a sludge pre-treatment method as help increase biogas production. PEF consists of applying energy to the substrate being treated in order to generate pores into the cell’s membrane (electroporation), making its content more easily available. Subjecting the wastewater sludge to this treatment prior to anaerobic digestion can help the microorganisms responsible for digesting the biomass have easier access to that organic material, increasing the overall biogas production.
PEF treatment can be characterized by a number of different parameters, one of them being treatment intensity, which is the energy input required from the treatment, generally expressed as energy/mass (J/kg).
This study compared the biogas production obtained from the digestion of sludge pre-treated by four different intensities with the gas produced from the digestion of untreated sludge and results showed that PEF-treated sludge generated up to 7.3% more biogas than untreated sludge and degraded around 7% more organic material.
Another impact of PEF treatment, besides electroporation, is the increase in the substrate’s temperature. This can lower the energy required to heat the sub-sequent anaerobic digester, helping offset the energy required by the PEF treatment. (Less)
Please use this url to cite or link to this publication:
author
Matilde, Milton LU
supervisor
organization
course
VVAM01 20201
year
type
H2 - Master's Degree (Two Years)
subject
keywords
PEF, AD, biogas yield, sludge pre-treatment, water engineering, environmental engineering, avloppsteknik, vattenförsörjningsteknik
language
English
id
9021229
date added to LUP
2020-06-26 09:13:24
date last changed
2020-06-26 09:13:24
@misc{9021229,
  abstract     = {This work analyzed the impact caused by different intensities of Pulsed Electric Fields (PEF) pre-treatment on the biogas production from small-scale anaerobic digesters of wastewater sludge under thermophilic conditions. PEF technology consists of passing the substrate through an electric field which generates a potential difference across the cells, resulting in electroporation.
Mixed sludge from Källby wastewater treatment plant was used and the biogas yield (Nm3/kg VS) obtained from the semi-continuous lab digesters with untreated sludge was similar to the yield registered by the plant’s full-scale version. Substrate submitted to higher intensities exhibited higher biogas yield improvements. The digestion of PEF-treated sludge reached values of biogas production up to 7.4% higher than values obtained from the digestion of untreated sludge with the same solids content. No relevant difference was seen in the methane content of the biogas produced by treated and untreated substrate.
PEF treatment causes an increase in temperature in the substrate. That energy can be used to reduce the external heating requirements of the digester, contributing to offset the energy input required from the treatment. In this study, treatments with intensity around 70 kJ/kg were shown to increase the temperature of the sludge by around 18°C.
Higher cumulative biogas production and VS degradation were achieved by increasing treatment intensity. Increases of 7.3% in cumulative biogas production and 7% in VS reduction were obtained from the anaerobic digestion of mixed primary and secondary sludge pre-treated with intensity of 95 kJ/kg. The increase in substrate temperature caused by the pre-treatment can decrease the energy required for heating the subsequent anaerobic digester and contribute to offsetting the energy required from the pre-treatment.
The treatments conducted in this work only differed in treatment intensity. However, PEF treatment design consists of many other parameters. Thus, the relationship between these parameters and anaerobic digestion should be further investigated so that the true impact of Pulsed Electric Fields can be determined. Additionally, the performance of PEF varies from substrate to substrate, so methods to determine optimal parameters based on sludge type should be developed.},
  author       = {Matilde, Milton},
  keyword      = {PEF,AD,biogas yield,sludge pre-treatment,water engineering,environmental engineering,avloppsteknik,vattenförsörjningsteknik},
  language     = {eng},
  note         = {Student Paper},
  title        = {Pulse Electric Field as a Pre-treatment Method of Wastewater Sludge prior to Anaerobic Digestion},
  year         = {2020},
}