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GAC filter Design Criteria for Wastewater Treatment for Removal of Organic Micropollutants – A Literature Review

Elavarthi, Bhargav Reddy LU (2021) VVAM01 20211
Chemical Engineering (M.Sc.Eng.)
Abstract
Granular Activated Carbon (GAC) is nowadays suggested as a fourth (quaternary) treatment step at municipal wastewater treatment plants to remove certain chemicals and particularly organic micropollutants (OMPs). This work investigated the different factors that affect the performance of the GAC filter for the removal of micropollutants in a municipal wastewater treatment plant. This study is purely based on compiling data and analyzing different studies. Carbamazepine, diclofenac and sulfamethoxazole were chosen as breakthrough indicators. The comparisons were made by plotting bed volumes versus dissolved organic matter (DOC) and bed volumes versus empty bed contact time (EBCT) for a breakthrough criteria of 20%. A breakthrough occurs when... (More)
Granular Activated Carbon (GAC) is nowadays suggested as a fourth (quaternary) treatment step at municipal wastewater treatment plants to remove certain chemicals and particularly organic micropollutants (OMPs). This work investigated the different factors that affect the performance of the GAC filter for the removal of micropollutants in a municipal wastewater treatment plant. This study is purely based on compiling data and analyzing different studies. Carbamazepine, diclofenac and sulfamethoxazole were chosen as breakthrough indicators. The comparisons were made by plotting bed volumes versus dissolved organic matter (DOC) and bed volumes versus empty bed contact time (EBCT) for a breakthrough criteria of 20%. A breakthrough occurs when the filter attains a breakpoint as saturation of OMPs, and the organic matter occurs. At that point, the filter cannot achieve the standard removal efficiency anymore. The pollutant concentration will then increase in the filter effluent after this breakpoint.
High pH makes the contaminants negatively charged, and activated carbon is also negatively charged, which causes repulsive force between the activated carbon surface and the OMPs. The increase in pH consequently decreases the adsorption of OMP's. The molecules are more stable at lower temperatures and tend to be adsorbed quickly. pH and temperature are essential for biological processes in the wastewater treatment plant. pH is recommended to be at a neutral phase of 6.5-7.5, and temperature is recommended at 20 – 35 0C. These conditions are perfect for organisms to thrive. Bitumen, lignite, coconut-based GAC did not show any significant difference in performance, which can be explained due to lack of data where characteristics of influent and pilot setups were diverse from the collected studies. EBCT is an essential factor for the removal of OMPs. Approximately 20 – 30 min is required for typical wastewater treatment and more than 30 min for physico-chemical where chemicals like coagulants and flocculants are used in wastewater treatment. Sulfamethoxazole showed higher resilience towards adsorption and required higher EBCT compared to carbamazepine, diclofenac.
SS and DOC play an essential role in predicting the bed life of the filter, where high DOC and SS can cause fouling (clogging of pores) through the accumulation of particulate matter by SS and buildup of biomass by DOC. The suspended solids content is recommended to be as low as possible, and DOC of less than 10mg/l is recommended for GAC filtration. The carbon usage rate for typical biological wastewater treatment is at 0.1 – 0.21 kg/m3 due to less use of chemical treatment, and for physico-chemical treatment, it is 0.21-1.04 kg/m3 where chemicals such as alum and iron salts are used for coagulation and flocculation to form flocs. Based on materials such as bitumen, lignite, and coconut, for US mesh size at 8x30, the effective grain size was found to be similar for all the materials at 1.25mm. (Less)
Popular Abstract
Granular Activated Carbon (GAC) is nowadays suggested as a fourth (quaternary) treatment step at municipal wastewater treatment plants to remove certain chemicals and particularly organic micropollutants (OMPs). Wastewater contains many organic micropollutants that can affect the environment if not treated well. Also, the pollutants studied are not well regulated. But new standards regulating these pollutants are being investigated. From these studies, we have found that only a certain amount of concentration is allowed to be discharged from wastewater treatment plants and a standard was made.
We see an uprising in granular activated carbon as a treatment for the removal of organic micropollutants. This study shows how a GAC filter... (More)
Granular Activated Carbon (GAC) is nowadays suggested as a fourth (quaternary) treatment step at municipal wastewater treatment plants to remove certain chemicals and particularly organic micropollutants (OMPs). Wastewater contains many organic micropollutants that can affect the environment if not treated well. Also, the pollutants studied are not well regulated. But new standards regulating these pollutants are being investigated. From these studies, we have found that only a certain amount of concentration is allowed to be discharged from wastewater treatment plants and a standard was made.
We see an uprising in granular activated carbon as a treatment for the removal of organic micropollutants. This study shows how a GAC filter function and how to design it using the various parameters. These parameters may need to be understood to use as a design factor since some of the parameters are interdependent, explained in the study. The compiled data on these parameters and how they influence the functioning of the carbon filter is discussed in the study. The data collected undergoes meta-analysis where different values from all the papers for one parameter are compared.
This study shows that pre-treating the wastewater before it enters the GAC step is a crucial step as it determines the effectiveness and working life of the filter. We compared different pre-treatment steps to configure the most efficient and found that ozonation of wastewater is recommended. We see that ozonation helps oxidising compounds making them insoluble, and also helps in speeding up the biological processes.
There are multiple design papers and studies on the GAC filter, but very few explain the influence of parameters on the design selection. For example, we see that parameters are essential for designing the filter, but we don’t see many studies showing the correlation of these parameters. This study is purely based on compiling data and analysing this data from online sources (journals, reports, books, web articles). The findings were structured so that co-relations were made to understand the influence of design parameters on the GAC filter. These co-relations were made using specific micropollutants as the indicator compounds. However, few minor assumptions were made in this study. A table of compiled data was made using Microsoft Excel. When designing a large-scale granular activated filter for municipal wastewater treatment, this study will help the reader understand the parameters and give design values to work with. (Less)
Please use this url to cite or link to this publication:
author
Elavarthi, Bhargav Reddy LU
supervisor
organization
course
VVAM01 20211
year
type
H2 - Master's Degree (Two Years)
subject
keywords
micropollutants, activated carbon filtration, empty bed contact time (EBCT), pharmaceuticals, breakthrough curves, adsorption, PFOS, carbon use, water and environmental engineering
language
English
id
9056775
date added to LUP
2021-07-06 13:12:25
date last changed
2021-07-06 13:12:25
@misc{9056775,
  abstract     = {{Granular Activated Carbon (GAC) is nowadays suggested as a fourth (quaternary) treatment step at municipal wastewater treatment plants to remove certain chemicals and particularly organic micropollutants (OMPs). This work investigated the different factors that affect the performance of the GAC filter for the removal of micropollutants in a municipal wastewater treatment plant. This study is purely based on compiling data and analyzing different studies. Carbamazepine, diclofenac and sulfamethoxazole were chosen as breakthrough indicators. The comparisons were made by plotting bed volumes versus dissolved organic matter (DOC) and bed volumes versus empty bed contact time (EBCT) for a breakthrough criteria of 20%. A breakthrough occurs when the filter attains a breakpoint as saturation of OMPs, and the organic matter occurs. At that point, the filter cannot achieve the standard removal efficiency anymore. The pollutant concentration will then increase in the filter effluent after this breakpoint. 
High pH makes the contaminants negatively charged, and activated carbon is also negatively charged, which causes repulsive force between the activated carbon surface and the OMPs. The increase in pH consequently decreases the adsorption of OMP's. The molecules are more stable at lower temperatures and tend to be adsorbed quickly. pH and temperature are essential for biological processes in the wastewater treatment plant. pH is recommended to be at a neutral phase of 6.5-7.5, and temperature is recommended at 20 – 35 0C. These conditions are perfect for organisms to thrive. Bitumen, lignite, coconut-based GAC did not show any significant difference in performance, which can be explained due to lack of data where characteristics of influent and pilot setups were diverse from the collected studies. EBCT is an essential factor for the removal of OMPs. Approximately 20 – 30 min is required for typical wastewater treatment and more than 30 min for physico-chemical where chemicals like coagulants and flocculants are used in wastewater treatment. Sulfamethoxazole showed higher resilience towards adsorption and required higher EBCT compared to carbamazepine, diclofenac.
SS and DOC play an essential role in predicting the bed life of the filter, where high DOC and SS can cause fouling (clogging of pores) through the accumulation of particulate matter by SS and buildup of biomass by DOC. The suspended solids content is recommended to be as low as possible, and DOC of less than 10mg/l is recommended for GAC filtration. The carbon usage rate for typical biological wastewater treatment is at 0.1 – 0.21 kg/m3 due to less use of chemical treatment, and for physico-chemical treatment, it is 0.21-1.04 kg/m3 where chemicals such as alum and iron salts are used for coagulation and flocculation to form flocs. Based on materials such as bitumen, lignite, and coconut, for US mesh size at 8x30, the effective grain size was found to be similar for all the materials at 1.25mm.}},
  author       = {{Elavarthi, Bhargav Reddy}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{GAC filter Design Criteria for Wastewater Treatment for Removal of Organic Micropollutants – A Literature Review}},
  year         = {{2021}},
}