Lakshminarasimman, Narasimman

Narasimman Lakshminarasimman is a final year PhD candidate at the University of Waterloo in Canada. He earned his bachelor’s degree in...

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About Lakshminarasimman, Narasimman

Narasimman Lakshminarasimman is a final year PhD candidate at the University of Waterloo in Canada. He earned his bachelor’s degree in Civil Engineering from SASTRA University in India and his Master’s degree in Environmental Engineering from University of Cincinnati. He also has 2.5 years of experience as an onsite technical contractor at the US EPA Testing and Evaluation Facility, Cincinnati studying the fate of physical, chemical, and biological contaminants in water infrastructure. He has been awarded the RBC Water Scholars Award and the Ivanhoe Foundation Graduate Research Fellowship for his research work. Narasimman is also an active YP member of the Water Environment Association of Ontario.

Lakshminarasimman, Narasimman

Titles from this speaker

Description: Behavior of Perfluoroalkyl Substance (PFAS) in Sludge Processing at Nine Canadian...

Behavior of Perfluoroalkyl Substance (PFAS) in Sludge Processing at Nine Canadian Sludge Handling Facilities

Abstract

The occurrence of emerging organic contaminants such as poly- and per-fluoroalkyl substances (PFAS) has raised concerns with beneficial land application of biosolids. The purpose of this study was to examine the occurrence and removal/formation of thirteen PFAS occurring in sludge and biosolids from nine Canadian sludge treatment facilities employing alkaline stabilization (AS), pelletization (P), aerobic digestion (AE1, AE2), and anaerobic digestion (AN1 to AN5) processes. Perfluorodecanoate (PFDA) was the most frequently detected compound (>85%) in the biosolids followed by perflurorooctane sulfonate (PFOS) and perfluorododecanoate (PFDoA). The ΣPFAS-F mass flows in the raw sludge and biosolids were estimated to study the removal performance of different sludge treatment categories. There was a significant increase in mass flow of ΣPFAS-F during pelletization and alkaline stabilization. On the other hand, the mass loadings of ΣPFAS-F decreased at AE2, AN1, AN3, and AN4 by 10 ± 0.2%, 34 ± 0.2%, 10 ± 0.1%, and 38 ± 0.2% through aerobic and anaerobic digestion processes, respectively. Substantial variability in removal/formation characteristics was observed between the biological treatment systems. The findings from this study will better inform the risk assessment and management of exposure to PFAS through biosolids.

SpeakerLakshminarasimman, Narasimman

Presentation time

13:30:00

13:50:00

Session time

13:30:00

14:10:00

SessionPFAS Management in Biosolids

Session number414

TopicMicroconstituents, Research and Innovation

Author(s)

N. LakshminarasimmanS. GewurtzS. SmythW. Parker

Author(s)N. Lakshminarasimman1; S. Gewurtz2; S. Smyth2; W. Parker1;

Author affiliation(s)University of Waterloo, ON1; Science and Technology Branch, Environment and Climate Change Canada2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2020

DOI10.2175/193864718825157406

Volume / Issue

Content sourceWEFTEC

Word count15

Description: From Seasonal to Year-round Nitrification: Performance Evaluation of North America's...

From Seasonal to Year-round Nitrification: Performance Evaluation of North America's Largest MABR Installation

Abstract

This study evaluated the performance of North America’s largest MABR installation under different operational and seasonal conditions. Total nitrogen (TN) removal improved from 40- 50% when the plant was in a conventional activated sludge configuration to 75-85% after the MABR upgrade. The MABR reduced effluent ammonia during winters and nitrate concentrations during summer to below 10 mg-N/L in both the cases. The nitrification rate in the MABR varied between 0.7-2.2 gNm-2 d -1 with lower nitrification rates observed during reduced airflow operation and winter conditions. The development of thicker biofilms limited ammonia diffusion into the biofilm that resulted in reduced nitrification rate. Increasing the flow of sparging air was able to control the biofilm thickness to improve nitrification. The denitrification rate in the MABR process was between 100-200 gNm-3 d -1 which followed a close trend with nitrification rate. The nitrification rate in the MABR was found to be the rate limiting step for TN removal in the process.

Addition of an MABR to an existing conventional activated sludge process substantially improved TN removal and reduces seasonal spikes in effluent ammonia. The improved TN removal in the plant was due to elevated levels of simultaneous nitrification and denitrification in the hybrid MABR process.

SpeakerLakshminarasimman, Narasimman

Presentation time

15:30:00

15:50:00

Session time

15:30:00

17:00:00

SessionAlternative Approaches to Intensify Secondary Treatment

Session locationRoom S404a - Level 4

TopicIntermediate Level, Municipal Wastewater Treatment Design, Nutrients

Author(s)

Lakshminarasimman, Narasimman

Author(s)N. Lakshminarasimman 1; D. Celmer-Repin 2 ; J. Mank 3; J. Gagnon 4; M. Reeve 5; J. Peeters 6; W.J. Parker 1; N. Lakshminarasimman 1;

Author affiliation(s)Department of Civil and Environmental Engineering, University of Waterloo, ON, Canada 1; Region of Waterloo, ON, Canada 2 ; Ontario Clean Water Agency, ON, Canada. 3; Veolia Water Technologies 4; Veolia Water Technologies 5; Veolia Water Technologies 6; Department of Civil and Environmental Engineering, University of Waterloo, ON, Canada 1; Department of Civil and Environmental Engineering, University of Waterloo, ON, Canada 1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159017

Volume / Issue

Content sourceWEFTEC

Word count14

Description: Insights into emerging organic contaminants behavior in different full-scale sludge...

Insights into emerging organic contaminants behavior in different full-scale sludge treatment systems

Abstract

1. Background Sludge treatment processes typically incorporate physical, chemical, and biological unit operations to reduce sludge volume, odour, vector attraction, and pathogens in the product biosolids [1]. Biosolids are regulated with respect to pathogen, nutrient, and heavy metal content if land applied [2]. However, biosolids may also carry a wide range of anthropogenic chemicals such as pharmaceuticals, personal car e products, surfactants, plasticizers, flame retardants, and water and stain resistant coatings [3], collectively called emerging organic contaminants (EOC). The presence of trace levels of EOCs has been identified as a concern associated with their land application as they could potentially mobilize into soil, infiltrate into ground water, or be uptaken by vegetation [4]. While the long-term risks of exposure to humans are relatively unknown, some of the EOCs are known to be toxic, persistent and bioaccumulative [3,4]. Hence, an understanding of the occurrence and fate of EOCs in sludge handling systems that produce biosolids will provide a basis on which risks can be quantified. Further, most studies pertaining to EOCs and wastewater solids only document the contaminant presence in the product biosolids and there is little information on their removal through sludge processing systems. Further, the relative performance of different physical, chemical and biological sludge treatment processes is also largely unknown The objective of this study was to study the behavior of five major classes of EOCs: per- and poly-fluoroalkyl substances (PFAS), polybrominated diphenyl ethers (PBDE), alkyl phenols and ethoxylate derivatives, bisphenol A (BPA), and triclosan in common sludge treatment systems. The final paper will highlight the key findings from this multi-plant study and discuss the practical implications for biosolids management practices. 2. Study Design Samples of raw sludge and the final stabilized biosolids were collected from nine sludge treatment systems that included pelletization (P), alkaline stabilization (AS), aerobic digestion (AE1 and AE2) and anaerobic digestion (AN1 to AN5) processes. Grab samples were collected in glass jars on three consecutive days within a one-month period in each of 2015 and 2016 and shipped overnight on ice to the lab for contaminant analysis. The target analytes included 13 PFAS, 21 PBDEs, 4 alkyl phenols and ethoxylate derivatives, BPA, and triclosan. All the EOC analyses were conducted by SGS AXYS International (Sidney, BC) following stringent quality control procedures. 3. Major Findings The measured concentrations were used to estimate contaminant mass flows (mg/day) in and out of the system (contaminant concentration ng/g x solids flow kg/day) to assemble contaminant mass balance through the system. Percent removal was then calculated to evaluate the relative performance of the treatment systems. An overview of five major findings from this study are subsequently presented. A detailed discussion on the influence of the contaminant and treatment plant related factors will be included in the final paper. 3.1 All types of sludge treatment lead to EOC removal: While sludge treatment systems are primarily designed to prepare biosolids for subsequent disposition, the results of this study suggest that some removal of EOCs also occurs during the process. Up to 87% removal of triclosan was observed in AE2 during aerobic digestion. Nonylphenol monoethoxylate and diethoxylates were removed in both aerobic (Mono: 59 to 86%; Di: 84 to 95%) and anaerobic digestion (Mono: 35 to 79%; Di: 69 to 96%). Alkaline stabilization, where the raw sludge was stabilized at high pH using lime and cement kiln dust, was effective in reducing Î£PBDE mass flows by 53 ±12%. During pelletization, where the raw sludge was thermally dried and compacted, there were low removals of perfluorodecanoate (PFDA) (17%) and Î£PBDE (6%) mass flows. Hence, all treatments resulted in some degree of contaminant removal but removals differed between technologies. 3.2 Contaminant formation is possible during sludge treatment: The conditions established in sludge treatment can also lead to transformation of contaminants resulting in an increase in mass flows through the systems. Such an effect was commonly observed for selected PFAS where the average mass flow of the measured compounds increased by 59%, 19%, 2%, 264%, and 13% in AS, P, AE1, AN1, and AN5, respectively (Figure 1). Further, a net increase in mass flow of 4-nonylphenol was consistently observed in all five anaerobic digestion systems. Evidence of reductive debromination of fully brominated PBDE congeners into partially brominated PBDE congeners was also seen in anaerobic digestion systems. Thus, sludge treatment systems can transform precursors to increase contaminant mass flows through treatment. 3.3 Removal is dependent on sludge feed characteristics: The raw sludge fed to sludge treatment processes can differ because of differences in the inputs of contaminants to the sewershed and in the types of wastewater treatment processes generating the sludge. EOC use and release in a given sewershed will be reflected in the contaminant loading from the sludge treatment process. For example, BPA was measured in the raw sludge in all treatment systems except AE2. Since BPA was not detected in the raw sludge at AE2, this substance was also not detected in the biosolids at this treatment system. Differences in upstream wastewater treatment processes design can also impact the EOC content in the final biosolids. For instance, the biosolids where the raw sludge was predominantly composed of primary sludge had less diversity in overall PFAS composition compared to blended raw sludge feeds (primary and waste activated sludge) where a wide variety in PFAS composition was observed. Hence, differences in raw sludge properties were found to impact the biosolids quality following treatment. 3.4 Removal is dependent on the type of sludge treatment: The target compounds behaved differently in physical, chemical and biological treatments leading to different final biosolids quality. For example, while alkaline stabilization was effective in removing PBDEs, anaerobic digestion led to an increase in PBDE mass flows. In addition, the behavior of perfluorodecanoate (PFDA) differed between treatment systems with responses ranging from moderate removal (41%) to substantial formation (-264%). Even in the studied biological processes, there were distinctions between aerobic and anaerobic sludge treatments. For example, PFOA had low levels of net removal (< 25%) during anaerobic digestion (AN3 and AN5) and contrarily a net increase in mass flow by -68% and -282% in aerobic digestion systems (AE1 and AE2 respectively). The differences in transformations was found to impact the final biosolids quality. 3.5 Removal is dependent on the plant operations: Site specific factors, especially in biological treatment systems, such as the solids retention time, staging of the treatment processes and the active microbial consortia appeared to impact contaminant fate through treatment and hence biosolids quality. For instance, BPA was removed in AN2 with an average efficiency of 75% whereas formation of BPA was seen in other anaerobic digestion processes (AN1, AN4 and AN5). In aerobic digestion, there were low levels of average removals of perfluorohexanoate (PFHxA) (28%) in plant AE1, whereas AE2 reported low average levels of formation (-11%). A detailed discussion on the site-specific factors and operating conditions that may be responsible for the observed removals and biosolids quality will be presented in the full paper. 4. Significance of the findings This study evaluated contaminant loadings and removal of five major classes of EOCs namely PFAS, PBDEs, alkyl phenol, BPA, and triclosan in different full scale sludge treatment systems. The lessons learned will benefit all stakeholders of the biosolids industry in understanding the responses of EOCs thorough sludge treatment. The removal efficiencies presented in this study will enable the treatment plant managers to appraise the performance of sludge handling systems with respect to EOCs. The contaminant loading estimates could be used to communicate the significance of biosolids quality to end users. Further, there is little information describing contaminant mass balances and overall removal through sludge treatment. This study bridged this critical knowledge gap and addressed major questions related to PFAS, PBDEs and phenolics in physical, chemical and biological sludge treatment processes.

The following conference paper was presented at Residuals and Biosolids 2021: A Virtual Event, May 11-13, 2021.

SpeakerLakshminarasimman, Narasimman

Presentation time

13:20:00

13:40:00

Session time

13:00:00

14:00:00

SessionPFAS and Contaminants of Concern in Biosolids

Session number1

Session locationSimu-Live

TopicBiosolids, PFAS/Emerging Contaminants, PPCPs

Author(s)

N. LakshminarasimmanS. GewurtzS. SmythW. Parker

Author(s)N. Lakshminarasimman1; S. Gewurtz2; S. Smyth3; W. Parker4

Author affiliation(s)University of Waterloo 1; Environment and Climate Change Canada 2; Environment Canada 3; University of Waterloo 4;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2021

DOI10.2175/193864718825157944

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count13

Description: Ten Years After: The Status of Polybrominated Diphenyl Ethers (PBDE) in Canadian...

Ten Years After: The Status of Polybrominated Diphenyl Ethers (PBDE) in Canadian Biosolids and Their Fate Through Solids Treatment Processes

Abstract

Occurrence of persistent organic pollutants such as polybrominated diphenyl ether (PBDE) flame retardants in biosolids are a concern as these contaminants may be transported into the environment during land application. This study monitored the concentration of 21 PBDE congeners in raw sludge and biosolids collected from nine sludge treatment facilities across Canada that employed 4 different solids treatment processes. The overall ΣPBDE-Br concentration varied between 0.25 to 1.5 μg-Br/g dry weight. Deca-BDE (BDE-209) was the predominantly occurring congener and its concentration constituted 40-65% of the overall ΣPBDE-Br concentration in both raw sludge and biosolids samples. Tri-, hepta-, and octa- BDE made up less than 1% of the overall ΣPBDE-Br in the raw sludge and biosolids samples. Contaminant mass balances were assembled around the treatment systems and the overall fate of the PBDEs was found to depend upon the treatment technology. While there was no significant change in mass flow during pelletization, ΣPBDE-Br mass flow was reduced by approximately 30% during alkaline stabilization. The removal of PBDE was not consistent in aerobic or anaerobic digestion treatment systems.

SpeakerLakshminarasimman, Narasimman

Presentation time

14:30:00

14:50:00

Session time

13:30:00

15:30:00

SessionEmerging Topics in Microconstituents

Session number402

TopicMicroconstituents

Author(s)

N. LakshminarasimmanS. GewurtzW. ParkerS.A. Smyth

Author(s)N. Lakshminarasimman1; S. Gewurtz2; W. Parker1; S.A. Smyth2;

Author affiliation(s)Department of Civil and Environmental Engineering, University of Waterloo1; Science and Technology Branch, Environment and Climate Change Canada2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2020

DOI10.2175/193864718825157392

Volume / Issue

Content sourceWEFTEC

Word count21

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Lakshminarasimman, Narasimman

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