Dursun, Derya

Dr. Derya Dursun is a Chief Innovation Officer leading CWTs operations. She has over twenty years of experience as an environmental engineer working on wastewater processes all across the nation from Florida, to California. Her environmental expertise spans from innovative technology assessments to sustainable solutions for water reclamation facilites with focus on biosolids management and resource recovery.Currently, she is working on demonstrating advanced wastewater treatment processes that target emerging contaminants, provide energy efficiency and resource recovery.

Titles from this speaker

Description: A New Biosolids Management Trend is Emerging: Biochar Producing Technologies are...

A New Biosolids Management Trend is Emerging: Biochar Producing Technologies are Rising to the Top, Wonder Why?

Abstract

The mounting pressure on land application of biosolids coupled with rising costs of processing, hauling and beneficial use is becoming a burden on utilities. The presence of PFAS and potential regulations for practicing land application require considering emerging technologies with PFAS reduction capabilities. Pyrolysis and gasification are emerging technologies that are gaining interest for biosolids management and in most cases, they are the top alternatives for consideration. This trend is mainly due to significant reduction in mass and volume, thus significant reduction in beneficial use costs making the overall economics favorable when compared to conventional technologies. Pyrolysis and gasification produce biochar that has no detectable PFAS, protecting utilities from any future regulation for biosolids land application. Finally, biochar is considered a carbon sink due to carbon sequestration, thus reducing overall greenhouse gas emissions. This paper presents the results from various evaluations for different utility sizes and geography.

This paper presents results from various biosolids management studies for facilities with different sizes and geography. Emerging technologies that convert biosolids to biochar, such as gasification or pyrolysis, are rising to the top, mainly due to reducing overall cost, ability to beneficially use biochar with non-detect PFAS and finally greenhouse gas emission reduction.

SpeakerAbu-Orf, Mohammad

Presentation time

14:00:00

14:25:00

Session time

13:30:00

15:00:00

SessionUnderstanding and Addressing PFAS in Biosolids

Session locationRoom N426b - Level 4

TopicMunicipal Wastewater Treatment Design, PFAS

Author(s)

Abu-Orf, Mohammed, Blate, Micah, Dursun, Derya, Knowles, Paul, Abu-Orf, Mohammed

Author(s)M. Abu-Orf 1; M. Blate 1 ; D. Dursun 2; P. Knowles 3; M. Abu-Orf 1;

Author affiliation(s)Hazen and Sawyer, New York, NY 1; Hazen and Sawyer, New York, NY 1 ; Hazen and Sawyer, New York, NY 2; Hazen and Sawyer, New York, NY 3; Hazen and Sawyer, New York, NY 1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159012

Volume / Issue

Content sourceWEFTEC

Word count18

Description: Alternate: Demonstration of Supercritical Water Oxidation to Diversify End Products,...

Alternate: Demonstration of Supercritical Water Oxidation to Diversify End Products, Destroy PFAS and Reduce Air Emissions

Abstract

Utilities have been investigating new technologies to diversify their end products from water reclamation facilities (WRRFs) due to strict regulations around land application of biosolids and recent concerns on presence and accumulation of poly-fluoroalkyl substances (PFAS) in biosolids. Supercritical Water Oxidation (SCWO) is a promising technology that converts organic material (biosolids) to inert gases, minerals and water and transforms materials into elemental forms. The technology is also identified by Environmental Protection Agency as an innovative technology to destruct PFAS. The SCWO process provides rapid destruction of a wide variety of organic species normally considered to be refractory or difficult to breakdown under conventional means such as incineration. Water above 374 °C and 22.1 MPa becomes supercritical, a special state where organic solubility increases, and oxidation processes are accelerated. Most hydrocarbons and oxygenated hydrocarbons are converted to CO2 and H2O. Nitrogen in the feed is mainly converted to N2. SCWO has been recently shown to destroy hazardous substances such as halogenated compounds including PFAS. Studies showed a greater than 99% reduction of the total PFAS identified in a targeted compound analysis, including perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) (Krause et al, 2022). As a destructive technology, SCWO is proposed as an alternative to incineration and other combustion processes and could be a permanent solution for PFAS-laden biosolids or solid matrices. However, reliability and operability and performance at commercial scale has not been proven yet. Also, additional investigation of reaction byproducts: water, solids and air emissions need to be conducted for a complete assessment of SCWO's potential as a safe and effective technology. This project aims to provide information for adapting the technology at full scale for public utilities and the engineering community and better understanding to the quality of byproducts. Figure 1 shows the process flow diagram for the technology, and process outputs. Orange County Sanitation District (OCSan) teamed with 374Water, Hazen and Sawyer, and Merrell Brothers to demonstrate the first commercial unit AirSCWO-6 at their Plant 1 for processing six (6) wet metric tons per day. OC San currently produces 250,000 wet tons of biosolids annually that must be treated, stored, and transported to appropriate beneficial use locations. The commercial unit was developed based on a Research and Development (R&D) prototype unit installed at Duke University which has a capacity of one (1) wet tons per day. This first unit was funded by Bill and Melinda Gates Foundation. The commercial unit is manufactured by Merrell Brothers based on 374Water Inc. design, and ready to be installed. SCWO aims to eliminate the combustion products and therefore reduce the air emissions. Still, OC San is in South Coast Air Quality Management District (SCAQMD) and an air permit (research permit) is required to install this unit and conduct the project. To characterize SCWO air quality impacts and to obtain necessary data for a research permit from SCAQMD, the research team, including OC San (Utility), 374Water (a private firm-technology provider), Hazen and Sawyer (a consulting firm), Yorke Engineering (permitting support), Alliance Testing (a source testing firm) worked together to develop a rigorous test plan. Since the prototype unit at Duke University is the only one in operation, air sampling was conducted at Duke by Alliance Testing. There are some differences between prototype and commercial unit, and questions were raised whether emission data between the two units will be comparable. The main difference between these two units was identified as the capacity rather than the process, inputs or operations. Hence, the results from prototype unit were considered as being representative. Table 1 presents the parameters included in the test plan. SCWO aims to eliminate the combustion products and therefore reduce the air emissions. Still, OC San is in South Coast Air Quality Management District (SCAQMD) and an air permit (research permit) is required to install this unit and conduct the project. To characterize SCWO air quality impacts and to obtain necessary data for a research permit from SCAQMD, the research team, including OC San (Utility), 374Water (a private firm-technology provider), Hazen and Sawyer (a consulting firm), Yorke Engineering (permitting support), Alliance Testing (a source testing firm) worked together to develop a rigorous test plan. Since the prototype unit at Duke University is the only one in operation, air sampling was conducted at Duke by Alliance Testing. There are some differences between prototype and commercial unit, and questions were raised whether emission data between the two units will be comparable. The main difference between these two units was identified as the capacity rather than the process, inputs or operations. Hence, the results from ptototype unit were considered as being representative. Table 1 presents the parameters included in the test plan. Testing was performed with biosolids transported from OCSan over the three phases of the unit operation, including start-up phase (when the system warms up and when organics are fed to the system), the initial warmup phase(when co-fuel is being pumped into the unit, and the temperature increases) and the steady state phase(when biosolids were fed to the system and were treated at a steady state). The results were gathered for all the parameters listed in Table 1. Emission calculations were conducted for criteria pollutants, toxic contaminants and greenhouse gas emissions. The results indicated that the air emissions from the demonstration unit will not exceed the threshold values and therefore vented gas from SCWO unit will not pose any health risk. The design for integrating the commercial unit with the plant for this project was completed by Hazen and evaluation of construction bids is underway. Figure 2 shows a process flow diagram of the facility once installed at Plant 1 of OCSan, including controlled screening and dewatering skid for consistent 12-15% TS feed to the AirSCWO-6 commercial unit. Our full paper and presentation will provide detailed information on SCWO process, pretreatment requirements, process inputs and outputs. The air emission results from vented gas will be presented in detail along with further information on process efficiency for organics destruction. The information will benefit utilities that seeks sustainable solution for their biosolids management considering recent concerns on PFAS compounds.

This paper was presented at the WEF/IWA Residuals and Biosolids Conference, May 16-19, 2023.

SpeakerDursun, Derya

Presentation time

8:30:00

11:15:00

Session time

8:30:00

11:15:00

SessionSession 21: Advances and Innovations in Thermal Processes II

Session number21

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicResearch & Innovations

Author(s)

D. Dursun

Author(s)D. Dursun1, M. Abu-Orf2, L. Grijalva3, B. Copp4,

Author affiliation(s)Hazen and Sawyer1; 374Water Inc.2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2023

DOI10.2175/193864718825158781

Volume / Issue

Content sourceResiduals and Biosolids

Word count17

Cost of Removing PFAS from WRRF Effluent and Biosolids

Abstract

This study developed capital and operation and maintenance (O&M) cost estimates and curves to remove and destroy per- and polyfluoroalkyl substances (PFAS) from municipal water resource recovery facility (WRRF) effluent and biosolids. Class 5 cost estimates (-30%/+50%) for the assumed design bases were estimated based on vendor quotes and standard design practices for combinations of technologies pre-screened to be both commercially applied and effective at PFAS separation and/or destruction. Three treatment alternatives were developed for 0.1 to 10 MGD of tertiary treated WRRF effluent and two treatment alternatives were developed for 1.0 to 10 dry tons per day (dtpd) of dewatered WRRF biosolids. Estimated costs for a 10 MGD facility producing 10 dptd biosolids are approximately $79 to $250 million in capital costs and $50 to $20 million in annual operating costs, including consideration of all alternatives developed. Cost per mass of targeted PFAS removed (7 compounds for WRRF effluent and 9 compounds for WRRF biosolids) ranged from $370,000 per pound of PFAS removed from a 50 dptd WRRF biosolids treatment facility to $8 million per pound of PFAS removed from a 0.1 MGD WRRF effluent treatment facility. These costs do not include any retrofits needed to add tertiary treatment upstream of PFAS separation processes for WRRF effluent or to achieve 15%-25% solids content prior to PFAS destruction processes for WRRF biosolids.

This study developed capital and O&M cost estimates to remove and destroy per- and polyfluoroalkyl substances (PFAS) from municipal water resource recovery facility (WRRF) tertiary effluent and dewatered biosolids. Estimated costs for a 10 MGD/10 dtpd facility are approximately $79 to $250 million in capital costs and $50 to $20 million in annual operating costs. 20-year costs per mass of PFAS removed ranged from $370,000 per pound to $8 million per pound of PFAS removed.

SpeakerLing, Alison

Presentation time

16:30:00

17:00:00

Session time

15:30:00

17:00:00

SessionPFAS Impacted WRFs: Knowledge Update

Session locationRoom S401d - Level 4

TopicDisinfection and Public Health, Intermediate Level, PFAS, Research and Innovation, Utility Management and Leadership

Author(s)

Ling, Alison

Author(s)A. Ling 1; B. Vermace 2 ; A. McCabe 3; K. Wolohan 4; D. Dursun 5; M. Blate 6; M. Abu-Orf 6; S. Kyser 7; A. Ling 1;

Author affiliation(s)Department of Civil Engineering, University of St. Thomas 1; Barr Engineering Company 2 ; Barr Engineering Company 3; Barr Engineering Company 4; Hazen and Sawyer 5; Hazen and Sawyer 6; Hazen and Sawyer 6; Minnesota Pollution Control Agency 7; Department of Civil Engineering, University of St. Thomas 1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159129

Volume / Issue

Content sourceWEFTEC

Word count10

Evaluation of Advanced Primary Treatment Technologies at Water Resource Recovery Facilities for Carbon Diversion and Management

Abstract

...Introduction Conventional primary treatment (CPT) technologies such as primary clarifier (PC) only remove 20-30% COD and 40-60% TSS, with a large footprint. To improve performance, Advanced Primary Treatment (APT) technologies have emerged. The primary goal of this project (funded by California Energy Commission) is to assess the treatment and hydraulic performances of four APT technologies (Cloth Disk Primary Filter-CDPF, Compressible Medium Biofilter-CMBF, Micro-Screen-MS, and Proteus Filter-PF) (Table 1) over long-term at Linda Water Resource Recovery Facility (WRRF) and is the first to incorporate long-term operation of these technologies in parallel with CPT. Following results will be included in the paper: (1) long-term performance of APT systems; (2) assessment of the improved treatment and hydraulic performances of APT systems; (3) impact of APT effluent on secondary processes; and (4) design and operational criteria. ...Methodology Four APT technologies have been operated at Linda WRRF located in Olivehurst, CA, at 0.06-1.2 MGD (see Figure 1, Tables 1-2). The CDPF and CMBF are in operation since January 2022 while the MS and PF are since April 2023 and July 2023, respectively. To evaluate hydraulic and treatment performance, each APT has inline turbidity/TSS sensors and flow meters to monitor treatment performance in real-time. Inline sensor data are complemented by 24-h composite sampling. Hydraulic performance includes solids loading rate (SLR), hydraulic loading rate (HLR), and backwash reject water (BRW) ratio. APT systems with high HLR, low BRW ratio, and high SLR have lower capital and operational costs. Treatment performances are measured using total COD (tCOD), soluble COD (sCOD), total BOD (tBOD), soluble BOD (sBOD), TSS and total Kjeldahl nitrogen (TKN) removal. ...Results and Discussion ...Treatment Performance of APT systems Cloth Disk Primary Filter: CDPF achieved an average COD and TSS removal of 51 and 78%, respectively, based on 24-hr composite samples (Figure 2). Although influent wastewater TSS concentrations varied greatly (SD = 163 mg/L), effluent TSS remained steady (Figure 2B). Overall, the CDPF performance in the current project is similar to previous projects with 75-85% and 50-60% removal for TSS and COD, respectively (Caliskaner et al., 2018, 2019, 2020, 2021). Influent/effluent turbidity was converted to TSS using TSS-to-Turbidity Ratio based on inline turbidity sensor and laboratory TSS results which is 1.4 for CDPF influent and 1.2 for CDPF effluent and influent and effluent TSS averaged at 188 and 44 mg/L, respectively (Figure 3). CPT achieved average removals of 36% for COD and 62% for TSS while the CDPF achieved removals of 52% for COD and 78% for TSS. Compressible Medium Biofilter: Since the CMBF unit's installation, the project team focused on gathering preliminary information on treatment performance and enhancing hydraulic performance. 24-hr composite samples obtained in October-November 2023 show that the CMBF achieved 63% and 81% in COD and TSS removal efficiency, respectively. Compared to PC, CMBF is able to increase the COD and TSS removal efficiency by 75 and 31%, respectively. Micro-Screen: The MS achieved an average total COD removal of 45% and TSS removal of 65%, based on 24-hr composite samples (Figure 4). The treatment performance was observed to be comparable with CPTs like PC given a footprint reduction of 70-80%. Overall, the MS unit achieved approximately 5 to 10 % increase in removal efficiencies compared to PC. Proteus Filter: The PF achieves an average total COD and TSS removals of 53 and 80%, respectively, based on 24-hr composite samples (Figure 5). When operated in parallel with PC, PF achieved 47 and 27% increase in COD and TSS removals, respectively. The average effluent TSS from the PF's effluent was found to be stabled around 80 mg/L, which is 16% lower than PC's. ...Hydraulic Performance of APT systems The hydraulic performances of APT units are given in Table 3. The CDPF is equipped with 8 discs, each with an effective surface area (SA) of 53.8 ft2. The average HLR is 0.7 gpm/ft2 and SLR is 2.3 lbs TSS/ft2/day. The daily average flow and BWR ratio for the CDPF is shown in Figure 5. The daily average BWR ratio varied from 2 to 11% and averaged 5%. The CMBF is a bed of individual fiber media balls with a total SA of 19.6 ft2. The average flow rate and HLR are 50 gpm and 2.5 gpm/ft2., respectively. The MS is a 5.5-ft diameter unit with a 200 µm stainless steel mesh. The average HLR is 5 gpm/ft2 and BWR is 3%. The PF is a 23.6-inch diameter tower with a layer of expanded polypropylene beads with a total SA of 3.05 ft2. The HLR and SLR of PF averaged at 6 gpm/ft2 and 17 lbs TSS/ft3 of media and the BWR averaged at 13%. ...Impact of APT systems on Secondary Treatment The project aims to compare and evaluate the impact of APT effluent on both activated sludge basins (ASB) and three Advanced Secondary Treatment (AST) technologies [Microvi, Aerobic Granular Sludge (AGS) and Membrane Aerated Biofilm Reactor (MABR)]. To demonstrate the impact of APT on MLE, the two ASBs at Linda were designed to receive either PC or APT effluent. PC and APT effluents are diverted to Conventional ASB and Enhanced ASB, respectively (Figure 8). Using sensors and real time monitoring, energy and treatment performance are measured directly. Parallel simulations are being conducted using SUMO.

Four advanced primary treatment (APT) technologies were evaluated at demonstration to full scale in this technology development project to replace or augment conventional primary treatment (CPT) system of primary clarification. The APT systems are: Cloth Disk Primary Filter, Proteus Primary Filter, Compressible Medium Biofilter, and Micro-Screen. Carbon diversion and management strategies for CPT and APT technologies are evaluated in detail as part of this project.

SpeakerCaliskaner, Onder

Presentation time

13:30:00

13:50:00

Session time

13:30:00

15:00:00

SessionPrimary, Secondary, and Tertiary Applications of Advanced Filtration Technology

Session number411

Session locationRoom 350

TopicFacility Operations and Maintenance, Intermediate Level, Municipal Wastewater Treatment Design, Nutrients

Author(s)

Caliskaner, Onder, Dursun, Derya, Wu, Yuanbin, Martinez, Everardo, Tchobanoglous, George, Davis, Brian

Author(s)O.T. Caliskaner1, D. Dursun2, Y. Wu3, E. Martinez3, G. Tchobanoglous4, B. Davis5

Author affiliation(s)1Caliskaner Water Technologies, Inc., CA, 2Hazen and Sawyer, CA, 3Caliskaner Water Technologies, CA, 4George Tchobanoglous, CA, 5Linda County Water District, CA

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159633

Volume / Issue

Content sourceWEFTEC

Word count17

Description: Evaluation of Innovative Biosolids Management Strategies with Considerations of...

Evaluation of Innovative Biosolids Management Strategies with Considerations of Circular Water Economy

Abstract

The circular water economy optimizes water resources and minimizes waste and emissions by recycling, recovering and regeneration. Biosolids, an organic and nutrient-rich byproduct of wastewater treatment, are an important and valuable resource that can be beneficially used to support improvements to the circular water economy. However, growing challenges associated with greenhouse gas emissions, limited land and resources, contaminants of emerging concerns (CECs), such as PFAS and microplastics, have begun to threaten the beneficial use of biosolids. In response to the rising challenges, a plethora of innovative biosolids management alternatives have been emerging, providing utilities new perspectives on biosolids treatment, end-use, and pathways to advance the circular water economy via beneficial co-product(s) generation, emissions control/capture, and cost reduction. To comprehensively understand the potential of innovative biosolids management alternatives in addressing these challenges, a holistic evaluation framework (Fig. 1) was developed. The framework encompasses environmental impacts, social impacts, cost-effectiveness, as well as integrability into the circular water economy through the sustainable management of end-products. This presentation will provide valuable and practical information to utilities including: 1) definition, function, and level of readiness of innovative biosolids treatment technologies and 2) a holistic evaluation framework developed to screen innovative technologies for implementation, featuring end-product evaluations. The presentation will inform utilities of innovative solutions to rising wastewater treatment challenges, offer insights to different end-products from innovative technologies, and provide an adaptable tool that utilities can use to select suitable, practical, and sustainable innovative technology(ies) for implementation. This project is funded by the Water Research Foundation (WRF 5169). Innovative Biosolids Treatment Technologies The comprehensive evaluation gathered information from 140 references, including published literature (focused on peer-reviewed literature), gray literature (information from vendors, including WRF's TechLink), information from associations, and responses from a distributed online survey. Technologies captured from the comprehensive search were required to provide at least one of the following benefits compared to established technologies to be considered as 'innovative technology': - Reduce biosolids quantity. - Improve end-product quality. - Enhance energy generation. - Reduce GHG emissions. - Address concerns on emerging contaminants. The findings from this initial evaluation were screened to determine whether the technology is classified as 'innovative,' in alignment with the definition developed by the EPA (2006), where at least one of the following categories must be met by the technology: - Tested at a full-scale demonstration site in this country. - Available and implemented in the United States (U.S.) for less than 5 years. - There is some degree of initial use. - Established technologies overseas with some degree of initial use in the U.S. Within the technology capture, there were 36 innovative treatment technologies identified. The technologies are grouped under several unit operations; thermal conversions, stabilization, thickening, dewatering, drying, and other innovative processes. The results from this evaluation will be presented on an interactive dashboard accessible to utilities and other interested parties. Holistic Evaluation Framework for Innovative Treatment Technologies The framework embraces end-product evaluation, technical capabilities, operation and maintenance requirements, social impacts, regulatory performance, and environmental impacts. The viability of end product biosolids and their co-products, such as energy content, plays a key role in closing the unsustainable loop of resource release to the environment. To this end, end-products are evaluated through the lenses of waste diversion, materials cycling and their benefit predominantly in the natural environment in comparison to the traditional management of biosolids. Key considerations of end-product evaluation are their inherent values, cost recovery potential, market viability, and destruction of CECs. Inherent value reflects the value of constituents in the end-products, such as nutrients and organic matter, and the indirect value of their use (e.g. energy content, carbon offset generation potential). Aggregated inherent values are not indicative of the market value of residuals, but are rather an indication of potential market access and suitability for beneficial use. Management fees and potential market values present opportunities for cost recovery which is typically not available to the baseline product of dewatered biosolids. The values are estimated based on the project team's experience, reports from US contractors, reports from technology vendors, or professional opinion. Figures 2 and 3 present an example result of inherent value and cost recovery potential of the end-products of innovative thermal conversion technologies. The range of beneficial constituents inherent within these residuals will influence market access. Residual products are assessed for their suitability for a range of traditional and innovative markets. Market suitability was assessed on a scale of 0-1 (with 0 being no suitability/access and 1 being full access) based on the project team's experience, industry knowledge, and academic trials and reporting. The environmental impacts of innovative technologies are quantified through energy demand and the greenhouse gas emission during the operation of technology as well as the application of its end-products. Technical performance, operational and maintenance requirements provide information on the robustness, consistency, and scaling flexibility of innovative technologies, helping utilities assess the potential staffing and operating requirements. Social impacts are also included in the evaluation framework, accounting for public opinion and nuisance risks such as odor and noise. The weights of evaluation categories and criteria represent the relative importance of each one and serve as channels to incorporate stakeholders' opinion. The weights are determined based on utilities, project advisory committee, and other stakeholders. Conclusion This project aims to assist utilities in understanding the cross-section and applicability of innovative and sustainable technologies that can fit into a circular water economy, while also meeting the current pressures being faced by the biosolids management community. This presentation will provide practical information on emerging solutions to the challenges in biosolids management and share tools that utilities can use to select options to meet their unique needs.

This paper was presented at the WEF Residuals and Biosolids Conference, June 18-21, 2024.

SpeakerSun, Yian

Presentation time

13:30:00

14:00:00

Session time

13:30:00

15:00:00

SessionLand Application

Session number17

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicCircular Economy, Innovative Technology, Research

Author(s)

Sun, Yian

Author(s)Y. Sun1, C. Evans2, M. Teshima2, A. Lewis1, D. Dursun1, M. Abu-Orf M. Blate1

Author affiliation(s)Hazen and Sawyer 1; Sylvis 2; Sylvis 2; Hazen and Sawyer 1; Hazen and Sawyer 1; Hazen and Sawyer1; Hazen and Sawyer1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159442

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count13

Description: Extracting value beyond meeting regulatory requirements: assessment of green house...

Extracting value beyond meeting regulatory requirements: assessment of green house gas emissions for environmental and economical sustainability of water resource recovery plants

Abstract

Goleta Sanitary District (GSD) a small sized utility located in California has collaborated with Hazen on the development of the Biosolids and Energy Strategic Plan to identify opportunities for codigestion, beneficial use of digester gas and biosolids, and reduced energy consumption and GHG emissions within the WRRP and the Water Reclamation Plant (WRP). Results showed that it would be possible to generate additional revenue from various sources in the future from plant improvements that are necessary to meet regulatory requirements. GSD is an excellent example of a public utility that looks for opportunities to leverage and communicate environmental and economic value from plant improvements needed to meet future regulations.

SpeakerDursun, Derya

Presentation time

10:30:00

10:50:00

Session time

10:30:00

11:10:00

SessionGreenhouse Gas Emissions, Sustainability, and Neutrality

Session number516

TopicEnergy Production, Conservation, and Management, Facility Operations and Maintenance, Municipal Wastewater Treatment Design, Odors and Air Quality

Author(s)

D. Dursun

Author(s)D. Dursun1;

Author affiliation(s)Hazen and Sawyer, CA1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2020

DOI10.2175/193864718825157528

Volume / Issue

Content sourceWEFTEC

Word count23

Getting Ready for Chemical Interruptions at WRRFs

Abstract

Introduction: The water and wastewater industry is facing new challenges in the chemical supply chain due to recent pandemic conditions, hurricanes, and wildfires. As a result, Water Resource Recovery Facilities (WRRFs) are looking ways to improve the chemical resiliency of their facilities during chemical shortages, emergencies, or any disruption in chemical supply chain. The main objective of this paper is to assess the risk from chemical shortages, and present strategies to WRRF's to mitigate risk through consequence and vulnerability reduction. Background: Recently, Hazen has teamed with Orange County Sanitation District (OCSan) to conduct the Chemical Resilience Study for their Plant 1 and Plant 2. The approach to quantitatively assessing and managing risk is based on the ANSI/AWWA J100 Standard: Risk and Resilience Management of Water and Wastewater Systems. The J100 standard provides the framework for assessing baseline conditions as well as improvements following the implementation of risk mitigation. Risk is defined as follows: RISK = Consequence X Vulnerability X Likelihood Table 1 summarizes the approach to reduce consequence and vulnerability for OCSan. This approach will allow to assess baseline risk for WRRFS, as well as provides clear path to reduce the risk, either by reducing the consequences of supply disruption or improving system resilience (i.e., reducing vulnerability). Table 1: Approach Adopted to Reduce Risk for OCSan Methodology: The following methodology was developed to reduce the risk of WRRFs to chemical shortages and disruptions - Chemical Risk Analysis: Estimating the likelihood of chemical shortage requires understanding the chemical supply chain and availability of substitutes. Industry trade groups and chemical suppliers were contacted to understand manufacturing locations and the sources of raw materials. - Vendor Alternatives. Alternative vendors were identified using information from industry trade groups, as well as reviewing chemical bids from OCSan and similar utilities. The use of chemicals in other industries which might be supplied by alternate vendors was also reviewed. - Delivery Alternatives. Alternative forms of deliveries including bulk liquid, totes, and dry chemical delivery with onsite dilution were also investigated - Chemical Alternatives. Alternative chemicals were identified to existing chemicals Findings The chemicals evaluated in OC San Chemical Resilience Study are grouped under four main categories and listed in Table 2. These chemicals are used in the following plant process areas: preliminary treatment, primary treatment, secondary treatment, odor control, effluent disposal, solids handling, and power generation. Table 2: Chemicals Evaluated at OCSan Chemical Resilience Study Chemical interruption to facilities could result from the following conditions: - Lack of delivery access due to a natural disaster - Interruptions from manufacturers and/or vendors - Chemical shortages - Increased cost of chemicals - Increased demand in other industries - Delays in deliveries - Regulatory changes Evaluation of the baseline conditions for OCSan's chemicals identified that most chemicals used have over two weeks of storage available in the event of interruption. The only chemical with less than a week of storage capacity was ferric chloride at Plant 1. Ferric chloride is the mostly used and frequently delivered chemical at Plant 1 and Plant 2 with less than 3 days between deliveries. Bleach was also identified as a chemical with frequent deliveries at Plant 1. Both ferric chloride and bleach are critical chemicals in order for OC San to meet permit requirements in their air quality and discharge permits. Table 3 was developed for OCSan to highlight the criticality (based on consequence score), average chemical use, and consequences of chemical interruption for chemicals used at Plant 2. Table 3: Summary of Chemicals Used at Plant 2 Figure 1 shows the overall risk score calculated for the chemicals used at OCSan. The score brings together the consequence, vulnerability and likelihood assessments. As can be seen in Figure 1, Bleach and Ferric chloride have the highest risk for chemical disruptions. Our full paper will include more details about the consequence, vulnerability and likelihood assessments and will provide a list of alternative chemicals that could be used to replace existing chemicals. Figure 1: Risk score for chemicals used at OCSan

This paper was presented at the WEF Residuals and Biosolids Conference in Columbus, Ohio, May 24-27, 2022.

SpeakerDursun, Derya

Presentation time

10:45:00

11:15:00

Session time

10:45:00

11:45:00

Session number11

Session locationGreater Columbus Convention Center, Columbus, Ohio

TopicChemical, Supply chain distruptions

Author(s)

D. Dursun

Author(s)R. Sobhani1; D. Dursun2; A. Gorzalski3; B. Danker4; S. Rossouw5; F. Gerringer6; M. Chebeir7

Author affiliation(s)OCSD; 1Hazen and Sawyer; 2Residuals and Biosolids Speaker; 3CH2M; 4Residuals and Biosolids Speaker; 5Hazen; 6Hazen and Sawyer; 7

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2022

DOI10.2175/193864718825158410

Volume / Issue

Content sourceResiduals and Biosolids

Word count8

Microplastics in Biosolids Treatment Stream: Abundance, Fate, and Methodologies

Abstract

Introduction and Objectives Water Resource Recovery Facilities (WRRFs) passively collect various contaminants which has led to concern about potential environmental impacts downstream. Of particular interest, microplastic (MP) contamination has remained a concern due to various sources of MPs into wastewater, including municipal waste, roadway runoff, and industrial discharge. Conventional wastewater treatment processes have been effective in separating MPs driven by physical separation technologies, consequently accumulating MPs in the solids stream and biosolids [1,2]. Land application of biosolids presents avenues for MPs in biosolids to enter and accumulate in landfills, agricultural soil, plants, soil biota, and further transport into the environment. Understanding MPs' occurrence, fate, and transformation in biosolids treatment is crucial to promote the beneficial and sustainable use of biosolids. Information on MPs across the solids stream is yet to be synthesized to assist stakeholders in understanding risks associated with MPs, and there is still a lack of consensus regarding reproducible analytical methods to quantify MPs by mass and count. To this end, a comprehensive critical review, capturing data and knowledge from 51 studies including peer-reviewed journals articles, reports, and conference proceedings, was conducted to 1) inform the state of knowledge of MPs in solids stream, including their occurrence, fate and characteristics; 2) identify knowledge gaps of MPs in solid unit processes (e.g. digesters); 3) inform the development standard operation procedures for empirical analysis. This study is part of the Water Research Foundation project #5221. Findings

*Abundance and Fate of Microplastics in Solids Stream The literature review found that the abundance of MPs in different solids process units varies by several orders of magnitude (Fig. 1). Moreover, the number of facilities studied, and concentrations reported vary dramatically across the world. The lack of consistent and representative sampling methods across the solid stream poses challenges in developing an understanding of how different sludge treatment processes affect MPs and quantifying the transformation of MPs. Based on a literature review of intra-facility variation of MPs in solids treatment stream (post-primary treatment), the quantity of MPs does not significantly change from sludge generation, thickening to stabilization, but decrease after dewatering, which indicates potential accumulation of MPs in side streams (Fig.2). These side streams often return to the headworks of WRRFs; therefore, these streams may represent an additional 'catch and release' point. A total of 31 types of polymers were reported in literature. Polyester, polypropylene, polystyrene, polyethylene, polyamide, polyethylene terephthalate are the most frequently reported and abundant polymers. Polyester and polyamide are commonly used for synthetic fabric and often appear as MP fibers in both wastewater and sludge.

*Accumulation of Microplastics in Biosolids Amongst 51 studies reviewed, a median of 14,900 pieces of MPs (Std. Dev = 476,498) were found to be deposited into soil per dry kilogram of biosolids applied. Maximum sludge value is significantly higher at 169,000,000 particles per kg. In comparison, MPs in soil are observed to range from single digits per kg to approximately 40,000 particles per kilogram. With land application of biosolids, MPs content in soil can increase hundreds of pieces per kg according to literature [4].

*Methodologies for Microplastics Quantification in Biosolids Sampling, sample processing, and analytical methods from literature reviewed is summarized in Table 1. The methods of the studies reviewed utilize automated sampling system and/or pumps for collecting samples with low solids content, e.g. secondary sludge, digested sludge, whereas high solids content samples are manually taken using buckets or shovels. The studies' sample processing procedures typically follow: density separation, chemical digestion, and vacuum filtration. The quantification of MPs in literature is count-based and relies on vibrational spectroscopy, which is faced with technical challenges including laborious sample preparation and analysis, spectral identification errors, higher size limit, miscounts due to fragmentation, and reduced number of samples due to the high cost associated with these types of analysis methods. To address these challenges in the later empirical analysis of WRF 5221, a dual quantification approach will be adopted (Fig. 3). Pyrolysis-gas chromatography /mass spectroscopy will quantify MPs in biosolids by mass, which is advantageous due to highly accurate quantification of polymers without time-intensive sample preparation or analysis, whilst Raman spectroscopy will provide the MPs characteristics for comparison with literature, including polymer type, size distribution, and morphology. Conclusion This literature review showcases the state of knowledge on MPs in solids treatment stream. It informs utilities of the abundance and fate of MPs in different process units and in relation to facility characteristics and location, providing information that utilities can use to assess potential risks. The project also addresses shortcomings associated with commonly used analytical methods by measuring repeatability as a core element of the study design which will be useful for future studies.

A l review, capturing data and knowledge from 51 studies including peer reviewed journals articles, reports, and conference proceedings, was conducted to 1) inform the state of knowledge of microplastics in solids stream, including their occurrence, fate and characteristics; 2) identify knowledge gaps of Microplastics in solid unit processes (e.g. digesters); 3) inform validated standard operation procedures for empirical analysis. This study is part of the Water Research Foundation.

SpeakerSun, Yian

Presentation time

16:00:00

16:30:00

Session time

15:30:00

17:00:00

SessionMicroplastics in WRRFs: Research, Risk, and Regulation Updates

Session number222

Session locationRoom 238

TopicBiosolids and Residuals, Disinfection and Public Health, Intermediate Level, Microconstituents and Contaminants of Emerging Concern (Non-PFAS), Research and Innovation

Author(s)

Sun, Yian, Walther, Shelly, Dursun, Derya, Abu-Orf, Mohammad, Cook, Cayla

Author(s)Y. Sun1, S. Walther2, D. Dursun1, M. Abu-Orf3, C. Cook4

Author affiliation(s)1Hazen and Sawyer, CA, 2LA County Sanitation Districts, CA, 3, NY, 4Hazen and Sawyer, AZ

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159533

Volume / Issue

Content sourceWEFTEC

Word count10

Description: Optimization of Advanced Primary Treatment Technologies for Carbon Diversion and...

Optimization of Advanced Primary Treatment Technologies for Carbon Diversion and Management at Water Resource Recovery Facilities

Abstract

Introduction Advanced Primary Treatment (APT) is a process in which filtration or micro-screening technology is used to replace or supplement Conventional Primary Treatment (CPT). In this project, the Cloth Disc Primary Filter (CDPF) and Proteus Primary Filter (Proteus PF) have been demonstrated for 3 and 1.5 years, respectively. Significantly higher treatment performance values (i.e., 40 to 50 % higher) were observed with both primary filtration (PF) technologies compared to CPT. PF increases capacities of primary and secondary treatment systems minimizing (or sometimes even eliminating) expansion requirements for existing installations or reduce the required footprint for new installations. Primary filtration is also the most effective carbon diversion strategy at Water Resource Recovery Facilities (WRRFs). Carbon diversion involves reducing the organic load on secondary systems by redirecting more biochemical oxygen demand towards the solids line at the primary treatment stage, which reduces the aeration requirements for aerobic biological processes downstream. Resultant benefits of PF are: (1) savings in aeration energy costs, (2) increase in digester gas energy production, and (3) reduction in primary and secondary treatment footprint and volume requirements. Significant CAPEX and OPEX savings are realized because of these benefits. One important design and operational challenge for PF is the high primary sludge volume produced during backwash operation. Sludge produced from PF backwash is also thinner (i.e., 0.2 to 0.4 %) compared to CPT sludge. Thickening is an essential process component of PF systems and its design conditions are quite different due to high sludge volumes, low solids concentrations, and significant differences in sludge characteristics. Optimization of PF systems to minimize backwash sludge volumes and still achieving high treatment efficiencies is one of the main objectives of this on-going technology research and demonstration project. Methodology Funded by California Energy Commission, the focus of this project is to evaluate the treatment and hydraulic performance of several PF technologies at Linda County Water District's (Linda) WRRF located in Olivehurst, CA (Fig. 1). General information for the Proteus PF and CDPF systems are provided in Table 1. The Proteus PF and CDPF units are shown in Figs. 2 and 3, respectively. CDPF unit has been in operation since January 2022 and Proteus PF has been in operation since July 2023. The specific objectives of the project include: (1) Evaluate the performance of PF technologies; (2) Improve the treatment and hydraulic performances; (3) Optimize the design & operational criteria including sludge treatment system, and (4) Evaluate impacts on downstream secondary process. Inline turbidity/TSS sensors and flow meters have been installed at each PF system and sensor data are synchronized to provide real-time monitoring of treatment performance. Inline sensor data are complemented by lab analysis of 24-h composite samples from influent and effluent channels of each unit. Overall, the evaluation is based on hydraulic and treatment performances. The hydraulic performance was assessed using solids loading rate (SLR), hydraulic loading rate (HLR), and backwash reject ratios (BRR) of both PF systems. High HLR, low BRR, and high SLR typically correlate to lower capital and operational costs. The key parameters impacting BRR include: HLR, SLR, pressure build-up rate, backwash flowrate, and backwash frequency and duration. The treatment performance was evaluated based on total COD (tCOD), soluble COD (sCOD), total BOD (tBOD), soluble BOD (sBOD), TSS and total Kjeldahl nitrogen (TKN) removal. Treatment Performance of APT systems The performance of the Proteus Filter and Cloth Disk Primary Filter are reported and compared to conventional primary sedimentation. Proteus Filter: The TSS and COD removal performances of the Proteus Filter are shown in Fig. 4 and Fig. 5, respectively. Results were obtained based on 24-hr composite samples collected between July 2023 and September 2024. More than 100 samples were used to evaluate the removal performances. As shown in Fig. 4, influent and effluent TSS concentrations averaged at 471 and 100 mg/L, respectively, when the unit was operated between its average and peak flow design conditions. Influent and effluent COD, as reported in Fig. 5, averaged 981 and 419 mg/L, respectively. Cloth Disk Primary Filter: The TSS and COD removal performances of the full-scale CDPF system are shown in Fig. 6 and 7, respectively. Results were obtained based on 24-hr composite samples collected between May 2022 and September 2024. More than 150 samples were used to evaluate the removal performances. As shown in Fig. 6, influent and effluent TSS concentrations averaged at 421 and 56 mg/L, respectively. It should be noted that even though influent wastewater TSS concentrations varied significantly, a relatively stable effluent TSS between 50 to 70 mg/L was observed. Influent and effluent COD, as reported in Fig. 7, averaged 805 and 335 mg/L, respectively. Overall, the CDPF performance has been observed to be similar to the results obtained from previous demonstrations where 75-85% and 50-60% removal for TSS and COD were observed, respectively (Caliskaner et al., 2018, 2019, 2020, 2021, 2022). Performance Comparison versus Primary Sedimentation: Both PF systems were operated in parallel with the existing primary clarifiers at the Linda WRRF, and performance comparisons were conducted using samples taken during the same 24-hr sampling intervals. As seen in Fig. 8, primary clarifier (PC) achieved average removals of 38% for COD and 66% for TSS. As seen in Fig. 8, the Proteus PF unit achieved average removals of 65% for COD and 85% for TSS when operated at 2 gpm/ft2, which are 40 to 50 % higher compared to PC removal efficiencies. Similar high treatment performances were also obtained with the CDPF system when compared to primary clarifier. Average removals of 56% for COD and 85% for TSS were achieved with the CDPF system. Hydraulic Performance of APT systems The optimum design and operational conditions are investigated in this project considering HLR, SLR, headloss development (across the filter media), and BRR ratios. Summary of hydraulic values observed for both PF systems are presented in Table 2. PF backwash is triggered by preset filtration time or maximum headloss development , whichever comes first. Headloss development is measured by pressure transducers. Headloss development rates were observed to change with changes in HLRs. Proteus PF: As illustrated in Fig. 9, headloss development increases as the HLR increases resulting in higher BRRs. The daily average headloss development under HLR of 2 gpm/ft2 and 6 gpm/ft2 were 5.2 and 6.2 psig, respectively. The increased flowrate and HLR caused increased accumulation of particulate material within the filter media resulting in larger headloss values and hence higher BRR values. The HLR and BRR values with respect to time are summarized in Fig. 10. The Proteus PF system has been operated between 2 and 9 gpm/ft2 most of the demonstration resulting in an average BRR of 9.4%. Daily average HLR and SLR for the Proteus PF System during the demonstration is shown on Fig. 11. Based on an analysis of HLR and BRR values, HLR ranging from 2 to 2.5 gpm/ft2 are considered for optimum average flow design conditions and 5 to 6 gpm/ft2 are considered for peak flow design conditions. Cloth Disk Primary Filter: The volumes of filtered effluent, backwash reject, and sludge wasting are all monitored along with HLR and SLR values. Recorded HLR and BRR values are shown in Fig. 12. Similar to Proteus PF system, headloss development and BRR increase as the HLR increases. Average daily BRR values were observed to be approximately 10 percent under average design flow/loading conditions. Based on an analysis of HLR and BRR values, HLR value of approximately 2 gpm/ft2 is considered for optimum average flow design conditions and 4 to 4.5 gpm/ft2 are considered for peak flow design conditions. Impact of Primary Filtration Systems on Energy Consumption and Recovery One major project objective is to demonstrate the energy and capacity impacts of PF on WRRFs. Specifically, impacts of PF on MLE process and three Advanced Secondary Treatment technologies including Microvi, AGS and MABR were evaluated. Energy savings and footprint reductions are measured directly in addition to the process modeling studies to further investigate the impacts on BNR kinetics. The impacts of PF on secondary treatment and anaerobic digestion were predicted with SUMO process modeling using the obtained PF demonstration data. PF results in 25% in aeration energy savings and 35% increase in digester gas production (Fig. 13).

This paper was presented at the WEF Residuals & Biosolids and Innovations in Treatment Technology Joint Conference, May 6-9, 2025.

SpeakerCaliskaner, Onder

Presentation time

13:45:00

14:00:00

Session time

13:30:00

15:00:00

SessionDifferent Approaches to Diverting COD Upstream of Nutrient Removal Facilities

Session numberITT Session 18

Session locationBaltimore Convention Center, Baltimore, Maryland, USA

TopicBiogas Production, Intensification, Primary Treatment, Process Intensification, Secondary Treatment, Solids Retention Time, wastewater

Author(s)

Caliskaner, Onder, Dursun, Derya, Wu, Yuanbin, Martinez, Everardo, Tchobanoglous, George, Davis, Brian

Author(s)O. Caliskaner1, D. Dursun1, Y. Wu1, E. Martinez1, G. Tchobanoglous2, B. Davis3

Author affiliation(s)Caliskaner Water Technologies, Inc.1, University of California at Davis2, Linda County Water District, 3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2025

DOI10.2175/193864718825159789

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count17

Description: Technologies and Processes for Pretreatment and Management of Source Separated...

Technologies and Processes for Pretreatment and Management of Source Separated Organics

Abstract

Introduction: Source Separated Organics (SSO) co-digestion with wastewater solids at Water Resource Recovery Facilities (WRRFs) offers promise to advance sustainability through beneficial reuse of the organic fraction of pre- and post-consumer waste streams (source separated organics), which would typically otherwise be disposed in landfills. Currently, several states have started implementing regulations restricting organics disposal to landfills to reduce green house gas emissions. A major outlet for SSO's has identified as anaerobic digesters already built-in water resource recovery facilities however most of the time SSO's cannot be accepted as they generated and requires pretreatment. The pretreatment could be conducted on-site at WRRFs, in centralized facilities and in some cases at decentralized sites. Objectives: This paper will present the findings from a recent project funded by the Water Research Foundation. The objective of this presentation is to comprehensively evaluate SSO pretreatment technologies and existing operational facilities and produce information that utilities with interest in SSO pre-treatment can use as guidance. The utilities could use the findings from this research for several important purposes: - successfully building or enhancing existing SSO pretreatment and co-digestion programs, - addressing challenges and opportunities involved with SSO pretreatment, - identifying SSO pretreatment requirements based on SSO feedstock quality and quantity, - and determining capital and O&M costs and potential impacts on WRRFs. Methodology: A systematic approach was developed for conducting global literature review and also to gather information from existing facilities and case studies. This approach was successfully used to draw the borders of the research and stay focused on the main objectives of the project. Fact sheets were developed for each case study to provide detailed information. Finally, all the results were transferred into Microsoft Power BI platform to visualize the results and generate dash boards. This presentation will provide an overview of the project, goals and anticipated outcome of the project, and an update on progress made to date. Findings: The literature review showed that the physical SSO pretreatment technologies are preferred around the globe in full scale applications. Considering high variable nature of SSO, the pretreatment processes are found to be mostly site specific. However, in majority of the facilities SSO pretreatment starts with initial Unit Operating Processes (UOP's), that generally includes separation technologies such as trommel screens, magnetic belts, and rock traps. After an initial process the core of the process includes pulping/mixing/blending technologies. Hydropulper, depacking equipment, extrusion units are generally used as the core of the pretreatment process to generate homogenized slurry. As a last polishing step, mixers, blending/mixing tanks and also separation technologies are also included in the process. Our results indicated that the SSO pretreatment can be performed on-site at the WRRFs or off site as a stand alone facility. Several facilities were selected around the globe to evaluate. Figure 1 shows the different type of SSO Pretreatment/Processing applied in facilities and also lists the Utilities that adopted these management strategies. Figure 1. Four Types of SSO Pre-treatment/ Processing by Utility A fact sheet was prepared for each facility listed in Figure 1 and the type of SSO pretreatment and processes were evaluated in detail. The fact sheets include information on type of SSO received, types of processes and technologies applied along with key O&M lessons learned. Furthermore, seven case studies (selected WRRFs have successfully implemented SSO feedstock pretreatment systems) were included to include more detailed information especially on costs and maintenance requirements.

This paper was presented at the WEF Residuals and Biosolids Conference in Columbus, Ohio, May 24-27, 2022.

SpeakerDursun, Derya

Presentation time

10:15:00

10:45:00

Session time

10:15:00

11:15:00

Session number20

Session locationGreater Columbus Convention Center, Columbus, Ohio

TopicCo-Digestion With Other Organic Sources, food waste, Sustainability

Author(s)

D. Dursun

Author(s)D. Dursun1; M. Blate2; K. Landry3; M. Abu-Orf4; R. Sharp5; N. Kaiser6

Author affiliation(s)Hazen and Sawyer; 1Residuals and Biosolids Speaker; 2Hazen and Sawyer; 3AECOM; 4Manhattan College; 5Residuals and Biosolids Speaker; 6

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2022

DOI10.2175/193864718825158406

Volume / Issue

Content sourceResiduals and Biosolids

Word count12

Thickening through Suspended Air Application Aims to Reduce Energy Consumption

Abstract

Conventional thickening processes use gravitational forces or mechanical methods such as centrifuges or belt filter presses for solids separation. Although these methods have proven to be efficient, gravity based thickening methods require large footprint and mechanical thickening processes can be energy intensive. Recently, several innovative technologies have been introduced that aim to enhance energy efficiency of thickening process while reducing the footprint. Dissolved Air Flotation (DAF) process has been around for over a century and initially used in the early 1900s, primarily in the pulp and paper industry to remove fibers and other solids from water. Interest in DAF resurged in the 1960s for wastewater treatment applications and since then DAF has been used as one of the main thickening processes. DAF introduces air into the wastewater solids, and creates tiny bubbles. Then these bubbles attach to the sludge particles, causing them to float to the surface, where they form a thickened sludge layer. This layer is then skimmed off, leaving clearer water below. However, DAF has shown to be energy intensive since it requires recirculation pumps, compressors. Lately, a new thickening technology called Suspended Air Flotation (SAF) was introduced into the wastewater industry. SAF operates similar to DAF by using air to float sludge. However, there is a key difference: SAF employs charged particles for bubble flotation. SAF also aims to float the particles but without the use of dissolved air. Therefore, thickening performance is not limited by changing conditions such as gas solubility, pressure, and temperature. The flotation occurs by the application of froth made from an anionic surfactant, water, and air instead of air bubbles for flotation. Similar to DAF, SAF mixes feed sludge with a conditioning polymer before it enters the flotation tank. Froth, composed of charged microbubbles called aphrons, is then introduced downstream of the polymer injection. The micron-sized air bubbles, ranging from 7 to 50 Âµm, in water to attain a volumetric air content of 40 to 50%. These bubbles are coated with a thin layer of soap film derived from an electrically charged anionic or cationic surfactant. The charged bubbles offer a substantial interfacial area for the adsorption of oppositely charged flocculated wastewater solids. In practice, suspensions of charged bubbles are introduced into the flotation tank to interact with wastewater solids. The solids then ascend to the surface and are skimmed off. The clarified effluent is recirculated to the headworks. SAF enhances traditional thickening methods like Dissolved Air Flotation (DAF) by eliminating the need for dissolved air, thus obviating the requirement for pressurization systems, recirculation pumps, compressors, and airlines, leading to considerable energy savings. SAF's capability to manage high solids loads also results in substantial footprint and power savings, high solids recovery (up to 98%), and a high solids loading rate (up to 40 lb/ft2/hr). Moreover, no polymer is needed to thicken sludge to 4% solids. Owing to these benefits, adopting SAF technology can lead to a reduction in greenhouse gas emissions by more than 60-70% and energy savings of up to 90% compared to its conventional counterparts, such as DAF. In a recent project funded by California Energy Commission (CEC), this innovative thickening process was selected to be tested at demonstration scale. The demonstration facility is located at Linda County California, north of Sacramento. The project includes several advanced treatment processes for biosolids. Another innovative technology Supercritical water oxidation (SCWO) is also included after SAF to replace anaerobic digesters. Figure 1 shows the process flow diagram at demonstration facility. SAF process have already shown promising results for their low energy consumption. Recent findings indicated over 90% savings in energy use by switching from DAF to SAF. Table 1 compares SAF process with conventional thickening processes. The cost savings for SAF process was also evaluated with other conventional thickening processes including Rotary Drum Thickener (RDT) and also DAF. Table 2 summarizes the 30 year net present value comparison of SAF process. This presentation will evaluate this novel technology, discuss the critical design criteria for this process and assess its performance focusing on energy savings.

This paper was presented at the WEF Residuals & Biosolids and Innovations in Treatment Technology Joint Conference, May 6-9, 2025.

SpeakerDursun, Derya

Presentation time

09:30:00

09:50:00

Session time

08:30:00

10:00:00

SessionAdvancements in Thickening Technologies: Operational Optimization and Cost Savings

Session number23

Session locationBaltimore Convention Center, Baltimore, Maryland, USA

TopicAsset Management, Efficiency, Solids Thickening