Maltos, Rudy

Rudy Maltos was a speaker at the WEFTEC 2024 conference in New Orleans, LA October 5-9, 2024.

Titles from this speaker

Combining Metabolic, Kinetic and Physical Selection to Achieve Full-Scale Continuous Flow Densified Activated Sludge and Nutrient Removal at Robert W. Hite Treatment Facility

Abstract

Introduction: Metro Water Recovery's (Metro) Robert W. Hite Treatment Facility (Hite) in Denver, CO is permitted for a maximum month (MM) flow of 220 mgd and has two parallel liquids treatment trains including the North Secondary (NSEC). The NSEC utilizes a modified Ludzack Ettinger (MLE) process with a sidestream anaerobic reactor (SAR) to achieve nutrient removal. In 2018, Metro's facility plan identified a need for increased aerobic solids retention time (aSRT) to meet future potential total nitrogen (TN) and total phosphorus (TP) regulations (Colorado Regulation 31). To avoid costly expansion, Metro commissioned a full-scale demonstration train (NAB2) to trial densified activated sludge (DAS). This work documents findings from the full-scale demonstration facility and discusses how Metro is translating DAS into a full-scale solution at the RWHTF. Specifically, this paper will discuss factors that have led to the development and long-term operation of DAS with biological and physical selection, as well as provide insights into how particle size distribution (PSD) may be impacted by operational parameters and influence nutrient removal. Materials and Methods: DAS facility: The DAS demonstration facility (denoted as NAB2) consisted of an isolated, paired aeration basin and secondary clarifier from NSEC. Description of the facility is provided elsewhere (Avila et al., 2021). Metro operated NAB2 to test multiple distinct metabolic and kinetic selector configurations, with two primary configurations, Fig 1. A 'control' train was also operated without physical and biological selection. Routine influent/eff concentrations of organics, solids and nutrient content were determined using Standard Methods for the Examination of Water and Wastewater. PSD of the MLSS, hydrocyclone UF, and hydrocyclone OF were routinely characterized. Settling Column Testing: Settling column testing of bulk DAS ML was conducted on multiple occasions to determine the Vesilind equation settling coefficients (V0 & k) as well as the PSD. Additionally, settling properties for particle size fractions: <200µm, 200-600µm, and >600µm were characterized across a concentration range of approximately 1,500 mg/L to 6,000 mg/L. Activity Testing: Batch scale activity testing of bulk mixed liquor and three particle size fractions was used to evaluate nutrient removal rates of activated sludge in 5-gallon reactors. Analytes (NH4, NO3, NO2, and PO4) were measured with HACH TNT kits. Hydrocyclone Nozzle Testing: Hydrocyclone UF nozzle sizes ranging from 15 to 25 mm were individually tested at a target pressure of 30 psi. Flow measurements from the hydrocyclone feed and OF were recorded via flow meter. Total suspended solids (TSS) and PSD samples were collected from the RAS, OF, and UF. Process and Capacity Modeling - Data from NAB2 testing were used to develop, calibrate, and validate AB2 specific and a whole plant process model in BioWinTM and computational fluid dynamics (CFD) models of the NSEC secondary clarifiers. These models establish system capacity of existing infrastructure and design criteria for full-scale implementation. Results and Discussion: Impact of biological selection on densification: PSD of NAB2 biomass during configuration 1 (SAR-MLE) mode) stabilized into a uni-modal distribution, with median size increasing from 100 to 200 um respectively (Fig 2A). The average SVI30 for the NAB2 versus control basins were 102 mL/g and 153 mL/g respectively. PSD of NAB2 biomass during configuration 2 (SAR-A2O) mode reflected a bi-model distribution (Fig 2B). The average SVI30 for the test versus control basins were 81 mL/g and 173 mL/g respectively. Cumulatively, results suggest that improved settleability is observed when the mass fraction of granules (particles >212 um) in the sludge exceeds 15%. This was observed on multiple occasions when NAB2 operated in SAR-A2O mode with anaerobic food to microorganism ratio (F/M) being sustained between 1.0 and 3.0 lb sCOD/lb MLVSS-day. Impacts on PSD on Settling Performance and Biomass Activity: Settling velocity and compressibility were observed to increase as the particle size fraction increased (Table 1). Biomass activity results indicated that larger particle size fractions had lower denitrification and nitrification rates versus smaller particle size fractions while Bio-P activity was highest in particles greater than 200 um. These results indicate that minimizing particles sizes greater than 600 um may allow Metro to exploit high nitrification/denitrification/Bio-P rates and with superior settling and compressibility (Quoc et al., 2021). Influence of Physical Selective Pressures on PSD in NAB2 (Fig 3): Results indicated that mass flow through the UF could be reduced when the nozzle size decreases (Fig 2). This phenomenon can potentially be exploited to craft a wasting strategy focused on developing and keeping a target PSD. DAS impacts on Capacity: Stress testing indicated that NAB2 could be loaded at surface overflow rates (SORs) >700 gpd/sf and solids loading rates (SLRs) >60 pounds per day per square foot (ppd/sf) while still maintaining reliable blanket control and stable effluent TSS (Fig 4). Whole plant process and CFD modeling indicated that the densified scenario could allow Metro to successfully treat 2040 flows without needing to invest in additional aeration basins or secondary clarifiers, allowing for savings of $50 million dollars.

To meet future nitrogen and phosphorus regulations without constructing new infrastructure, Metro Water Recovery conducted a full-scale demonstration of densified activated sludge (DAS) at its Robert W. Hite Treatment Facility. This study evaluated the DAS system, focusing on metabolic and kinetic selector configurations, particle size distribution, and nutrient removal efficiency. Results include impacts of configurations, particle size, and nozzle size and projected capital cost savings.

SpeakerMaltos, Rudy

Presentation time

09:00:00

09:30:00

Session time

08:30:00

10:00:00

SessionFull-scale Intensification Experience

Session number510

Session locationRoom 343

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

Author(s)

Maltos, Rudy, Rauch-Williams, Tanja, Freedman, Daniel, Cavanaugh, Liam, Scopp, Anna, Priest, Ryan, Griborio, Alonso, Mayer, Alyssa, Noteboom, Haley, Latimer, Ron, Sun, Yewei, Khunjar, Wendell

Author(s)R. Maltos1, T. Rauch-Williams1, D. Freedman1, L.M. Cavanaugh1, A. Scopp2, R. Priest2, A. Griborio3, A.J. Mayer4, H. Noteboom5, R.J. Latimer6, Y. Sun7, W. Khunjar8

Author affiliation(s)1Metro Water Recovery, CO, 2Hazen and Sawyer, CO, 3Hazen & Sawyer, FL, 4Hazen & Sawyer, OH, 5Hazen & Sawyer, NY, 6Hazen and Sawyer, GA, 7Hazen and Sawyer, VA, 8Hazen & Sawyer PC, VA

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159645

Volume / Issue

Content sourceWEFTEC

Word count24

Densified Activated Sludge: Successful Analytical Methods for Process Performance Monitoring

Abstract

Introduction The densified activated sludge (DAS) process is a relatively new procedure that Water Resource Recovery Facilities (WRRFs) are adding to improve treatment efficiency. Certain inherent properties of DAS, however, can cause interferences with conventional laboratory methods. Overlooking these inherent granule properties can result in compromised laboratory results and misinformation for DAS process monitoring and operation. Metro Water Recovery's (Metro's) process engineers, operations, and laboratory worked together throughout a 2-year DAS demonstration project to identify, refine, and modify appropriate analytical methods for DAS. This presentation will summarize four of Metro's analytical methods developed for DAS as described below. Methods Metro initially assessed the applicability of standardized and newer wastewater methods for settling velocity1, TSS2, microscopy3, and PSD4 to DAS. Over the duration of the DAS pilot operation, Metro adjusted these conventional methods in response to analytical problems and errors noted in the datasets as discussed in the following. Particle Settling Characteristics Conventional Method Issues (CMI) Sludge volume index (SVI) is a routine method that has been used to assess the settleability of sludge for over 90 years5. Settling velocity is a variation of the SVI method which provides valuable process information for DAS, specifically in the first 6 minutes when much of the DAS settling occurs1. Despite the value in settling velocity, there is some inherent variability from the need for nearly immediate readings before a clear defined front has formed making it difficult to accurately measure settling. Modified Procedures (MP) Metro defined three method adjustments to improve the reproducibility of the method: 1) using flashlights to aid in the readings, 2) standardizing the method for readings between laboratory staff to ensure consistency, and 3) optimizing sample homogenization time to clarify front formation. Metro will present images and videos to illustrate these findings and share recommendations to standardize this method in other laboratories. Total suspended solids (TSS) CMI TSS is a commonly used laboratory method to assess solids inventory, solids residence time, wasting rates, and granulation efficiency. Due to the rapid settling of DAS, measuring the exact sludge volume for TSS using graduated cylinders and standard pipettes can underestimate TSS. Metro developed modified analytical protocols for accurate TSS measurements. DAS can also cause online and handheld TSS measurements to systematically underestimate true concentrations due to particle settling and stratification in the basins. MP Metro's laboratory modified their standard operating procedures (SOPs) for DAS to overcome interference due to DAS settling. Using wide-bore pipettes to measure and transfer sample to filter from the sample container (rather than graduated cylinders), better maintains granules in suspension through the sample volume measurement process. The fact that TSS online and handheld probes read lower values compared to laboratory TSS controls was overcome by determining instrument calibration reference factors (ratio of laboratory values to probe readings) and correction factors used to adjust online readings. These adjustment methods resulted in more consistent readings closer to the true TSS (lab) values. Microscopy CMI Microscopy is used to assess sludge properties such as microbial community and filament abundance6. It is an equally important tool for DAS providing details on the size and morphology of the granules, density, and filaments. Appropriate techniques for wet mount slide preparation ensures the structure of granules is not compromised and quality images are produced. MP Metro developed a modified wet mount procedure for DAS analysis, emphasizing how to place the cover slip to avoid DAS compression. Metro will demonstrate this method in the presentation. Figure 1 shows the granules in-tact which prevents errors and Figure 2 shows flattened granules. Particle Size Distribution (PSD) CMI Particle size distribution (PSD) is not a common wastewater analysis method but can be extremely important when working with granular sludge. It is beneficial to quickly quantify the size distribution of the granules being produced so operational changes can be made to maintain the appropriately sized granules and sufficient nutrient removal. Sieving and PSD via instrumentation were assessed by Metro. MP Sieving is a common method for PSD analysis, but it is slow, labor intensive, prone to bias, and only provides information on the discrete sieve sizes used. While PSD measured with instrumentation using light diffraction methods is more of a qualitative method, Metro demonstrated that PSD analysis by instrumentation provides reliable, reproducible PSD results (Figure 3). This is done in less than ten minutes per sample allowing for timely data for operational decisions, whereas the sieving procedure can take between 30 minutes and two hours. Conclusions Metro's team has identified important method modifications that laboratories should consider when analyzing the characteristics of DAS. By validating and adopting these recommendations in other laboratories, operators and process engineers will increase confidence in the data being used

The densified activated sludge (DAS) process allows water resource recovery facilities to improve treatment capacity or effluent quality. However, certain properties of DAS can cause interferences with laboratory methods leading to misinformation for DAS operational decision-making. Metro Water Recovery modified four analytical methods to improve results including, (1) particle settling characteristics, (2) total suspended solids, (3) microscopy, and (4) particle size distribution.

SpeakerLove, Natalie

Presentation time

14:30:00

15:00:00

Session time

13:30:00

15:00:00

SessionInnovative Approaches to Address Traditional Operational Challenges

Session number211

Session locationRoom 344

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

Author(s)

Love, Natalie, Bruhn, Ashley, Fielder, Tracy, Caley, Cassandra, Maltos, Rudy

Author(s)N. Love1, A. Bruhn1, T. Fielder1, C. Caley1, R. Maltos1

Author affiliation(s)1Metro Water Recovery, CO

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159643

Volume / Issue

Content sourceWEFTEC

Word count11

Evaluating Full-Scale Impacts of Activated Sludge Densification on Disinfection Efficacy: A WRF Tailored Collaboration

Abstract

Background Water resource recovery facilities (WRRFs) around the world are constantly faced with significant challenges 1, 2. It is estimated that WRRFs are operating at an average of 81% of their design capacity, while 15% of systems are at or have exceeded that threshold3. As the most prevalent biological nutrient removal (BNR) process, any improvements to conventional activated sludge (CAS) processes are highly desirable in our industry4. However, upgrading CAS trains is costly and alternative technologies often tend to be more energy-intensive, expensive1, and time consuming to install, commission, and operate. Thus, the use of physical selectors (e.g., hydrocyclones) for biomass densification has emerged as a front-runner for increasing secondary clarifier capacity and improving nutrient removal. Objective and Approach Despite the many studies exploring the advantages of densified activated sludge (DAS) systems compared to CAS systems, DAS impacts on microbial communities and fecal indicator bacteria (FIB) are unknown2, 5. In 2023, the Water Research Foundation funded a tailored collaboration with the Metro Water Recovery (MWR) in Denver. The collaboration aimed to investigate FIB removal and disinfection kinetics. This study focused on CAS and DAS treatment trains at three North American full-scale operating WRRFs (Figure 1). The WRF project aims to: A) Compare E. coli concentrations over a 15-month period and investigate factors influencing differences (e.g., granulation size distribution, floc/granule mass fraction, floc/granule aSRT, microscopy, COD, Turbidity, TSS, NH3, pH, Temperature, Color, UV-254, TKN, TP, TOC). B) Determine how changes in Secondary Effluent (SE) properties between DAS and CAS affect disinfection efficacy using chlorine, peracetic acid (PAA), performic acid (PFA) and ultraviolet disinfection (UV) seasonally (n=12), with the same water quality parameters listed in Objective A. C) Assess impacts of operational variables on DAS and provide utilities with recommendations. These can include how to utilize modeling and statistics to improve performance using demand and decay values and mechanistic disinfection efficacy models D) Determine if additional analyses (e.g., protozoa counts, granule sieving analyses) provide operational value to utilities adopting DAS. Results Data collected for one year at the MWR Hite Treatment Facility highlights the statistically significant difference in E. coli concentrations between the CAS and the DAS trains (Figure 2). This could be explained by a variety of variables that have not yet been evaluated. FIB counts may be impacted by the predator protozoan community5, but this has yet to be supported by data (Figure 3). While percent mass fraction (Figure 4) and seasonality (Figure 5) have been hypothesized to impact DAS E. coli counts6, this has not been shown by the preliminary data collected, which highlights the importance of a more detailed study to explain the differences observed . Summary DAS is able to be implemented with low capital cost while increasing the capacity of CAS systems. However, there is little data on how SE from DAS systems impact downstream disinfection processes. This WRF project will evaluate the impact DAS systems have on disinfection processes compared to CAS systems. Data collection and testing for this project will begin in April 2024.

Densification has emerged as a cost-effective means to increase the capacity of conventional activated sludge (CAS) processes at WRRFs. While many studies have explored the advantages of densified activated sludge (DAS) systems, its impacts on disinfection are unknown. This project will compare the E. coli concentrations between full-scale CAS and DAS systems; will compare disinfectants by performing disinfection dose response testing; and will develop efficacy models based upon the results.

SpeakerHilts, Brian

Presentation time

14:30:00

15:00:00

Session time

13:30:00

15:00:00

SessionEvaluating Plantwide Impacts of AGS and DAS

Session number606

Session locationRoom 343

TopicIntermediate Level, Municipal Wastewater Treatment Design, Nutrients, Research and Innovation

Author(s)