Guo, Hui

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

Titles from this speaker

Densification Index/SVI Model: An Efficient Way to Predict Benefits of Biomass Densification in Full-scale MBR and MABR Wastewater Treatment Plants

Abstract

Abstract Densification of biomass is an efficient technology to improve sludge settleability which benefits wastewater treatment plants (WWTPs) by increasing the capacity of the secondary clarifiers. In this study, a densification model was developed and validated to predict the level of densification performance to help capture expected benefits and new capacity limits for operations. The first version of the VWTS (Veolia Water Technologies & Solutions)-SUMO model was developed based on the growth kinetic for various microorganisms (e.g., nitrifiers and polyphosphate-accumulating organisms). Then the model was calibrated with the filed data collected from full-scale WWTPs (WWTPs with membrane-aerated biofilm reactors and WWTPs with membrane bioreactors). Although more filed data under steady-state operating conditions need to be collected to validate the model, the current simulation results demonstrated the settleability in the full-scale WWTP can be improved significantly by the densification processes. In addition, the proposed model can predict the settleability reliably. 1.INTRODUCTION Densification and granulation of biomass have been demonstrated to be efficient in improving sludge settleability which determines the design and performance of secondary clarifiers (i.e., the hydraulic capacity) in wastewater treatment plants (WWTPs). For instance, a full-scale granule-floc hybrid process in Dijon (France) proved that 20% of aerobic granular sludge (AGS) guarantees a sludge volume index (SVI) lower than 100 mL/g while 30% of AGS reduced the SVI to 50 mL/g [1]. The improved settleability (i.e., lower SVIs) further contributed to a better performance of clarifiers with two to three times higher surface loading rates (SLR) and surface overflow rates (SOR). However, the densification and granulation processes, configurations, and mechanisms still need to be understood more deeply. Thus, a densification model is needed to predict the level of densification performance (i.e., SVI) to help capture expected benefits and new capacity limits for operations. Densification Index (DI), which is the percentage of biomass larger than 200 µm in the mixed liquor, was proposed to quantify the level of biomass densification and partial granulation in continuous-flow biological treatment systems. In this study, a simple and reliable protocol was built to capture the DI in a full-scale WWTP with selective wasting (i.e., densification). These sites' DI and SVI data were used to implement and validate an SVI prediction model. With the predicted SVI from this model, the hydraulic capacity in WWTPs can be upgraded to reach new levels of process intensification. 2.METHODS 2.1 VWTS-SUMO Model The VWTS (Veolia Water Technologies & Solutions)-SUMO model [2][3] provides a simple method of calculating and predicting DI on the state variables from the process simulator. The model introduced separate growth kinetics for granular nitrifiers (i.e., ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB)), polyphosphate-accumulating organisms (PAOs), and ordinary heterotrophic organisms (OHOs) that contribute significantly to the formation of denser and granular biomass (> 200 µm). The half-saturation coefficient (Ks) of PAOs, AOBs, NOBs, and OHOs and their effects on granular growth were implemented based on the previous framework [4]. The contribution of influent inorganic suspended solids (ISS, > 200 µm) was also added to the model. 2.2 Field Data Collection and Calibration A simple and reliable protocol (i.e., sieve tests) has been implemented to measure the DI of a full-scale A2O (anaerobic-anoxic-aerobic)-MABR (membrane aerated biofilm reactor) WWTP and a full-scale A2O-MBR (membrane bioreactor) WWTP. The configuration of the treatment plant is shown in Figure 1. A SUMO model was developed and validated by the influent wastewater characteristics using VWTS blocks specially designed and developed for MABR, Secondary Settler, and External selector. RESULTS AND DISCUSSION The first version of the DI-SVI prediction model was proposed based on the VWTS-SUMO model (Table 1). The VWTS-SUMO model was re-calibrated by the collected data from the full-scale WWTPs. According to the site data, the model can reliably predict SVI before the densification process (Figure 1) for both MABR and MBR applications. However, modified equations should be used after the densification process since the SVI (i.e., settleability) in the full-scale WWTPs was improved significantly. For instance, the SVI can be reduced from 101 mL/g to 65 mL/g while the DI increases from 30% (typical DI in an aeration tank of CAS) to 50% in a densified MABR WWTP (Figure 2a). It should be noted that the densification process in this full-scale WWTP has not reached a steady state since the operating time for the densification process was around 7 months for the MABR plant and 5 months for the MBR plant. An updated model will be proposed by VWTS with more field data. In addition to the settleability improvement by the densification process, a modified VWTS-SUMO model will be developed to predict carbon, nitrogen, and phosphorus removal.

The study developed a densification model to predict the performance of biomass densification, a technology that improves sludge settleability and increases the capacity of secondary clarifiers in wastewater treatment plants. The model, based on the growth kinetics of various microorganisms, was calibrated with data from full-scale wastewater treatment plants.

SpeakerGuo, Hui

Presentation time

13:30:00

13:50:00

Session time

13:30:00

15:00:00

SessionMechanistic Modeling Developments for Newer Processes

Session number410

Session locationRoom 244

TopicAdvanced Level, Biosolids and Residuals, Industrial Issues and Treatment Technologies, Municipal Wastewater Treatment Design, Research and Innovation

Author(s)

Guo, Hui, Donnaz, Sylvain, Shaw, Chris, Astrand, Niclas, Houweling, Dwight

Author(s)H. Guo1, S. Donnaz2, C. Shaw3, N. Astrand4, D. Houweling5, H. Guo1, S. Donnaz2

Author affiliation(s)1Veolia WTS, Ontario, 2Veolia WTS, MT, 3Veolia Water Technologies and Solutions, Ontario, 4Veolia Water Technologies & Solutions, ON, 5Dynamita North America Inc., QC

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159686

Volume / Issue

Content sourceWEFTEC

Word count21

MBR-DAS: Densification Improves MBR Performance at the City of Detroit Lakes

Abstract

Membrane bioreactors are often selected as secondary treatment technologies where small footprint and water reclamation are desired. Sludge densification by means of an external selector such as memDENSE with adequate biological configuration helps maximize sludge densification and quality, thereby improving biological performance. We investigated the resulting oxygen transfer efficiency and membrane performance of an MBR before and after upgrade with densification and recorded an improvement in aeration performance and permeability. Densified biomass has been shown to be more resilient and efficient than CAS in terms of overall settleability performance (SOR, SLR, sludge blanket level, RAS rate, RAS concentration; Donnaz et al, 2020; Roche et al, 2021). MBR mixed liquor quality can be enhanced by using hydrocyclones as gravimetric selectors, whereby MBR performance has been improved due to the removal in overflow of lighter flocs and colloidal fraction from the mixed liquor (Nogushi et al, 2018). External gravimetric selectors help regulate particles and granules size below 1 mm, which is believed to minimize pore blocking (Zhang & Jiang, 2018). MLSS was found to be the main parameter controlling the α-factor in MBRs, corroborating several studies which have established the negative effects of solids concentration on oxygen transfer (inter alia, Krampe and Krauth, 2003; Germain et al., 2007). However, although several investigators focused on the concentration and viscosity of the sludge (e.g., Cornel et al, 2003; Racault et al, 2011; Amaral et al, 2018), none included MBRs with densified sludge. We investigated here the effects of densification on oxygen transfer in a full-scale MBR. Densified biomass is expected to have beneficial impacts on MBR membrane filtration performance. Particle size distribution of densified biomass has shown to be 200 to 500 µm in majority, with 1,000 µm maximum (Roche et al, 2021). An external gravimetric selector such as memDENSE technology helps regulate particle and granule sizes above 100 µm and below 1 mm, which is believed to minimize pore blocking fouling observed with full granulation process by remaining below the 1 to 1.2 mm critical value range described by Zhang & Jiang (2018). A full-scale evaluation has been underway at the City of Detroit Lakes for over nine months to capture the benefits of biomass densification in a plant with challenging seasonal operation. Figure 1 shows the configuration of this MBR plant: anaerobic, anoxic and aerobic tanks in series (A2O configuration), with memDENSE incorporated as the external selection process on the RAS stream. Comprehensive characterization of mixed liquor properties and membrane fouling is being conducted before and during densification in this plant. The memDENSE system accumulates the large and dense biomass in the underflow while wasting the small and light biomass from the overflow (Fig. 1). In the first stage of intensification, the particle size and density increased in both underflow and overflow. Preliminary testing at full-scale at Detroit Lakes MBR facility showed early improvement of membrane filtration correlated to rapid drops of SVI, time-to-filter and superfine colloids (sfCOD) in the membrane tank mixed liquor (Donnaz et al, 2023). Time-to-filter is a direct test of filterability and membrane performance. Results of these tests show a very close correlation with settleability, meaning that improved settling and higher densification also improve filterability. With results similar to those of SVI, Figure 2 shows that poorly filterable sludge is wasted while a much more stable biomass is achieved with densification. This led to a significant improvement in the MBR performance. Preliminary results shown in Figure 3 indicate that with selective wasting and continuous flow densification, permeability is improved and TMP stabilized. Allowing an acclimation period of 4 months of memDENSE operation to achieve a new early steady state, oxygen transfer efficiency (OTE, % and αSOTE, %) was compared at the two process conditions. The OTE was measured using the ASCE method (ASCE, 2018). Since the clean water performance of the disc diffusers was available, the alpha factors could be calculated and compared. An increase in air flux after densification corresponds to increased oxygen uptake (Table 1). The efficiency (OTE and αSOTE) is higher, despite the increase in aeration, indicating an improvement in the quality of the biomass-wastewater matrix. In fact, the α-factor improved and is now reaching the design value of 0.50, despite the diffuser aging. In the presentation, we will discuss in detail the field results and their comparison with the design criteria.

MBR coupled with Densified Activated Sludge (memDENSE) tailors mixed liquor characteristics to optimise membrane & biological performance. memDENSE provides lower OPEX, the lowest and most stable TTF and TMP on the market. Preliminary study of biological sludge wasting (WAS) characteristics from the DAS system shows clear improvement in terms of thickening ability, dewaterability and biogas potential of the DAS sludge.

SpeakerShaw, Chris

Presentation time

13:30:00

14:00:00

Session time

13:30:00

15:00:00

SessionOptimization of MBR Technology

Session number210

Session locationRoom 343

TopicAdvanced Level, Facility Operations and Maintenance, Municipal Wastewater Treatment Design

Author(s)

Shaw, Chris, Donnaz, Sylvain, Bredeson, Rob, Danzl, Susan, Guo, Hui, Peeters, Jeff, Rosso, Diego

Author(s)C. Shaw1, S. Donnaz1, R. Bredeson2, S.R. Danzl4, H. Guo5, J.G. Peeters6, D. Rosso7

Author affiliation(s)1Veolia Water Technologies and Solutions, Ontario, 1, 2City of Detroit Lakes, MN, 3Veolia WTS, MT, 4, MN, 5Veolia WTS, Ontario, 6Veolia Water Technologies & Solutions, ON, 7University of California, Irvine, CA

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159555

Volume / Issue

Content sourceWEFTEC

Word count12

Base text size -

Guo, Hui

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