Session 03C: Wastewater Process: Biological Intensification - Livestream
3:00pm - 3:45pm
CFD Modeling Provides Insights into Granular Sludge Separation Devices
1Carollo Engineers, United States of America; 2NEWhub; 3HRSD; 4UOSA; 5DC Water;
Granular activated sludge (GAS) consist of dense particles with stratified microbial colonies that provide efficient organics, nitrogen and phosphorus removal along with improving liquids/solids separation in activated sludge systems. GAS has gained broad interest and traction in recent years A growing number of water resource recovery facilities (WRRFs) in the U.S. and abroad have implemented inDense, a technology that uses hydrocyclones to select for GAS by separating it from lighter mixed liquor flocs. While hydrocyclones are an established approach to classify and separate particles in many fields, their application to GAS leaves key questions yet to be answered. Hydrocyclones have been designed, tested, and operated primarily based on empirical field performance data. To date, no group has successfully modeled GAS separation in AS systems by hydrocyclones despite the broad benefits this would bring to many WRRFs, until now. A team comprised of technical experts from equipment inventor, VA and DC utilities, and a consulting team collaborated on this effort to combine inDense installation and performance data from current full-scale inDense U.S. installations, state-of-the-industry understanding of GAS and inDense systems, and state-of-the-art CFD modeling capabilities. Project findings will be presented, illustrating that CFD modeling developed in this project simulating hydrocyclone GAS separation is a useful tool to inform the design and operation of external selector systems. This will lead to clear visualization of internal separation process, expanding our understating of how to adjust operations to different process and seasonal conditions.
3:45pm - 4:30pm
Experience With Densified Mixed Liquor And Nutrient Removal At Two WWTFs In Washington
RH2 Engineering, Inc, United States of America; ,
The Cashmere and Peshastin WWTFs discharge to the Wenatchee River, which has a TMDL for phosphorus. The Cashmere WWTF was the subject of the article “Cashmere Quality – Experience with enhanced biological phosphorus removal, surface wasting, and aerobic granular sludge” which appeared in the July 2020 edition of the Water Environment and Technology magazine. This presentation will expand upon that article and share recent findings related to the densified mixed liquor and biological nutrient removal at both WWTFs.
The Cashmere WWTF is a plug flow modified Bardenpho process and the Peshastin WWTF is a sequencing batch reactor. The two WWTFs have significantly different influent characteristics. Cashmere has a moderate strength influent due to a large apple slicing facility that discharges to the City’s system. Peshastin has relatively weak wastewater as the community is served by a septic tank effluent system, which removes settleable solids prior to discharge to the WWTF. Additionally, the Peshastin WWTF receives widely varying flows throughout the year from two fresh fruit packing warehouses that discharge significant quantities of rinse water to the system.
Each WWTF is configured to favor biomass with good settling characteristics. Both plants exhibit significant fractions of aerobic granules as part of the biomass and each process achieves exceptional settling at relatively high mixed liquor concentrations. For instance, the Cashmere WWTF routinely has mixed liquor suspend solids concentrations in excess of 6,000 mg/L with SVIs below 50, in conjunction with a clarifier blanket below 2 feet.
The capacity of a WWTF is generally proportional to the mass of mixed liquor suspended solids that can be carried within the system. The settleability of these solids is a critical parameter as it can significantly affect the footprint necessary to support the process. Implementing bacterial selection processes through WWTF design and process controls can change the structure and function of the microbial communities to provide a densified mixed liquor, as can be found at the Cashmere and Peshastin WWTFs. Insights into these two WWTFs may be useful to other plants needing to increase treatment capacity relative to plant footprint while achieving biological nutrient removal.
4:30pm - 5:15pm
Advanced Aeration Control with Densification Achieves BNR Intensification: A Full-scale Demonstration of the Ntensify Process
Brown and Caldwell, United States of America;
Driven by stringent new nutrient standards and increasing costs of nutrient removal, utilities in the Pacific Northwest must look towards innovative approaches to solve the issue. Advanced aeration controls like ammonia vs NOx (AvN) or ammonia-based aeration control, lower the aeration energy while promoting a more carbon-efficient nitrogen removal via simultaneous nitrification and denitrification (SND). Low dissolved oxygen (DO) maintained by advanced aeration control is the key to aeration savings and SND but often leads to poor settling sludge. The Ntensify approach combines low DO operation with hydrocyclone based wasting to achieve continuous flow aerobic granulation and enhanced nutrient removal. This presentation will describe the results from the full-scale Ntensify installation at the James R. Dolorio Water Reclamation Facility (JRD WRF) in Pueblo, Colorado.
The JRD WRF is a 19 mgd biological nutrient removal (BNR) facility that operates a Johannesburg process. The recently upgraded facility includes hydrocyclones that feed a portion of the RAS to target lighter organism waste in the mixed liquor. Upgrades implemented AvN control, allowing DO setpoints to fluctuate between 0.2 – 2 mg/L while maintaining equal effluent ammonia and NOx concentrations.
Improvement results showed that hydrocyclone-based wasting helped improve settling characteristics [sludge volume index (SVI) < 100 mL/g values ranging from 130 to 300 mL/g before implementation] within weeks of operation. Phosphorus accumulating organisms (PAO) and nitrifiers are preferentially retained in dense flocs and granules, while lighter heterotrophic and filament-type organisms are preferentially wasted. The hybrid floc-granules combination at Pueblo achieved excellent effluent turbidity (effluent TSS < 6 mg/L, turbidity < 2 NTU). AvN control resulted in low DO conditions (< 0.4 mg/L) that reduced air demands by 50% while supporting excellent nitrogen [effluent total inorganic nitrogen < 11 mg/L] and total phosphorus (TP) removal (effluent TP < 1 mg/L)] at low influent carbon conditions (primary effluent COD/N <6) without supplemental chemicals.