Brown and Caldwell (United States)

In this manuscript, we report niche differentiation among important groups of organisms involved in phosphorus and nitrogen cycling, and the interplay between relevant metabolic pathways carried out by these key organisms. We employed nanopore-based long-read and Illumina-based short-read sequencing techniques for metagenomics and metatranscriptomics, respectively, on samples collected from an integrated fixed film activated sludge (IFAS) bioreactor run in the conventional A2O mode under low dissolved oxygen (DO) conditions. Among the recovered metagenome-assembled genomes (MAGs), >90 MAGs from each community were high-quality, including 39 and 30 MAGs that were close-circularized, from the floc and biofilm communities, respectively, with no or minimal contamination. Some Candidatus Accumulibacter strains encoded for either full or partial denitrification. Ca. Accumulibacter were very efficient in aerobic and anoxic inorganic phosphorus (Pi) uptake, while the second highly enriched Ca. Accumulibacter was as competitive for denitrification metabolism. The potential of nitrous oxide (N2O) emissions in both the floc and biofilm communities was nearly 20 times higher in the aerobic zone than in the anoxic zone. As opposed to our initial hypothesis that slow growers will mostly reside in biofilms, the expression of ammonium monooxygenase (amoABC) was higher in flocs than in biofilm communities.

The presence of 41 per- and polyfluorinated alkyl substances (PFAS) was investigated in raw and finished drinking water and in influent and effluent wastewater sampled from facilities in the Great Lakes Basin region of Southern Ontario, Canada (September–November 2023). Based on US Environmental Protection Agency Method 1633A, the method developed for analysis of these species demonstrates high sensitivity and recovery with limits of quantitation that range between 0.075 ng L–1 and 3.0 ng L–1. Linear chain PFAS with carboxylic acid and sulfonic acid groups were detected in finished water from all drinking water treatment plants (n = 6). Wastewater effluents (n = 2) had PFAS concentrations approximately 1 order of magnitude higher than those in finished drinking water samples and included several fluorotelomers and ether-linked species. Across all sites, 13 of the 41 PFAS were detected in drinking water and 21 in wastewater. Average sum of 25 PFAS in finished drinking water ranged between 8.69 and 14.0 ng L–1, well below Health Canada’s objective of 30 ng L–1. These results highlight the persistence of PFAS across treatment systems and suggest a potential feedback loop where wastewater effluents reintroduce PFAS into surface waters used as drinking water sources.

This work investigated byproduct formation and in vitro genotoxicity and cytotoxicity at four facilities using UV/chlorine advanced oxidation for potable reuse or drinking water treatment. In arguably the most common application of UV/chlorine, treating reverse osmosis permeate for potable reuse, organic byproduct formation was always either not detected or well-below typical drinking water levels. At a groundwater-source drinking water treatment plant, the trihalomethanes and haloacetic acids each increased by up to 12 μg/L through the UV reactor and 40 μg/L during secondary disinfection, but the final concentrations remained low relative to regulatory limits. Overall, and aside from the known pathways of chlorate formation, the UV/chlorine byproduct and in vitro toxicity formation observed in this study was lower than what is generally found in many chlor(am)inated drinking waters, although there was some observed shift to more brominated species, which might be deserving of future research, given their higher in vitro toxicity compared to typical chlorinated species.

The Potomac Interceptor (PI) is a 48-mi-long multijurisdictional large diameter sewer operated by DC Water. It conveys flow from surrounding counties to the Blue Plains Advanced Wastewater Treatment Plant. The PI is one of the DC Water’s most critical sewers with a peak flow of 90 million gallons per day (mgd) with no redundancy. Rehabilitation of this section is particularly challenging, because it is directly adjacent to the Potomac River, within a Northern Virginia (NOVA) Park, on federally funded land, and only accessible through private roads. This intersection of state, federal, and private land presented challenges that spanned the technical, political, and public spheres. The presentation will focus on why Progressive Design Build (PDB) was chosen for this high-risk and complex linear pipe rehabilitation. It will highlight how an experienced Design–Build Institute of America (DBIA)-certified Owner’s Advisor guided DC Water in Design–Build Best Practices, leading to the successful planning, procurement, and contracting of the project. The presentation also includes drivers for choosing of PDB, critical stakeholder engagement, building a high-performing team, risk allocation and mitigation during design development (integral to price negotiation), “in-the-dry” concept to maintain flow throughout construction without bypass pumping, flow conversion and final commissioning, utility owner’s experience during the PDB, lessons learned, as well as cost and time efficiencies using PDB.

The Davis Aqueduct is a 22.5-mi-long pipeline made of reinforced concrete pipe ranging in diameter from 84 in. to 21 in. It is the only source of water for several cities in Weber and Davis Counties and in the Great Salt Lake Basin. The Aqueduct sits along the Wasatch front range of the Rocky Mountains and is within the Wasatch Fault Zone (WFZ) for much of the alignment. In addition to the seismic risk, the aqueduct is also at risk of damage from landslides, debris flows, and liquefaction. The Weber Basin Water Conservancy District (WBWCD) serves a population of over 500,000 in Weber and Davis Counties. WBWCD performed a risk assessment, condition assessment, and hydraulic evaluation of the Davis Aqueduct to define its long-term repair and replacement strategy and coordinated that strategy with the State of Utah’s Prepare60 initiative. To mitigate the risk associated with loss of service, the District proposed a parallel pipeline to accomplish two objectives: (1) increase hydraulic capacity, and (2) provide redundancy for the existing pipeline. A goal for the parallel pipeline project was to design the most resilient system possible to help WBWCD maintain high level-of-service goals for critical turnouts. In preliminary design, Brown and Caldwell conducted an alignment study and a geologic hazard assessment to identify, characterize, and define geological and seismic hazards in a potential pipeline corridor from the start of the existing aqueduct to the turnout to Weber Basin’s Davis North Water treatment plant. Seven alignments were considered, and a preferred alignment was selected that prioritized hazard avoidance before hazard mitigation. This paper focuses on the strategy implemented to avoid risks during preliminary design and how the pipe was designed to be resilient when crossing of the Wasatch Fault and passing through three zones with anticipated liquefaction and an area with slope instability. The final design included upgrading the bifurication structure which controls flow at the start of the pipeline, designing a pump station that allows the Davis Aqueduct to divert flow from or into an adjacent canal, and protecting the pipe from landslides on unstable slopes near the terminus of the pipeline and the hydraulic structure which controls flow at the end of pipeline.

A 5 mg L−1 PAA/H2O2 (mixture) pre-oxidation decreased the DBP formation potential by up to 40%.

Great Lakes Water Authority (GLWA) experienced a catastrophic failure of a prestressed concrete cylinder pipe (PCCP) segment in the 14 Mile Rd. Transmission Main (TM). This TM was not part of a looped system, and this failure resulted in the loss of water service to residents in GLWA service area. GLWA decided that the 14 Mile Rd. TM must be interconnected to the 8 Mile Rd. TM so it is in a looped system. A route study determined that the 14 Mile Rd. TM Loop should be placed in Michigan Department of Transportation (MDOT) right of way (R/W) and in the City of Novi’s city streets. This paper discusses the need for the pipeline, benefits and challenges associated with installing the pipe in an MDOT R/W, the tunnel design and construction requirements, the micropile design and bidding strategy, as well as other construction and design lessons learned.

The growing need to access recycled water as a source for drinking water supply necessitates management of perceived risks. This study aimed to use quantitative microbial risk analysis (QMRA) to evaluate microbiological risks of indirect water recycling. Scenario analyses of risk probabilities of pathogen infection were conducted to investigate four key quantitative microbial risk assessment model assumptions: treatment process failure, drinking water consumption events per day, inclusion or exclusion of an engineered storage buffer, and treatment process redundancy. Results demonstrated that the proposed water recycling scheme could meet WHO pathogen risk guidelines of ∼10-3 annual risk of infection under 18 simulated scenarios.