Rivanna Water & Sewer Authority

Overview

The Rivanna Water & Sewer Authority (RWSA) produces safe drinking water for public water customers in the City of Charlottesville, portions of Albemarle County, and the University of Virginia. Serving a population of ~120,000, the RWSA also treats wastewater to safely return unused drinking water to the Rivanna and James rivers.

Since 2013, SEH has partnered with the RWSA on 100+ work authorizations for its water treatment and distribution system and wastewater treatment facilities. The continuous partnership between has been nurtured through accountability, innovation, efficiency, and trust.

The following highlights notable efforts from the SEH-RWSA partnership.

Project Highlights

Town of Crozet Water Treatment Plant Improvements (2016-2021)
SEH led a series of improvement projects for the 1 million gallons per day (MGD) Crozet Water Treatment Plant (CZWTP) to address rising water demands and mitigate aging treatment, electrical, and mechanical components. SEH conducted a facility conditions assessment and detailed report to outline the CZWTP’s deficiencies.

These efforts advanced to a preliminary engineering report (PER) which defined the scope and design parameters of a design and construction project plan for expansion and improvements to the CZWTP; these efforts moved the plant from a 1 MGD facility to a 2 MGD facility. This multidisciplinary effort covered improvements to nearly every aspect of the CZWTP.

The SEH team’s work included upgrading the pretreatment train by reconfiguring the existing rapid mix and flocculation basins to improve total organic carbon removal and to enhance the coagulation and flocculation process. These improvements also included:

• Installing plate settlers in the existing sedimentation basins
• Reconstructing the plant’s two concrete gravity filters
• Replacing one of the treatment residuals lagoons with a backwash waste tank connected to the sanitary sewer
• Improving the chemical feed systems and operator safety by replacing dry chemical feed systems with liquid chemical feed systems

Observatory Water Treatment Plant and South Rivanna Water Treatment Plant Improvements (2015-present)
The RWSA owns and operates the 5 MGD Observatory Water Treatment Plant (OBWTP) and the 12 MGD South Rivanna Water Treatment Plant (SRWTP) in Charlottesville. The RWSA partnered with SEH to prepare a PER that would help expand and improve the two plants. Following the PER, the project moved into design, bidding, and construction; SEH led the overall effort under a single contract.

The capacity of the 7.7 MGD OBWTP is being expanded to 10 MGD. The project team is building a new pretreatment chemical storage and feed building to house these systems for the OBWTP’s treatment chemicals – including coagulant, powdered activated carbon, liquid lime, sodium permanganate, corrosion inhibitor, and fluoride. Additional OBWTP improvements include reconstructing 5 gravity filters and incorporating filter face piping. 

The SEH team’s efforts for the SRWTP include the addition of two new 3 MGD filter cells, a new administration building, and miscellaneous treatment process, electrical power, and SCADA improvements.

Moores Creek Area Water Reclamation and Reuse Facility Solids Stream Operations Evaluation (2016)
SEH provided a solids stream operations evaluation for the Moores Creek Area Water Reclamation and Reuse Facility (MCAWRRF), RWSA’s largest advanced water resource recovery facility. The facility handles all the urban area and City of Crozet wastewater. Helping to optimize solids generation and processing, the operations evaluation included operational recommendations, optimization of the solids stream to potentially reduce chemical use and odors, and labor optimization.

SEH operation’s specialists and MCAWRRF staff collaborated to create a solids mass balance flow schematic worksheet that identified benchmark targets as well as the cause and effect of modifications for the primary clarifiers, secondary clarifiers, septage waste, gravity thickener, in-plant clarifier, primary and secondary digesters, solids storage, and centrifuge. The SEH team recommended removing the in-plant clarifiers to reduce potential odors and associated costs.

Anaerobic Digesters Coating Project (2017)
Three 90 ft. in diameter primary anaerobic digesters at the MCAWRRF leaked methane gas above the normal digester water level through the concrete cover. Based on previous testing conducted, Digester 1 was leaking over 30% methane, while Digesters 2 and 3 were leaking between 10-20% methane.

SEH coating specialists and structural staff removed Digester 1 from service and carefully inspected it. The team developed a detailed conditions report identifying deficiencies. This document was included in bid documents and used as the foundation of required repair work. Digesters 2 and 3 were determined to be similar to Digester 1, eliminating the need for additional assessments and reporting.

Operation Resources and Operator Training (2017-2019)
SEH operation specialists worked closely with RWSA staff to update and develop operator resources (e.g., log sheets and standard operating procedures) and operator training (e.g., PowerPoint presentations and videos). The SEH team broke the project into four phases to ensure efficiency and maximize the long-term impact for the RWSA:

1. Cataloging existing operator resources
2. Conducting a needs analysis
3. Developing operator resources
4. Operator training

The resources and training developed by the SEH team created a foundation and guide that RWSA staff could use to continuously learn, train, and develop key team members.
 
Grit Removal System and Reporting (2015-2018)
To ensure the proper grit removal system was provided for the facility, SEH conducted a grit characterization study. The project team measured the quantity and type of grit entering the facility on-site during peak flow events. The results of this grit sample characterization were used for the selection of a grit removal system specifically designed for the fine grit which enters the MCAWRRF.

The SEH team’s report provided a concept level layout for the grit removal system and probable construction and operational costs.

3D Laser Scanning and Autodesk Revit (2016)
The current MCAWRRF was constructed over many years; original plant drawings don’t always capture changes made years later. In response, the SEH team used laser scanning in a grit improvement project to provide accurate record drawings.

The laser scans were coupled with 3D modeling (Autodesk Revit) to provide update plans of the facility. The model created was extremely useful in selecting the best option and layout. In fact, the SEH team was able to place equipment at various locations throughout the site, discuss the placement with RWSA, and visually see how the grit system’s footprint impacted existing equipment and structures on-site.

Holding Ponds Solids Removal (2020-2021)
Two RWSA holding ponds hold excess flow during storm events. The ponds provide a combined capacity of 17 MGD when empty. However, over the years, solids settled out in the holding ponds. The project team raised the water level several feet above the solids in the ponds and aerated to mitigate the potential for odors. The SEH team removed the solids to ensure more capacity is available for storm events and minimize the potential for odors.

Cogeneration Facility Project (2018-2019)
The MCAWRRF currently utilizes a cogeneration facility which accepts the digester gas and uses it to create electricity and heat. SEH analyzed the cogeneration facility’s existing installation and known issues. The final report investigated four distinct options and provided a return on investment analysis for each option to determine the best use of the digester gas. The SEH team’s report evaluated:

• Digester gas output, present and future
• Gas conditioning and storage
• Generator equipment – including generator, enclosure, electrical gear, cooling systems, heat recovery, boiler equipment
• Provided recommendations for improving existing system performance
• Improved operation of the existing engine/generator