WQIF - ASA - Alexandria Advanced WTF

 

 Project Grant Amount Grant Percentage
Alexandria Sanitation Authority (Alexandria Advanced Wastewater Treatment Facility) $37,766,339 35%
Revolving Loan Fund Project  DEQ Regional Area Date Agreement Signed
 Yes Northern Virginia Regional Office TBD
 

Brief Project Description

Grantee: Alexandria Sanitation Authority

Grant:    #440-S-10-07                                                  

The existing Alexandria Sanitation Authority (ASA) facility was designed to achieve an effluent total nitrogen (TN) concentration goal of 8.0 mg/l on an annual average basis and an effluent total phosphorus (TP) concentration limit of 0.18 mg/l on a monthly average basis at the design flow of 54 MGD. To achieve the effluent TN goal, a biological nitrogen removal (BNR) process was added that can use either the Modified Ludzack Ettinger (MLE) process or a step feed nitrogen removal mode of operation. The bioreactors were started up in December 2002 and achieved the desired level of treatment after a year long initial operation period. The BNR upgrade was cost-shared under WQIF Agreement #440-S-98-10, which provided $19,702,869 in grant funds.
 
In 2006, regulations were revised in order to meet the goals of the Chesapeake 2000 Agreement. DEQ developed a General Permit to implement these regulations which became effective January 1, 2007. As a result of the revised regulations, the ASA facility must meet final effluent annual waste load allocations for nitrogen and phosphorus beginning in January 2011, meet future concentration TN limitations of 3.0 mg/l on an annual average basis and continue to meet current TP limits of 0.18 mg/l on a monthly basis.  The results of recent process modeling indicate that the existing phosphorus removal system at ASA is adequate to meet the current TP limit.  However, the ASA facility will require an upgrade to meet the TN limit.
 
ASA underwent a comprehensive long range planning process to develop a strategy for compliance with the regulatory requirements and also to address other future drivers. The objective of the long range planning process was to create a scope for the next phase of facility upgrade. As a result, ASA developed a multiphase project approach to achieve compliance called State of the Art Nitrogen Upgrade Program (SANUP). The SANUP will ensure that ASA reliably meets the future TN requirements and provides a robust nitrogen removal system with enough flexibility to guarantee treatment performance to meet the future effluent limits.
 
In order to meet ASA annual capital improvement funding limits, the program has been developed into multiple phases. Below is a brief description of the phases for the program that are included in this grant agreement:
 
Package
Work Elements
0
C1A
System modifications for current flows/loads

1

A
Supplemental Carbon Facility
B Centrate Pretreatment and Effluent Flow Measurement

 

2

 
C1 Nutrient Management Facility Site Preparation, bridge and roadway improvements
C2
Nutrient Management Facility(including pump station and odor control) and Electrical Substation
D  Biological Reactor Basin 6
 
Contract 1A (C1A)         
Contract 1A, which has been designed and constructed, was the first step towards ASA achieving enhanced nitrogen removal. The project contained process mechanical improvements to the Biological Reactor Basins (BRBs), the Secondary Settling Tanks (SSTs), the dewatering centrate system and the primary scum system to provide Enhanced Nitrogen Removal (ENR) treatment at the current plant flows and loads and provide additional operational flexibility.
 
Design of the C1A improvements was completed in November 2006, and DEQ issued a Certification to Construct (CTC) on July 16, 2007. Final completion of this project was certified on December 23, 2008, and DEQ issued a Certificate to Operate (CTO) on March 3, 2009.  On May 14, 2008, DEQ issued WQIF Agreement #440-S-08-14, to provide cost-share for the completed Contract 1A. On March 26, 2009, ASA requested to terminate this grant agreement and confirmed that this grant eligible project and grant eligible costs would be included in the Authority’s planned state of the art nitrogen removal upgrade project at a 54 MGD design flow.  The cost of project C1A is included in the Scope of Work for this grant agreement (#440-S-10-07).
 
Phases 1 and 2
The work that is currently under contract is design of the first two State of the Art Nutrient Upgrade Project (SANUP) phases that include five design packages: A, B, C1, C2 and D.
 
Phase 1 includes two projects which are located within the existing Main Plant site; Phase 2 includes an additional two projects which are located on newly acquired property to the west of Hooffs Run as well as adding a sixth biological reactor basin to ensure state of the art nitrogen removal at design flows and loads on the existing site. The new development is referred to as the West Plant for this agreement.   The five separate design packages are summarized as follows:

Phase 1 – Main Plant, Nutrient Control

  • Package A – Supplemental Carbon Facility Improvement
  • Package B – Centrate Pretreatment Facility, Final Effluent Flow Measurement, and Pumping Station

Phase 2 – West Plant, Nutrient Control and Access; Main Plant, Nutrient Control

  • Package C1 – Site Access/Roadway Improvements, Site Preparation for Nutrient Management Facility (NMF)
  • Package C2 – Facility construction for NMF
  • Package D – Construction of a new Biological Reactor Basin #6 on the main plant site. Package D includes the construction of a sixth Biological Reactor Basin (BRB). The new BRB 6 would be located between the existing BRBs and the Secondary Settling Tanks (SSTs). The additional volume would increase treatment capacity by reducing solids loading rates to the SSTs and by providing sufficient aerobic and anoxic SRT to maintain nitrifying and denitrifying biomass at design winter conditions. The tank will be sized to roughly match the volume of the existing BRBs. The package will include additional control structures to direct existing BRB flow to the new BRB 6 and to convey the effluent from BRB 6 to the SSTs. Also, additional controls will be installed to provide for two parallel BRB operations of three basins each for additional performance, reliability and improved hydraulics.
In summary, the selected approach is to implement a combination of strategies that include adding reactor volume to increase biological removal of nitrogen, a nutrient management facility to reduce the peak mass loadings to the bioreactors and a centrate pretreatment process to reduce the nitrogen loading that is returned from the solids treatment process. Together, these upgrades will provide a robust nitrogen removal system with enough flexibility to meet the required effluent limits at the design average annual flow of 54 MGD.
 
In addition to the liquid process upgrades needed to meet the required effluent limits, the facility will have to increase the capacity of some of the solids handling process under future phases (not included in this scope of work)  in order to continue to produce Class A biosolids under the mass loading conditions expected at the 54 MGD design flow.
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Virginia Department of
Environmental Quality
P.O. Box 1105
Richmond, VA 23218
(804) 698-4000


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