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Warrenton Wastewater Treatment Plant (2.5 MGD) Nutrient Removal Upgrade. Warrenton, Virginia.

The 2.5 MGD Warrenton WWTP was upgraded for nutrient removal to achieve Total Nitrogen (TN) and Total Phosphorous (TP) of less than 4 mg/l and 0.3 mg/l, respectively.

Based on the plant performance evaluation, the screening of nutrient removal alternatives was focused on tertiary processes that would treat the nitrified secondary effluent. A comprehensive evaluation of tertiary denitrification processes was conducted, including deep bed denitrification filters, continuous backwash filters, upflow filtration technologies, and upflow fluidized bed processes. This evaluation indicated that deep bed denitrification filters with supplemental methanol addition was the most reliable and cost effective alternative for the Town of Warrenton WWTP. The final design included the following components: An intermediate pumping station including submersible pumps with variable speed control; denitrification filters with four filter cells, backwash holding tank, clear well, piping gallery, blower equipment, backwash pumps, and control room/building; methanol feed facilities, including outdoor storage tank with metering pumps; phosphoric acid feed system; new in-coming electrical service equipment; and new plant-wide emergency generator.

Warrenton Wastewater Treatment Plant (2.5 MGD) Nutrient Removal Upgrade
Project Highlights

Wastewater Treatment

Design included a 10 MGD denitrification pumping station, deep bed denitrification filters, backwash and compressed air systems, chemical systems, modifications to existing treatment units, conversion of gas chlorination to UV for effluent disinfection, and plant process control.


Building mechanical designs for the denitrification pumping station, filter control building and piping galleries.


Electrical designs for the new facilities and various upgrades to existing buildings included a new plant-wide standby generator with automatic transfer switch for operation during plant power outage.

Instrumentation and Controls

Instrumentation designs and process control for the new facilities and various upgrades to existing processes.

SWM/Drainage/ESC Design

Site design included grading, paving, sediment and erosion control, stormwater management, permitting and related work.


The architectural design concept for the denitrification facilities was developed to match existing plant facilities. New facilities included the denitrification pumping station, and filter building with process control, chemical storage, and electrical building.


The structural design included the denitrification pumping station, filter building, pipe gallery and chemical storage area.


A geotechnical report was developed with basis for the foundation design for each structure. Field investigations and soil borings were conducted to establish the foundation design criteria.