Brief Project Description

The City of Richmond Wastewater Treatment Plant has an existing dry weather flow design capacity of 45 million gallons per day (MGD). The City also operates a Combined Sewer System (CSS), which conveys municipal sewage and storm water in a single pipe. The plant’s VPDES permit requires wet weather flow treatment of at least 75 MGD until all CSS storage facilities are emptied. The plant’s existing liquid processes includes preliminary treatment, primary clarification, biological activated sludge process, secondary clarification, deep bed/gravity effluent filtration, disinfection and dechlorination prior to discharge to the James River. Solids handling processes include separate thickening of primary and waste activated solids, digestion, and dewatering prior to land application.  Under this Agreement the City is installing Nutrient Reduction Technology, portions of which are being cost-shared to meet effluent concentration limitations of 8.0 mg/l for total nitrogen, and 0.50 mg/l for total phosphorus, both on an annual average basis. The City’s preliminary engineering report identifies improvements which will be implemented in five construction contracts, described as follows.

Contract 1:

• Total Phosphorus Control: (grant funds not requested) Chemical storage and new feed pumps will be installed to dose ferric chloride in the primary and secondary sedimentation tanks. 
• Methanol Feed and Storage: (grant funds not requested) Existing effluent filters will be upgraded to denitrification filters, which includes methanol storage tanks, chemical metering pumps, and controls.
• Filter Upgrades: (grant eligible) Existing filters will be upgraded to reliably remove particulate phosphorus and nitrogen to meet the new permit limitations of the Watershed General Permit. 

Contract 2:

• Ultraviolet Disinfection: (not grant eligible) Existing chlorination facilities will be replaced with UV disinfection.
• Main Plant Incoming Electrical Switchgear: (partially grant eligible) Existing switchgear and portions of the electrical distribution system will be replaced within a new building. 

Contract 3 - Scum Control Upgrades: (partially grant eligible) Existing primary sedimentation tanks will be upgraded with new troughs and electrically actuated gates to improve control of scum in the activated sludge process. Scum will be conveyed to a new scum concentrator building.

 

Contract 4:

• Aeration Upgrades: (grant eligible) Aeration tanks will be upgraded and improved to operate as a Step Feed process. Improvements to the aeration tanks include new internal mixed liquor recycle pumps and baffles, as well as an upgrade of gates and the fine bubble diffuser system.   
• Return Activated Sludge (RAS) Capacity Upgrades: (partially grant eligible) RAS pumping will be increased from an existing capacity of 45 MGD to about 60 MGD; thereby, reducing the solids carryover to the effluent filters during wet-weather flows.
• Bioaugmentation Upgrades: (grant eligible) Existing sludge holding tanks will be upgraded to accommodate the bioaugmentation process and facilitate restarting the activated sludge system and shorten the period to recover nitrification. 

Contract 5:

• Final Sedimentation Tanks: (partially grant eligible) Two new sedimentation tanks are proposed to improve the solid capture efficiency and reduce the solids loading to the effluent filters.
• Fermentation: (grant eligible) One existing digester will be converted to a fermentation reactor to produce volatile fatty acids (VFA) from primary sludge. The VFA will be returned to the anoxic zone to improve the efficiency of the denitrification in the aeration tanks and lessen the dependency on methanol. The upgrades include odor control, transfer pumps, and electrical/instrumentation