Brief Project Description

HRSD owns and operates the York River wastewater Treatment Plant (YRTP), which provides secondary treatment at the existing design capacity of 13.7 MGD.  The existing YRTP consists of preliminary treatment (grit and screening), primary treatment, secondary treatment (step feed activated sludge), effluent disinfection and dechlorination, with discharge to the York River.  Solids handling processes include gravity thickening for primary solids, dissolved air floatation thickening for waste activated solids thickening, anaerobic digestion, centrifuge dewatering and contract composting. 

Under new nutrient discharge control regulations for the Chesapeake Bay and its tributaries, HRSD has received a combined, “bubble” waste load allocation for nitrogen and phosphorus for its three treatment plants discharging within the York watershed.  Providing nutrient removal at the YRTP is a key element for meeting the waste load allocation for the York River and improving local water quality.

Under a plan referenced as the YRTP Expansion Phase I, HRSD will upgrade the existing secondary treatment process to a nutrient removal system designed for annual average effluent concentrations of 8.0 mg/l total nitrogen and 0.70 mg/l total phosphorus.  The Phase I project consists of three contracts (A, B, and C); only Contract A is the subject of this grant agreement.     

Facilities included in the Phase I – Contract A portion are described as follows.

Secondary Treatment (grant eligible) 

• Distribution chamber #4 and intermediate pump station to convey secondary effluent to the new denitrification filters. 
• Methanol storage and feed facilities to provide a supplemental source of carbon to the denitrification filter process.
• Denitrification filters.
• Modification of the water reclamation facility to convert the structure to a centrate treatment and equalization facility, along with the addition of a caustic soda chemical system.

Process Piping Improvements (partially grant eligible): 

• Gravity pipe connection from the secondary clarifiers to distribution chamber #4 and force main to the denitrification filters. 
• Piping changes associated with centrate (side stream) treatment.  

Electrical System Improvements (partially grant eligible):  An electrical power distribution upgrade – including a new generator building, power center, duct banks, and standby generator – will be installed under Contract A.  The installation will be designed to serve all three contracts. 

Distributed Control System:  A new plant-wide distributed control system will be installed over the three contracts to improve treatment plant automation and control.