Virginia, Minnesota

Population: 8,750
Employees: 4

Responsibilities:

Operation, maintenance and management of the wastewater treatment, and operations and management of the water treatment facility.

Description of Facilities:

3.1 MGD activated sludge facility, 5.0 MGD conventional surface water plant.

Obstacles:

  • New WWTF system start-up with process control, maintenance and management systems placement from day one of the contract
  • The general tightening of governmental regulations including the highly restrictive Great Lakes-Lake Superior basin regulations
  • NPDES requirements for development and implementation of regulatory programs such as phosphorous reduction, salt reduction and mercury reduction plans
  • The requirements to maintain the current NPDES mercury standard which is set at 1.8ng/l
  • Management of complex NPDES permit issued for the Virginia facility

Accomplishments:

  • Completing and startup associated to the WWTF construction project
  • Created and implemented the operation and maintenance programs for the new WWTF
  • Provided trained and certified operation staffing for each facility
  • Developed standard of O/M procedures for each facility
  • Implemented computer controlled maintenance management and personnel safety systems
  • Worked side by side with the city and the engineer in negotiations with the MPCA for the requirements outlined in the draft of the NPDES permit
  • Manage each system for severe cold weather conditions of Nebraska and Minnesota

Project Summary:

The Virginia wastewater treatment facility went through an upgrade which was completed in 2013 at a cost of $18.5 million dollars. Its design average daily flow is 3.1 MGD, 30 day wet weather flow is 4.3 MGD and peak hourly wet weather flow at 9.9 MGD. The treatment process includes flow measurement, screening , raw sewage pumping, vortex grit removal, flow retention primary clarification, biological treatment (conventional activated sludge) final clarification, effluent filtration (dual media gravity for reduction of mercury), effluent disinfection (ultra violet light), chemical phosphorous reduction primary and secondary anaerobic digestion, bio-solids dewatering (belt filter press) bio-solid storage (concrete walled bituminous pad with partial membrane cover) and land application of bio-solids. The WWTF is a Minnesota Class A facility. The water treatment is managed by the Virginia Department of Public Utilities. The WWTF is a Minnesota Department of Health Class A facility. The WWTF is a conventional surface water treatment plant with its source water from Mesabi Mountain Mine Pit Lake. The Mesabi Mountain pump station which provides raw water to the plant was constructed in 1989 consisting of two – 24” vertical wells which enter a constructed 7’ X 8’ X 300’ horizontal drift. The well pumps entering the drift wells are two – 225 hp, 2000 gpm VFD controlled submersible pumps. The WWTF was constructed in 2001 at the cost of 6.2 million dollars. The design flow for the ultimate maximum daily demand is 5.0 MGD. The treatment processes include static chemical mixing, flocculation, sedimentation, filter feed pumping, dual media gravity filtration, clearwell, ground level reservoir, 3 elevated storage tanks high service pumping and backwash settling tanks. The WWTF chemical feed processes include coagulation, pre polymer application, filtration polymer, backwash treatment polymer along with corrosion control, pre and post.

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