Loading...
07.a 2023-03-21 Scandia Public Hearing Bliss WWT Facility PlanBolton-Menk.com Scandia Bliss Wastewater Treatment Facility Plan Public Hearing Presented by Bolton & Menk, Inc. March 21, 2023 Bolton-Menk.com Background •The Bliss Wastewater Treatment Facility is located in Scandia, MN •Serves 75 residential homes •Soil-Based Subsurface Sewage Treatment System (SSTS) •Consists of gravity and pressure collection system with two lift stations, three septic tanks in series, one lift station that feeds the sand filters, three sand filters, one lift station that feeds the drainfield, and three drainfield trench cells •Original system was designed to treat BOD and TSS, not nutrients. •Rated as a Class D facility by Minnesota Pollution Control Agency (MPCA) •Originally constructed in 1986 •Improvements to correct the flow from the influent lift station were completed in 2020 along with the addition of new restrictor plates to the drainfield splitter boxes and new flow meters for flow going to the drainfields •Nitrate + Nitrite levels in groundwater monitoring wells higher than the 10 mg/L MPCA limit Bolton-Menk.com Bliss System Service Area The service area for the Scandia Bliss Wastewater Treatment Facility (WWTF) is not expected to expand Bolton-Menk.com Bliss Wastewater Treatment Facility Layout Bolton-Menk.com Existing Wastewater Facilities The existing wastewater treatment facility is in fair condition Drainfield Trench Caps Infiltration Trench C Bliss Control Panel, Dosing Station, Influent Septic Tanks Bolton-Menk.com State Disposal System (SDS) Permit •Requires four ground water monitoring wells surrounding the WWTF. •The city must monitor a variety of wastewater constituents. On the current permit, nitrogen is the only one with an associated discharge limit. •Total Nitrogen limit is 10 mg/L per MPCA requirements. A Nitrogen Mitigation Plan was submitted in 2016. Bolton-Menk.com Future Considerations and Alternatives •Nitrogen removal processes will be required as nitrogen concentrations at GW 004 range from 6.3 mg/L to 53.10 mg/L, with the average being 28.34 mg/L •No other constituents have limits in the new SDS permit •Nitrogen Removal Alternatives •Alternative 1: Denitrification •Alternative 2: Nitrification/Denitrification Bolton-Menk.com Alternative 1: Denitrification System •Would require: influent BOD and TSS to be low and would not require additional treatment and that the ammonia is already nitrified •No guarantee that all ammonia is nitrified as part of existing system •Additional Components Required •Denitrification reactor dosing tank •Denitrification reactor with chemical addition •Polishing tank •Drainfield dosing tank Bolton-Menk.com Alternative 2: Nitrification / Denitrification System •Would Require: Influent to be high in Nitrogen •Additional Components Required •Settling tank •Equalization basin •Nitrification reactor •Denitrification reactor dosing tank •Denitrification reactor with chemical addition •Polishing tank •Drainfield dosing tank Bolton-Menk.com Recommendation Alternative 2: Nitrification/ Denitrification is recommended as it is the only option that can guarantee nitrogen removal to meet the limit Alternative 2: Nitrification/ Denitrification System Mobilization $ 55,000.0 Influent Metering Manhole $ 30,000.0 Settling Tank $ 60,000.0 Equalization Tank $ 75,000.0 Nitrification Reactor $ 310,000.0 Dosing Tank $ 25,000.0 Denitrification with Carbon Addition $ 90,000.0 Polishing Tank $ 55,000.0 Drainfield Dosing Tank $ 120,000.0 Chemical Feed Equipment $ 10,000.0 Installation/Electrical/ Misc. $ 400,000.0 Subtotal $ 1,230,000.0 Engineering and Contingency (30%)$ 370,000.00 Total Cost $ 1,600,000.0 Bolton-Menk.com Improvements Schedule Improvements Implementation Schedule Item Date Submit Permit Modification Application February 2023 Submit Facility Plan March 2023 Apply for IUP June 2023 Submit Plans & Specifications and Apply for PSIG July 2023 IUP/PSIG Lists Finalized and MPCA Certifies Project Fall 2023 Begin Construction of Improvements Spring 2024 Substantial Completion Fall 2024 *IUP = Intended Use Plan, PSIG = Point Source Implementation Grant QUESTIONS?