City of Northfield, Minnesota Wastewater Treatment Facility Plan Council Workshop September 8, 2015
Introduction Background of Wastewater Treatment Facility Approach to Evaluation Study Results Implementation and Financing
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NPDES Permit National Pollution Discharge Elimination System (NPDES) Permit issued by Minnesota Pollution Control Agency Permit issued on 5 year basis Permit limits are mass based
NPDES Permit Existing Effluent Limits SD001 City of Northfield, Minnesota Parameter Limit 322 Kg/d, 25 mg/l, 85% removal Monthly Ave. CBOD 5 515 Kg/d, 40 mg/l Max. Weekly Ave. 386 Kg/d, 30 mg/l, 85% removal Monthly Ave. TSS 578 Kg/d, 45 mg/l Max. Weekly Ave. Copper 1.45 Kg/d, 113 µg/l Daily Max. 19.6 Kg/d, 1.0 mg/l Monthly Ave. Total P 7174 Kg/yr Annual Max. 393 Kg/d, 20 mg/l April May Monthly Ave. Nitrogen Ammonia 175 Kg/d, 8.9 mg/l June Sept. Monthly Ave. 668 Kg/d, 34 mg/l Oct. Nov. Monthly Ave.
Community Development Population growth based on 16% increase per decade Dundas growth to mirror Northfield growth Industrial users to remain at existing agreement levels
Community Development Year Historical and Projected Service Population City of Northfield Population City of Dundas Population Total Service Population Notes 1990 14,684 473 14,684 (1) 2000 17,147 547 18,067 2010 20,007 1,367 21,374 2010 census 2015 21,608 1,476 23,084 Estimated 2020 23,208 1,586 24,794 Projected 2025 25,065 1,713 26,777 Projected 2030 26,921 1,839 28,761 Projected 2035 29,075 1,987 31,062 Projected (1) Dundas connected to the Northfield system in 1996.
Community Development Parameter Projected Design Flows and Loadings City of Northfield, Minnesota Existing Design Basis 2015 2020 2025 2030 2035 Population 26,400 23,084 24,794 26,777 28,761 31,062 AWW Flow (MGD) 5.2 4.09 4.28 4.51 4.74 5.01 PHWW Flow (MGD) 10.41 8.07 8.56 9.13 9.70 10.36 PIWW Flow (MGD) 11.74 9.35 9.84 10.41 10.98 11.64 CBOD5 Ave. Day (kg/d) 2818 1821 2501 2653 2804 2980 CBOD5 Max. Month (kg/d) 3636 2840 3520 3672 3823 3999 CBOD5 Max. Day (kg/d) 4545 3841 4521 4673 4824 5000 TSS Ave. Day (kg/d) 2273 1891 2407 2586 2764 2971 TSS Max. Month (kg/d) 2909 2765 3281 3460 3638 3845 P Ave. Day (kg/d) 157 36 39 42 45 49
Approach Facility improvements are generally required to meet three criteria: Improvements required to provide adequate treatment to meet effluent discharge requirements Improvements required to provide adequate treatment capacity to meet community development requirements Improvements required to maintain and/or replace treatment facility infrastructure and equipment
Study Results Treatment capacity adequate to meet existing permit levels Changes in NPDES Permit may require additional treatment in 5-10 years Facilities in need of upgrade/replacement to maintain functionality
Study Results Biosolids handling/treatment/storage requires upgrade to continue to function properly New liquid storage Upgrade treatment capacity New dry cake storage Ultraviolet disinfection (U.V.) equipment needs replacement Biological aerated filters (BAF) need hydraulic gate replacement
Study Results Supervisory controls and data acquisition (SCADA) system needs technology upgrade/replacement Influent lift pumps require replacement Aeration blowers to be replaced to improve reliability and increase efficiency Water reuse system will reduce use of clean water resources Ongoing maintenance projects (roofing and mechanical HVAC replacement) will be undertaken on a yearly basis
Study Results Green technology option Solar power has potential to provide electricity for use at the facility. Will require investment up front. Hydrothermal recovery utilization of geothermal concepts using wastewater as the heat sink may have potential Solar air heating preheating of facility make-up air using solar walls may have potential to reduce energy use at facility Further study of green design option recommended
Implementation Proposed Implementation Schedule Project Design Phase Bid Phase Construction Phase Biosolids Liquid Storage Jan. 2016 Oct. 2016 Nov. 2016 Feb. 2017 March 2017 Dec. 2017 BAF Gate Replacement Oct. 2018 Jan. 2019 Feb. 2019 April 2019 May 2019 Nov. 2019 UV Disinfection Biosolids Treatment Upgrade Biosolids Cake Storage May 2019 May 2020 May 2020 July 2020 Aug. 2020 - Dec. 2021 SCADA Upgrade Jan. 2012 Sept. 2021 Sept. 2021 Dec 2021 Jan. 2022 Dec. 2022 Influent Lift Pumps Oct. 2022 Mar. 2023 April 2023 May 2023 July 2023 Dec. 2023 Blower Replacement Oct. 2023 Mar. 2024 April 2024 May 2024 July 2024 Dec. 2024 Water Reuse System Oct. 2024 Mar. 2025 April 2025 May 2025 July 2025 Dec. 2025 On-Going Maintenance Projects (Roof replacement, MAU Replacement, Miscellaneous Items) will be addressed on an annual basis.
Proposed Site Improvements
Finance Capital Cost Opinion City of Northfield, Minnesota Item Cost 1. UW System $151,250 2. UV Disinfection $893,750 3. Biosolids Treatment and Dewatering $3,025,000 4. Biosolids Cake Storage $618,750 5. Liquid Biosolids Storage $1,038,125 6. BAF Gate Replacement $756,250 7. Influent Lift Pumps 1,134,375 8. Blower Replacement $742,500 9. SCADA Upgrade 1,375,000 10. Make-up Air Units $171,875 11. Roof Replacement $810,000 12. Miscellaneous $112,000 TOTAL $10,828,875
Ultraviolet Light Disinfection Unit Upstream Lamps (16) Downstream Lamps (16)
Biosolids Storage Building
Influent Lift Pumps
Biologically Active Filter (BAF) Building
Northfield MN Wastewater Treatment Facility Project Implementation Schedule Project Capital Cost 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 1 Water Reuse System $ 151,250 $ 192,088 2 UV Disinfection $ 893,750 $ 1,027,813 3 Biosolids Treatment Upgrade $ 3,025,000 $ 3,478,750 4 Biosolids Cake Storage $ 618,750 $ 711,563 5 Biosolids Liquid Storage $ 1,038,125 $ 1,069,269 6 BAF Gate Replacement BAF Cell 1 $ 75,625 $ 82,431 BAF Cell 2 $ 75,625 $ 82,431 BAF Cell 3 $ 75,625 $ 82,431 BAF Cell 4 $ 75,625 $ 82,431 BAF Cell 5 $ 75,625 $ 82,431 BAF Cell 6 $ 75,625 $ 82,431 BAF Cell 7 $ 75,625 $ 82,431 BAF Cell 8 $ 75,625 $ 82,431 BAF Cell 9 $ 75,625 $ 82,431 BAF Cell 10 $ 75,625 $ 82,431 7 Influent Lift Pumps $ 1,134,375 $ 1,372,594 8 Blower Replacement Blower 1 $ 61,875 $ 76,725 Blower 2 $ 61,875 $ 76,725 Blower 3 $ 61,875 $ 76,725 Blower 4 $ 61,875 $ 76,725 Blower 5 $ 61,875 $ 76,725 Blower 6 $ 61,875 $ 76,725 Blower 7 $ 61,875 $ 76,725 Blower 8 $ 61,875 $ 76,725 Blower 9 $ 61,875 $ 76,725 Blower 10 $ 61,875 $ 76,725 Blower 11 $ 61,875 $ 76,725 Blower 12 $ 61,875 $ 76,725 9 SCADA Upgrade $ 1,375,000 $ 1,622,500 10 MAU Replacement MAU-1 $ 15,813 $ 16,287 MAU-2 $ 26,813 $ 28,421 MAU-3 $ 15,813 $ 17,236 MAU-4 $ 16,500 $ 18,480 MAU-5 $ 15,813 $ 18,184 MAU-6 $ 19,250 $ 22,715 MAU-7 $ 15,813 $ 19,133 MAU-8 $ 14,438 $ 17,903 MAU-9 $ 15,813 $ 20,082 MAU-10 $ 15,813 $ 20,082 11 Roof Repacement BAF Building $ 275,000 $ 324,500 PreTreatment /Clarifier Building $ 305,000 $ 359,900 Biosolids Building $ 100,000 $ 115,000 UV Disinfection building $ 30,000 $ 34,500 Operations Building $ 100,000 $ 106,000 12 Miscellaneous Items Access hatches safety equipment $ 12,000 $ 12,000 Air Compressor at Pretreatment/clarifier building $ 25,000 $ 25,000 Boiler replacement at operations building $ 75,000 $ 75,000 Annual Inflation rate ( %) 3.0% Total Expense w/o Inflation $ 10,828,875 Total Expense w/ Inflation $ 12,470,010 $ 112,000 $ 1,085,556 $ 134,421 $ 841,548 $ 18,480 $ 5,385,809 $ 2,329,615 $ 1,391,727 $ 938,603 $ 232,251
Waste Water with 3% increases Net Annual Cash Flow 2015 2016 2017 2018 $527,024 $690,439 $766,031 $726,606 Capital Projects ($686,814) ($438,356) ($1,223,122) ($471,539) Bond Proceeds 0 0 $1,000,000 0 Net Cash flow after projects Ending Cash Balance Targeted Working Capital Over/(Under) Target Working Capital ($159,790) $252,082 $542,909 $255,067 $1,183,411 $1,435,494 $1,978,403 $2,233,470 $3,524,538 $3,604,719 $3,702,243 $3,873,346 ($2,341,126) ($2,169,225) ($1,723,841) ($1,639,877)
Waste Water with 3% increases Net Annual Cash Flow 2019 2020 2021 2022 $838,558 $900,787 $912,264 $2,058,991 Capital Projects ($1,173,129) ($785,799) ($6,931,335) ($3,267,779) Bond Proceeds - - $6,000,000 - Net Cash Flow after Projects ($334,570) $114,988 ($19,071) ($1,208,788) Ending Cash Balance $1,898,900 $2,013,888 $1,994,817 $786,029 Targeted Working Capital Over/(Under) Target Working Capital $3,842,294 $3,866,936 $2,757,394 $2,712,139 ($1,943,394) ($1,853,049) ($762,578) ($1,926,111)