GreenStep City Best Practices: Environmental Management
Efficient Water and Wastewater Systems {BP No. 20}
Assess and improve city drinking water and wastewater systems and related facilities.
Best Practice
Best Practice Actions
Optional Best Practice for Step 3 Recognition
Category A and B cities: implement this best practice by completing actions 1 and 2 and one additional action.
Category C cities that provide drinking water services: implement this best practice by completing actions 1 and 2, or action 4.
Step 4 Recognition Metric
Metric # 10 and # 11: Drinking Water and WasteWater
Summary
Conserving water in and reducing wastewater flows from homes and businesses effectively adds capacity to city infrastructure. Cities can promote such actions, which are found in several other best practices, including Existing Buildings and Green Business Development. Actions in this best practice include using pricing signals and making water and wastewater infrastructure more energy and materials efficient so as to achieve significant environmental and economic benefits to a city. Benefits of taking actions in this best practice include reducing the mining of water from aquifers, and reducing the carbon emissions and costs from water and wastewater systems, which can easily make up 25-40% of the city operations' carbon footprint.
In addition to actions under this best practice is, under another best practice, the related risk-management-focused climate adaptation/community resilience action 29.7: Protect water supplies and wastewater treatment facilities to reduce physical damage and sustain their function during extreme weather events.
Greenstep Advisor
Gabrielle Martin, Assoc. Engineer, Minnesota Technical Assistance Program: 980.329.2647, gamartin@umn.edu, http://www.mntap.umn.edu/us/staff/gm/
Connection to State Policy
- Allowing inflow - clear water that enters a wastewater system through rain leaders, sump pumps or foundation drains that are connected to the sewer lines - has been illegal in Minnesota since 1968.
- Every public water utility serving more than 1,000 people has been required, since 2015, to adopt a conservation rate structure or a uniform rate structure combined with demand reduction methods.
- Every water utility must create a capacity use plan and verify that there is enough water to meet projected needs out 25 years in the metro area and out 10 years beyond the metro. In the metro area such planning is urgent because more than half the water supplied by municipal utilities comes from only one aquifer, which is being mined, with groundwater levels going down across the metro region. The Met Council 2040 drinking water goal is consumption at/under 90 gal/person/day.
- New state plumbing code rules that took effect in 2016 allow reuse of treated rainwater within buildings for toilet flushing, vehicle washing, industrial processes, water features, cooling tower makeup, and similar uses.
- The State Legislature requires (Minn. R. 7077.0272, Subp. 2, D), as part of any wastewater financial assistance from the state, an analysis of all feasible treatment alternatives, guidance for which is the SB 2030 Wastewater Treatment Plant Review Process.
Benefits
- About 75% of Minnesota’s drinking water comes from groundwater. Groundwater trends across parts of Minnesota show declines in quantity and quality. A proactive approach to building local groundwater resilience and long-term cost savings is to stretch local groundwater supplies by implementing the basic 3Rs: 1) reduce groundwater use, 2) reuse groundwater before discarding it, and 3) recharge groundwater (and have strong wellhead protection measures in place).
- Every drop of water saved by residents and businesses means less treatment and less cost to treat, pump, and treat again. Incentivizing water conservation in your city can also help reduce the risk of added cost due to new well development, added pumping requirement, and increased treatment capacity.
- Minnesota's 1000 wastewater and drinking water plants use 1 billion kWh of energy per year, costing $80 million. Energy efficiency upgrades of 10% at all of them would result in 100 million kWh and $7 million saved.
- Between 2007 and 2015, Twin Cities metropolitan cities have spent over $157 million to reduce inflow and infiltration (I & I). These investments are ensuring that the region can avoid the unnecessary expense, estimated at $1 billion, to build excess capacity in the regional wastewater collection system and in the treatment capacity to handle excess I&I. Viewing I&I as an opportunity, New Ulm, which in 2016 estimated I&I at 35% of total wastewater flow, will accommodate increases in the number of sewer hook-ups by disconnecting sump pumps from the sewer system.
- When cities work with their businesses to implement pollution prevention programs to minimize water use and contaminant loading, including phosphorus, publicly owned treatment works can benefit by:
- Maximizing existing sewer and treatment capacity to avoid further investments in water supply and treatment infrastructure.
- Reducing chemical, energy, and sludge management costs.
- Improving bio-solids quality through reduced loading of heavy metals.
- Help meet the increasingly strict National Pollutant Discharge Elimination System (NPDES) permit limits by reducing wastewater loading from industrial users.
- Strengthening local industry by helping businesses reduce wastes, cut costs and meet regulatory requirements.
- Minimizing risk of damage to pipes and sewage treatment equipment from industrial solvents and corrosives, thus reducing costs.
- Lessening workplace exposure of toxic chemicals to employees at publicly owned treatment works (POTWs).
- Protecting drinking water sources in the community by minimizing discharge of contaminants, especially in wellhead protection areas.