Water Reuse Case Study: Richmond Hill, Georgia

Overview

To comply with both NPDES permit requirements and aquifer pumping restrictions, the city of Richmond Hill, Georgia, created a new water reclamation facility that treats 3 million gallons per day of municipal wastewater. The facility uses the reclaimed water for landscape irrigation and for maintaining wetlands on the property. Other benefits of the project include: 1) reducing groundwater overdrafts; 2) preventing saltwater intrusion in the community water supply; 3) creating wildlife habitat through wetland creation; 4) increasing wastewater treatment capacity to allow for population growth; and 5) educating the public about the value of wetland habitat. population growth; and 5) educating the public about the value of wetland habitat.

Context

Population Growth and Groundwater Overextraction

The population of Richmond Hill, Georgia rose from 7,000 in 2000 to 17,000 in 2021, due to an increase in the number of resort and retirement homes in the area and its role as a commuting town to neighboring Savannah. The community depends on the Floridan Aquifer System for its water supply, which covers about 100,000 square miles (260,000 square kilometers) and holds billions of gallons of freshwater beneath Georgia, Florida, Alabama, Mississippi, and South Carolina. On average, the Floridan Aquifer System has a depth of 347 feet (106 meters) and a thickness of 985 feet (300 meters). Groundwater has been over drafted during the past decades, with water levels falling by over 3 meters in some areas of coastal Georgia. Overextraction - combined with sea level rise, diminished recharge levels, and increased rainfall variability - is leading to saltwater intrusion in the Floridan Aquifer System, where saline water enters the aquifer and contaminates the fresh groundwater within.

Under the Floridan Aquifer System is an ancient saltwater sea, which pushes upward but has traditionally been kept in place by the weight and pressure of the aquifer. As levels of groundwater decrease, the saltwater can migrate upward and seep into the Floridan Aquifer System. Sea level rise also increases saltwater intrusion into the aquifer. This is a severe, high-consequence problem, as saltwater intrusion contaminates municipal, agricultural, and industrial water supplies and degrades freshwater-dependent ecosystems. It also does not take much saltwater contamination to render freshwater non-potable. The U.S. Environmental Protection Agency’s (EPA’s) standard for chloride is 250 milligrams per liter (mg/L) for drinking water; typically, saltwater’s chloride concentration is roughly 19,000 mg/L. An effective solution to halt saltwater intrusion is to decrease groundwater extraction rates, which will ensure there is adequate pressure underground to keep the “saltwater sea” in place. Due to the risk of saltwater intrusion, Richmond Hill is restricted to incremental water withdrawals from the Florida Aquifer System. In addition to withdrawal restrictions, permitting plans in the area implement measures for efficient and effective use of water that is withdrawn from the aquifer and the use of reclaimed water to the maximum practical extent.

Original Wastewater Treatment Approach

Richmond Hill’s original wastewater treatment facility, the Sterling Creek Water Reclamation Facility (WRF), was built in 1996 and put into operation in 1997. This treatment facility employed low-input treatment technologies, such as aerated lagoons and an artificial wetland that treated the wastewater using natural processes. The treatment system consisted of a three-step process:

• Wastewater first entered a lagoon at the highest point of the grounds. There, it was aerated to enhance the wastewater treatment processes.
• Then the water travelled down a pipeline using gravity into 11 grassy fields that acted as filters for insoluble debris and removed other contaminants, such as nitrogen, phosphorus, fats, and sugars.
• Last, the water was pumped into the artificial wetlands, where natural treatment processes such as microbial biodegradation further treated the water.

The treated effluent was then discharged to Elbow Swamp and eventually flowed into the Ogeechee River. This original Sterling Creek WRF could process 1.5 million gallons per day (MGD) (5.7 million liters per day, MLD) and used only 10 percent of the energy that a traditional wastewater treatment facility needs to process the same flow of wastewater.

Benefits and Challenges

There were several benefits to the original Sterling Creek WRF. The artificial wetlands acted as an important habitat for a variety of wildlife, including alligators, deer, cougars, bald eagles, osprey, and a wide array of plants and trees. Because of the high levels of biodiversity, the wetlands have become a popular tourist center (particularly for bird watchers) and provide educational opportunities for schools and universities. The entire 500-acre (200-hectare) treatment site was declared a wildlife sanctuary and was awarded the 2007 Trendsetter award by Georgia Trend magazine for its innovative design and use.

Despite these benefits, there were issues with the WRF’s treatment capabilities and capacity. Because the WRF almost entirely relied on natural processes and was open to the environment, changes in temperature and vegetation over time meant that its treatment effectiveness fluctuated. Additionally, the facility was working at near capacity for many years, and required maintenance to continue operation, such as the need to remove sludge from the lagoons to restore the original hydraulic retention time. There was also insufficient ammonia removal in the wetlands, leading to higher-than-expected nitrogen loading into the Ogeechee River.

Richmond Hill recognized in 2004 that it needed a new wastewater treatment facility to increase the capacity, but also wanted to maintain the wetlands that brought other ecosystem benefits. The city entered a consent order with the Georgia Environmental Protection Division (EPD) for noncompliance of the original Sterling Creek WRF, which required the design and construction of a new wastewater treatment facility. The entire consent order process lasted over six years and cost the city $1,000–1,500 per month. In 2015, Richmond Hill began to plan for the construction of its new, state-mandated wastewater treatment facility, which could treat a larger flow of water in less space than the original lagoon and wetland system. The treated wastewater from the new treatment facility would be used to preserve the original wetlands and for other uses that would reduce the community’s reliance on freshwater withdrawals from the aquifer.

Solution

The original Sterling Creek WRF was not a sustainable and cost-effective option for Richmond Hill in part because it was unable to treat the increased flow of wastewater generated by the growing city. The goal of the newly constructed facility was to increase treatment capacity, while preserving the wetlands ecosystem. Construction of the new $25 million wastewater treatment facility, still known as Sterling Creek, was completed in 2016. The facility uses a highly advanced wastewater treatment technology, consisting of a five-stage biological nutrient removal process and an Ovivo Kubota flat plate membrane bioreactor (MBR). The system includes:

• An influent lift station.
• Rotary drum fine screens.
• A vortex grit removal system.
• Anaerobic, anoxic, and aerobic basins.
• A membrane bioreactor.
• An ultraviolet disinfection system.
• An effluent pump station.
• A septage receiving station.
• Aerobic digestion of sludge with membrane thickening.
• A belt filter press dewatering and solids handling facility.
• A drain lift station.

Additional design features include: internal equalization through a feed forward design, supervisory control and data acquisition digital networks, a control building, a chemical storage and feed system, and a plant watering and irrigation system. The facility design is state-of-the-art, as it uses membrane technologies, including for sludge thickening, and is the first of its kind in coastal Georgia.

The new Sterling Creek facility doubled Richmond Hill’s capacity to treat wastewater from 1.5 MGD (5.7 MLD) to 3.0 MGD (11.4 MLD). If additional membrane cassette equipment is installed, the facility will be able to expand to 4.0 MGD (15 MLD), for which Richmond Hill has already received permits. The reclaimed water is predominately used for non-potable irrigation of recreational grounds, public parks, and golf courses. However, it is also used to maintain the artificial wetlands that were part of the original WRF, providing wildlife habitat for native species. These wetlands lost their main water supply when the WRF transitioned from a lagoon treatment system to the high-tech membrane bioreactor system. Finally, the reclaimed water is also pumped into an outfall at Elbow Swamp, which assists in the preservation of the Ogeechee River Watershed.

Richmond Hill’s new facility received an Engineering Excellence Award in the “Waste and Storm Water” category from the American Council of Engineering Companies of Georgia in 2017. The facility’s upgrades produce a high-quality effluent, generate alternative sources of water to irrigate green spaces in the area, and lower the overall dependence on groundwater in an area with restricted aquifer withdrawals.

Policy, Institutional, and Regulatory Environment

In the United States, the Clean Water Act and the Safe Drinking Water Act provide a foundation for managing wastewater and public health protection, respectively, through drinking water and discharge standards at the federal level. However, there are no such overarching federal regulations for water reuse, thus states have used their primacy to develop select reuse regulations as needed.

Georgia’s regulations define requirements for recycling treated municipal wastewater for non-potable landscaping applications, such as the irrigation of recreational grounds, public parks, and golf courses. The state does not have dedicated regulations for reusing treated municipal wastewater for environmental restoration (including wetlands) but has used the authority delegated under the Clean Water Act to permit reuse of treated municipal wastewater for beneficial applications. The treatment requirements for both landscaping and environmental restoration applications are enforced through the state-issued permit. The new Sterling Creek WRF has been issued a National Pollutant Discharge Elimination System (NPDES) permit for up to 3.0 MGD (11.4 MLD) of treated wastewater discharged to Elbow Swamp, which flows into the Ogeechee River Basin via the Sterling Creek Tributary. The permit contains effluent limitations for expansion up to 4.0 MGD (15 MLD).

A consent order between the city and the Georgia EDP mandated Richmond Hill to upgrade their treatment facilities, and a subsequent decision was made to increase the wastewater treatment capacity from a 1.5 MGD (5.7 MLD) lagoon and wetlands system to a 3.0 MGD (11.4 MLD) high-tech wastewater treatment facility. Although it would have been physically possible to expand the capacity of or improve upon the lagoons system, it would have required significantly more space than the high-tech treatment plant. Additionally, in 2010 the city was issued an enforcement order for the violation of its NPDES permit, as it had exceeded its discharge limitations for pollutants, while using the aging lagoon and wetlands treatment system.

In 2006, Georgia EPD established the Coastal Georgia Water & Wastewater Permitting Plan for Managing Saltwater Intrusion based on a seven-year study of groundwater use in the coastal area. As a result of this plan and because of its location, Richmond Hill is restricted to incremental water withdrawals from the Florida Aquifer System. In addition to withdrawal restrictions, the permitting plan implements measures for efficient and effective use of water that is withdrawn from the aquifer, wastewater discharge limitations to protect the sensitive ecosystem of coastal Georgia, and the use of reclaimed water to the maximum practical extent.

Financial and Contractual Agreements

The new Sterling Creek WRF is the largest single infrastructure expenditure in Richmond Hill’s history, costing approximately $25 million. The project was funded through three loans totaling $23.5 million, including a loan of $10.5 million from the Georgia Environmental Finance Authority (GEFA) and two prior loans totaling $13 million. Richmond Hill will pay 1.03 percent interest on the GEFA’s 20-year loan and will receive $1 million in debt forgiveness, obtained via green credit because of additional energy-efficient technologies implemented within the WRF.

These loans will be partly repaid through increased water and sewer rates in Richmond Hill, meaning that users will pay a portion of the cost. Monthly base rates for residential and commercial customers increased by $4 in January 2015 and once again in 2016, just as the construction of the WRF was being completed. Richmond Hill now re-evaluates its water rates on a yearly basis.

Benefits

Increased wastewater treatment capacity: The new WRF facility can treat up to 3.0 MGD (11.4 MLD)—double its previous capacity of 1.5 MGD (5.7 MLD)—and could be expanded to 4.0 MGD (15 MLD) if additional membrane cassette equipment is installed. This will allow for the area to economically develop further without concerns about how to treat increased flows of wastewater, which has hindered Richmond Hill in the past.

Lower dependence on groundwater resources through water reuse: Richmond Hill’s location has restrictions in place relating to how much groundwater can be extracted. The WRF project has lowered dependence on groundwater for irrigating the community’s green areas by producing reclaimed water of a sufficient quality for irrigation applications.

Wetland preservation: Even though the wetlands are no longer used to comply with discharge permits, their ecological significance and use by the community for education and recreation have been recognized, and thus a portion of the water treated at the new Sterling Creek facility is used for wetland preservation. Sustainability of the wetlands provides valuable habitat for a wide variety of flora and fauna, boosts the economy through eco-tourism, and allows opportunities for educational and scientific learning.

No more fines: Richmond Hill was under the EPD’s consent order for six years and incurred fines during that time. The new Sterling Creek WRF alleviates Richmond Hill from the consent order and there is no longer a monthly fine for noncompliance. This means more money will be available to be spent on improving social, economic, and environmental conditions in the area.

Lessons Learned and Conclusions

Lessons Learned

New technologies and reuse approaches can be useful for environmental sustainability: As the City of Richmond Hill’s population expanded, the Sterling Creek WRF replaced its lagoon and wetland treatment system with a highly advanced wastewater treatment technology. Although the treatment function of the wetlands was no longer necessary, the reclaimed water from Sterling Creek is used to maintain and preserve the wetlands and flows to the Ogeechee River, highlighting the fact that new technologies can be a key part of preserving and conserving different ecosystems.

Enforcement can provide opportunities to re-evaluate and upgrade water management approaches and facilities: Richmond Hill incurred economic penalties under its consent order with Georgia’s EPD to change its previous WRF to a new facility with a higher capacity. Although Richmond Hill might have eventually upgraded to a more traditional WRF and included a reuse component, it is likely that its fines and the state mandate to construct a new facility sped up the process considerably.

Saltwater intrusion is still an issue: While this project lowers Richmond Hill’s dependence on groundwater, overextraction in the Floridan Aquifer System remains a significant issue. This is partially because the aquifer lies beneath five different states, making it a transboundary basin. Activities in one state may positively or negatively affect the groundwater quantity and quality in another. Therefore, coordinated multi-state governance is needed to ensure that effective regulation and monitoring take place to lower the risk of saltwater intrusion.

Conclusions

The story of the Sterling Creek wastewater treatment and reclamation facility shows how infrastructure that is unsuitable to meet the needs of a growing population can be transformed into a highly efficient facility using new technologies, while maintaining the integrity of the surrounding environment. It also provides an excellent example of how a natural ecosystem can be important to the local community and economy because preserving the wetlands, which were originally created to treat the community’s wastewater in the original treatment facility, was a community priority throughout the process. While saltwater intrusion may still be a high risk to those who depend on the Florida Aquifer System, transitioning to water reuse is a step toward establishing sustainable practices of groundwater management.

Background Documents

• Bates Engineers/Contractors, Inc. n.d. Sterling Creek Water Reclamation Facility.
• E&D Contracting Incorporated. 2022. Sterling Creek Wastewater Treatment Plant. Date accessed: Aug. 2. 2022.
• Georgia Department of Natural Resources. 2012. Guidelines for water reclamation and urban water reuse. 
• Georgia Department of Natural Resources. 2016. Public notice no. 2016-07ML. 
• Georgia Environmental Finance Authority. n.d. Investing in Georgia's energy, land, and water resources.
• Georgia Environmental Protection Division. 2006. Coastal Georgia water & wastewater permitting plan for managing salt water intrusion.
• Hussey Gay Bell. 2022. Sterling Creek Water Reclamation Facility: An evolution in wastewater treatment.
• Parker, J. 2016. Richmond Hill cuts ribbon on wastewater plant. Savannah Morning News.
• Smith, J. 2015. Wetlands becomes city’s first water reuse customer. TPO: Treatment Plant Operator.
• U.S. Environmental Protection Agency. 2022. Georgia (treated municipal wastewater for other centralized non-potable reuse).