Water Reuse Case Study: Oswego, Kansas

Overview

The City of Oswego, Kansas reclaims treated municipal wastewater from a lagoon treatment system, a low-input treatment technology to irrigate a local golf course during the warm months of the year. This helps to reduce potable water demands and save costs for both the city and the Oswego Golf Association. Water reuse also ensures a reliable water supply to keep the golf course green and operational during periods of drought. Although Kansas does not have dedicated state regulations for reusing treated municipal wastewater for landscaping, state regulators have used the authority delegated to them under the federal Clean Water Act to permit multiple beneficial reuse projects within the state.   

Context

Oswego is in the southeastern corner of the Kansas, near a tributary of Labette Creek. It has a relatively stable population of about 1,600 people. To treat its wastewater, the city uses a lagoon treatment system with a maximum capacity of 305,000 gallons (1,155,000 liters) per day during normal flow and 709,000 gallons (2,684,000 liters) per day during wet weather flows. Many small or rural communities use lagoon treatment systems to treat their wastewater prior to discharge into the environment. Lagoon treatment systems can achieve the same level of treatment as conventional wastewater treatment plants when they are properly designed and maintained. Effective lagoon treatment systems are usually comprised of multiple interconnected treatment cells and require a large amount of land area. Their large size retains the wastewater in the lagoon treatment system for enough time to sufficiently reduce the concentration of contaminants and pathogens. More information about lagoon treatment systems can be found in the background documents section of this case study. 

The City of Oswego initiated its efforts to reclaim wastewater in the late 1990s. The decision to incorporate water reuse into the city’s wastewater management plans evolved from a collaboration with the Oswego Golf Association, which began looking for a lower cost and suitable alternative to using treated drinking water to irrigate its golf course. In response, the city decided to add an additional treatment step to their lagoon wastewater treatment system to enable reuse of treated municipal wastewater for golf course irrigation. Water reuse was not commonplace in the state when the project was initiated, but the Golf Association and the city were open-minded and willing to start a new project, recognizing the short- and long-term benefits of the drought-resistant water supply.  

The landscape irrigation system using reclaimed water has been operational for over two decades, long before the area began experiencing major droughts. During the warmer months (typically between May and September), a portion of the reclaimed water is used to irrigate greens and fairways at the Oswego Golf Association golf course. The reclaimed water provides a steady supply. With increased and prolonged periods of scarce rainfall now affecting the city, this water source has proved critical for golf course maintenance and continued operation. Additionally, the city considers the landscape irrigation system to be of low maintenance. Three city employees help with its operation and daily maintenance, and maintenance primarily entails cleaning filter screens and priming pumps. 

Solution

The City of Oswego’s municipal wastewater treatment assets mainly consist of a gravity-flow collection system, consisting of polyethylene pipe and brick manholes, and a lagoon treatment system with three lagoon treatment cells. The collection system has nine lift stations that pump sewage over various high elevation points throughout town, from which it eventually flows via gravity to the lagoon treatment system. The lagoon treatment system is in the southwestern area of town, with a surface area of 33.8 acres (13.7 hectares). The lagoon treatment system has a maximum treatment capacity of 709,000 gallons (2.7 million liters) per day during wet weather. 

Figure 1 provides an overview of the lagoon treatment system and non-potable reuse system. To provide reclaimed irrigation water that meets additional permit requirements set by the state for reuse, the city adds chlorine to enough treated municipal wastewater from the lagoon treatment system for golf course application—up to 305,000 gallons (1.2 million liters) per day during the warm months. The treated municipal wastewater that is routed for chlorination is referred to as reclaimed irrigation water in this case study (i.e., reclaimed irrigation water is the water within the “non-potable reuse” box in Figure 1). The reclaimed irrigation water is pumped to a holding pond before flowing into a pumping pond used to irrigate the golf course. If the golf course does not need additional water for irrigation, such as during the winter or wet periods, the treated municipal wastewater from the lagoon treatment system is not chlorinated or sent to the golf course, but instead is directly discharged to a tributary of Labette Creek. This is because the lagoon treatment system satisfies separate permit requirements for discharging the effluent, without the need for additional disinfection via chlorination.  

 Figure 1.  A schematic of the flow of water through the lagoon treatment system and to the reuse system. Water is piped 3.5 miles from the lagoon treatment systems to the golf course. Reclaimed irrigation water is water that enters the “non-potable reuse” box on the right-hand side of the figure. 

Additional Disinfection for Golf Course Irrigation 

Because the golf course is approximately 3.5 miles (5.6 kilometers) away from the lagoon treatment system, reclaimed irrigation water is pumped from the third lagoon treatment cell to a holding pond at the golf course where it flows into a pumping pond used for irrigation. Prior to arriving at the holding pond, the reclaimed irrigation water is disinfected with a 10 percent available chlorine bleach solution (sodium hypochlorite). Dosage of the solution changes based on chlorine demand, but it is adjusted to achieve a total chlorine residual of about 1.0 mg/L. The city decided to use the liquid bleach rather than granular chlorine mix or chlorine gas because it is cost effective and does not cause calcium buildups within the piping system. Details about the pumping system and bleach addition are included: 

The chlorinated reclaimed irrigation water flows from the holding pond via a gravity feed to the main pumping pond where it is used to irrigate the Oswego Golf Association golf course. The lagoon treatment system also has a foot valve to prevent backflow of the chlorinated reclaimed irrigation water into the lagoon cell when operations are halted. For public safety, access is restricted to the portions of the golf course undergoing active application of the reclaimed irrigation water. 

 Figure 2. Various equipment used in the reuse system. A: Electric panel, pump, and lagoon. B: Six-stage 2-inch (5-centimeter) booster pump. C: Bleach injection point before the pump and 3-inch (7.6-centimeter) green suction line. D: Suction line and primer hose. E: Primary holding pond and gravity feed to main pumping pond for the golf course. F: Chemical building housing bleach barrels and positive displacement pump. Photos provided courtesy of the City of Oswego and the Oswego Golf Association (November 2022). 

Water Quality Testing for Golf Course Application   

The city samples the irrigation water in the holding pond, at a location that is about 100 feet (30.5 meters) from the discharge point into the holding pond. The samples are tested for E. coli and chlorine residual. The project permit requires monthly testing for E. coli and weekly testing for chlorine residual, but the city monitors the chlorine residual daily through grab samples as well. The irrigation water is also tested weekly for residual chlorine and monthly for E. coli at the irrigation sprinkler heads. Target values for each analyte are included in Table 1. Laboratory analyses follow methodologies published in the following: 

All analyses are performed on samples as received. Water quality testing is outsourced to Meridian Labs, which sends the results to the City of Oswego. Results indicate that the city regularly meets the limits set by their permit.  

Table 1. Analyte and target values for irrigation water samples collected in the holding pond.

Analyte	Target Value	Quantitation Limit*	Units	Sampling Frequency
E. coli	Must not exceed 400	1.0	MPN/100 mL	Monthly
Total residual chlorine	1.0	0.0800	mg/L	Weekly

*The quantitation limit is the lowest concentration that the lab doing the analysis can reliably measure and report.
Abbreviations: milliliters (mL), milligrams per liter (mg/L), most probable number (MPN).

Policy, Institutional, and Regulatory Environment 

Kansas does not have any dedicated state regulations for reusing treated municipal wastewater for landscape irrigation, but has used the delegated authority under the federal level Clean Water Act to permit the reuse of treated municipal wastewater for beneficial applications. The Kansas Department of Health and Environment (KDHE) permits 140 municipal facilities under the National Pollutant Discharge Elimination System (NPDES) program to use treated wastewater for irrigation. Many of these permits are for local efforts to reduce discharges to waterways. In 1999, KDHE issued a NPDES permit to the City of Oswego to reuse their treated municipal wastewater. If the treated wastewater is being pumped to the golf course for irrigation, the permit requires weekly testing for total chlorine residual and monthly testing for E. coli of the reclaimed irrigation water in the holding pond at the golf course (Table 1).  

NPDES Permit Requirements for the City’s Stream Discharges Permit  

NPDES Permit Requirements for the Landscape Irrigation System 

There was not a formalized communications campaign to inform the public about the reclaimed water used for landscape irrigation, but many townspeople were familiar with the project, including city and golf course employees and landowners whose properties the pipe installation affected. There has never been opposition toward this project from the community or affected parties. 

Financial and Contractual Agreements 

The overall cost of the golf course irrigation system has not been calculated, but most of the project funding came from private sources. The largest cost of the reuse project was adding a pipe to transport the reclaimed irrigation water 3.5 miles (5.6 kilometers) to the golf course. The City of Oswego, the golf course owners, and other private sources contributed to the pipe cost. A contracting firm installed the pipe, and, in return, the Oswego Golf Association promoted the firm as a hole sponsor. Although the pump line crosses private property, landowners showed no opposition to pipe placement because they were made aware of, and understood, the project benefits. The City of Oswego installed the pumps after obtaining the permit; otherwise, they used infrastructure that was largely already in place for the water reuse project.  

The maintenance budget for the system is funded by the city’s water and sewer line items fund. As part of the agreement between the City of Oswego and the Oswego Golf Association, the city funds the reclaimed irrigation water supply and pumping to the golf course, as well as the lagoon treatment system maintenance.  

Benefits 

Cost effective: This project benefits the Oswego Golf Association and the City of Oswego because it lowers the amount of costly potable water needed for golf course irrigation. A formal study has not been conducted to evaluate cost savings.  

Secure, reliable water supply: Oswego has experienced more severe and prolonged droughts over the last decade during the warm months. For example, during the summer of 2022, the holding pond was 2 feet (0.6 meters) shallower than average, due to lower rainfall in the area. Regardless, this reuse project provides a reliable water supply to keep the golf course green and operational when other water sources are scarce. Notably, the holding pond stores about three weeks’ worth of water for the Golf Association’s needs. Therefore, irrigation could continue regularly for almost a month, even if the City of Oswego stopped pumping water to the holding pond due to low water levels in the lagoon treatment system caused by prolonged drought.   

Community collaboration and communication: The golf course and the city were willing to collaborate on a project that provided benefits to them both. Oswego Golf Association employees and golfers are excited about the project because they recognize that without water reuse, the golf course would not be well-maintained. The city saves costs associated with water treatment and pumping potable water to the course. Communication of these benefits between the city and golf course employees—as well as other stakeholders, such as landowners affected by pipe installation—proved key to initial and continued success.  

Lessons Learned and Conclusions 

Lessons Learned 

Use existing infrastructure to save costs: When the City of Oswego and the Oswego Golf Association partnered to irrigate the golf course, they decided to use water from the existing lagoon treatment system to reduce construction costs. Therefore, the main project cost derived from pipe placement rather than construction of an entirely new system. Although not all communities may be able to duplicate this model, creative thinking, proactive planning, and the use of existing infrastructure can enhance resilience and efficiency. 

Designing and modifying with future scenarios in mind: The City of Oswego continues to adapt and modify the lagoon treatment system in response to extreme climate events. For example, the lagoon treatment system was expanded in 2020 to increase capacity during wet weather events. Perhaps the most valuable lesson learned from this project is related to the pump line that transports the reclaimed irrigation water from the lagoons about 3.5 miles (5.6 kilometers) to the golf course holding pond. The 2-inch (5-centimeter) pump line that was installed at the start of this project produces about 80 to 100 pounds (36 to 43 kilograms) of pressure at the pump and cannot handle more pressure. Using a 4-inch (10.2-centimeter) oversized pipe from the start, while more costly, would have alleviated head pressure at the 2-inch (5-centimeter) booster pump, allowing an increase in the water flow rate between the third lagoon cell and the holding pond. With the current setup, the City of Oswego can meet the golf course water demands—so an upgrade is not required, but a larger pipe would increase efficiency and allow them to increase reuse capacity in the future.   

Evolving environmental conditions can present operational challenges: Algae growth is typical in lagoon treatment systems and is exacerbated during dry periods. This has presented a suite of challenges. For example, algae growth (combined with higher water temperatures) increases chlorine demand, making it more difficult to meet the 1.0 mg/L chlorine residual required in the holding pond as stipulated in the permit. Algae growth also caused the city to stop operations of the reuse system every four to five days and remove algae from the pump screens. In response, the city upsized the 2-inch (5-centimeter) intake line with a 4-inch (10.2-centimeter) line to reduce clogging from algae growth. It also built a 24-by-24-inch (61-by-61-centimeter) stainless steel cage, suspended 16 inches (41 centimeters) in the lagoon, to keep the suction line clean: the cage helps remove algae, keep fish away, and reduce sediment uptake into the pump system.  

Open-mindedness and creativity enable implementation: Stakeholders involved in this project adopted an agreeable and enthusiastic mindset, which aided in early adoption of water reuse by the state. Since Kansas does not regulate water reuse, the city and state regulators collaborated to use their available legal authorities to implement the project quickly after applying for a permit. The City of Oswego noted that achieving permit compliance has been easy and that it has not faced opposition from landowners affected by pipeline construction because the project benefits are apparent and worthwhile to them. Project modifications involved innovations championed by city employees who sought solutions to help keep costs low and operations safe and efficient.  

Replicability and Conclusions 

The City of Oswego’s reclaimed landscape irrigation system is a cost-effective solution that keeps the local golf course green and operational despite periods of drought. The largest costs associated with the project were for laying pipe, which increases with longer pumping distances, and the energy used for pumping itself. The layout of this project is unique in that the golf course is several miles away from the lagoon treatment system, but its simple design offers a high potential for it to be adopted elsewhere. A similar project may be useful for landscape or agricultural irrigation in areas close to a wastewater treatment site. The reuse project’s success and longevity are tied to enthusiastic and innovative champions, proactive planning, stakeholder collaboration and acceptance, and the ability to meet permit requirements. There are no plans to expand the system, but operation is anticipated to continue for years to come.  

Background Documents 

• Location: Oswego, Kansas
• Capacity: 305,000 gallons per day (1,155,000 liters per day)
• Status: Operational since 1999
• Source of Water: Treated municipal wastewater
• Reuse Application: Landscaping (golf course irrigation)
• Benefits: Provides a drought resilient water supply, reduces demands on and costs for potable water supplies
  • A six-stage, 2-inch (5-centimeter) booster pump pumps the reclaimed irrigation water from the third lagoon cell to the holding pond (Figure 2B). 
  • To disinfect the water, bleach is injected into the suction side of the booster pump so that the water is treated entirely through the line (Figure 2C). 
  • A positive displacement pump eliminates the siphoning of bleach from the barrels and controls the amount of bleach that is administered (Figure 2F).  
  • Screening is used to keep algae and moss from infiltrating the pumps. A 24-inch by 24-inch (61-centimeter by 61-centimeter) stainless steel strainer basket, custom built by the city, is attached to the end of the 3-inch (7.6-centimeter) suction line to prevent algae and moss from entering the pumps.  
  • The most recently promulgated update of the EPA's publication SW-846, third edition. 
  • Title 40 of the Code of Federal Regulations, Part 136. 
  • Applicable ASTM methods. 
  • Standard Methods for the Examination of Water and Wastewater, 20th edition. 
  • Treated municipal wastewater from the third cell of the lagoon treatment system is tested quarterly for various parameters including total suspended solids, biological oxygen demand, pH, total phosphorus, ammonia, and E. coli prior to discharge. 
  • Public access to the golf course is restricted during application of the reclaimed irrigation water.  
  • Irrigation must occur in a manner that avoids runoff and ponding.  
  • Signs that read “DO NOT DRINK OR SWIM, RECLAIMED WASTEWATER” are posted around the holding and pumping ponds. 
  • City of Oswego. n.d. Sewer—waste water.    
  • U.S. Environmental Protection Agency. 2023. Regulations and End-Use Specifications Explorer (REUSExplorer).  
  • Western States Water Council. 2021. Water reuse in the West: Western state water reuse governance and programs. 
  • World Population Review. 2022. Oswego, Kansas population 2022.   
  • U.S. Environmental Protection Agency. 2022. Compliance Tips for Small Wastewater Treatment Lagoons with Clean Water Act Discharge Permits.
  • U.S. Environmental Protection Agency. 2023. Lagoon Wastewater Treatment Systems.