Park A Wastewater Summary and Park B Subsurface Sewage Treatment System Assessment
Sara Heger and Sondra Larson November, 2019
Summary
The University of Minnesota’s Onsite Sewage Treatment Program did a two-part assessment of septic systems at Park A and Park B, both owned and managed by the Department of Natural Resources (DNR). Park A currently treats all their wastewater using a centralized wastewater treatment pond and vault toilets. The pond is not meeting the requirements of its state permit and therefore the DNR is having a new wastewater treatment system designed. One of the purposes of this assessment was to produce a summary of the wastewater stream from the RV dump station and campground bathroom at the park. The wastewater contaminant levels at each of the locations on this site demonstrate that the waste stream is not typical domestic-strength waste. Since this was only one data collection before a new system is designed, more wastewater contaminant data should be collected and flow rate data for the park analyzed as well. The other part of this project was to evaluate the new septic systems at Park B that have been installed to treat waste from the RV dump station and a shower house. Both of these systems include a secondary treatment unit. The data shows that the systems are currently treating wastewater as designed but recommendations on the management of these systems are provided to improve performance. Introduction
The University of Minnesota Water Resources Center’s Onsite Sewage Treatment Program (OSTP) was asked to provide an analysis for four septic systems managed by the Department of Natural Resources at Park A and Park B. The purpose of these analyses is to
1) At Park A, to provide an evaluation of the wastewater stream from a a. recreational vehicle (RV) dump station and b. campground bathroom and 2) At Park B, to evaluate the new septic systems with secondary treatment units, treating waste from a. an RV dump station and b. a campground shower house, are performing
3) Provide recommendations to the DNR on how to move forward with the management of these systems.
Park A
Currently, Park A handles wastewater using a wastewater treatment pond and vault toilets at the park. The current system needs replacement and a new system is scheduled to be designed and installed in
Page | 1
2020. Sampling was done at this site as a starting point to better understand the waste strength being produced.
Park B
The system for the RV dump station was designed for 1,800 gallons per day. There is a 6,000 gal septic tank, a 4,000 gallon surge tank, a 2000 gallon clarifier tank and a 2000 gallon surge tank. The secondary treatment unit consists of two 4,200 gallon Nibbler tanks, each holding one 10-pod pretreatment unit. Treated effluent is directed to two drainfield mounds using pressure distribution. There is a sludge return pump in the clarifier tank which on a monthly basis is manually operated to return sludge to the septic tank.
The mound system that services the campground shower house is designed for 1,900 gallons per day. 1,085 gallons per day to Mound #1 and 815 gallons Figure 1. Park B RV Dump Station Nibbler Unit per day to Mound #2. The system has three tanks: a 6,000 gallon septic tank, a 4,000 gallon pump tank and a 2,000 gallon recirculation tank. The system has an Advantex AX-100 recirculating secondary treatment unit. Methods/Observations
Park A and Park B sites were both assessed and sampled by the Onsite Sewage Treatment Program on September 5th, 2019 during the campgrounds’ busy summer season. All samples were brought to Pace Analytical and processed using laboratory methods EPA 351.2 rev.2 (1993) for Total Kjeldahl Nitrogen (TKN), Hach 10360 Rev 1.1 for Biochemical Oxygen Demand (BOD), SM 2540D for Total Suspended Solids (TSS), EPA 300.0 for Chloride, SM 4500-P F for Total Phosphorus, SM 9222D (m-FC) (1997) for Fecal Coliforms and EPA 353.2 for Nitrate + Nitrite. To the knowledge of the OSTP, this sampling event is the only time either of these systems have been sampled.
Park A
RV Dumping Station
The outlet inspection port was opened and wastewater samples were obtained. There was 5 feet of wastewater in the tank and about 28 inches of sludge at the bottom indicating the tank needed to be pumped out as more than 25% of the liquid capacity was sludge. According to the DNR this tank was last pumped in the fall of 2017.
Page | 2 Figure 2. Park A RV Dump Station Sampling Location Figure 3. Park A Campground Sampling Location
Campground Bathroom
Samples were taken out of the outlet baffle of the septic tank. There was 5 feet of wastewater in the tank, 12 inches of sludge and about 1 inch of scum at the top. This tank was also pumped last in the fall of 2017.
Park B
RV Dumping Station
• At the inlet of the first septic tank there was 5 feet of wastewater, 2 feet of sludge and 3 inches of scum at the top. • The second tank (flow equalization tank for the Nibbler)) was where the samples were drawn from. This tank had about 4 feet of water, 4 inches of sludge and no scum but a light film on top. • The lift station which doses the mounds was where the second samples were drawn from to analyze the treatment achieved by the Nibbler. This tank had only about 2 to 3 inches of sludge.
Figure 4. Park B RV Dump Station Sampling Location
Page | 3
Campground Shower House and Bathroom
• Samples were drawn from the outlet of the septic tank from where there was 5 feet of water, 18 inches of sludge and less than 1 inch of scum. • The inlet of the tank was observed to have about 5 feet of liquid depth, 3 feet of sludge and about 4 inches of scum. • In the recirculation tank in the middle, 3 feet of liquid depth and about 6 inches of sludge was observed. • Samples were drawn from the lift station to understand the treatment achieved by the Advantex pre-treatment system. This tank had about 4 feet of liquid depth and 2 inches of sludge.
All tanks at Park B were pumped in the fall of 2017.
Figure 5. Park B Campground Shower House and Bathrooms Advantex Unit Results and Discussion
Park A The wastewater contaminant levels at both sampled locations tested show, at the time of sampling, that this is not typical domestic strength waste. Flow data and more wastewater sampling for the site must be obtained to fully understand the general contaminant mass loading at the site. It also must be noted that this is assessment only included one round of sampling and the numbers represented in Table 1 should not be used the sole characterization of the wastewater characteristics.
Table 1. Park A Wastewater Concentrations Park A Product Performance RV Dump Station Campground Typical Domestic Requirement Effluent Bathrooms Effluent Effluent (Treatment Level C) Wastewater Concentrations (mg/L) TKN 769 135 60*** - BOD 1280 195 140-200* 170 TSS 230 74 50-100* 60 Chloride 395 48.9 18*** - Phosphorus 56.4 17.8 6-12** - *USEPA (2002) **Siegrist (2017) ***Lowe (2009)
Page | 4
Park B
The RV dump station wastewater contaminant findings (Table 2) show that this wastewater sample is very concentrated compared to typical domestic effluent. The Nibbler pre-treatment unit is working well, reducing the BOD by more than 99% and TSS by 84%. The incoming nitrogen and phosphorous concentrations are being reduced but there may be an opportunity for further treatment.
Table 2. Park B RV Dump Station Wastewater Concentrations Park B - RV Dump Station Wastewater Concentrations (mg/L) % Product Performance Septic reduction Requirement Tank After pre-treatment (Nibbler) (Treatment Level C) BOD 1530 < 20.0 >99 170 TSS 92 15 84 60 Chloride 372 328 12 - Phosphorus 85.5 32.3 62 - Nitrate + Nitrite - 0.58 - - TKN 757 154 80 - Total nitrogen 757 273 64 - Fecal Coliform - 74 CFU/100 mL 99.9 -
Table 3. Park B Campground Shower House and Bathrooms Wastewater Concentration Park B - Campground Shower House and Bathrooms Wastewater Concentrations (mg/L) % Product Performance Septic reduction Requirement Tank After pre-treatment (Advantex) (Treatment Level A) BOD 213 6.8 97 15 TSS 60 < 10.0 >83 15 Chloride 74.6 82.1 - Phosphorus 25.7 28.3 - Nitrate + Nitrite - 0.58 - TKN 139 20.4 85 Total nitrogen 139 21 85 < or = 20 Fecal Coliform - 200 CFU/100 mL 99.9 1,000 CFU/100mL
The total nitrogen and phosphorus levels in the septic tank are double domestic strength due to the high amount of toilet flushing. The Advantex is performing well in terms of BOD, TSS and Fecal Coliform. The nitrogen reduction is at 85% during our sampling.
Page | 5
Recommendations
Park A
The OSTP recommends, since only one set of grab-samples are represented in this study, that more wastewater testing be conducted at this site and typical flow rates established prior to the new system design. It is likely, in order to properly treat this wastewater, the design must include a secondary treatment unit to reduce the RV waste and potentially the nitrogen as the shower house. The range of parameters tested in this report should be repeated monthly during the summer months of 2020 park operation.
Park B
The OSTP recommends that flow data be gathered and analyzed to gain a better understanding of how the systems are working compared to how much use they are getting. The program also recommends that a MPCA certified service provider be hired to manage and maintain these systems to ensure they are consistently evaluated and operating properly.
1. RV Dump Station a. The septic tank needs to be pumped. b. To improve nitrogen treatment the sludge return pump should be changed to be controlled with a time-dosed control panel. Flow data will be needed to set the panel. 2. Campground Shower House and Bathrooms - The septic tank needs to be pumped. 3. Shower house reuse system - We had hoped to sample this system, but it was not operating due to odor issues in the facility. It is recommended that the designer and manufacturer (Water Control Corporation, Ramsey, MN) should be consulted. The UMN could be involved moving forward but would need to review the design and operation and maintenance manual.
Future Work
To gain a better understanding of wastewater characteristics at DNR facilities including shower houses and RV dump stations this sampling program should be extended and expanded to include more sites with multiple sampling event per site. This data could serve as the basis for future state park and similar wastewater treatment system designs.
Page | 6
References
Lowe, KS, Tucholke MB, Tomaras JMB, et al (2009) Influent constituent characteristics of the modern waste stream from single sources. Water Environment Research Foundation, 04-Dec-01, p. 66. www.decentralizedwater.org/research_project_04-DEC-1.asp
MPCA (2016). Minnesota Rules Chapters 7080 through 7083. Minnesota Pollution Control Agency, Subsurface Sewage Treatment Systems Program. St. Paul, Minnesota. 7081.0130 Subpart 2. Waste Concentrations.
Siegrist, Robert L. Decentralized Water Reclamation Engineering. Cham, Switzerland. Springer International Publishing, 2017.
United States Environmental Protection Agency (USEPA) Onsite Wastewater Treatment Systems Manual. February 2002. Office of Water, Office of Research and Development. p.3-29. https://www.epa.gov/sites/production/files/2015- 06/documents/2004_07_07_septics_septic_2002_osdm_all.pdf
Page | 7