Case Study: Assessment of Campground Wastewater Treatment Systems

Case Study: Assessment of Campground Wastewater Treatment Systems

Wastewater sampling at the campground shower house

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The University of Minnesota’s Onsite Sewage Treatment Program did an assessment of septic systems at two state parks, both owned and managed by the Department of Natural Resources. Two waste streams were evaluated at each site:

  1. An RV dump station
  2. A campground shower house with no laundry

The parks were sampled during 2019 during the campgrounds’ busy summer season.

Current system overview

1. Park A - The current system needs replacement, and a new system is scheduled to be designed and installed in 2020. Sampling was done at this site as a starting point to better understand the waste strength being produced. The samples were collected after primary settling in a septic tank.

2. Park B - The system for the RV dump station was designed for 1,800 gallons per day. There is a 6,000-gallon septic tank, 4,000-gallon surge tank, 2,000-gallon clarifier tank and 2,000-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 that on a monthly basis is manually operated to return sludge to the septic tank. The system has three tanks: a 6,000-gallon septic tank, 4,000-gallon pump tank and 2,000-gallon recirculation tank. The system has an AdvanTex AX-100 recirculating secondary treatment unit (Orenco Systems).


Park A - The wastewater contaminant levels at both sampled locations indicated 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 assessment only included one round of sampling, and the numbers represented in Table 1 should not be used as the sole characterization of the wastewater characteristics.

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 pretreatment 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. 

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.

What did we learn?

For Park A that needs a new system, since only one set of grab samples are represented in this study, more wastewater testing be conducted at this site and typical flow rates established prior to the new system design. It is likely that, 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.

The Park B RV dump station with the Nibbler pretreatment unit.
The Park B RV dump station with the Nibbler pretreatment unit.

For Park B, it is recommended 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 Minnesota Pollution Control Agency-certified service provider be hired to manage and maintain these systems to ensure they are consistently evaluated and operating properly.

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 events per site. This data could serve as the basis for future state park and similar wastewater treatment system designs. View a full version of this report for more information.


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