No-Discharge Wastewater Treatment
No-Discharge Wastewater Treatment
The Missouri Clean Water Law is intended to conserve, protect, maintain, and improve the quality of Missouri’s waters. In addition, the goal of the federal Clean Water Act is the elimination of all discharges. Therefore, the Missouri Department of Natural Resources encourages wastewater treatment systems to achieve no-discharge. Water quality standards and effluent limitations will only become more stringent in the future. While a no-discharge system may not be feasible for every wastewater system, it must be evaluated during the department’s antidegradation, construction permit, and operating permit review processes.
Did you know?
- 53 percent of publicly owned treatment works (POTWs) in Missouri have a design flow of 100,000 gallons per day or less and serve a population equivalent of 1,000 or less.
- Missouri has 861 discharging lagoon wastewater treatment facilities.
- Missouri has 147 no-discharge facilities.
- 25 percent of the construction permit applications received by the department from 2013 to 2016 were for the construction of no-discharge facilities.
Of the 861 discharging lagoon wastewater treatment facilities in Missouri, 79 percent are considered a small facility with a design average flow of less than 0.1 million gallons per day (MGD); 17 percent are a medium facility with a design average flow of 0.1 MGD to 0.5 MGD; and 4 percent are a large facility with a design average flow of 0.5 MGD or greater. Refer to Figure 1. below. These lagoon wastewater treatment facilities are facing increasingly more stringent effluent limitations.
Figure 1. Discharging lagoon facilities in Missouri and the corresponding size breakdown.
Of the 147 no-discharge wastewater treatment facilities in Missouri, 71 percent are considered a small facility with a design average flow of less than 0.1 million gallons per day (MGD); 21 percent are a medium facility with a design average flow of 0.1 MGD to 0.5 MGD; and 8 percent are a large facility with a design average flow of 0.5 MGD or greater. Refer to Figure 2. below.
Figure 2. No-discharge facilities in Missouri and the corresponding size breakdown.
* This data was collected from the department’s Missouri Clean Water Information System on June 23, 2016.
Regionalization can range from physically connecting to another wastewater system or consolidating two or more treatment facilities, to administrative solutions such as cooperative purchasing, contract billing, or shared operator employment. Physically connecting to another wastewater system reduces the number of discharges to waters of the state because only the discharging wastewater treatment facilities are required to have a Missouri State Operating Permit (MSOP).
Typically, regionalization decreases the operation and maintenance portion of user rates. Larger wastewater systems have greater technical, managerial, and financial capabilities in general. This leads to quicker response during emergencies and a better position to finance capital improvement projects.
Barriers to regionalization include local opinion, geography, and large upfront capital costs. Local issues could be improved upon with open communication with neighboring systems. In remote rural areas, the geographic distance between wastewater systems may be too great for a physical connection. In these instances, administrative solutions should be considered. Where physical connection or consolidation is assessed, large upfront capital construction costs are often necessary. The Department of Natural Resource’s State Revolving Fund loan program awards additional priority points for regionalization projects. A low-interest State Revolving Fund loan could help financing construction projects. More information on the State Revolving Fund loan program can be found online here.
Regionalization is a complex process and not feasible for every system, but it could be a cost effective approach for some. In addition, a regional connection is a requirement in some MSOPs; 10 CSR 20-6..010(8)(A) requires a facility to connect within 90 days of notice of connection availability by a higher level continuing authority.
Surface Land Application
Surface land application is defined as the application of wastewater to the land surface at a controlled rate. Surface land application benefits the crop, soil, and eliminates a discharge to waters of the state. Below are the most common methods of surface land application in Missouri.
A center pivot is a truss supported sprinkler system with a fixed central wastewater supply. The center pivot moves in a circle to irrigate 20 to greater than 400 acres. The center pivot is the most common land application method for high acreage sites with crop fields or hay. This option has a higher capital cost but is less labor intensive and offers efficient irrigation.
Solid Set Sprinklers
Solid set sprinklers apply wastewater by means of permanently or semi-permanently installed sprinklers using a rotating nozzle. These sprinklers allow a high volume of wastewater to be applied. Harvesting a crop can be difficult to maneuver around these sprinklers so they are frequently used with hay.
Traveling gun systems are self-propelled, single large gun sprinkler units that are connected to the wastewater supply by a hose. Since the operator has to reposition the traveling gun after each pass, this system is more labor intensive.
Operation and Maintenance
Surface land application should occur whenever weather and soil conditions are suitable, while adhering to the application rates listed in the MSOP. These application events must occur during the daylight hours unless a nighttime plan is approved by the department. The wastewater treatment facility is required to maintain the storage basins in good operational condition, including but not limited to: mowing, removing any woody vegetation, sludge monitoring and removal, and maintaining any security features such as fences and lockable gates. Rodents, such as muskrats, will need to be eliminated and any damage sustained to the berms repaired as appropriate. Also, the operational control monitoring requirements in the Clean Water Commission Treatment Plant Operations, 10 CSR 20-9, must be performed as well as any MSOP specific monitoring.
Subsurface Soil Dispersal Systems
A sustainable management plan must be devised and followed to ensure any subsurface soil dispersal system is sustainable, protective of public and the environment.
Conventional subsurface application includes the collection system, followed by a septic tank and then flows by gravity to a drain field for ultimate dispersal. Conventional subsurface systems in the past have been referred to as “septic systems” but the septic system is just a component of the overall treatment system. This option works well for single family dwellings or. Drawbacks to the conventional system include more land required for the drain field than with other subsurface methods and Equal dispersal is another drawback once the field has greater than 500 linear feet.
Low-Pressure Piping (LPP)
A low-pressure distribution system is a shallow, low pressure-dosed subsurface soil dispersal system with a network of small diameter perforated pipes placed about 10 to 12 inches deep in narrow trenches, spaced 5 feet apart. The system also includes a dosing tank where the effluent is held until one or more pumps deliver it under relatively low pressure to the lateral lines within the soil. Some of the limitations with low-pressure distribution systems are soils with shallow water tables or limiting layers, steep slopes, and limited available area. The potential for clogging the lateral line holes with solids or roots is also a shortcoming, along with limited storage capacity around the laterals. Also, while a low-pressure piping system can function in a variety of climate conditions, protection from freezing temperatures for some of the components must be provided.
The flexibility in geometry, design, construction and the ability to distribute effluent uniformly allows the drip tubing to be installed in wooded areas; on steep slopes; in soils with high water tables or a limiting layer; and in areas where the depth to bedrock is limiting. Drip systems have the potential to be used in higher risk areas near sensitive water bodies that were previously unsuitable for wastewater treatment systems.
Also, while a low-pressure piping system can function in a variety of climate conditions, protection from freezing temperatures for some of the components must be provided.
Source: Iowa DNR Sand Mound Technology Assessment and Design Guidance, August 2007
The mound is the treatment and dispersal component of a complete on site wastewater treatment system. Major components of the mound system are the primary treatment septic tank, the pressure dosing component and the optional, but recommended secondary treatment component to further treat the wastewater. Following the treatment in the primary and secondary treatment components, the water is dosed into the mound system.
The soil is the ultimate receiver of the wastewater and the most important part of the mound component. It is also the most variable and must be carefully evaluated. The discharged wastewater moves through the soil vertically and/or horizontally and must remain underground. Mound systems are designed to overcome site limitations, such as slow or fast permeability soils, shallow soil cover, and a high water table.
Operation and Maintenance
Operations and Maintenance is a crucial component of subsurface systems working. An Operation and Maintenance manual must include a detailed discussion of the operation, controls, site and equipment maintenance, expected dosage rate, sampling and analysis, trouble shooting, chemicals management, personnel records, reporting, safety and emergency response procedures. The manual must be maintained and updated regularly, be available on site, and submitted to the department when required.
The objective of a geohydrologic evaluation is to examine site-specific geologic and hydrologic conditions and determine the potential impacts to groundwater. The Missouri Geological Survey also determines whether a stream is considered gaining or losing. These evaluations are required for new and modified earthen basins and surface and subsurface land application sites. Refer to 10 CSR 20-8.020(17)(A)1. – 3. and 10 CSR 20-8.110(4)(C)8.C.(VII).
Earthen basins shall not be located in areas receiving a severe overall geological collapse potential rating. Severe overall geological collapse potential ratings are more common in southwest Missouri which has karst features. Karst features are underlain by highly permeable soils and bedrock and are susceptible to contamination from the surface and the formation of sinkholes.
A soils report is required for all proposed subsurface soil dispersal systems to determine the soils loading rate. Additionally, a soils report is required for proposed surface land application systems desiring to land apply greater than 24 inches per year. A qualified individual must conduct the soils evaluation and prepare the report. This individual must have successfully completed fifteen semester credit hours of soil science course work including at least three hours of course work in soil morphology and interpretations.
The soils report can be generated only after a thorough, systematic investigation of the soil properties and landscapes of the proposed soil treatment area(s) has been conducted. Soil observation pits (backhoe or hand dug) must be dug to a depth to reveal the major soil horizons. The number of observation pits must be sufficient to adequately represent the primary and reserve soil treatment area and may be supplemented with soil borings to help determine the extent of similar soil properties. Detailed soil profile descriptions for each observation pit shall be submitted as described in the Soil Survey Manual. (Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18; www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ref/?cid=nrcs142p2_054262) The soils report shall also contain a map that clearly delineates the extent of the soil treatment area (primary & reserve), different soils and landscapes within the soil treatment area, observation pits (numbered), supplemental borings, water wells, sinkholes, existing and proposed easements, natural drainages, known and proposed utilities, and any other soil and site characteristics that could influence the soils ability to effectively treat the effluent. A copy of the US Geological Survey topographic map and US Department of Agriculture County Soil Survey must be provided with the soil treatment area clearly delineated. The soils report shall provide an application loading rate for each different type of soil present and/or zone of treatment.
The report should include a conclusion summarizing the results and shall be signed and dated by the individual responsible for the documentation contained within it.
Missouri State Operating Permits
A common misperception is that a no-discharge wastewater treatment facility does not require an operating permit. However, a Missouri State Operating Permit is required. These operating permits contain reporting requirements and conditions to be met. Please read through the permit carefully.
General Permit MO-G823
General permits are issued to multiple locations and entities where activities are similar enough to be covered by a single set of requirements. The conditions in general permits are placed on public notice prior to being issued to applicants. After the master general permit is finalized, it cannot be modified. All facilities receiving a general permit must adhere to the conditions contained in the permit until it expires or the facility obtains a site-specific permit.
The general permit MO-G823XXX is for private domestic wastewater no-discharge facilities with a design flow of less than 50,000 gallons per day. Refer to the Applicability section of the MO-G823 permit template for more details which can be found online here.
Site Specific Permit
Most no-discharge MSOPs are site specific and reflect the unique site of the no-discharge facility and land application area. These permits usually have a five year cycle. As the permit expires, it is re-drafted, modified if needed, then placed on public notice for 30 days. When on public notice, the draft permit is open for comments. After the 30-day public notice period ends, comments are reviewed and the permit is issued with any needed changes.
- Conversion to a No-Discharge Irrigation System From a Discharging Lagoon System--PUB2669
- Evaluating Wastewater Treatment Alternatives for Small Communities with Lagoons--PUB2587
- Minimum Storage Days Map
- Missouri Climatic Atlas for Design of Land Application Systems
- No-Discharge Alternative Evaluation--PUB2665
- No-Discharge Operation and Maintenance Manual Checklist--PUB2704
- No-Discharge Operator Math
- Planning a Wastewater System Project--PUB 2648
- Subsurface Soil Dispersal Systems--PUB2435
- Wastewater Irrigation Frequently Asked Questions--PUB2668