An Onsite Wastewater Treatment System Owner’s Manual

Although a septic tank system is more commonly used, a wastewater lagoon system may be an option for single-family residences with slowly percolating, high clay content soils that are not steeply sloped. Lagoon systems include one or more pond-like bodies of water designed with long retention times to receive and treat WASTEWATER. While in the lagoon, WASTEWATER receives treatment through a combination of physical, biological, and chemical processes.

A lagoon system must fit its specific site and use. Designs are based on such factors as the type of soil, the amount of land area available, the slope, the climate, and the amount of sunlight and wind in the area. The most common type of wastewater treatment lagoon used by individual households is the FACULTATIVE lagoon, which are also called stabilization ponds, oxidation ponds, and photosynthetic ponds. They can be adapted for use in most climates, require no machinery, and treat WASTEWATER naturally, using both AEROBIC and ANAEROBIC processes.

How a Lagoon Works

Physical, biological, and chemical processes take place throughout a lagoon to treat WASTEWATER. In FACULTATIVE lagoons, WASTEWATER naturally settles into three fairly distinct layers or zones. Different conditions exist in each layer and treatment takes place in all three.

The top layer is an AEROBIC zone where wind and sunlight play important roles. The WASTEWATER in this part of the lagoon receives oxygen from air, surface agitation caused by wind and rain, and produced by algae. This oxygen makes conditions favorable for AEROBIC bacteria and other organisms living in this zone to treat WASTEWATER. This zone also serves as a barrier for the odors from gases produced by treatment processes occurring in the lower layers.

Names for the middle layer include the facultative, intermediate, or AEROBIC-ANAEROBIC zone. Both AEROBIC and ANAEROBIC conditions exist in this layer in varying degrees. Depending on the specific conditions in any given part of this zone, different types of bacteria and other organisms contribute to WASTEWATER treatment.

The ANAEROBIC zone is the layer at the bottom of a lagoon where little oxygen is present. This area includes a layer of SLUDGE, which forms from the solids that settle out of the WASTEWATER. Here ANAEROBIC bacteria and other organisms provide treatment to reduce the overall organic strength of the WASTEWATER and to slow the accumulation of SLUDGE.

Lagoons provide reliable and passive treatment of WASTEWATER. The US Environmental Protection Agency has established five management models with progressively increasing management controls as sensitivity of the environment and/or treatment system complexity increases. MANAGEMENT MODEL I specifies appropriate program elements and activities where treatment systems are owned and operated by individual PROPERTY OWNERS in areas of low environmental sensitivity.

The objective of this model is to ensure that-

• Systems are designed and installed in accordance with appropriate state and local regulations;
• Homeowners are knowledgeable of their particular system and provide routine MAINTENANCE (INSPECTIONS and pumping) necessary for the system to operate properly, and, if needed;
• Homeowners ensure a MALFUNCTIONING system is repaired in accordance with Missouri law.

This model is generally appropriate for lagoon systems. However, in some sensitive environments, MANAGEMENT MODELS II or III may be recommended.

Figure 1: Lagoon. Lagoons hold WASTEWATER in a watertight basin where AEROBIC and ANAEROBIC processes help treat the water. A lagoon’s large surface area and long retention time use sunlight, air movement and natural processes for WASTEWATER treatment.

Design and Construction

In Missouri, lagoons may not be allowed on lots with less than two and one-half acres of usable land area. During the design and construction phase, the following standards need to be taken into account.

A properly sized and constructed septic tank or aeration treatment unit is recommended preceding the lagoon. Lagoons should be located:

• On slopes of 12% or less.
• In an area open to prevailing winds with the waters edge at least 50 feet from trees that could inhibit wind action or shade the water surface;
• Out of any natural drainage way; and
• To meet the set back distances specified in 19 CSR 20-3.060 Minimum Construction Standards for Onsite Systems.

The water surface area of the lagoon is based on the number of bedrooms (see Table 1: Size of Lagoon at the Three Foot Operating Level). Storm water runoff should be directed away from the lagoon and the design of the berms must prevent entrance of surface water into the lagoon. Any overflow from the lagoon must be kept out of natural drainage ditches and must be dispersed into the soils on the property from which it originated. The lagoon area must be enclosed with a fence.

Table 1: Size of Lagoon at the Three Foot Operating Level

Wastewater Management

WASTEWATER overflow from a lagoon must be dispersed into the soils on the property from which it originated. This may be accomplished by the following methods or as approved by the ADMINISTRATIVE AUTHORITY.

Overflow Pipe

• The pipe should be located as far away from property lines as possible.
• Minimum distance from the outlet to the down slope property line is one hundred feet.
• The outlet pipe must be located out of any natural drainage ditches or swales.

WASTEWATER cannot be concentrated; it should spread out and soak into the soil.

Constructed Terrace Swale

• A swale can be used to lengthen the flow path, spread the WASTEWATER out, and help disperse it into the soil.
• If the distance to the down slope property line is less than 100 feet, a swale must be at least one hundred fifty feet long.

Storage and Controlled Irrigation

This may be needed when there is less than twelve inches of permeable soil over a RESTRICTIVE LAYER.

• To utilize controlled surface irrigation, the pond must be capable of operating up to five feet (5') deep or have a second cell for storage.
• WASTEWATER cannot be irrigated when soils are frozen, covered with snow, or SATURATED.
• During and up to a month after irrigation, access to the application area must be restricted.
• Spray irrigation is not allowed.

Detention/Infiltration Pond

• Detention/infiltration ponds can be used to temporarily store overflow for infiltration into the soil.
• The detention/infiltration pond must be enclosed by a fence.

Maintenance - Grounds keeping, Inspections, Pumping

Although required lagoon MAINTENANCE is not complicated, regular upkeep of the lagoon area is important to ensure the system operates properly.

Grounds keeping

Wind and sunlight at the water surface play important roles in the treatment of WASTEWATER in a lagoon. Surface agitation, of any kind, adds oxygen to the WASTEWATER. Therefore, vegetation around a lagoon should be maintained at least monthly in the spring and summer; lagoons need more frequent upkeep when grass and weeds grow more quickly. 

Mowing grass and controlling weed growth in and around the lagoon is one of the easiest and most important tasks in lagoon MAINTENANCE. Long grass and weeds block wind and provide breeding areas for flies, mosquitoes, and other insects. In addition, weeds can trap trash, grease, and SCUM, which create odors and attract insects, as well as, provides food for burrowing animals that can cause damage to banks and berms. Roots of woody shrubs and trees can create holes in the berm, which become paths for water to leak out of the lagoon.

Inspections

The following should be inspected at least once per year to assure the lagoon is operating safely and properly:

• The fence and gate are in good repair and maintained in a manner that prevents the entrance of children and/or domesticated animals;
• The berm is in good condition, free from evidence of leakage, erosion, or animal burrows;
• The berm is covered with grass or other similar vegetation and maintained, within the fenced area, at a height that does not restrict adequate air movement over the lagoon;
• No trees or bushes are growing close enough to the lagoon to cause shading, organic loading, or root damage;
• Floating vegetation growing in the lagoon is controlled, so as not to interfere with natural treatment processes;
• A minimum distance of 18” inches (24” inches recommended) is maintained between the highest level of WASTEWATER and the top of the berm;
• The depth of WASTEWATER is maintained at a working water level of at least 2’ feet and no more than 5’ feet. For most lagoons, 3’ feet is normal; and
• WASTEWATER overflow is managed and dispersed into the soil on the site.

Pumping

The depth of the SLUDGE layer in lagoons should be checked every two years or as needed. In lagoon systems, SLUDGE eventually accumulates to a point at which it must be removed. How often SLUDGE needs to be removed varies depending on the climate, lagoon design, use, and how well it is maintained. A properly maintained septic tank or aeration treatment unit preceding the lagoon significantly reduces SLUDGE build up in the lagoon.

It is the responsibility of the homeowner or user of the lagoon to contract with a REGISTERED ONSITE WASTEWATER TREATMENT SYSTEM PROFESSIONAL or other qualified SERVICE PROVIDER for the periodic removal and treatment of the accumulated SLUDGE in the lagoon. The owner or user of the system must schedule for the removal and sanitary disposal of excess SLUDGE to manage the WASTEWATER level to prevent WASTEWATER from discharging from the lagoon and flowing off of the property, while maintaining at least eighteen inches of water above the SLUDGE layer.

Lagoon MAINTENANCE includes cutting grass, weeds, and trees growing near the lagoon. The lagoon berm can be damaged when woody plants are allowed to grow. Duckweed growing on the water surface and grass or weeds growing over the waters edge can interfere with treatment and harbor mosquitoes.

The WASTEWATER TREATMENT SYSTEM PROFESSIONAL or other qualified SERVICE PROVIDER is responsible for the proper treatment and disposal of all hauled WASTEWATER by transporting to a municipal sewage treatment plant capable of receiving the waste; transporting to a SLUDGE handling facility which possesses a current and valid permit issued for such activity; or land applying under a current and valid permit for such activity.

Warning Signs of System Malfunctioning

While proper use, INSPECTIONS, and MAINTENANCE should prevent most lagoon problems, it is still important to be aware of changes in your system and to act quickly if you suspect the system is MALFUNCTIONING. The most obvious lagoon issues are easy to spot.

• The presence of weeds and long grass along the berm. The berm must be mowed and weeded regularly;
• The presence of duckweed, watermeal, or hyacinth growing on the water surface. These plants should be physically removed;
• The presence of blue-green algae. This algae is stringy and can clump and block sunlight; it can dominate lagoons when conditions are poor, when pH is low, or when protozoa eat all of the green algae. Blue-green algae can be physically removed like duckweed;
• The presence of an algal bloom. This may occur after periods of cloudy weather or abrupt temperature changes. Matted algae on the surface can block sunlight and cause foul odors and should be broken up and dispersed;
• The presence of odors. Lagoons may occasionally have odors from algal blooms, ANAEROBIC conditions, SCUM, and turnover of the lagoon contents in spring or by temporary overloading, ice cover, or atmospheric conditions. These odors may be controlled by broadcasting sodium or ammonium nitrate over the surface of the pond. In general, the amount of sodium or ammonium nitrate should not exceed two pounds per day until the odor dissipates;
• The observation of short circuiting, or dead spots in the flow pattern, due to obstructions in the lagoon or to wind on the surface. This can cause WASTEWATER to leave the lagoon too quickly, resulting in inadequate treatment of the WASTEWATER;
• The presence of erosion. Controlling burrowing animals around the lagoon can help prevent erosion of berms;
• The presence of burrowing animals; muskrats and other burrowing animals can be discouraged by weeding and mowing the lagoon berms;
• The change of water color. Bright rich green color indicates good conditions; dull green or yellowish color can indicate an undesirable type of algae is becoming dominant in the lagoon; gray or black color can indicate ANAEROBIC conditions; and tan, brown, or red color can indicate either soil in the water from berm erosion or the presence of algae with different pigmentation; and
• The presence of SLUDGE accumulation. SLUDGE in the bottom of lagoons should be measured at least once per year and removed as needed.

Onsite systems fail when partially treated WASTEWATER comes into contact with groundwater. This type of failure is not easy to detect, but can result in the pollution of wells, nearby streams, or other bodies of water.

If you notice any of these signs or you suspect your system may be having problems, contact a qualified SERVICE PROVIDER or the local onsite WASTEWATER ADMINISTRATIVE AUTHORITY for assistance.

Lagoon Do’s and Don’ts

Proper OPERATION and MAINTENANCE of your onsite system can prevent costly repairs or replacement and can protect your property value. Observing the following recommendations will help to keep your system operating properly.

Do’s

• Obtain the necessary permits from the appropriate ADMINISTRATIVE AUTHORITY before making any repairs.
• Use REGISTERED ONSITE WASTEWATER TREATMENT SYSTEM PROFESSIONALS and qualified SERVICE PROVIDERS.
• Keep the system accessible for INSPECTIONS and pumping, yet locked or otherwise secured to prevent accidental entry.
• Have your septic tank inspected annually if it has an EFFLUENT screen or every two years if it does not.
• Have your septic tank pumped routinely. Pumping your septic tank when needed may be the single most important thing you can do to protect your soil treatment system and your investment.
• Keep detailed records regarding the system, its location, contract service agreement, service visits, and MAINTENANCE performed.
• Conserve water to avoid overloading the onsite system, use high-efficiency fixtures, and promptly repair any leaky faucets or toilets.
• Divert other sources of water, like roof drains, house footing drains, and sump pumps, away from the soil treatment area.
• Have your private water well tested periodically or if you experience any warning signs of the system MALFUNCTIONING (contact your local public health agency).

Don’ts

• Don’t enter a sewage tank. Poisonous gasses or a lack of oxygen can be fatal.
• Don’t allow the overflow from the lagoon to leave your property, even during wet weather.
• Don’t plant a garden, trees, or shrubbery near the lagoon. This could cause shading, SLUDGE build-up, and increase odor levels.
• Your sewage system is not a trash can. Don’t put dental floss, feminine hygiene products, flushable wipes, condoms, diapers, cotton swabs, cigarette butts, coffee grounds, cat litter, paper towels, paint, pesticides, or other hazardous chemicals into your system.
• Don’t allow children or pets to play in the lagoon; they could come into contact with WASTEWATER that could make them sick.
• Don’t drive or park vehicles or allow livestock on any part of your sewage tank system. Doing so can compact the soil or damage the pipes, tank, or other onsite system components.
• Don’t build over any part of your system; this includes patios, carports, and other structures.