An Onsite Wastewater Treatment System Owner’s Manual

The most common type of ONSITE WASTEWATER TREATMENT SYSTEM, a conventional septic tank and gravity dispersal trenches, is not suited for all soil conditions. For sites with limited land area, poor soil conditions, or where the water table is too high to allow the soil adequate time to treat the WASTEWATER before it reaches groundwater, additional treatment can be provided by constructed wetlands systems, also called vegetated submerged beds. Subsurface flow constructed wetlands are designed to use natural processes to remove impurities from WASTEWATER through a combination of physical, biological and chemical processes. Free water surface wetlands are not allowed for onsite wastewater treatment because people and animals would be exposed to WASTEWATER at the wetlands surface. Wetlands systems are usually passive and require no energy, however, some effort will be needed to ensure a wetlands wastewater treatment system fits with your landscaping.

How a Wetlands Works

Natural wetlands, marshes, swamps, and bogs play an important role in protecting water quality. Constructed or artificial wetland systems mimic the treatment that occurs in natural wetlands by relying on plants and a combination of naturally occurring biological, chemical and physical processes to remove pollutants from the water. Because constructed wetland systems are designed specifically for WASTEWATER treatment, they typically work more efficiently than natural wetlands and can serve as an alternative when conventional systems are not suitable.

A wetlands may be designed to contain two cells or zones. They are constructed by excavating shallow earthen ponds, which may be lined, and are filled with up to 18 inches of river rock or other granular media and planted with aquatic vegetation. A septic tank or other pretreatment component precedes the wetlands to keep grease and larger solids from clogging the wetlands. WASTEWATER from the septic tank enters the front end of the wetlands and is spread out across the width of the bed through a perforated pipe. WASTEWATER flows through the media and plant roots where it is treated by attached bacteria and other microorganisms. At the back, or outfall, of the wetlands is another perforated pipe that collects the treated water. An adjustable device controls the water level and allows treated WASTEWATER to flow into a second cell, to a soil treatment system, or lagoon for further treatment.

The quality or level of treatment is determined by how long the WASTEWATER takes to pass through the media. During the growing season, plants use more water and increase the retention time; although roots still filter WASTEWATER when plants are dormant, retention time and water treatment is decreased.

Wetlands 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 wetlands systems. However, in some sensitive environments, MANAGEMENT MODELS II, III, or IV may be recommended.

Design and Construction

Wetlands may be constructed with one or two zones or cells; the first cell must be sealed or lined to hold water and the second cell may be unlined to allow for some percolation of water.

Wetlands must be located:

• In an area easily accessible for MAINTENANCE;
• To meet sewage tank set back distances specified in 19 CSR 20-3.060 Minimum Construction Standards for Onsite Systems;
• To ensure drains and dispersal methods work properly.

Wetlands sizing is based in part on winter temperatures; in mid-Missouri a typical wetlands’ surface area would be 330 square feet per bedroom.

Importance of Proper Plant Selection

Selecting the correct plants reduces MAINTENANCE and increases the life of the system. Plants should be native and noninvasive and selected for their ability to grow root systems in the media and WASTEWATER, while not producing excessive amounts of growth above the wetlands surface.

The ideal design of a wetland has two sections or zones of treatment. The first section receives and mixes WASTEWATER from the septic tank. Plants that pump oxygen to their roots and are nutrient loving should be placed here. These plants are usually hard-stemmed marsh plants that have tiny tubes for transporting oxygen to their roots. Commonly used plants are bulrushes and reeds. These plants are able to grow extensive roots even in ANAEROBIC conditions.

In the second section or the back of the wetlands, nutrients are reduced. Flowering, soft-stemmed, nutrient tolerant plants work best in this section. These plants help transport water out of the system by evapo-transpiration.

Maintenance - Grounds keeping, Inspections, and Service

Required MAINTENANCE is not complicated; however, it is important to keep the system operating properly. Some additional work may be needed if the appearance of your wetlands is important.

Grounds keeping

A homeowner can expect to spend some time weeding and trimming plants to maintain the wetlands. The amount of MAINTENANCE required is largely determined by the type of plants growing in the wetlands. Controlling plant growth in the wetlands is important. Weeds may provide food for burrowing animals that can cause damage to berms or dig in the wetlands, and dead plant material left in the wetlands can clog the system. Another important MAINTENANCE task is assuring that the gravel surface is relatively level and no WASTEWATER is exposed on the wetlands surface.

Inspections

Wetlands should be inspected at least annually and as recommended by the designer. The INSPECTION may be conducted by the homeowner, a REGISTERED ONSITE WASTEWATER TREATMENT SYSTEM PROFESSIONAL, or other qualified SERVICE PROVIDER. The INSPECTION should include assuring:

• The water level in the wetlands cell(s) is approximately two inches below the gravel media surface at the inlet end, with no evidence of ponding at the surface;
• There is no evidence of burrowing animal activity;
• The berm and liner are in good condition, free from evidence of leakage, erosion, or animal burrows;
• The water level control structure and lid/cover is watertight;
• Lids and covers are locked or otherwise secured to prevent accidental entry;
• A minimum freeboard distance of six inches is maintained between the surface of the media and the top of the berm;
• No solids have collected in the inlet pipe;
• Vegetation is maintained, with no trees or shrubs near the cells;
• The pretreatment component, such as a septic tank or ATU, is operated and maintained in accordance with Chapter 1 or 2 of these guidelines;
• If applicable, pump(s) function in accordance with Chapter 6 of these guidelines; and
• The soil treatment system is maintained in accordance with Chapter 8, 9, or 10 of these guidelines.

Service

The following MAINTENANCE items should be routinely conducted to assure a properly functioning wetlands:

• Repair any leaks;
• Manage water level to promote vegetation growth and minimize freezing;
• Remove brown or dormant vegetation during winter months;
• Level the gravel/media surface;
• Check water level in cleanouts on the inlet distribution pipe;
• If applicable, clean the distribution pipe and tees; and
• Repair any erosion on berms.

Final Treatment and Dispersal

Although properly operated and maintained wetlands can produce cleaner EFFLUENT than a septic tank alone, the WASTEWATER leaving the wetlands must receive further treatment before it is ready to be returned to the environment. Final treatment and dispersal options include gravity or pressure distribution soil treatment systems or a lagoon system. Rainfall onto the wetlands surface area should be considered when designing a soil treatment system.

Warning Signs of System Malfunctioning

While proper use, INSPECTIONS, and MAINTENANCE should prevent most onsite system 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 onsite system failures are easy to spot.

• Surfacing SEWAGE, pooling water or soggy soil around your wetlands;
• Plumbing or septic tank backups;
• SEWAGE odors in the house or yard;
• Plants displaying signs of stress, such as, wilting or refusal to bloom; and/or
• Tests show the presence of bacteria in well water.

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 onsite system may be having problems, contact a qualified SERVICE PROVIDER or the local onsite WASTEWATER ADMINISTRATIVE AUTHORITY for assistance.

Wetlands Do’s and Don’ts

Proper OPERATION and MAINTENANCE of an 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 SYSTEM PROFESSIONALS and qualified SERVICE PROVIDERS for routine INSPECTIONS, MAINTENANCE, and pumping; and if you experience problems or observe any warning signs that the system may be MALFUNCTIONING.
• Conserve water to avoid overloading the onsite system, use high-efficiency fixtures and promptly repair any leaky faucets or toilets.
• Have your system inspected annually and as recommended by the designer.
• 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 wetlands system and your investment.
• Landscape the system with appropriate aquatic vegetation; routinely check for signs of diseases and/or stress.
• Replace dead plants as needed and remove “volunteer” weeds, trees, and shrubs from the wetland.
• Use commercial bathroom cleaners and laundry detergents in moderation and only according to manufacturer’s directions.
• Keep detailed records regarding the system, its location, make/model, contract service agreement, service visits, and MAINTENANCE performed.
• 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 lack of oxygen can be fatal.
• Your sewage system is not a trash can. Don’t put dental floss, feminine hygiene products, condoms, flushable wipes, diapers, cotton swabs, cigarette butts, coffee grounds, cat litter, paper towels, paint, pesticides, or other hazardous chemicals into your system.
• Don’t use caustic drain openers for a clogged drain. Instead, use boiling water or a drain snake to open clogs.
• Don’t drive or park vehicles or allow livestock on any part of your system. Doing so can compact the soil in your soil treatment area or damage the pipes, tank, wetlands, or other onsite system components.
• Don’t apply herbicides or pesticides on or near the system.
• Don’t plant a garden in your wetland. You risk the possibility of food contamination.
• Don’t allow children or pets to play in the wetlands; they could come into contact with WASTEWATER that could make them sick.