An Onsite Wastewater Treatment System Owner’s Manual

The simplest ONSITE WASTEWATER TREATMENT SYSTEM, a septic tank and a gravity dispersal trench system, will not work on every site. Even a pressure distribution network installed in dispersal trenches cannot be expected to treat and disperse WASTEWATER adequately in some soils. Subsurface drip dispersal, also called drip irrigation, systems use small flexible drip lines with emitters to spread WASTEWATER uniformly in the soil treatment area. Drip lines are installed so that there is an emitter for every four square feet, which means more uniform dispersal than is possible with a trench system. Because drip systems can spread small doses of wastewater evenly over large areas, they can be used on many difficult sites.

Drip lines can be installed on sloping and irregular shaped lots. Drip dispersal systems generally use the better soil properties six to eight inches below the surface for treating WASTEWATER, which is also in the plant root zone. Emitters discharge WASTEWATER at slow rates, generally a gallon per hour or less. This combination of versatile installation and shallow, slow, controlled dispersal in the root zone allows effective WASTEWATER treatment on almost any site.

How Subsurface Drip Dispersal Works

AEROBIC pretreatment, such as a bio-filter or an aeration treatment unit, is used before most drip dispersal systems. A very fine EFFLUENT screen (or filter) is essential to prevent solids from clogging the drip line emitters. In addition, MAINTENANCE of the pretreatment component is vital. If neglected, WASTEWATER solids can pass through pretreatment and clog the screen, emitters, and the soil.

Some sites with soil suitable for treating and dispersing primary treated WASTEWATER can use a septic tank for pretreatment. However, when dispersing primary treated WASTEWATER, a larger soil treatment area may be needed and the drip system EFFLUENT screens must be flushed automatically because the WASTEWATER contains more organic matter and solids.

A pump tank then collects the pretreated WASTEWATER and when there is enough for a full dose, timer controls activate the pump. Screened WASTEWATER is dosed to the network of drip lines and distributed evenly over the soil treatment area through emitters spaced in an approximate 2-foot by 2-foot pattern. Soil treatment areas are sometimes split into smaller zones and dosing alternates between these zones.

Drip lines can be plowed into the soil or installed in narrow trenches that are backfilled with soil. The drip lines are installed in direct contact with the soil without using any gravel. Because storage volume in the soil is limited, small doses ensure the soil is not SATURATED and that WASTEWATER is not forced to the soil surface. Resting time between doses can also help provide better treatment and dispersal. WASTEWATER should be applied at a rate that matches the soil conditions to help prevent saturating the soil; a range of drip emitter rates are available to match different soil types.

Benefits of drip dispersal include:

• Small flexible drip lines have the ability to fit to site contours and irregular shaped areas;
• Narrow trenches or plowed-in drip lines create less site disturbance;
• Shallow drip line installation uses the surface soil layers that are usually best for wastewater treatment;
• Shallow drip lines in the root zone promotes water reuse through plant evapotranspiration;
• Matching slow emitter rates and dose sizes to the soils improves wastewater treatment.

In limiting soil conditions, subsurface drip systems can disperse pretreated WASTEWATER uniformly and enhance the soil's ability to provide final treatment and recycle the 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 II specifies program elements and activities where more complex designs are employed to enhance the capacity of conventional systems to treat and disperse WASTEWATER. Because of system complexity, contracts with qualified SERVICE PROVIDERS are needed to ensure proper and timely MAINTENANCE.

The objectives of this model are to ensure that:

• Alternative systems are designed and installed in accordance with appropriate state and local regulations;
• Homeowners are knowledgeable of their particular system and maintain a contractual agreement with a qualified SERVICE PROVIDER to provide routine MAINTENANCE (INSPECTIONS, flushing, and pumping) necessary for the system to operate properly;
• Homeowners ensure a MALFUNCTIONING system is repaired in accordance with Missouri law.

This model is generally most appropriate for subsurface drip dispersal systems. However, in some sensitive environments, MANAGEMENT MODELS III or IV may be recommended.

Design and Construction

Effective soil treatment depends on matching the distribution and dispersal methods to the site and soil. The size of the soil treatment system is determined by the anticipated WASTEWATER flow and the soil properties in the soil treatment area. Soil properties and the depth to bedrock or the water table also help determine the depth of the dispersal system. Drip dispersal can often be installed shallower than other distribution systems. A thorough site evaluation must be conducted when the wastewater treatment system is in the planning stages. Wastewater system failures are often caused by the improper choice of the system type and/or location. Subsurface drip dispersal systems must be designed by a Missouri Professional Engineer.

Drip Dispersal

Minimum treatment area must be based on an accurate site/soil evaluation;

Minimum drip line length is based on 2-foot spacing;

A drip emitter can be considered to cover at most four (4) square feet;

Drip lines must be located:

• To follow the contours of the ground and be installed level;
• Out of any surface water drainage;
• To allow drip lines and manifolds to drain back to sewage tanks to reduce the potential for freezing;
• To observe required setback distances as specified in 19 CSR 20-3.060.

Distribution

A drip dispersal pressure distribution network design includes the:

• Drip line model and drip emitter rate in gallons per hour;
• Maximum length of drip lines;
• Zoning requirements if applicable;
• Diameter of the supply and return manifolds;
• Air release/vacuum breaker valves and locations;
• EFFLUENT screen or disc filter model to protect drip emitters from clogging;
• Flow and pressure required for dosing to ensure uniform WASTEWATER distribution;
• Flow and pressure necessary to effectively flush the drip lines and manifolds to prevent buildup of slime or solids;
• Pump capacity requirements;
• Dose volume needed for the system to function properly. It must be large enough to include the volume to fill and pressurize the drip lines and ensure uniform distribution, and it must not be so large that WASTEWATER is forced to the ground surface; and
• Timer dose control settings.

Maintenance

The importance of proper design, installation, MAINTENANCE, and monitoring of drip systems including the pretreatment component can not be overstated. If a design focuses on the long term performance of the system, some of the OPERATION and MAINTENANCE requirements for drip systems can be automated. Programmable timers can adjust dose volumes to accommodate daily flows from the typical water use up to the maximum design flow. Valves and controllers are available to alternately dose different zones and automatically flush EFFLUENT screens and the drip lines. Options are available to remotely monitor alarms or to monitor and even control system performance.

Inspection

An onsite INSPECTION of drip dispersal soil treatment systems must be conducted at least every six months and must include assuring:

• The pretreatment component(s) is operating properly (see Chapters 1, 2, 3, and 4 of these guidelines);
• The pump and controls functions according to design (see Chapter 6 of these guidelines);
• Air release/vacuum relief valves at high points of system/zones function properly;
• EFFLUENT screens (or disc filters) are in good condition and not clogged;
• If applicable, automatic flushing of screens and/or drip lines functions properly;
• There are no signs of surfacing WASTEWATER;
• There is no evidence of unequal WASTEWATER distribution in the soil treatment area;
• No strong, foul odors are present near the soil treatment area;
• Vegetation is maintained on and around the soil treatment area;
• The surface of the soil treatment area has no areas of depression for surface water to collect;
• The soil treatment area is not subject to traffic, heavy equipment, or used as pasture for domesticated animals;
• The soil treatment area is not used for outbuildings and/or structures, such as patios and above-ground swimming pools;
• There is no visible damage to the drip dispersal lines;
• There is no evidence of ponding or saturation along the supply or return lines and the lines drain freely after each dose.

Service/Pumping

• Service the pretreatment component as needed and recommended by the manufacturer;
• Service the pump in accordance with Chapter 6 of these guidelines;
• Contract with a REGISTERED ONSITE WASTEWATER TREATMENT SYSTEM PROFESSIONAL or other qualified SERVICE PROVIDER for the removal and treatment of the contents of the pretreatment component and pump tank in accordance with Chapter 1 or 2 of these guidelines;
• Manually flush or replace EFFLUENT screens (or disc filters) as needed and recommended by the manufacturer;
• Manually flush solids that may accumulate in the drip lines and manifold lines (return flow to the system) at least every six (6) months;
• Check operating pressure and flow rate while the pump is running to ensure they meet design specifications; and
• Perform any additional MAINTENANCE recommended by the manufacturer.

Warning Signs

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

• Odors, surfacing WASTEWATER, or wet spots in the soil treatment area.
• Standing liquid over the soil treatment system, even during dry weather. This may indicate an excessive amount of WASTEWATER is moving up through the soil, instead of downward.
• Plumbing or sewage tank backups (often a black liquid with a disagreeable odor).
• Slow draining fixtures.
• Gurgling sounds in the plumbing system.
• An alarm that is activated.
• If you have a well and tests show the presence of coliform (bacteria) or nitrates, your soil treatment system may be MALFUNCTIONING.

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.

Subsurface Drip Dispersal 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.
• Conserve water to avoid overloading the onsite system, use high-efficiency fixtures and promptly repair any leaky faucets or toilets. Soil treatment systems do not have an unlimited capacity to disperse WASTEWATER.
• Divert other sources of water, like roof drains, house footing drains, and sump pumps away from the soil treatment area.
• Keep your sewage tank(s) accessible for inspections and pumping; yet locked or otherwise secured to prevent accidental entry.
• Have your septic tank, ATU, or other pretreatment component inspected and pumped according to the guidelines for that component.
• Have your pump tank inspected at the same frequency as your septic tank or other pretreatment component and pumped if needed.
• If your pump tank alarm is activated – contact your SERVICE PROVIDER promptly to repair the system and minimize your water usage in the interim.
• Plan ahead—soil treatment systems do not last forever. If you have additional space, consider reserving some area from development so that it can be used for a replacement soil treatment system when needed.
• Know where the soil treatment system and replacement area are located. It is easier to protect the system when you know where the components are.
• Landscape the system properly. Plant and maintain grass over the soil treatment system to prevent soil erosion.
• Keep heavy equipment off the soil treatment area, cars and equipment must not be driven or parked over the soil treatment system.
• Contact a qualified SERVICE PROVIDER if you experience problems with your system, such as surfacing WASTEWATER in your yard or other warning signs the system may be MALFUNCTIONING.
• Keep detailed records regarding the system, its location, make/model, contract service agreement, service visits, and MAINTENANCE performed.
• Use commercial bathroom cleaners and laundry detergents in moderation and only according to manufacturer’s directions.
• 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 septic tank, pump tank or any sewage tank. Poisonous gasses or a lack of oxygen can be fatal.
• Your septic tank 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 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 on any part of your onsite wastewater system. Doing so can compact the soil in your soil treatment area or damage the pipes, tanks, or other system components.
• Don’t allow large animals and livestock to roam over the soil treatment system. Soil compaction prevents oxygen from getting into the soil and prevents water from flowing away from the soil treatment system.
• Don’t build over any part of your onsite wastewater system; this includes patios, carports, and other structures.
• Don’t pave or use landscaping plastic over the soil treatment system; bacteria in the soil need oxygen to properly treat WASTEWATER.
• Don’t dig in the soil treatment area, as damage to the pipes may occur.
• Don’t plant a garden over the soil treatment system. You risk the possibility of food contamination.
• Don’t plant more trees and shrubs in or near the soil treatment area.
• Don’t attempt to pump your own sewage tank; use the services of a qualified SERVICE PROVIDER.