Septic systems, when properly designed, installed, operated and maintained, provide effective treatment of household sewage at a very reasonable cost. Unfortunately because the septic system is buried "out of sight" in the backyard, it often becomes "out of mind." But, a septic system, just like a car, appliance, or tractor must be properly operated and maintained to ensure long-term, cost effective service.
Management = Operation + Maintenance + Monitoring Systems
The goal of on-site sewage treatment is to protect human health and the environment by safely recycling wastewater back into the natural environment in a cost-effective manner. Effective on-site treatment of wastewater is dependent on proper design, installation, operation and maintenance of the system. A well-designed system will not properly treat sewage over its intended life without appropriate operation and timely maintenance! Good management of an on-site system will improve the performance and extend the life of the system resulting in reduced total cost to the owner with increased reliability and satisfaction.
Management = Operation + Maintenance + Monitoring
One of the 'hottest topics' in on-site sewage treatment today is the management of systems! Once a well-designed system — including provisions for management - has been properly installed (the responsibility of the designer, installer and inspector) it must be used, watched and taken care of to meet its owner's expectations. This is no different than any other piece of equipment we own.
"Standard" systems have been designed to require minimal management. Existing codes and rules have paid minimal attention to management and few if any enforcement agencies have provided significant encouragement for owners to follow good management practices. This lack of attention to good management has often proved costly to homeowners and the environment. We must now make a concerted effort to increase our attention to management of all systems — standard and 'alternative'.
'Operation' is the day-to-day use of the system by the residents. The 'users' of the system control the quality, quality and pattern of the wastewater entering the system. The performance of septic systems is greatly influenced by what enters it!
"Using" water does not mean it goes away forever but rather means that we are changing it from 'clean water' to 'dirty water' by adding human wastes, food particles, cleaners, soil, lint, and other materials. These additions contain pathogens, organic and inorganic solids, nutrients, and chemicals. We are counting on the system to clean it again for reuse later. Users determine the quantity of water used by the number of gallons per flush of the toilet, the length of showers, the number of loads of clothes washed, faucets running while brushing teeth or washing dishes, as well as the frequency of doing each of these things, and all other water use practices.
'Maintenance' is the work of doing periodic upkeep on the system. It includes the repair, replacement, and cleaning of existing components. It can also be the addition of new components to enhance performance.
Examples of maintenance are: the repair of leaking fixtures and appliances, the replacement of septic tank baffles or weak pumps, the cleaning of effluent screens or lint filters, the removal of solids from a septic tank or composting toilet, or the addition of an effluent screen to the outlet baffle.
The monitoring of a system is the frequent observation or testing of all on-site system components. It could even mean the testing of effluent or contents! An important aspect of monitoring is to know what needs to be watched, when it should be done and who's going to do it — a plan! The results of monitoring should be recorded and the information used by those doing 'operation' and 'maintenance'. The use of the information is what makes it valuable!
Examples of monitoring may include: knowing what goes down the drain; reading and recording the results of a flow meter; checking baffles, screens, pumps, and alarms for proper function; noting wet spots near the drainfield or mound; recording the date and condition of the septic tank when it is pumped; or sampling and testing effluent from a performance system and reporting the information to a local agency as required.
Management of alternative treatment systems
Specific operation, maintenance and monitoring procedures should be planned and followed to provide good management of all systems. 'Alternative' treatment systems (i.e. sand/peat filters, constructed wetlands, aerobic tanks, composting units, etc.) typically involve special mechanical components, living plants, or other devices, which require special knowledge, skill and attention to perform as designed. Owners may wish to or be required to hire professional management of an 'alternative' system. The complexity and costs of management must be an important criteria considered in the initial selection of an 'alternative' system.
Who, when and how
Total management of a system must involve the residents generating the sewage with varying levels of assistance from professionals. The individual owner will likely determine management responsibilities of a single household system. Traditional trench and mound systems requiring relatively simple management are typically managed by the owner using licensed pumpers and other professionals as needed. Homeowners are capable of handling typical management tasks if they are aware of what needs to be done and make a commitment to it. Owners of complex systems or those unwilling to make the commitment may feel the necessity or be required to hire outside professional management. More opportunities to 'contract out' some steps will likely be available in the future.
Multiple-household systems have another dimension to management — other users. Each homeowner is responsible for the content and quantity of the wastewater generated and must rely on co-users to do the same. All users collectively are responsible to each other and for the management of the commonly used portions of the system. Common components could include large 'community' septic tanks, pre-treatment units or the soil treatment/dispersal system (i.e. trench, mound, wetland, drip lines, etc.).
A good management plan will specify 'who will do what' and 'when and how' they will do it. Each system is unique. The plan must be for the specific system and must be followed to be effective! In some multi-household systems residents can do some management tasks, such as reading water meters, but most functions will require additional equipment, skill and commitment.
The amount and cost of management will vary considerably with the size, type, and complexity of the treatment system. Owners must be willing to pay for the necessary management to achieve effectiveness and efficiency of their investment.
The bottom line is that a responsible person or entity — resident, business or private/public organization, must be designated to know and carry out the specific management practices required for successful treatment of wastewater in any system including on-site systems. For individual or multi-household systems in Minnesota there are several management structure options to choose from:
- Environmental Subordinate Service Districts
- Sanitary Sewer Districts
- Homeowner Associations
- Municipal Utilities
- Homeowner Cooperatives
- Private Joint Ventures
Each option has strengths and weaknesses to be considered for any local application. These options will be discussed in detail in the August/September issue of Focus 10,000.
A properly designed, installed, operated, and maintained on-site system = safely recycled water!
Parameters to monitor septic system performance
Monitoring wastewater characteristics
There are many characteristics to monitor an on-site wastewater treatment system’s performance. They vary from something as simple as checking for sewage on the surface, to complicated laboratory analysis. All cost and required amount of sample vary from lab to lab, but estimates are given. Be sure to contact a lab prior to dropping off samples.
When choosing a lab to perform analysis of wastewater characteristics, a certified lab is always the best choice. These labs use standard procedures. The Minnesota Department of Health maintains a list of labs across Minnesota that are certified.
There are many locations where samples can be taken. It is best if the sample locations are determined when the system is being designed. These sample locations must be built into the design. Effluent chambers, pump tanks and designed sampling ports are suggested locations to obtain samples.
Some obvious locations where the wastewater characteristics are of interest are:
- Out of home
- After septic tank.
- Sampling at system’s "end-of-pipe"
- Sampling groundwater (lysimeter, sampling wells)
- Sampling soil (dry g/microgram fecal)
Piezometers can be used to determine the amount of separation. Lysimeter or soil access ports can be used to determine the amount of fecal under system.
Biochemical Oxygen Demand (BOD5) is the most widely used parameter applied to wastewater. It is a measurement of the dissolved oxygen used by microorganisms in the oxidation of organic matter in sewage in five days. Because of the timeliness of these results the samples for a BOD5 test must be run within 24 hours of taking the sample. An average cost for a BOD5 test is $12. A minimum of 500 milliliters is required to run the test. A typical BOD5 value for septic tank effluent is 100- 250 milligram per liter (mg/l).
Color is an indication of how ‘clean’ the wastewater is. A black sample represents wastewater that is anaerobic and still need significant treatment. A clear sample represents a sample where the BOD5 and TSS have been minimized. The amount of fecal coliform cannot be estimated with a visual inspection.
Dissolved Oxygen (DO) is a measure to determine how much oxygen is in wastewater. Septic tanks usually have very low values of DO because the microorganisms in the septic tank use up all oxygen initially present. A typical value for DO in a septic tank is less than 1 mg/L. This can be measure with a probe or kits are available which evaluate the DO by comparing the color of sample after a chemical is added. The DO must be measured when the sample is taken or soon after because the level will decrease over time.
Fecal Coliform is an indicator organism. There are many pathogenic organisms present in wastewater. They are difficult to isolate and identify. The intestinal tract of man contains countless coliform bacteria. The presence of fecal coliform organisms, which are easily tested for, is an indication that pathogenic organisms may be present. The number of fecal coliform organisms will change over time; therefore fecal coliform test must be run within 6 hours of taking the sample. An average cost for a fecal coliform test is $16. A 500-milliliter sample is sufficient. An average value for septic tank effluent is 100,000- 100,000,00 cells/100 milliliter.
Fats, Oils and Grease (FOG) are added to wastewater through the use of butter, lard, margarine, vegetable oil, and meat. A typical value for FOG from a septic tank is 10 — 50 mg/L. A restaurant can produce very high values, often greater than 100 mg/L. A quart of more of the effluent is required to run this test. An average cost of this test is $42. The cost is so high because of the chemicals required for this test.
Nitrogen is a nutrient essential to the growth of plants and microorganisms and in high levels can be toxic to humans. Wastewater naturally contains fairly high levels of nitrogen, typically in the range of 50-90 mgN/L. It is found in four different forms: organic nitrogen, ammonia, nitrite and nitrate. High nitrate (greater than 10 mg/L) and nitrite (greater than 1 mgN/L) in drinking water (greater than 10 mg/L) can cause blue baby syndrome in infants, which is potentially fatal blood disorder. At high concentrations of ammonium and if the pH gets about above 9, unionized ammonia may be formed which is toxic to fish and other aquatic animals. High ammonium also adds to the BOD load of the effluent when it is oxidized to nitrate. Typical ammonium levels in the septic tank effluent are 30-50 mgN/L. A 100-milliliter sample should be sufficient for a nitrogen test. An average cost for a nitrogen test is $10.
Phosphorus is a nutrient essential to the growth of plants and microorganisms. This nutrient may cause increased growth of aquatic vegetation and algae in surface waters that can result in eutrophication impacts. A typical value for septic tank effluent is 7- 20 mg/L of phosphorus. A 100-millilter sample is needed at a minimum. An average cost for a total phosphorus test is $10.
Total Suspended Solids (TSS) is a measure of the organic and inorganic solids, which remain in wastewater after separation occurs in the septic tank. Typical suspended solids values of septic tank effluent range from 20-140 mg/L. A 100-millilter sample is needed. An average cost for a TSS test is $4.
Temperature of wastewater is a very important parameter because of its effect on chemical reactions. Temperature of wastewater varies from 45-70 ° F depending on the season. Wastewater temperature is usually not a problem for individual residents, but very low or very high temperatures can be a problem from restaurants and infrequently used homes. The temperature of the wastewater must be done when the sample is being taken.
Turbidity is a measure of the light-transmitting properties of water. It is another test to easily measure the quality of waste with respect to suspended matter. Turbidity can be roughly measured in the field or a lab analysis can be performed. A 100-milliliter sample should be collected. An average cost of the lab test is $4.
Odor is often detected when a system is not performing properly. A properly functioning system will have little or no odor.
Flow Meters are used to measure the volume of wastewater going to an on-site system. They are usually located in the basement. This data, when collected on a regular basis can indicate how much water is being delivered to the on-site system. A typical flow for a 3-bedroom home is 450 gallons per day, but this is highly variable depending on the water conservation measures used by the residents.
Tchobanoglous, George and Franklin L. Burton. Wastewater Engineering: Treatment, Disposal and Reuse. Metcalf and Eddy, Inc. Boston, MA. 1991.
Abney, Jack, L. Selection of an Appropriate Wastewater Disposal System. Proceedings of the Seventh National NSF Conference 1980. Ann Arbor, MI. 1981.
Canter, Larry, W. and Robert C. Knox. Septic Tank System Effects on Ground Water Quality. Lewis Publishers, Chelsea, MI. 1986.
Crites, R and G. Tchobanoglous. Small and Decentralized Wastewater Management Systems. McGraw-Hill. Boston, MA. 1998.