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Septic System Testing

The first septic systems were built in the 1860’s. Prior to this sewage was discharged directly into streams, rivers and lakes. This created a number of human health hazards. Since that time the modern septic system has evolved and is more efficient at protecting the environment and our health. A septic system should have a permit that is administered by the IDRN or Iowa Department of Public Health.

The purpose of a septic system is to remove large solids and grease that can reduce the soil absorption abilities. A typical septic system is located between the house and drain field. The waste water from the house flows into a water tight container that settles out the solids and allows for anaerobic bacteria to break down the waste. Non-biodegradable solids and scum are kept in the septic tank. The effluent flows into a leach field where materials are absorbed be the soil and the process of moving through the leach field reduces bacteria and viruses.

Typical tests that are conducted to determine the effectiveness of the septic system is carbonaceous biological oxygen demand (CBOD), total suspended solids (TSS), fats oil and grease (FOG), pH and E. coli bacteria. To conduct these tests you need to only collect a sample of the effluent that is being discharged from your leach field. For permit compliance testing the samples must be collected by a qualified sampler, or contact the county health department. Q.C. Environmental will provide the proper sampling containers to you at no charge. The IDNR requires that CBOD, TSS and E. coli be tested at least annually.

The allowable effluent limit from your septic system is determined by the surface water class that it discharges into. The effluent limits are listed below based on the receiving water and a description of the water classes are provided below the table.

Discharge Limits

Surface Water Class CBOD
E.coli Bacteria
Class A1 & A3 25 25 235
Class A2 25 25 2880

Class A1 – Primary Contact Recreational Use: Water in which recreational or other uses may result in prolonged and dirt contact with the water, involving considerable risk or ingesting water in quantities sufficient to pose a health hazard. Such activities would include, but not be limited to, swimming, diving, water skiing, and water contact recreational canoeing.

Class A2 – Secondary Contact Recreational Use: Waters in which recreation or other uses may result in contact with the water that is either incidental or accidental. During the recreational use, the probability of ingesting appreciable quantities of water is minimal. Class A2 uses include fishing, commercial and recreational boating, any limited contact incidental to shoreline activities and activities in which users do not swim or float in the water body while on a boating activity.

Cass A3 – Children’s Recreational Use: Water in which recreational uses by children are common. Class A3 waters are waters having definite banks and bed with visible evidence of the flow or occurrence of water. This type of use would primarily occur in urban or residential areas.

If you are having problems with your septic system such as poor drainage backups, high CBOD, TSS or E. coli bacteria, we recommend contacting a certified Septic System Inspector. They can assess your system and determine the cause of the problem. Septic systems that have high FOG or low pH can adversely affect the bacteria that the system needs to biodegrade the solids. High FOG’s can also damage the soil absorption abilities in the drain field.

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