Acceptable is a condition in which a component is performing its intended purpose and is considered to be in an operable state.

Adsorption allows contaminants in wastewater to bond with media particles to slow the rate of movement through the media and to allow uptake of nutrients by plants and microorganisms in the media.

Aerobic is a condition where oxygen is required. Aerobic microorganisms require oxygen to live and breakdown pathogens in wastewater.

Alkalinity refers to a wastewater’s ability, or inability, to neutralize acids.

Ammonia is a compound of nitrogen and hydrogen with the formula NH3. The main uses of ammonia are in the production of fertilizers, and it is also an ingredient in certain household glass cleaners. The form of nitrogen in septic tanks is ammonium.

Anaerobic is a condition in which there is no oxygen present. Anaerobic organisms get their oxygen supply by breaking down chemical compounds that contain oxygen.

Aquifer is a geological formation that can store, transmit, and yield water to a well or spring.

Assimilation is the transformation of a nutrient into another form that can be digested by an organism.


Biochemical is a treatment process that combines biological treatment and chemical treatment. The two processes overlap and sometimes it is hard to distinguish which treatment activities are biological and which are chemical.

Biochemical Oxygen Demand (BOD5) is the amount of oxygen consumed by microbes during the decomposition of organic matter. It is an indicator of the overall strength of the wastewater.

Biological oxidation occurs when bacteria break down organic matter into water and carbon dioxide (CO2). Oxidation reduces BOD5, removes pathogens, and works best under aerobic conditions.

Biological processes for treatment include natural die-off, predation, biological oxidation, and mineralization.

A biomat is the biological buildup of wastewater treating organisms on a treatment media.

Blackwater includes flush water from toilets and urinals and wastewater from food preparation sinks. Blackwater contains relatively higher concentrations of nitrogen and human pathogens than graywater and decomposes more slowly.


Cation exchange allows contaminants in wastewater to bond with media particles to slow the rate of movement through the media and to allow uptake of nutrients by plants and microorganisms in the media.

Chemical Oxygen Demand (COD) is a measure of the amount of organic matter oxidized by a strong chemical oxidant.

Chemical processes that can treat wastewater include cation exchange, adsorption, and precipitation.

Chlorine residual is the total amount of chlorine remaining in effluent at the end of a specified contact time following chlorination.

Clean water is water that never comes into contacts with humans but that is discharged into the wastewater stream. Clean water sources include condensate from ice-machine drains, condensate from air conditioners and coolers, footing drains or basement drains, and water treatment devices such as water softeners, reverse osmosis units and anion exchange processes.

Compensation is the action of being paid a fair price for a proper service.

Contact time is the time in which effluent is in contact with a reacting chemical or constituent.


Demand-dosed systems deliver wastewater to the next component in the treatment train when the wastewater becomes available. A pump activates when a pre-determined volume of effluent flows into the pump tank. The flow patterns to the next component are subject to the variations in water usage patterns from the source.

Denitrification is the process in which nitrates are transformed to gaseous nitrogen. Denitrification occurs in anaerobic conditions.

Detention time is the amount of time wastewater spends in the onsite wastewater treatment system. The longer the detention time, the better the quality of treatment.

Dispersion is the process by which wastewater mixes with groundwater. Dispersion dilutes the remaining contaminants but does not remove them.

Dissolved Oxygen (DO) is the concentration of oxygen dissolved in an effluent.


Endocrine disruptors include medicines, medicine metabolites, antibiotics, and chemotherapy drugs. They can seriously alter the performance of a system through their effect on the biological activity of organisms in the septic tank.


Facultative organisms can survive in aerobic or anaerobic conditions.

Failure is a condition in which a component of or the entire system is not performing its intended purpose.

Fats, oils, and grease (FOG) in domestic wastewater will generally originate in the kitchen or bathroom. Kitchen FOG usually comes from disposing of animal- or vegetable-based food scraps down the sink and into the system. Households using garbage disposals will have 30-40% more FOG than households not using garbage disposals. Bath oils, sun tan lotions, and moisturizing creams are bathroom sources of FOG that enter the wastewater stream.

Fecal coliform is an indicator microorganism that can be cultured in standard tests to indicate contamination. Fecal coliform originates in the digestive system of humans and animals.

Filtration works by moving wastewater through pore spaces in various media. Physical treatment processes can remove large particles, pathogens, and suspended solids. The smaller the pore space size, the smaller the size particle or microorganism that can be physically trapped.

Flocculation usually occurs when a chemical is added to induce the process, but it essentially when suspended solids or nutrients in the wastewater are attracted to each other and form larger clumps of particulates. Flocculated particles can then be removed through sedimentation or filtration.

Flow Equalization prevents short term, high volumes of incoming flow, called surges, from forcing solids and organic material out of the treatment components. Surge or flow equalization tanks are typically designed to hold twice the normal daily flow of the home. The flow from a surge or flow equalization tank is controlled by a timer which allows the wastewater to be distributed to the next component in fixed amounts.


Graywater is the water from showers, bathtubs, handwashing lavatories, sinks that are not used for disposal of hazardous or toxic materials or for food preparation or disposal, and clothes-washing machines. It contains less pathogens and nutrients than blackwater, but still has constituents of concern.

Gravity-fed refers to distribution of effluent onto a treatment component without the use of a pump. The process uses gravity to move the effluent from one component to the next.


Inorganic materials in domestic wastewater include minerals, metals, dissolved salts, sand, and silt. These are relatively stable compounds and are not easily broken down by microorganisms.

Inspection is the process of identifying the current status of a system for reporting purposes.


Maintenance is the action of performing routine activities to ensure proper performance, extend the life of the system, or meet performance requirements.

Management is a term describing all the steps necessary to conduct operational services, including maintenance, monitoring, and compensation.

Metals are inorganic chemical compounds that are stable and resistant to decomposition. While primarily a concern in industrial discharges, they can be present in residential wastewater when strong chemicals and/or vitamins are used in the home. While some metals are essential for animal and plant nutrition, at higher levels they may be toxic. In soils, metals generally become more soluble as the pH decreases.

Mineralization transforms organic nitrogen into other inorganic forms of nitrogen that can become part of yet other biologically driven treatment processes.

Mitigation is the act of fixing a system that is in failure. Fixing the system should be preceded by an evaluation of all the components (source, collection and storage, pretreatment, final treatment and dispersal) to determine the reason for the malfunction. Certain jurisdictions may require a permit before mitigation occurs.

Monitoring is the action of verifying performance requirements for a regulatory authority.


Natural die-off occurs when pathogens are held in nutrient-poor aerobic conditions.

Nitrate has the chemical formula NO3-. Nitrate is one of the most water soluble anions known, and is common in fertilizers. Nitrate is a wide spread contaminant of groundwater and surface waters.

Nitrification is the process in which ammonia is oxidized to nitrite and nitrate, in aerobic conditions. Two groups of microorganisms are involved in nitrification. Nitrosomonas oxidizes ammonia to nitrite and water. Subsequently, Nitrobacter oxidizes the nitrite ions to nitrate.

Nitrite quickly converts to nitrate in the nitrification process. It is rarely found in wastewater.

Nitrogen makes up 78% of the Earth’s atmosphere and is a constituent of all living things. Nitrogen is available in many forms, including ammonia, nitrate, nitrite, and nitrogen gas.

Nutrients are elements essential for the growth of living organisms. However, humans do not utilize all of the nutrients that we consume, and residual nutrients become a potential contaminant. Of particular concern are nitrogen and phosphorus.


Observation ports, also known as inspection ports, are an access point in an onsite wastewater treatment system that allow an operation and maintenance service provider to look at a buried treatment component.

Operation is the action of assessing the functionality of each component of the system while it is in service.

Organic materials are compounds that contain carbon. They develop an oxygen demand in water.


Pathogens include bacteria, viruses and microorganisms that can cause disease.

Performance Requirements are specific and measurable parameters that effluent must meet.

Persistent organic compounds are stable compounds that decompose slowly and can persist in soil and groundwater for years. Like metals, they are primarily a concern in industrial wastewater, but can be found in household solvents, cleansers, paint, and medical products.

pH measures the acid or base quality of wastewater. It is measured on a scale from 1-14, with 1 being the most acidic, 14 the most basic, and 7 neutral.

Phosphorous is found in body wastes, food residues, fertilizers, and detergents. Primary and secondary orthophosphates (H2PO4- and HPO42-) are the forms available to plants. Phosphorous moves with the soil absorption plume but at a retarded rate. Phosphorus retardation in soil absorption areas is dependent upon sorption and precipitation reactions. It can also move in surface water or in groundwater, during erosion episodes, or under anaerobic soil conditions.

Physical processes include filtration, dispersion, and dilution.

Predation occurs when microorganisms attack and destroy pathogenic bacteria and viruses.

Precipitation happens when constituents in wastewater or in the media combine together to make a new compound and become heavy enough to physically settle from the effluent. Precipitation processes are important for phosphorus removal.

Pressure-dosed systems use a pump to distribute effluent to a component.

Primary Treatment is the first in a series of treatment processes. It removes constituents in the wastewater that easily settle or float. A septic tank is considered primary treatment.


Recirculation is the action of designing wastewater to go through an advanced pretreatment unit more then once. Recirculation increases the efficiency of the wastewater treatment.

Recirculation Ratio is the ratio between the recirculated volume through the media and the volume that goes to the final treatment and dispersal component.

Repair is the action of fixing or replacing substandard or damaged components. Repairs may be required repairs, recommended repairs, or upgrades.

Replacement is the process of exchanging a component with an equivalent component.

Reporting is the action of submitting a detailed report of operation and maintenance activities performed on a system.


Secondary Treatment is a biological treatment process that reduces constituents in the wastewater such as BOD5, nitrates, or organic matter.

Sedimentation is the process in which suspended solids or other particles in wastewater settle out of the effluent and gather at the bottom of a treatment component.

Service is the action of performing activities such as, but not limited to, inspection, assessment, and maintenance of system components.

Single-pass refers to the flow of wastewater through a treatment component. It is only treated by a component one time in the treatment train.

Solids analysis measures the amount of solids present in wastewater. Typical analyses include total suspended solids (TSS), total dissolved solids (TDS), or total solids.


Time-dosed systems use an adjustable timer on a pump to control the flow of wastewater to the next treatment component. The system operator can set the timer to turn on the pump for a set amount of time to deliver only a pre-determined volume of wastewater to the next component.

Total Kjeldahl Nitrogen (TKN) is the sum of organic nitrogen and ammonia in a water body.

Total Phosphorus (TP) is a measure of all the forms of phosphorus, dissolved or particulate, present in water.

Total Dissolved Solids (TDS) are the solids in water that are able to pass through a filter.

Total Solids refers to matter suspended or dissolved in water. It is the term used for material left in a container after evaporation and drying of a water sample. Total Solids includes both total suspended solids and total dissolved solids.

Total Suspended Solids (TSS) are solids in water that can be trapped by a filter.

Treatment Train is the unique combination of technologies that make up an individual onsite wastewater treatment system. An example of a treatment train would be a septic tank and a soil adsorption area. All components in a treatment train require operation and maintenance.

Troubleshooting is the act of identifying and correcting sources of system malfunction.

Turbidity is the physical clarity of the water and is an indicator of the presence of total suspended solids in wastewater.


Unacceptable is a condition in which a component is not operable. This condition indicates the need for implementing maintenance, upgrades, repairs, or further investigation.

Upgrade is the action of creating a better system by adding or modifying a component to improve the level of treatment provided by a system.


Water Table is the upper limit of abundant groundwater. Below it, every available space is saturated with water.

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