Alternative Septic System Designs

Septic systems for wet, steep, rocky, small, poor percolation sites

Examples of site conditions that lead to consideration of an alternative septic design

• Bad soils:
  
  building sites with soils with very low percolation rates or no soil percolation such as clay soils
• Difficult soils:
  
  building sites with other soil problems such as too-fast percolation rate, perhaps too sandy
• Failed septic systems:
  
  sites where an existing septic system has failed and there is limited space or other constraints on septic system repair
• Rocky building sites:
  
  or sites with bedrock and not enough topsoil to treat and dispose of wastewater.
• Small building sites:
  
  which lack adequate space to install a conventional septic drainfield
• Steep building sites:
  
  which do not permit installation of a conventional drainfield or sand bed
• Wet building sites:
  
  with high groundwater or subject to surface runoff (that cannot be fully diverted)

8 General Categories of Onsite Residential Wastewater Treatment Systems

Because various texts provide so many different views of categorizing wastewater systems, I've made this simple list which groups wastewater treatment systems into a few major categories:

[Readers should see our Master List of Septic System Types or our list of alternative septic system designs and products in the links at the left of these pages.]

1. Conventional Septic Tank and Drainfields
   
   in native soils for effluent absorption and treatment. Up to 45% of effluent treatment, often less, occurs in the septic tank, the remainder occurring in the drainfield. Some "advanced" septic system designs may be simple modifications to a conventional septic tank and leachfield, such
   
   as ALTERNATING BED SEPTIC SYSTEMS.
2. Raised Bed and Septic Mound systems
   
   which take a similar approach as conventional systems cited above, but which require extra steps of soil preparation or the necessity to bring in fill to treat effluent. A common raised bed design is the sand-lined filter bed septic system.
   
   See MOUND SEPTIC SYSTEMS
   and
   
   see  RAISED BED SEPTIC SYSTEMS
3. Advanced Material Media Filtration systems
   
   (sand beds, filter beds, peat filters, synthetic textile filters, rotating biological contractor systems, trickling filters, foam media filters including above-ground self-contained systems).
   
   See MEDIA FILTER SEPTIC SYSTEMS
4. Aerobic Septic Systems or ATUs,
   
   which insert additional oxygen into and agitate sewage in the primary treatment tank
   
   See AEROBIC SEPTIC SYSTEMS, ATUs
5. Packaged septic mini treatment plants
   
   or centralized septic designs or STEP systems - a small onsite wastewater treatment plant can be sized and have capacity for individual homes or for large commercial facilities.
   
   See details at SEWAGE TREATMENT PLANTS, RESIDENTIAL
6. Wetlands and Constructed Wetlands
   
   for sewage or effluent treatment. This category may also include greenhouse treatment systems or other methods involving the use of constructed or natural water/land formations. Also
   
   see LAGOON SEPTIC SYSTEMS
7. Disinfection Systems
   
   which perform a final treatment of effluent by use of disinfectant chemicals (chlorine) or perhaps UV light so that effluent can be discharged to the surface or to ground water or even streams and waterways. Also
   
   see AEROBIC SEPTIC SYSTEMS, ATUs
8. Waterless and Low-Water and Greywater-Separation systems,
   
   which may not really treat effluent, may not discharge anything into the environment, but which form another set of alternative designs where water supply or land use restrictions mean that a conventional system is not permitted. Examples include composting toilets, incinerating toilets, chemical toilets, and graywater systems.
   
   See GREYWATER SYSTEMS
   
   and ALTERNATIVE & WATERLESS TOILETS.
   
   See EVAPORATION-TRANSPIRATION SEPTIC SYSTEMS for wastewater treatment and disposal in areas where there is no electrical power and limited or no place for effluent disposal.

Our Master List of Septic System and Wastewater Treatment Alternative Designs

below offers a complete list of alternative septic system designs and major septic system component designs along with a description of each septic system/onsite wastewater treatment approach. For each system we link to articles providing more in-depth design, installation, repair, inspection, maintenance and product source information.

Levels of Wastewater Treatment - How Sanitary is the Final Effluent?

In case the above list of wastewater treatment categories is not enough, there are also various levels of degree of treatment of septic effluent achieved by different versions of these systems, by natural wetlands septic systems, or by use of septic effluent disinfection systems.

For example, you may read about more than one type of gravity dosing or pressure-dosing sand filter beds system which look a lot alike but which achieve different degrees of effluent treatment.

Jantrania (see Alternative Septic Designers) describes eleven Onsite Wastewater Treatment Types in a confusing list (Table 1.3 in his text) since the same type of system may appear more than once (drainfields) depending on the level of treatment achieved by a specific implementation.

In the same text the author proposes a Pollution Scale numbered from 0 Drinking Water) to 10 (Sewage). (p.36). An overall sewage treatment level of 50% would be 5.0 on this scale, and a treatment level of 100% would mean that the output of the system was equivalent to drinking water in purity.

Because over time the concentration of contaminants in incoming sewage and wastewater varies by type of use, level of building occupancy, changing soil moisture and temperature, and other factors, it is risky to assume that a regulation or a septic system design level requiring or claiming 90% treatment (pollution scale 1.0) is always producing effluent treated to exactly that level.

Awareness of the variation in level of contaminants in sewage arriving at a treatment system, as well as awareness of variations in site conditions (level of ground water, temperature, frequency of inspection and maintenance) is behind the very conservative standards adopted by many health departments regulating septic system installations.

The terms percentage of treatment and level of treatment of sewage or wastewater are used in different and perhaps confusing ways. A writer may say that "45% of the effluent treatment occurs in the septic tank".

I take this to mean that whatever the overall or final level of wastewater treatment that the whole system is going to provide, from input to the system to final discharge of effluent into the environment, 45% of it is occurring inside the septic tank. This does not necessarily mean that the effluent discharged from the septic tank is 45% of the way along the pollution scale or nearly half way to being pure drinking water.

The term "level of treatment" should be reserved to mean the overall or final degree of purity of the effluent which is discharged to the environment.

Sewage contaminants- what's in sewage, and typical sewage contaminant levels are discussed in more detail

at SEPTIC SYSTEM CONTAMINANTS

General Categories of Wastewater Dispersal Methods

Adding to the complexity of what to call various septic systems, there are also categories of methods of septic effluent dispersal (to the final treatment and soil absorption or other effluent disposal system) such as:

1. Gravity-Fed Perforated Pipe in Gravel-Filled Trenches:
   
   these are conventional gravity-fed drainfields, using gravity to permit wastewater to flow from the septic tank to the absorption system or drainfield. Wastewater moves out of the septic tank to the drain field by gravity in response to and equal in volume to new waste entering the septic tank. The absorption system consists of perforated pipes in gravity-filled trenches dug into native soils.


2. Drip or Spray systems
   
   which may disperse effluent above or below ground.


3. Gravity Dosing systems,
   
   which distribute wastewater to the drain field in irregular batches or "doses", permitting the absorption system to rest and recover between doses.


4. Pressure Dosing
   
   effluent dispersal methods for septic effluent handling such as sprinkler dispersal, and intermittent effluent dosing systems which using pressure dosing by pressure manifold, rigid pipe systems, or pressurized drip irrigation systems

An individual septic system design may use a combination of these methods to treat, disperse, and dispose of septic effluent. For example, a sand filter bed septic system might be fed by gravity, by a gravity-operated dosing system, or by a pump operated pressure dosing system.

Keeping these types of of septic systems

see details at TREATMENT METHODS

and keeping these types of wastewater dispersal systems

see details at DISPOSAL METODS

in mind when reviewing various off-the-shelf packaged septic systems or wastewater treatment systems with interesting but non-descriptive names (like the "magic bullet treatment box") will help you to understand the general approach which has been taken in any specific case and will help you choose among alternative septic system designs and products.

Further reading will be needed to understand the installation cost, maintenance cost, and level of management required of each type of septic system. I collect and publish here additional details on alternative septic system design, installation costs, and maintenance costs.

Links at the end of this article and most of our septic information website pages offer descriptions, design suggestions, product sources for each of these septic system types.

Jantrania (see Alternative Septic Designers) sorts alternative or advanced onsite wastewater treatment systems into five major groups: aerobic septic effluent. treatment systems, media filters, natural systems such as wetlands, waterless toilet systems, and disinfection systems.

Here, however, our list of septic system designs and effluent. treatment alternatives is organized alphabetically and includes not only alternative methods of primary treatment but also methods of effluent final treatment, dispersal, and disposal. Conventional gravity septic tank and effluent drain field systems (Jantrania/Gross wastewater system type I) are discussed at the "Septic Systems Home" and "Septic Design Basics" links at the left of these pages.

Consultants in this field can be listed at our alternative septic designers page at no charge by contacting me.

Alternative Designs for Onsite Sewage Treatment - References

• New York State Department of Health, APPENDIX 75-A WASTEWATER TREATMENT STANDARDS - INDIVIDUAL HOUSEHOLD SYSTEMS , [PDF] New York State Department of Health, 3 February 2010, retrieved 3/1/2010, original source: https://www.health.ny.gov/regulations/nycrr/title_10/part_75/appendix_75-a.htm
• TAFGARD SOIL BASED WASTEWATER EVAPORATION / TRANSPIRATION SYSTEM [PDF] (in Japanese) by Taisei Kogyo Co., Ltd., Japan. Contact Shuichi Sato, Manager of Taisei Kogyo Co., Ltd., 15-36 Yonehara 6-chome, Yonago, Tottori, 683-0804 Japan Tel. +81-859-32-1135 Fax. +81-859-34-0933, info@taisei-wastewater.jp Web: http://www.taisei-wastewater.jp/TSSEng/tafgard_home1.html [Dead Links April 2022)
• Bio-Microbics Inc., 800-753-FAST (3278), (913) 422-0707, (913) 422-0808(fax) Email sales@biomicrobics.com - web: https://biomicrobics.com/
  
  Bio-Microbics manufactures wastewater and storm water Treatment systems for decentralized homes, communities, and commercial properties located around the globe. With tens of thousands of installations all over the world, the FAST® technology is used successfully in municipal, industrial, marine, commercial and residential type applications for over 35 years.
  
  Bio-Microbics manufactures clean technologies for the onsite residential, commercial, and marine wastewater treatment markets that harness renewable water sources from wastewater and storm water to offer significant benefits for water redistribution.
  
  Our product qualifies under the Innovative Wastewater Technologies for most “Green” building certification programs.
• Septic Tank/Soil-Absorption Systems: How to Operate & Maintain [ copy on file as /septic/Septic_Operation_USDA.pdf ], Equipment Tips, U.S. Department of Agriculture, 8271 1302, 7100 Engineering, 2300 Recreation, September 1982, web search 08/28/2010, original source: http://www.fs.fed.us/t-d/pubs/pdfimage/82711302.pdf.
• Pennsylvania State Wastewater Treatment Fact Sheet SW-161, Septic System Failure: Diagnosis and Treatment
• Pennsylvania State Wastewater Treatment Fact Sheet SW-162, The Soil Media and the Percolation Test
• Pennsylvania State Wastewater Treatment Fact Sheet SW-l64, Mound Systems for Wastewater Treatment
• Pennsylvania State Wastewater Treatment Fact Sheet SW-165, Septic Tank-Soil Absorption Systems
• Galbraith, J.M., C.E. Zipper, R.B. Reneau Jr., ON-SITE SEWAGE TREATMENT ALTERNATIVES [PDF] (2015) Virginia Cooperative Extension, Va Tech, Va State U., - retrieved 2022/04/25 original source: https://commed.vcu.edu/IntroPH/WaterPrograms/2016/VaTechessay.pdf
  Preface:
  The purpose of this publication is to describe on-site technologies for treating domestic sewage where conventional systems (septic tank with drainfield) are not an option (U.S. EPA 2002). These technologies are described as alternatives in this publication.
  
  Our goal is to provide information that can be used by property owners and residents to initiate action to rectify sewage disposal problems, especially where current wastewater treatment is inadequate.
  
  This document is intended to provide information on alternative wastewater treatment options that will help the reader make informed decisions when dealing with oversight agencies and contractors; it is not intended to serve as a stand-alone reference for design or construction.