Executive Summary

On-lot system technology components in use or under evaluation have been reviewed nationally and internationally from published reports and direct contact with researchers, regulators, and industry people. A data base has been developed to organize, store, and access this information. Six system technologies (A through F) consisting of various primary treatment components, secondary treatment components, and soil based components have been chosen for study as a result of the selection process. The proposed technologies could provide options which are cost competitive or less expensive than existing systems for 21 million acres in Pennsylvania. These technologies also offer potential to provide alternatives on 1 million acres where current technologies are not available. From a land use planning perspective development often occurs on prime agricultural soils because these are the only soils which currently can be permitted for on-lot wastewater systems. The technologies under study offer the potential for communities to utilize non prime agricultural soils for on-lot wastewater systems. Full scale systems to handle 400 gallons per day flow have been constructed on the campus of Delaware Valley College in Doylestown Pennsylvania for each technology. Technology A is a constructed wetland system. Technology B consists of a denitrification system coupled with an at grade pressure distribution soil absorption system. Technology C consists of the evaluation of four different types of sand filters. Technology D couples an intermittent sand filter with a time dosed pressure distribution soil absorption area. Technology E couples an intermittent sand filter with a trickle irrigation system. Technology F uses septic tank effluent coupled with a time dosed at grade pressure distribution system. Systems have been constructed and data has been collected over a two year period. This presentation will report on some of the findings to date.

Task Summary

This project was divided into several different tasks. Information on several relevant tasks is presented.

Task: Consolidate data and information regarding all on-lot sewage system technology and small flow discharge technology used or under evaluation in other states and other countries.

A library search was initiated using Dialogue Information Retrieval Service. Article titles were reviewed and articles of interest were collected from interlibrary loan, NTIS, as well as directly from publishers. Each article was identified by a locator code number which served as a reference identification for future use. This initial process of gathering information was accomplished from August of 1994 through December 1994. Also during that same time period contacts were made with the National Small Flows Clearing House at West Virginia University, with surrounding states, and with researchers, industry, and regulatory people at the American Society of Agricultural Engineers 7th National Symposium on Individual and Small Community Sewage Systems in Atlanta Georgia.

In all approximately 350 articles were evaluated of which approximately 225 were relevant to this project. These articles were subsequently entered into a data base developed for this purpose.

A summary of limiting zone depth, renovation thickness required, maximum slope, and percolation rate ranges for the United States was prepared. The US data was also summarized for the 12 Northeastern States. Information on systems used in various countries, including Japan, Netherlands, Canada, Switzerland, and France was gathered as part of the literature search. Most articles on foreign systems dealt with an evaluation of the same types of systems currently used in the United States.

As part of this information gathering effort site visits were made to Meadville Pennsylvania to examine a subsurface sand filter system, Maryland to examine a wetland system, and Penn State University to examine field pan zero tension water samplers considered for use in the sampling of the soil based system technologies. Contacts were also made with North Carolina State University and University of Wisconsin regarding their demonstration centers.

All articles and information is currently available in the Agronomy & Environmental Science Department at Delaware Valley College.

Task: Evaluate and compile the information into a data base, establish selection criteria, and begin technology selection.

A data base management program was developed in Paradox and subsequently transferred to Access to input information from each article. In addition to title, and author, information on system type, site data, parameters evaluated, system reliability, keywords, and comments were entered into the data base where applicable. The research team was expanded at this time to include eleven junior and senior level students in Environmental Science, Biology, and Chemistry. This expanded team met on a weekly basis from January 1995 through April 1995 to review articles and enter them into the database. Most work reviewed by the research team focused on components of systems. These components are summarized in Table 1.

As part of the information gathering phase of this project three nationwide trends emerged from the review of existing research information, discussions with regulatory people and discussions with industry people.

1. Place systems in the Bio-Active soil zone. The bioactive soil zone would be the soil horizons close to the soil surface, the A and B horizons. Traditionally soil based systems, especially conventional type systems, are placed in the C horizons beneath the bio active zone. Most renovation occurs in the bio-active zone.

2. Solids and BOD removal is needed to increase effluent infiltration rates of soil, especially slowly permeable soil.

3. There is a need to attempt to determine the thickness of the soil required to adequately renovate the effluent. (Renovative thickness)

Treatment technologies listed in Table 1 appear to have possible application to Pennsylvania. Selection criteria for choosing the combination of primary, secondary, and soil based components consisted of the objectives as outlined in the request for proposals (RFP), the Current System Matrix Table (Table 2), and the three nation wide trends. The charge of this project was to establish technology priorities that would be applicable to the climate, geologic, and soil conditions in Pennsylvania, or specific areas of Pennsylvania. These technologies should have the potential to provide an alternative for those areas where no current alternative is available or provide an alternative which may be more cost effective than current alternatives. The Current System Matrix Table (Table 2) was developed to show systems currently approved and where gaps exist which new technologies could possibly fill. System depth to limiting zone (seasonal high water table or bedrock) is listed in inches across the top of Table 2. Slope of the site is listed on the left.

Slope										Depth to limiting zone

1. Technology should be one that can be placed close to the surface to take advantage of the bio-active soil zone.

2. Technologies that reduce solids and BOD should be used on slowly permeable soils.

3. Attempt to address the key issue of renovative thickness

Task: Determine the system technologies to be field evaluated

The approach taken was to combine various Primary, Secondary, and Soil Based Components from Table 1 into a system technology and evaluate that technology against the selection criteria. It was also decided that monitoring would be set up to evaluate each individual component of the technology. The data gathered could then allow the use of Table 1 to put together combinations of primary, secondary, and soil based components to overcome specific site problems or meet specific site objectives. The following system technologies were chosen:

A. Technology A - Wetland System

This system will consist of a septic tank and two wetland cells in series. Each cell is approximately 16 feet by 16 feet. The first cell will be a vertical flow cell and will perform most of the treatment. The second cell will be a horizontal flow cell and be used to allow infiltration of treated effluent into the soil. Three replicates will be constructed. Each of these systems will be connected to individual homes. This system could be applicable on an estimated 1 million* acres in Pennsylvania where soil requirements currently cannot be met for any system. The location of Technology A within the Current System Matrix is shown below.
* Based on USDA data base for PA.

B. Technology B - Septic tank, recirculation sand filter, effluent distribution at the surface of the soil using a pressurized distribution system within crushed stone.

This system utilizes effluent from three single family homes and serves as an example of a community system with denitrification. The soils on this site are moderately well drained to somewhat poorly drained. Three replicates will be constructed. The system design proposed will allow an alternative to the elevated sand mound which would be more aesthetically acceptable and less costly. This system could be applicable on moderately well drained soils with slopes from 0 to 15 percent and could have the potential to substitute for an elevated sand mound on an estimated 3 to 8 million* acres in Pennsylvania. The location of Technology B within the Current System Matrix is shown below.
*Based on USDA data base for PA.

The following systems C,D,E, and F will all utilize effluent from the campus sewer system.

C. Technology C - Sand filter testing

Recirculating, intermittent, upflow, and gravity intermittent sand filters will be evaluated. In addition round, rectangular single compartment, rectangular dual compartment, and dual round septic tanks in series will be evaluated. Similar sand will be used in each filter. The sand will be of grain size and coefficient of uniformity that allows a high gallons per square foot application rate. The goals of the sand filter test bank are to evaluate effluent quality from different types of filters and to attempt to decrease the size of the sand filter. Once these initial sand filters are running and evaluated for eighteen months a decision will be made to possibly change media material for another set of evaluations. Two replicates will be constructed This test area will provide data on secondary treatment by different types of sand filters for possible use with soil absorption areas, spray irrigation, and stream discharge for NPDES permits. These filters will provide data applicable for all of Pennsylvania and could have an affect on systems used on 18 million* acres.
*Based on USDA data base for PA.

D. Technology D - Septic tank, intermittent sand filter, application of effluent at grade in a pressure dosed bed on somewhat poorly drained soils.

This system will be an alternative for the spray irrigation system. Effluent from a septic tank will be pass through an intermittent sand filter and then be applied at the surface of a somewhat poorly to poorly drained soil using a pressurized distribution system within crushed stone. This system will utilize the bioactive zone of the soil and we will be able to control the amount of effluent applied to the soil to better determine required absorption area. Three replicates will be constructed. This system could potentially be utilized on approximately 4 million* acres in Pennsylvania and is shown within the Current System Matrix below.
*Based on USDA data base for Pa.

E. Technology E - Septic tank, intermittent sand filter, application of effluent on moderately well drained soils with steep slopes utilizing a drip irrigation system.

This system will allow utilization of moderately well drained soils on slopes of 15 to 25 percent. Effluent from the sand filter will be applied on steep slopes(15-25%) of a moderately well drained soil utilizing a drip irrigation system. The drip irrigation tubing is placed in the soil surface several inches. Three replicates are planned. This system could potentially be used on an estimated 5 million* acres. The location of Technology E is shown within the Current System Matrix.
* Based on USDA data base for Pa.

F. Technology F - Septic tank, at grade pressurized distribution system within crushed stone on a well drained soil.

This system will examine renovation thickness. This test site will utilize the bioactive zone of soils in an attempt to determine the amount of soil renovative thickness required. These systems will be sampled at a depth of one, two, and three, and four feet beneath the surface. This system could allow sites currently requiring an elevated sand mound to utilize septic tank primary treatment and a pressurized distribution system at the surface of the soil. This could result in considerable cost saving on sites currently requiring an elevated sand mound and could potentially be implemented on between 3 and 8 million* acres. The location of Technology F within the Current System Matrix is shown on the following page.
* Based on USDA data base for PA

Table 3 is a modified version of the Current System Matrix with the Technologies that will be evaluated shown on the matrix.

Task 2.5 Site selection.

Over fifty auger and backhoe test pits were evaluated over the College's 600 acres to establish sites for testing. Technology A (constructed wetland) will utilize existing homes. Technology B (community sand filter, denitrification, at grade distribution) will utilize the three homes associated with site B.
Technologies C, D, E, and F will utilize effluent from the college campus.

Task: Monitoring

Data have been gathered on each step of the treatment process. For each soil based component zero tension gravity samplers (construction modeled after Simmons & Baker, Journal of Environmental Quality 22:207-212 (1993) were installed to sample at one, two, three, and four feet beneath the surface. In addition porous ceramic cup pressure-vacuum samplers were also be placed at two feet beneath the surface. Observation ports (4 inch PVC) were installed at the stone soil interface to observe saturation on each soil based system. On the somewhat poorly drained and moderately well drained soils, perched water tables were sampled by installing 2" PVC shallow wells.

Primary and Secondary system components were sampled once each month. Soil based components were sampled once each month. Analysis was be performed for Solids(total, suspended, dissolved), Total N, Nitrate, Ammonia, Phosphate ,Potassium, Total Carbon, COD, BOD, Fecal Coliform, Fecal Strep, and Fats Oil & Grease.
Monitoring began January 1997.

This page created by Roland O. Coburn
Reasearch Tech I
on 3/20/00.
Last updated 4/25/00.