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PERFORMANCE EVALUATION OF ALTERNATIVE ON-SITE PA SMALL FLOW TREATMENT FACILITIES IN TWO STATE PARKS
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Paper number 701P0104, . (doi: 10.13031/2013.15790)Authors: R. F. Kaintz, W. A. Snyder
Keywords: On-site systems, recirculating sand filter, A/B soil infiltrative treatment
The soil suitability requirement, where seasonal high water table is the limiting zone (LZ), is 20
inches for an elevated sand mound in Pennsylvania. A state permitted chlorinated-intermittent
sand filter system with a stream discharge is commonly used where the LZ is <20 inches.
Pressure dosed intermittent and recirculating sand filters using final soil treatment/disposal units
consisting of A/B soil horizon infiltrative beds and trenches were installed in two state parks.
Performance of the sand filters as well as the shallow placed and at-grade infiltrative/treatment
soil units were monitored. The residential prototype system at Bendigo State Park demonstrated
median removal efficiencies for CBOD5, TSS and NH3-N of greater than 98%. Actual pollutant
concentrations reaching groundwater, as measured by vacuum lysimeters below the treatment
trenches, averaged 0.6 mg/L CBOD5, 9.0 mg/L TSS, less than 0.1 mg/L NH3-N, 9.87 NO3-N and
less than 12.0 mg/L Total N. Transport of fecal coliform (FC) bacteria into the shallow perched
water table, as measured in samples from shallow monitoring wells, indicated 0 FC/100ml in 106
of 154 samples. Virus transport was not monitored.
Based on these results, Pennsylvania has added an alternate on-site sewage treatment system to
its 25 Pa. Code Section 73 Alternate Systems Guidance (DEP, 2002) document referred to as the
A/B Soil System. The design requirements consist of a two-compartment septic tank, a
recirculating subsurface sand filter, UV disinfection, with final treatment and disposal using an
at-grade absorption area. The final treatment and dispersal configuration is based on linear
loading rates derived from soil morphological analysis and a hydraulic linear loading chart
developed at the University of Wisconsin-Madison (Tyler, 2001).