Description of Technology

The GPC Filter is a stratified bottom drained sand filter treatment system with carbon addition (the System), installed after a MassDEP approved innovative/alternative system capable of providing an effluent concentration of 30 mg/l or less of BOD and TSS, and prior to the soil absorption system (SAS) designed and constructed in accordance with 310 CMR 15.100 – 15.279. The System provides attached growth and nitrogen reducing wastewater treatment. The GPC Filter may also be designed and installed as a bottomless sand filter with a crushed stone base instead of a solid base. In the case of bottomless sand filter design the bottom drain is used as a sampling port. If designed as a bottomless sand filter the GPC Filter must meet the standards for site preparation and installation contained in the remedial use approval for Bottomless Sand Filters. There shall be no additional credit for nitrogen loading or absorption area reduction beyond that for the approved alternative technology installed prior to the GPC Filter.

The wastewater treatment process consists of an appropriately sized septic tank, followed by a MassDEP approved alternative technology capable of providing an effluent BOD & TSS concentration of 30 mg/l or less. The effluent then flows to a pump chamber with a GPC carbon addition. The pump chamber then doses the carbon fortified treated wastewater to the GPC Filter consisting of the following:

– a 6” bottom layer of ¾” to 1-1/2” crushed stone which contains a centrally placed collection pipe for sampling and effluent covered by filter fabric overlain by,

– 12” of filter sand* which is covered by 6” of ¾” to 1-1/2” crushed stone

– which in turn is covered by a layer of filter fabric

– which is covered by 5” of filter sand *

– on top of which is a 7” indrain with filter sand* layer

– which is covered by a 4” layer of ¾”- 1-1/2” crushed stone in which 1-1/2”influent laterals are imbedded equally spaced across the filter to dose the unit

– a filter fabric layer on top of this completes the filter

*the filter sand shall have a D10 (particle diameter at the 10% finer point) of between 0.16 to 0.20 mm, and a ratio of D60/D10 of less than 5, with less than 4% to pass the #100 sieve. A grain size analysis of the sand shall be provided with each sand delivery.

Massachusetts Technology Approvals

Approval Type	General	Remedial	Provisional	Pilot
Secondary Treatment
Nitrogen Removal Credit
Phosphorus Removal Credit

Please check the Title 5 Innovative/Alternative Technology Approval Letters webpage at Massachusetts DEP for the most up-to-date information.

Real-World Data

Test Center Reports & Data