MassDEP is reviewing on-site wastewater systems regulated under 310 CMR 15.00. There has not been a change in design flows since 1978 (except for one bedroom elderly housing units). There have not been major revisions since 1995 when certain Title 5 innovative/alternative systems were approved (RSF, FAST, BIOCLERE, ORENCO, RUCK). Additional pilot, provisional and remedial systems can be viewed on the MassDEP website.
Septic systems are the largest source of nitrogen pollution in Cape Cod embayments. Traditional Title 5 systems do not remove nitrogen. Falmouth and the Buzzards Bay Coalition are conducting a pilot program to reduce nitrogen from homes on West Falmouth Harbor. Using grant money, 20 homeowners will upgrade their old systems with “layer cake” systems which have multi-layer leach fields to remove nitrogen. Septic tank effluent passes through a layer for nitrification (18 inches of sand), for denitrification (mixed sand and sawdust, which causes nitrogen gas to dissipate into the air), and then discharge through gravel layer to groundwater. Testing in Florida showed 85% removal of nitrogen. Early results in Falmouth show 88% removal. The systems will be monitored for three years.
The regulatory review should dovetail with the groundwater discharge permit regulations at 310 CMR 5.00 to potentially change the requirement for private wastewater treatment facilities and to allow innovative treatment under Title 5 for flows greater than 10,000 gpd to 15,000 gpd. The costs for hydrogeo investigations, permitting, purchase, and O&M for wastewater treatment plants is prohibitive. Conventional, innovative and alternative systems can treat effluent at significantly lower costs than treatment plants.