Typical Existing Onsite Wastewater Treatment Systems for Single-Family Homes Suffolk County, NY
If your home is older than 1973 and your house has not been expanded, your onsite wastewater system is likely to be a cesspool. If, when a hauler opens the manhole to your system, the first pit on the pipe exiting your home is made of brick, concrete block or has openings in the sidewall, it is a cesspool. Often there are two cesspools in line, as owners just added the second as an overflow when the first one clogged. Some are preceded by small grease traps. A cesspool does not treat wastewater or even provide for the separation of solid waste. It just disperses it to the soil. With its open joints, a cesspool is more susceptible to flooding and more likely to be a source of pathogens when depths to groundwater are shallow. Nitrogen is not reduced at all. These systems are currently grandfathered, but the EPA and Suffolk County are considering regulations that could change this.
In 1973 new codes required installations of septic systems. Wastewater first enters an enclosed septic tank to allow solids to settle to the bottom of the tank and fats, oils and grease to float to the top. Microorganisms process the solids, reducing their volume by 50% to 90%. Cleaner effluent from the middle layer then enters either a leaching pit or field. A leaching pit, which has open sides to allow the wastewater to enter the ground, looks like a cesspool, but when located after a septic tank is the leaching part of a septic system. Where groundwater is high, there may be many, shallower leaching pits or a leaching field. A septic system treats wastewater by reducing total nitrogen by roughly 5-15% and minimizing pathogen contamination. A leaching field disperses wastewater over a larger area, closer to the surface, usually using perforated pipe on stone beds. Very shallow fields dispersing to the top 12 inches help to treat wastewater even further due to the oxygen and microbes found in the soils. Recent studies by the Massachusetts Alternative Septic Systems Test Center (MASSTC) show that this configuration removes contaminants of emerging concern, such as pharmaceuticals and personal care products. While leaching pits are prevalent in Suffolk County, most other jurisdictions prefer leaching fields to pits.
When septic tanks are used as pretreatment for enhanced treatment systems a two-chambered tank is preferred, as fewer solids migrate to the treatment unit. If an existing septic tank is in good condition, simply adding another in sequence will achieve the same results.