Understanding Onsite Systems

This website offers information regarding the function of onsite wastewater treatment (septic) systems. A list of the information available is below.

When properly sited, designed, installed, and maintained, onsite wastewater treatment systems are often the best choice for wastewater treatment in many areas, from public health, environmental, and economic standpoints. Onsite wastewater treatment allows water used in homes and businesses to be treated and recycled to replenish local groundwater supplies. This benefit of onsite treatment is not realized with municipal wastewater treatment, which discharges partially treated wastewater directly to rivers and coastal waters, sending wastewater either further downstream or out of the watershed entirely, and returning none to the landscape to replenish groundwater aquifers. This loss of groundwater recharge reduces the amount of groundwater available for drinking water wells. In coastal areas, depletion of ground water resources can lead to salt-water intrusion and loss of potable freshwater supplies. Because groundwater is the main source of flow to streams during dry weather, loss of recharge can also lower streamflow to levels that can no longer support healthy aquatic life.

The two main classes, or groups, of onsite wastewater treatment systems are explained in the following sections, and are termed conventional treatment systems and advanced treatment, or innovative and alternative systems.

The conventional and advanced treatment system designs described and explained below are those currently approved for use in Rhode Island (as of November 2006). Many of these designs are used elsewhere in North America. Information and regulations about onsite wastewater system design for New England states can be found at the following sites: