Effluent Disposal via Groundwater Recharge Systems
Groundwater recharge systems are a viable alternative when surface water discharge options are limited, or where water quality constraints are severe.
Groundwater recharge systems are certainly more challenging than surface water discharge systems. They require specific hydrogeological conditions and are more sensitive to treatment process upsets. They do, however, provide significant benefits in the right applications. Effluent that is discharged to the groundwater receives significant
additional treatment as the effluent flows through the vegetative layer (in the case of surface land application) and through the soil to the groundwater.
Leach Field Systems
The most common groundwater recharge system, particularly for smaller flow applications, is the conventional leach field system, of which there are many variations. These systems require a fair amount of land and soils with at least a moderate permeability. They have minimal aesthetic impact on the landscape, but are fairly sensitive to treatment process upsets.
Drip Irrigation Systems
A relatively new recharge system – drip irrigation – is being used on a trial basis in areas where the soil and topographical conditions do not allow a conventional leach field.
Slow Rate Land Applications
In areas that have access to large quantities of land, slow rate land application to either grass crops or woodlands is fairly common. Land application to vegetated surfaces provides significant additional treatment. These systems are typically used seasonally, which make them a good summer supplement to a year-round traditional discharge, or requires large effluent storage capabilities for winter months. An alternative to winter storage in northern New England is to employ snow making. These groundwater recharge systems are the most forgiving relative to the treatment facility performance but they are the most land intensive. Thus they are most applicable to the rural areas of New England.
Rapid Infiltration
A less land intensive application is rapid infiltration, wherein large quantities of effluent are discharged to earthen basins. Rapid infiltration requires deep deposits of well drained soils. These systems can be used year round and are common on Cape Cod where the soils are favorable and where ocean discharge is prohibited. Rapid infiltration systems are also relatively resilient to treatment process upsets.
Reuse, Irrigation
Another groundwater recharge option gaining acceptance is utilization of the effluent for irrigation, particularly at golf courses. This sort of reuse typically requires a higher level of treatment before discharge, but makes valuable use of the effluent.
Vertical Recharge Systems
One of the latest innovations with respect to groundwater recharge is the use of vertical recharge systems (recharge wells and wicks). These sorts of systems have been used mostly in California and Florida. There are a couple of installations in New England. The systems offer significant siting advantages as compared to conventional groundwater recharge systems, but are the most sensitive system relative to effluent quality and therefore require higher levels of treatment prior to discharge.
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