Delaware Geological Survey Issues Report on Wastewater Treatment used for Rapid Infiltration Basin Systems

The Delaware Geological Survey released a new technical report entitled “Evaluation Of Wastewater Treatment Options Used In Rapid Infiltration Basin Systems (RIBS)” which was prepared by Müserref Türkmen of the Izmir Water and Sewearge Administration, Turkey, A. Scott Andres of the Delaware Geological Survey, Edward Walther of the South Water Management District, Florida, and William Ritter and Anastasia Chirnside of the University’s College of Agriculture and Natural Resources. DGS Bulletin 21A documents the results of a detailed study of wastewater treatment plant technologies and effectiveness of treatment types that are used to treat wastewater prior to disposal into the ground by rapid infiltration basin systems.

DGS Bulletin 21A is the first of four reports that evaluate RIBS, which are one of several land-based wastewater disposal methods used in Delaware. The study was prompted by concerns that RIBS may pose a threat to groundwater quality that would cause problems with the quality of water in our aquifers and in bodies of surface water. Other study components and reports evaluate hydraulic performance of RIBS, groundwater quality impacts of RIBS, and the use of simulation techniques to predict hydraulic and water quality impacts of RIBS.

This study evaluated results of testing of treated wastewater quality from plants located in Delaware, Massachusetts, North Carolina, and New Jersey that discharge the treated wastewater to RIBS. These plants used several different treatment technologies to remove pollutants prior to discharge. Test results amongst the different treatment types were compared to performance standards published in USEPA guidance documents and standard wastewater engineering textbooks. The evaluation found that all treatment types did not always meet performance standards, a finding that is not unusual, but does present a risk for Delaware’s hydrogeologic setting as many previous studies have documented that the shallow Columbia aquifer is especially vulnerable to contamination by nitrate from wastewater disposal. The Columbia aquifer is an important source of potable water and is the source of water for fair-weather streamflow.

The report fulfills part of the DGS’s mission to understand hydrologic systems and to advise, inform, and educate Delawareans about the results of such investigations for use in such topics as water supply and pollution, agriculture, public health, economic development, land-use planning, geologic hazards, environmental protection, energy and mineral resources, emergency management, and recreation.
Bulletin 21A is available in pdf format from the DGS web site at

For additional information, contact the Survey at (302) 831-2833 or via email at

For questions and information, contact DGS at, 302-831-2833