On-Site Purification of Nitrate-Polluted Groundwater Using Electrodialysis Reversal (EDR) System and Granule-Type Denitrification System

Abstract

The on-site purification system used is composed of an Electrodialysis Reversal (EDR) System and a Granule- Type Denitrification System. A pilot-scale experiment on using the on-site purification system was carried out for 14 months to investigate the characteristics of nitrogen removal from groundwater and the influence of the purification system on the surroundings. The results revealed the following : (1) Ninety-six kilograms of nitrogen was removed from groundwater in the examination area. (2) On investigation of the annual flux of nitrogen in the examination area in the same period, the calculated amount of nitrogen in flux in the examination area was 769kg as estimated by precipitation, fertilization, infiltration, denitrification and crop removal. As a result, 12.5% of infiltrated nitrogen was removed by the purification system. (3) The purification system did not affect the seasonal changes in chemical oxygen demand (COD) and the phosphorus (PO₄-P) concentration in the pond drain from the purification system. (4) It was observed occasionally that nitrous oxide (N₂O), an important greenhouse gas, was markedly produced in using the Granule-Type Denitrification System.