Treatment of agricultural and domestic effluents in constructed downflow reed beds employing recirculation

摘要

In this paper, the efficacy of a full-scale three-stage downflow reed bed treatment system employing water recirculation was examined for the treatment of medium strength waste effluent with an average BOD_5 of 464 mg l~-1 and ammoniacal-nitrogen of 253.2 mg l~-1. Different methods of dosing the sub-beds in the downflow stages wer first tested. Dosing half of the sub-beds in a stage for 3-4 days per week while the other were resting gave a satisfactory operation. In the main experimental trials with recirculation the average BOD_5 of the influent was reduced by 99.1 /100 form 464 to 4 mg l~-1, whereas (CD was reduced by 70.1 /100 form 1006 to 271 mg l~-1.