Process for minute dosing of gravity media filters

Abstract

A process for minute dosing of effluent in a gravity media filter includes filtering incoming sewage in a pre-filter to produce a liquid effluent filtered to less than 100 microns, and pumping the effluent from the pre-filter to a pulse-feeding device preferably comprising a pressure vessel having a controlled pulsing unit. Effluent in the vessel is intermittently discharged in short pressure pulses volume controlled at preselected time intervals. The effluent from the pulse feeding device is forward pulse-fed to an array of drip irrigation emitters spread out over a surface area of a gravity filter containing a filter media such as a sand and gravel filter. Small doses of effluent are fed to the surface area of the gravity media filter by the emitters at a rate substantially less than a standard drip irrigation rate, owing to the intermittent pressure pulses. One preferred drip rate is greatly less than 2 liters per hour. The pre-filtering combined with the slow drip rate enhances continuous treatment of pathogens by available oxygen which avoids biological matter forming in the filter media while also maintaining a reasonable load rate.