Pig slurry treatment by a combined helophytes-biodiscs system.

Abstract

Pig slurry was treated in a pilot wastewater treatment plant composed of a rotobioreactor based on rotating microalgae-biofilm discs, and a helophytes floating filter. Slurry in this work included cleaning water and its main characteristics were: 8,400-5,500 mg O2?L-1 COD, 1,575-800 mg O2?L-1 BOD5 and 2,275-1,799 mg?L-1 total nitrogen. Prior to the experiment, the rotobioreactor was conditioned adding pig slurry for 15 days in order to adapt the microorganisms biofilm to that substrate; at the end of the conditioning period, COD was 3,200 mg O2?L-1. The experiment was carried out for 10 days, adding 200 L pig slurry?day-1 to the rotobioreactor. The mixture in the reactor (diluted pig slurry) flowed by plug-flow to the helophytes floating filter to continue the depuration process. After 10-day treatment, the daily average reduction achieved was 88.3% COD, 97.6% BOD5, 78.5% phosphorous and 85.6% total nitrogen. From the results it was estimated that a load of 1 m3?day-1 pig slurry would require about 1,008 m2 discs area in the reactor and 54 m2 of helophytes floating filter.