Separation of liquid pig manure by flocculation and ion exchange - Part 1: Laboratory experiments

A method of treating pig manure is described, such that the necessary storage volume is reduced to 25-30% of the original volume. The manure is separated into a water fraction with a low content of dry matter and nutrients, and into a slurry fraction which contains most of the dry matter and nutrients. The water fraction can be purified to appear like pure water with a desired nitrogen concentration. The separation is made by flocculation, a process whereby a flocculation agent collects the organic matter in the liquid manure into bigger particles, which causes them to sink. The experiments showed that it is possible to flocculate the volatile solids in 14 d old pig manure. For this purpose, a dosing of 0.2% of the clay mineral bentonite was sufficient to obtain adequate sedimentation. The liquid fraction can be purified by ion exchange with clinoptillolite or glauconite. It is possible to reach as low a content of ammonia as is wanted with an appropriate processing time. (C) 1998 Silsoe Research Institute.