An evaluation of clay minerals as support materials in anaerobic digesters

Abstract

The use of different clay rninerals as support in anaerobic digestion has been studied: The suppon materials were evaluated in a batch microd.igester and their effect in the digestion process was measured ar the beginning of the process (scartup) and at an intermed iate point of the digescíon process when the maxim um differences between supporc rnaterials were observed (working digester). Ali the systems with support were more efficient than the control (support-free). The follow ing arder of purification was established: STARTUP: Bentonite > tale > vermicul ite > nontronite > montmori llonite > pyrophyll ite > stevensire > sepiol ite.

WORKI NG DIGESTER: Sepiolite > stevensite > tale > nontronite > bentonite > rnoncmorillonice > ver m icu l ice > pyrophyllite.

Bentonite, montmorillonite, tale and vermieulite were favourable for startup, as they rapidly

reteased Ca1

or MgH to che medium.

The best COD removal efficiencies were obtained with sepiol ite and scevensite which release MgH progresively to the med ium . The presence of FeH , Co2 • and Nii... in the structure of che mineral stimulated anaerobic digescion.