ANAEROBIC DIGESTION OF WASTEWATER WITH HIGH SULFATE CONCENTRATION USING MICRO-AERATION AND NATURAL ZEOLITES

S Montalvo,P Pérez,L Guerrero,C Huiliñir,M González,H Prades

doi:10.1590/0104-6632.20160334s20150261

Abstract

Abstract - The behavior of anaerobic digestion in batch and UASB reactors using a microaerobic process and natural zeolites was studied. Laboratory assays were carried out across 4 sets of variables: different COD/SO 42- ratios, different airflow levels, with and without natural zeolites and room and mesophilic controlled temperatures. The microaerobic process demonstrated hydrogen sulfide removal levels exceeding 90% in most cases, while maintaining the flammable condition of the generated biogas. The level of COD removal exceeded 75% in UASB reactors despite their operation under very low hydraulic retention times (2.8–4.8 hours). The effectiveness of natural zeolites in accelerating UASB reactor startup was demonstrated. Results showing the positive influence of zeolites on the granulation process in UASB reactors were also achieved. Keywords : Granulation process; Micro-aeration; Sulfate; Sulfide; Temperature; UASB; Zeolite. INTRODUCTION The advantages of anaerobic technology in or-ganic matter removal from wastewater have been fully demonstrated in multiple studies and full-scale implementations (Pabon

Highlights

The advantages of anaerobic technology in organic matter removal from wastewater have been fully demonstrated in multiple studies and full-scale implementations (Pabón et al, 2013; Kothari et al, 2014; Zhang et al, 2014)
This paper evaluates the performance of the anaerobic process operating at different airflow levels and COD/SO42- ratios, with and without the presence of natural zeolites and at both room and mesophilic controlled (35 oC) temperatures
COD removal was nearly 100% after 30 days of anaerobic digestion for all COD/SO42- ratios. Another cause for the persistence of sulfates after the aeration phase may be that the sulfate-reducing bacteria (SRB), which can be autotrophic or heterotrophic, requires substrates such as hydrogen, carbon dioxide, acetate, propionate, butyrate and ethanol, which are mainly generated in the anaerobic fermentative process step

Summary

Introduction

The advantages of anaerobic technology in organic matter removal from wastewater have been fully demonstrated in multiple studies and full-scale implementations (Pabón et al, 2013; Kothari et al, 2014; Zhang et al, 2014). It is known that sulfide in the liquid phase can be toxic to MA at certain concentration values depending on several factors such as wastewater characteristics, temperature, pH and others (Cohen et al, 1982; Iza et al, 1986; Rinzema and Lettinga, 1988; Nanqi et al., 2002). For this reason it is more convenient to remove the sulfides in the liquid phase.

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Results

Conclusion