Sewage Sludge Microbial Structures and Relations to Their Sources, Treatments, and Chemical Attributes.

Altina Lacerda Nascimento,Fernando Dini Andreote,Aline Renée Coscione,Fernando Carvalho Oliveira,Pedro Avelino Maia Andrade,Adijailton Jose Souza,Jussara Borges Regitano

doi:10.3389/fmicb.2018.01462

Abstract

Sewage sludges generation and their disposal have become one of the greatest challenges of the 21st century. They have great microbial diversity that may impact wastewater treatment plant (WWTP) efficiency and soil quality whether used as fertilizers. Therefore, this research aimed to characterize microbial community diversity and structure of 19 sewage sludges from São Paulo, Brazil, as well as to draw their relations to sludge sources [domestic and mixed (domestic+industrial)], biological treatments (redox conditions and liming), and chemical attributes, using molecular biology as a tool. All sludges revealed high bacterial diversity, but their sources and redox operating conditions as well as liming did not consistently affect bacterial community structures. Proteobacteria was the dominant phylum followed by Bacteroidetes and Firmicutes; whereas Clostridium was the dominant genus followed by Treponema, Propionibacterium, Syntrophus, and Desulfobulbus. The sludge samples could be clustered into six groups (C1 to C6) according their microbial structure similarities. Very high pH (≥11.9) was the main sludge attribute segregating C6, that presented very distinct microbial structure from the others. Its most dominant genera were Propionibacterium > > Comamonas > Brevundimonas > Methylobacterium ∼Stenotrophomonas ∼Cloacibacterium. The other clusters’ dominant genera were Clostridium > > Treponema > Desulfobulbus ∼Syntrophus. Moreover, high Fe and S were important modulators of microbial structure in certain sludges undertaking anaerobic treatment and having relatively low N-Kj, B, and P contents (C5). However, high N-Kj, B, P, and low Fe and Al contents were typical of domestic, unlimed, and aerobically treated sludges (C1). In general, heavy metals had little impact on microbial community structure of the sludges. However, our sludges shared a common core of 77 bacteria, mostly Clostridium, Treponema, Syntrophus, and Comamonas. They should dictate microbial functioning within WWTPs, except by SS12 and SS13.

Highlights

Urban centers fast growth and industrial activities intensification generate high volumes of effluents daily (Atashgahi et al, 2015), which are collected or discharged into the sewage network reaching wastewater treatment plants (WWTPs) (Shchegolkova et al, 2016)
The biological aims to degrade toxic organic compounds and reduce pathogenic organisms, mitigating effects on human health and environment (Seviour and Nielsen, 2010; Yang et al, 2011; Biswas and Turner, 2012; Xia et al, 2015). The residue of this activity, the sewage sludge, has great microbial diversity, which may vary depending on sewage origin, treatment condition, industrial activity, among others
Many factors may modulate microbial community structure within WWTPs, which may change from autotrophic to heterotrophic bacteria depending on effluent source, for example (Cydzik-Kwiatkowska and Zielinska, 2016)

Summary

Introduction

Urban centers fast growth and industrial activities intensification generate high volumes of effluents daily (Atashgahi et al, 2015), which are collected or discharged into the sewage network reaching wastewater treatment plants (WWTPs) (Shchegolkova et al, 2016). Many factors may modulate microbial community structure within WWTPs, which may change from autotrophic to heterotrophic bacteria depending on effluent source, for example (Cydzik-Kwiatkowska and Zielinska, 2016). Proteobacteria phylum (21–65%) was predominant in municipal WWTPs (domestic sewage), mostly belonging to Betaproteobacteria that represents a class of microorganisms related to organic matter degradation and nutrient cycling. Proteobacteria was abundant in industrial sewages that often have high concentrations of recalcitrant compounds originating from pharmaceutical industries, petroleum refineries, animal feed factories, and others (Ibarbalz et al, 2013; Ma et al, 2015). Microorganisms were most abundant in both anaerobic and anaerobic-aerobic than in aerobic system, but Proteobacteria was most abundant in aerobic whereas Bacteroidetes was most abundant in anaerobic bioreactors (Hu et al, 2012)

Objectives

Methods

Results

Conclusion