T. Mahony

Methanogenic population structure in a variety of anaerobic bioreactors

The methanogenic community structures of six anaerobic sludges were examined using culture-independent techniques. The sludges were obtained from full-scale and laboratory-scale bioreactors, treating a variety of low- and high-strength, simple and complex wastewaters at psychrophilic (10-14 degrees C), mesophilic (37 degrees C) and thermophilic (55 degrees C) temperatures. Amplified rDNA restriction analysis identified 18 methanogenic operational taxonomic units in the six samples. 16S rRNA gene sequencing and phylogenetic reconstruction demonstrated that five separate groups of methanogens were represented with Methanosaeta-like species dominant in all sludges, but particularly in samples from a psychrophilic bioreactor treating low-strength synthetic sewage (75% of all clones detected).

Biofilms in Medicine, Industry and Environmental Biotechnology - Characteristics, Analysis and Control

Biofilms are of great practical importance for beneficial technologies such as water and wastewater treatment and bioremediation of groundwater and soil. In other settings biofilms cause severe problems, for example in 65% of bacterial infections currently treated by clinicians (particularly those associated with prosthetics and implants), accelerated corrosion in industrial systems, oil souring and biofouling. Until recently, the structure and function of biofilms could only be inferred from gross measures of biomass and metabolic activity. This limitation meant that investigators involved in biofilm research and application had only a crude understanding of the microbial ecology, physical structure and chemical characteristics of biofilms. Consequently, opportunities for the exploitation and control of biofilms were very limited. The past decade has witnessed the development of several new techniques to elucidate the structure and function of biofilms. Examples include: the use of molecular probes that identify different microbes in complex communities as well as their metabolic functions; the use of microsensors that show concentration gradients of key nutrients and chemicals; the use of confocal laser scanning microscopy to describe the physical structure of biofilms and the development of a new generation of mathematical models that allow for the prediction of biofilm structure and function. However, much progress remains to be made in efforts to understand, control and exploit biofilms. This timely book will introduce its readers to the structure and function of biofilms at a fundamental level as determined during the past decade of research, including: Extracellular polymers as the biofilm matrix; Biofilm phenotype (differential gene expression, interspecies signalling); Biofilm ecology; Biofilm monitoring; Resistance of biofilms to antimicrobial agents and Biofilm abatement. Biofilms in Medicine, Industry and Environmental Technology offers a holistic and multi-disciplinary description of the topic, including biofilm formation and composition, but also biofilm monitoring, disinfection and control. All these aspects are presented from three points of views: medical, industrial and environmental biotechnological in a compact, easy to read format.

The hydrolysis and biogas production of complex cellulosic substrates using three anaerobic biomass sources.

In this study, the ability of various sludges to digest a diverse range of cellulose and cellulose-derived substrates was assessed at different temperatures to elucidate the factors affecting hydrolysis. For this purpose, the biogas production was monitored and the specific biogas activity (SBA) of the sludges was employed to compare the performance of three anaerobic sludges on the degradation of a variety of complex cellulose sources, across a range of temperatures. The sludge with the highest performance on complex substrates was derived from a full-scale bioreactor treating sewage at 37 °C. Hydrolysis was the rate-limiting step during the degradation of complex substrates. No activity was recorded for the synthetic cellulose compound carboxymethylcellulose (CMC) using any of the sludges tested. Increased temperature led to an increase in hydrolysis rates and thus SBA values. The non-granular nature of the mesophilic sludge played a positive role in the hydrolysis of solid substrates, while the granular sludges proved more effective on the degradation of soluble compounds.

Low temperature anaerobic biotreatment of priority pollutants

The effect of low operating temperature and pollutant concentration on the performance of five anaerobic hybrid reactors was investigated. Stable and efficient long-term (>400 days) treatment of a cold (6-13 degrees C), volatile fatty acid (VFA)-based, wastewater was achieved at applied organic loading rates (OLRs) of 5 kg chemical oxygen demand (COD) m(-3) d(-1) with COD removal efficiencies c. 84% at 6 degrees C (sludge loading rate (SLR) 1.04-1.46 kg COD kg [VSS](-1) d(-1)). VFA-based wastewaters, containing up to 14 g pentachlorophenol (PCP) m(-3) d(-1) or 155 g toluene m(-3) d(-1) were successfully treated at applied OLRs of 5-7 kg COD m(-3) d(-1). Despite transient declines in reactor performance in response to increasing toxicant loading rates, stable operation (COD removal efficiencies > 90%) and satisfactory toxicant removal efficiencies (>88%) were demonstrated by the systems.

Cold adaptation and replicable microbial community development during long-term low temperature anaerobic digestion treatment of synthetic sewage

ABSTRACT The development and activity of a cold‐adapting microbial community was monitored during low‐temperature anaerobic digestion (LtAD) treatment of wastewater. Two replicate hybrid anaerobic sludge bed‐fixed‐film reactors treated a synthetic sewage wastewater at 12°C, at organic loading rates of 0.25‐1.0 kg chemical oxygen demand (COD) m−3 d−1, over 889 days. The inoculum was obtained from a full‐scale anaerobic digestion reactor, which was operated at 37°C. Both LtAD reactors readily degraded the influent with COD removal efficiencies regularly exceeding 78% for both the total and soluble COD fractions. The biomass from both reactors was sampled temporally and tested for activity against hydrolytic and methanogenic substrates at 12°C and 37°C. Data indicated that significantly enhanced low‐temperature hydrolytic and methanogenic activity developed in both systems. For example, the hydrolysis rate constant (k) at 12°C had increased 20‐30‐fold by comparison to the inoculum by day 500. Substrate affinity also increased for hydrolytic substrates at low temperature. Next generation sequencing demonstrated that a shift in a community structure occurred over the trial, involving a 1‐log‐fold change in 25 SEQS (OTU‐free approach) from the inoculum. Microbial community structure changes and process performance were replicable in the LtAD reactors.