Activated sludge characterization through microscopy: A review on quantitative image analysis and chemometric techniques

Abstract

In wastewater treatment processes, and particularly in activated sludge systems, efficiency is quite dependent on the operating conditions, and a number of problems may arise due to sludge structure and proliferation of specific microorganisms. In fact, bacterial communities and protozoa identification by microscopy inspection is already routinely employed in a considerable number of cases. Furthermore, quantitative image analysis techniques have been increasingly used throughout the years for the assessment of aggregates and filamentous bacteria properties. These procedures are able to provide an ever growing amount of data for wastewater treatment processes in which chemometric techniques can be a valuable tool. However, the determination of microbial communities' properties remains a current challenge in spite of the great diversity of microscopy techniques applied. In this review, activated sludge characterization is discussed highlighting the aggregates structure and filamentous bacteria determination by image analysis on bright-field, phase-contrast, and fluorescence microscopy. An in-depth analysis is performed to summarize the many new findings that have been obtained, and future developments for these biological processes are further discussed.

Experimental Methods in Wastewater Treatment

“…Further details about the analytical PHA determination techniques can be found in the original sources (Baetens et al, 2002;Oehmen et al, 2005b). From a microscopic visualization perspective, Nile blue A stain can be used to qualitatively visualize PHAs and Neisser stain for poly-P (Mino et al, 1998;Mesquita et al, 2013). Further details about the microscopic observation of these and other intracellular polymers and the use of different stains can be found in Chapter 7 on Microscopy.…”

“…However, as previously discussed, their determination in sludge samples from full-scale systems may not be accurate enough. Tentatively, Periodic Acid-Schiff (PAS) stain can be used to get a rough microscopic qualitative estimation of glycogen and other carbohydrate granules present in the cells (Mesquita et al, 2013).…”

“…While some research groups have been developing specific image analysis software to infer this information (Amaral and Ferreira, 2005;Da Motta et al, 2001a, 2001bJenneé et al, 2004;van Dierdonck et al, 2013), also freeware software is available (such as ImageJ or FIJI (http://fiji.sc/Fiji)) to perform a basic analysis. A comprehensive overview of what is currently available in this image analysis domain is available in dedicated literature (Mesquita et al, 2013). For microscopic monitoring that is more focused on revealing the specific microbial communities present, FISH analysis can be interesting; the reader is referred to the FISH handbook for biological wastewater treatment .…”

Avaliação Do Desempenho Das Estações De Tratamento Por Lodo Ativado No Grande Recife Associada Com Análise De Imagens Dos Micro-Organismos Presentes No Lodo Ativado

“…Estes procedimentos são capazes de fornecer uma quantidade cada vez maior de dados para o controle das estações de tratamento de efluentes (Mesquita et al, 2013). Papadimitriou et al (2010) investigaram a correlação ente espécies de protozoários e parâmetros físico-químicos de monitoramento, como o pH, NO3, NH4, OD.…”

“…Atualmente, esse processo é um dos mais utilizados mundialmente para o tratamento de efluentes domésticos e industriais caracterizados por carga orgânica biodegradável e substratos nitrogenados, e essa popularidade se deve por possuir eficiência entre 95 e 98% de redução da poluição (Hammer e Hammer, 2006;Wiesmann et al, 2007). O princípio deste processo está ligada à oxidação bioquímica de diversos poluentes orgânicos e inorgânicos a partir da participação efetiva de uma variada biomassa microbiana, suspensa no meio e mantida sob concentração constante de oxigênio dissolvido (Bento et al, 2005;Mesquita et al, 2013).Um exame microscópio do lodo ativado revela que ele é formado por uma população Área temática: Engenharia Ambiental e Tecnologias Limpas 1 …”