Tracking relations among bacterial and protozoan communities in wastewater treatment plants

Background: Understanding the interactions between prokaryotic and eukaryotic populations in complex environments can be challenging. Particularly, there is a recognized difficulty in establishing how the interactions between the bacterial and the protozoan populations can affect the performance of wastewater treatment plants (WWTP). Objectives: In order to determine the relationships between microbial communities (protozoa, metazoa and filamentous bacteria) and abiotic parameters (physical-chemical and operational), thirty seven WWTP with activated sludge process were studied in Portugal, during two years, in a trimestral sampling strategy. Methods: Samples were collected to enable a molecular characterization of the microbiota. In order to ensure the diversity of microorganisms, 100 samples were selected based on their geographic localization and time-spaced to track relationships within bacteria and protozoa. A 16S rRNA gene PCR-DGGE approach was carried out for bacterial community fingerprinting. The resulting profiles were analysed together with the results obtained from the survey of the protozoa populations. Finally, the study of the correlations between the physical-chemical and operational parameters and the microbial communities was also investigated. Conclusions: The study of these interactions constitutes a strategy for the understanding of how the different metabolic groups of prokaryotic and protozoa are affected by the relations between this populations, allowing a better prediction of the overall community dynamics. This will allow setting the conditions that better contribute to improve the wastewater treatment while increasing the knowledge of overall communities networking in complex environments

Interactions between eukaryotic and prokaryotic microorganisms in activated sludge: a molecular approach to improve wastewater treatment

Wastewater treatment is one of the most important biotechnological processes which are used worldwide to treat municipal and industrial sewage. Activated-sludge processes aim to achieve a maximal reduction of the Biological Oxygen Demand (BOD) of wastewater with a minimal production of biological solids. Even though many microbiological methods are available to study the activated sludge communities, many recent questions on the role of certain microorganisms are kept unanswered. A crucial addressed by the present work is to know if the presence of different groups of bacteria and protozoa lead to significant consequences on the process performance. Focusing on the importance of the interactions between the prokaryotic and the eukaryotic populations, the work will contribute to the knowledge of how microbial communities are established in a complex environment as the activated sludge processes

Prokaryotic and eukaryotic populations in activated-sludge

Protozoa play a direct role by reducing through grazing the amount of freely-suspended and loosely-attached bacterial cells. Also, filamentous bacteria, although endangering the performance of wastewater treatment plants (WWTP), should be considered as normal components of the activated-sludge microbial community.Correlations between plant performance and the abundance of certain species have been studied, being the Sludge Biotic Index (1) the best known method to assess the activated-sludge plant performance through the analysis of protozoa and small metazoan communities. However, few studies have established reliable relationships between the prokaryotic and eukaryotic populations (2). The present work presents data on the prevalence, abundance and distribution of protozoa, small metazoa and filamentous bacteria on 37 activated-sludge Portuguese WWTP operating under different environmental conditions, during one year, including data on the correlations between the prokaryotic and eukaryotic components. The most frequent protozoa were the crawling (CC) and the attached sessile (ASC) ciliates, being Aspidisca cicada, Epistylis spp. and Microthorax sp. the most abundant. The most frequent filamentous bacteria were Types 0041/0675, 0092, 1851, Nocardioforms, Microthrix parvicella, Nostocoida limicola II and Haliscomenobacter hydrossis; only the former four were found dominant in all samples. Correlations were found to be significantly positive (p<0,05) between Nostocoida limicola II and Type 0092 and negative between Thiothrix II and Microthrix parvicella. Correlations between filamentous bacteria and protozoa were significantly positive (p<0,05) for freely swimming ciliates (FSC) and Type 0092 and for flagellates (F)/Thiothrix II. Negative correlations were found for FSC and Microthrix parvicella, F and Nocardioforms

Biodegradation of diethylketone by two fungi

Two morphologically different fungi (one green and one white) from contaminated bioreactors with an aqueous solution of diethylketone and Streptococcus equisimilis were isolated and characterized at molecular level by sequencing the amplified ITS region. The ITS region sequence showed 99% match with Alternaria genera for the green fungi and 99% match with the Penicillium genera for the white fungi. The performance of these two fungi to biodegrade different concentrations of diethylketone from aqueous solutions was evaluated. The biodegradation of diethylketone was studied for an initial diethylketone concentration ranging from 0.5 to 4g/L in a batch mode of operation. The biodegradation rate found for both fungi followed the pseudo-second order kinetics for initial concentrations higher than 0.5 g/L and the resulting kinetic parameters are reported. The removal percentages obtained were approximately 100%, for all the initial concentrations tested

PROTOFILWW: two year-sampling of protozoa, little metazoa and filamentous bacteria in 37 Portuguese wastewater treatment plants

European Biotechnology Congress 2015, BucharestActivated-sludge represents a component of the largest biotechnology in the world: wastewater treatment. Yet it differs substantially from the large-scale production of economically important metabolites or biomass: for decades, the aerating tanks of the wastewater treatment plants (WWTP) have remained black boxes, its complexity discouraging most microbiologists. Moreover, studies integrating both the prokaryotic and the eukaryotic populations in activated-sludge are, even presently, rare. Particularly, there is an assumed difficulty in establishing how the interactions between the bacterial and the protozoa populations can affect the performance of the activated sludge system. On the other hand, excessive growth of filamentous bacteria is considered the main concern of WWTP managers. It is said that every WWTP in the world went, go or will go through the well-known phenomena of filamentous bulking or foaming. It is also said that the basis for understanding and fighting these problems depends on the proper identification of the causing microorganisms: by acting upon the factor favoring the problematic species, one can expect to control its overgrowth. In the 80s and 90s of the last century, some surveys suddenly revealed the extent and severity of filamentous overgrowth. In Portugal, a detailed investigation has been carried out recently through the PROTOFILWW Project: protozoa, little metazoa and filamentous bacteria populations of 37 WWTP were extensively studied during two years. The prevalence and the correlations among the prokaryotic and eukaryotic components and between them and the operational and performance parameters will be presented

PROTOFILWW: insights in the ecology of activated-sludge systems

Treatment of wastewater by activated sludge processes represent s a component of the largest biotechnology in the world. Yet activated sludge system s correspond to microbial ecosystems complex enough to discourage most microbial ecologis ts. The importance and the role of the protozoa and little metazoa community in the pu rification process of activated- sludge plants are well established. Even though, very few studi es have established reliable relationships between the microfauna and the operational condit ions or physical-chemical parameters [1,2]. Another component that deserves particular in terest by managers and technicians is the excessive growth of filamentous bacteria, ca using the known phenomena of bulking and foaming. The present investigation being carried on aims at the identifi cation of the microfauna (protozoa plus small metazoa) and filamentous bacteria on a wid e set of activated-sludge wastewater treatment plants (WWTP), working on different region s of Portugal, under different operational and physical-chemical conditions in order to allow for the establishment of consistent relationships between the former and the latter. Each of the WWTP will be studied several times allowing for the identification of the causes and for the answer of questions such as Why do different filame ntous or microfauna species appear in similar conditions? Do the WWTP tend to maintain the same populations or do these changes often? Are the changes cyclic or occasional? One of the most important objectives of the present proposal is the implementation of molecular techniques to allow for the confirmation of the ident ifications of the filamentous bacteria: the identification by morphological features can be p roblematic and erroneous

Biodegradation of diethylketone by Penicillium sp. and Alternaria sp.: a comparative study biodegradation of diethylketone by fungi

Two contaminating fungi were isolated from a bioreactor containing diethylketone and Streptococcus equisimilis, subsequently characterized at molecular level and identified as belonging to the Alternaria and Penicillium genera. The ability of these fungi to biodegrade DEK is evaluated. The kinetic parameters are estimated using four growth kinetic models for biodegradation of organic compounds available in literature. The experimental data for Alternaria sp. and Penicillium sp. was found to be better fitted by the Haldane and the Luong respectively. Biodegradation rate kinetics was evaluated using zero-order, pseudo-first order, pseudo-second order and three-half order models. The pseudo-second-order model was found suitable for all the concentrations of DEK tested for the biodegradation assays using Penicillium sp. whereas for the Alternaria sp. this model just describes properly the assays with initial concentrations of DEK higher than 0.5 g/L. The percentage of biodegraded DEK were approximately 100%, for all the initial concentrations tested