Microbiologically induced deterioration of concrete--a review

Investigation of the interface of fungal mycelium composite building materials by means of low-vacuum scanning electron microscopy

Low-vacuum scanning electron microscopy (low-vacuum SEM) is widely used for different applications, such as the investigation of noncoated specimen or the observation of biological materials, which are not stable to high vacuum. In this study, the combination of mineral building materials (concrete or clay plaster) with a biological composite (fungal mycelium composite) by using low-vacuum SEM was investigated. Fungal biotechnology is increasingly gaining prominence in addressing the challenges of sustainability transformation. The construction industry is one of the biggest contributors to the climate crises and, therefore, can highly profit from applications based on regenerative fungal materials. In this work, a fungal mycelium composite is used as alternative to conventional insulating materials like Styrofoam. However, to adapt bio-based products to the construction industry, investigations, optimisations and adaptations to existing solutions are needed. This paper examines the compatibility between fungal mycelium materials with mineral-based materials to demonstrate basic feasibility. For this purpose, fresh and hardened concrete specimens as well as clay plaster samples are combined with growing mycelium from the tinder fungus Fomes fomentarius. The contact zone between the mycelium composite and the mineral building materials is examined by scanning electron microscopy (SEM). The combination of these materials proves to be feasible in general. The use of hardened concrete or clay with living mycelium composite appears to be the favoured variant, as the hyphae can grow into the surface of the building material and thus a layered structure with a stable connection is formed. In order to work with the combination of low-density organic materials and higher-density inorganic materials simultaneously, low-vacuum SEM offers a suitable method to deliver results with reduced effort in preparation while maintaining high capture and magnification quality. Not only are image recordings possible with SE and BSE, but EDX measurements can also be carried out quickly without the influence of a coating. Depending on the signal used, as well as the magnification, image-recording strategies must be adapted. Especially when using SE, an image-integration method was used to reduce the build-up of point charges from the electron beam, which damages the mycelial hyphae. Additionally using different signals during image capture is recommended to confirm acquired information, avoiding misinterpretations.

Fabrication of green anti-microbial and anti-static cement building bricks

The design cement mix of grade 350 was created in accordance with Egyptian Standards by partially substituting the fine aggregate with WPVC waste in various weight percentages (10, 20, 30, 40, 50, 75, and 100%). A control mix with 0% replacement was also prepared. The W/C ratio was about 0.5 for all mixes. Compressive, flexure strength, bulk density, and absorption tests were studied. For WPVC replacement, until 30%, compressive strength and flexure strength are acceptable with respect to standerds. Thermal treatment at 200 °C improves the compressive strength, flexure strength and water absorption for 20% WPVC only. The dielectric properties of all cement paste mixes before and after heat treatment, over a frequency range (0.1-106 Hz), were measured as a function of frequency. For dielectric properties and conductivity, an improvement was obtained until 30% WPVC. After this percentage, the dielectric properties and the conductivity got worse. So, cement paste with 30% WPVC as replacement of sand is the optimum ratio with conductivity in range of 10-12 S/cm, which is a good choice for antistatic cement paste applications (10-10-10-12 S/cm). The antimicrobial efficacy of the prepared cement samples of WPVC concentrations (0, 20 and 30) % were studied, the number of grown microbial colonies decreased for all the samples compared to control tap water and decreased by introducing WPVC into the cement paste sample. So, it is recommended to use these samples in places that should be carefully shielded from bacterial infections and static electric charge dangers.

First Genome Sequence of the Microcolonial Black Fungus Saxispiralis lemnorum MUM 23.14: Insights into the Unique Genomic Traits of the Aeminiaceae Family

Saxispiralis lemnorum MUM 23.14 is an extremotolerant microcolonial black fungus, originally isolated from a biodeteriorated limestone artwork in Portugal. This recently introduced species belongs to the Aeminiaceae family, representing the second member of this monophyletic clade. This fungus exhibits a unique set of characteristics, including xerophily, cold tolerance, high UV radiation tolerance, and an exceptional ability to thrive in NaCl concentrations of up to 30% while also enduring pH levels ranging from 5 to 11. To gain insights into its genomic traits associated with stress resistance mechanisms, specialization, and their potential implications in stone biodeterioration, we conducted a comprehensive genome sequencing and analysis. This draft genome not only marks the first for the Saxispiralis genus but also the second for the Aeminiaceae family. Furthermore, we performed two comparative genomic analyses: one focusing on the closest relative within the Aeminiaceae family, Aeminium ludgeri, and another encompassing the genome of different extremotolerant black fungi. In this study, we successfully achieved high genome completeness for S. lemnorum and confirmed its close phylogenetic relationship to A. ludgeri. Our findings revealed traits contributing to its extremophilic nature and provided insights into potential mechanisms contributing to stone biodeterioration. Many traits are common to both Aeminiaceae species and are shared with other black fungi, while numerous unique traits may be attributed to species-specific characteristics.

Cytotoxic-Ag-Modified Eggshell Membrane Nanocomposites as Bactericides in Concrete Mortar

Against the backdrop of escalating infrastructure budgets worldwide, a notable portion-up to 45%-is allocated to maintenance endeavors rather than innovative infrastructure development. A substantial fraction of this maintenance commitment involves combatting concrete degradation due to microbial attacks. In response, this study endeavors to propose a remedial strategy employing nano metals and repurposed materials within cement mortar. The methodology entails the adsorption onto eggshell membranes (ESM) of silver nitrate (ESM/AgNO3) or silver nanoparticles (ESM/AgNPs) yielding silver-eggshell membrane composites. Subsequently, the resulting silver-eggshell membrane composites were introduced in different proportions to replace cement, resulting in the formulation of ten distinct mortar compositions. A thorough analysis encompassing a range of techniques, such as spectrophotometry, scanning electron microscopy, thermogravimetric analysis, X-ray fluorescence analysis, X-ray diffraction (XRD), and MTT assay, was performed on these composite blends. Additionally, evaluations of both compressive and tensile strengths were carried out. The mortar blends 3, 5, and 6, characterized by 2% ESM/AgNO3, 1% ESM/AgNPs, and 2% ESM/AgNPs cement replacement, respectively, exhibited remarkable antimicrobial efficacy, manifesting in substantial reduction in microbial cell viability (up to 50%) of typical waste activated sludge. Concurrently, a marginal reduction of approximately 10% in compressive strength was noted, juxtaposed with an insignificant change in tensile strength. This investigation sheds light on a promising avenue for addressing concrete deterioration while navigating the balance between material performance and structural integrity.

Review on Microbially Influenced Concrete Corrosion

Microbially influenced concrete corrosion (MICC) causes substantial financial losses to modern societies. Concrete corrosion with various environmental factors has been studied extensively over several decades. With the enhancement of public awareness on the environmental and economic impacts of microbial corrosion, MICC draws increasingly public attention. In this review, the roles of various microbial communities on MICC and corresponding protective measures against MICC are described. Also, the current status and research methodology of MICC are discussed. Thus, this review aims at providing insight into MICC and its mechanisms as well as the development of protection possibilities.

Comparison of bacterial communities on the surface of concrete breakwater structures and ambient bacterioplankton

Breakwater structures made of concrete are used widely around the world, and the bacteria living on these surfaces can cause the concrete to deteriorate. In this study, we collected bacterial biofilms from concrete breakwater structures located along the coast of an island, a mainland coast, and a freshwater riverbank as well as planktonic water samples from each site, and we analyzed their bacterial community structures using Illumina sequencing. At the phylum level, Proteobacteria and Actinobacteria dominated planktonic samples, whereas Cyanobacteria, Proteobacteria, and Bacteroidetes dominated the biofilm samples. High Cyanobacteria abundance was found in all biofilm samples. Bacterial communities significantly varied between planktonic and biofilm samples and between biofilm samples from seawater and freshwater. Only a small number of bacterial operational taxonomic units were shared by planktonic and biofilm samples from each sampling site. The permanganate index in ambient water had a more significant impact on biofilm bacterial communities than on planktonic samples. Additionally, ammonia nitrogen and total nitrogen contents were positively correlated and salinity was negatively correlated with bacterial beta diversity in biofilm samples.

Design and Experimental Evaluation of a New RNA-FISH Probe to Detect and Identify Paenibacillus sp

Paenibacillus, rod-saped gram-positive endospores forming aerobic or facultative anaerobic bacteria, colonize diverse ecosystems and are involved in the biodegradation of cultural heritage assets. Biodeteriogenic microorganisms can be easily detected/identified by ribonucleic acid- fluorescent in situ hybridization RNA-FISH with specific probes. In this work, probes designed in silico were analyzed to calculate hybridization efficiency and specificity by varying the formamide concentration in the hybridization. The Pab489 probe showed excellent in silico performance with high theoretical maximum efficiency hybridization (99.99%) and specificity and was selected for experimental assays with target Paenibacillus sp. and non-target biodeteriogenic microorganisms. Results assessed by epifluorescence microscopy and flow cytometry revealed that, regardless of the formamide concentration, it was possible to observe that the Pab489-Cy3 probe had a similar signal intensity to the EUB338-Cy3 probe (positive control), so the presence of formamide, a highly toxic and carcinogenic compound used to aid the hybridization process, is not necessary. The designed probe used in FISH assays allows specific in situ identification of Paenibacillus spp. in microbial communities in a culture-independent way. This approach can be employed for screening Paenibacillus spp., showing great potential for future application in biodeterioration of heritage assets, in the search for Paenibacillus strains that produce compounds with biotechnological or medical potential.

The effect of low-pH concrete on microbial community development in bentonite suspensions as a model for microbial activity prediction in future nuclear waste repository

Concrete as an important component of an engineered barrier system in deep geological repositories (DGR) for radioactive waste may come into contact with bentonite, or other clays, rich in indigenous microorganisms, with potentially harmful impacts on barrier integrity. Our study aimed to assess the effect of a concrete environment on indigenous bentonite and groundwater microbial communities as these particular conditions will select for the potentially harmful microorganisms to the concrete in the future DGR. The two-month experiment under anoxic conditions consisted of crushed, aged, low-pH concrete, Czech Ca-Mg bentonite, and anoxic groundwater, with control samples without concrete or with sterile groundwater. The microbial diversity and proliferation were estimated by qPCR and 16S rRNA gene amplicon sequencing. The presence of concrete had a strong effect on microbial diversity and reduced the increase in total microbial biomass, though low-pH concrete harbored indigenous bacteria. The growth of sulfate reducers was also limited in concrete samples. Several genera, such as Massilia, Citrifermentans, and Lacunisphaera, dominant in bentonite controls, were suppressed in concrete-containing samples. In contrast, genera such as Bacillus, Dethiobacter and Anaerosolibacter specifically proliferated in the presence of concrete. Genera such as Thermincola or Pseudomonas exhibited high versatility and proliferated well under both conditions. Because several of the detected bacterial genera are known to affect concrete integrity, further long-term studies are needed to estimate the effect of bentonite and groundwater microorganisms on concrete stability in future DGR.

Development of Antibacterial and Antifouling Innovative and Eco-Sustainable Sol-Gel Based Materials: From Marine Areas Protection to Healthcare Applications

Bacterial colonization of surfaces is the leading cause of deterioration and contaminations. Fouling and bacterial settlement led to damaged coatings, allowing microorganisms to fracture and reach the inner section. Therefore, effective treatment of surface damaged material is helpful to detach bio-settlement from the surface and prevent deterioration. Moreover, surface coatings can withdraw biofouling and bacterial colonization due to inherent biomaterial characteristics, such as superhydrophobicity, avoiding bacterial resistance. Fouling was a past problem, yet its untargeted toxicity led to critical environmental concerns, and its use became forbidden. As a response, research shifted focus approaching a biocompatible alternative such as exciting developments in antifouling and antibacterial solutions and assessing their antifouling and antibacterial performance and practical feasibility. This review introduces state-of-the-art antifouling and antibacterial materials and solutions for several applications. In particular, this paper focuses on antibacterial and antifouling agents for concrete and cultural heritage conservation, antifouling sol-gel-based coatings for filtration membrane technology, and marine protection and textile materials for biomedicine. In addition, this review discusses the innovative synthesis technologies of antibacterial and antifouling solutions and the consequent socio-economic implications. The synthesis and the related physico-chemical characteristics of each solution are discussed. In addition, several characterization techniques and different parameters that influence the surface finishing coatings deposition were also described.

Flow cytometric approach to evaluate the impact of hydro-technical concrete compounds' release to the freshwater microbiome

The aim of this research was to test the potential of applying a flow cytometric procedure to evaluate the impact of concrete compounds' release to the freshwater microbiome. Cells from the collected samples were stained with a fluorogenic redox indicator dye that measures the redox potential of microbial cells. This novel approach was combined with the assessment of microorganisms' penetration into the internal structures of concrete using the Rose Bengal sodium salt staining. Rose Bengal staining revealed an intense fouling of the upper and side walls of the concrete cubes and also indicated the penetration of microorganisms inside the concrete as observed for the cubes' cross-sections. Flow cytometric cellular redox potential measurement revealed high percentages of active cells within the concrete's porous structures and in non-exposed water (32.7% and 30.2% of active cells) versus samples from exposed water and concrete's outer surfaces (6.8%, 6.1%, and 3.3% of active cells). The results demonstrated a detrimental impact of hydro-technical concrete on the vitality of microbial cells within the freshwater environment. Tested protocol by analyzing the physiology of microbial cells improved the functional description of complex communities to evaluate the fate of contaminants present in the concrete-based hydro-technical infrastructure.

The role of pH on sewer corrosion processes and control methods: A review

The production and emission of hydrogen sulfide (H₂S) in sewer systems is associated with the corrosion of sewer structures and harmful odour. Numerous studies have been conducted to find the best solution to overcome this issue. The pH plays a critical role not only on microbial and chemical processes that are responsible for all processes of corrosion but also on the efficiency of several control methods. This paper first critically reviews the literature on the interplay between pH and various chemical and microbial in-sewer processes, followed by a review of the control methods that depend on pH or indirectly alter pH. The paper argues that proper evaluation of each method should include the impact the control method has on downstream processes. This paper concludes the raising of pH has several benefits but is operationally difficult to implement. It also emphasises single control method may not be as efficient as combination of one or two methods in controlling the production and emission of H₂S. Finally, the research requirements and future directions in relation to emerging and potential methods that are not heavily reliant on pH control are discussed.

Utilization of induction furnace steel slag based iron oxide nanocomposites for antibacterial studies

Metals and metal oxide-based nanocomposites play a significant role over the control of microbes. In this study, antibacterial activity of iron oxide (Fe2O3) nanocomposites based on induction furnace (IF) steel slag has been carried out. IF steel slag is an industrial by-product generated from secondary steel manufacturing process and has various metal oxides which includes Al2O3 (7.89%), MnO (5.06), CaO (1.49%) and specifically Fe2O3 (14.30%) in higher content along with metalloid SiO2 (66.42). Antibacterial activity of iron oxide nanocomposites has been revealed on bacterial species such as Micrococcus luteus, Bacillus subtilis and Staphylococcus aureus. Micrococcus luteus has undergone maximum zone of inhibition (ZOI) of 12 mm for 10 mg/mL concentration of steel slag iron oxide nanocomposite. Growth inhibitory kinetics of bacterial species has been studied using ELISA microplate reader at 660 nm by varying the concentration of steel slag iron oxide nanocomposites. The results illustrate that IF steel slag is a potential material and can be utilized in building materials to increase the resistance against biodeterioration.

Graphic abstract

The effects of surface variation on the decomposition of pig carcasses

Studies investigating the differential decomposition of remains on different surfaces have been limited to qualitative data. This study statistically analyses the differences in rate and pattern of decomposition between concrete, gravel and grass surfaces. A total of 11 pigs (Sus scrofa domesticus) were used in the study: three for the concrete and gravel surfaces each, and 5 for the grass surface. Results showed that there was no difference in the overall rate of decomposition between surfaces (p > 0.05); however, there were significant differences in the pattern of decomposition. Mummification was observed on all subjects in the study and may have been the reason for the similarities in the decomposition rates between surfaces. The results of this study show that in the intertwined relationship between factors affecting decomposition surface type may be overshadowed by other environmental factors.

Antimicrobial concrete for smart and durable infrastructures: A review

Concrete structures in sewer systems, marine engineering, underground engineering and other humid environments are easily subjected to microbial attachment, colonization and, eventually, deterioration. With careful selection and treatment, some additives including inorganic and organic antimicrobial agents were found to be able to endow concrete with excellent antimicrobial performance. This paper reviews various types of antimicrobial concrete fabricated with different types of antimicrobial agents. The classification and methods of applying antimicrobial agents into concrete are briefly introduced. The antimicrobial and mechanical properties as well as mass/weight loss of concrete incorporating antimicrobial agents are summarized. Applications reported in this field are presented and future research opportunities and challenges of antimicrobial concrete are also discussed in this review.

Amorphous Polyphosphate and Ca-Carbonate Nanoparticles Improve the Self-Healing Properties of both Technical and Medical Cements

Cement is used both as a construction material and for medical applications. Previously, it has been shown that the physiological polymer inorganic polyphosphate (polyP) is morphogenetically active in regeneration of skin, bone, and cartilage. The present study investigates the question if this polymer is also a suitable additive to improve the self-healing capacity not only of construction cement but also of inorganic bone void fillers. For the application in the cement, two different polyP-based amorphous nanoparticles (NP) are prepared, amorphous Ca-polyP NP and amorphous Ca-carbonate (ACC) NP. The particles are integrated into poly(methyl methacrylate) in a concentration ratio of 1:10. This material applied onto Portland cement blocks either by brush application or by blow spinning strongly accelerates the self-healing property of the cement after a 10 day incubation period. Most likely, this process depends on bacteria and their membrane-associated alkaline phosphatase, resulting in the formation of calcite from ACC. In a second approach, polyP is integrated into a calcium-silicate-based cement used in reconstitutive medicine. Subsequently, the cement becomes softer and more elastic. The data show that bioinspired polyP/ACC NP are suitable additives to improve the self-healing of construction cement and to biologize bone cement.

What is the resource footprint of a computer science department? Place, people, and Pedagogy

Internet and Communication Technology/electrical and electronic equipment (ICT/EEE) form the bedrock of today’s knowledge economy. This increasingly interconnected web of products, processes, services, and infrastructure is often invisible to the user, as are the resource costs behind them. This ecosystem of machine-to-machine and cyber-physical-system technologies has a myriad of (in)direct impacts on the lithosphere, biosphere, atmosphere, and hydrosphere. As key determinants of tomorrow’s digital world, academic institutions are critical sites for exploring ways to mitigate and/or eliminate negative impacts. This Report is a self-deliberation provoked by the questionHow do we create more resilient and healthier computer science departments: living laboratories for teaching and learning about resource-constrained computing, computation, and communication?Our response for University College London (UCL) Computer Science is to reflect on how, when, and where resources—energy, (raw) materials including water, space, and time—are consumed by the building (place), its occupants (people), and their activities (pedagogy). This perspective and attendant first-of-its-kind assessment outlines a roadmap and proposes high-level principles to aid our efforts, describing challenges and difficulties hindering quantification of the Department’s resource footprint. Qualitatively, we find a need to rematerialise the ICT/EEE ecosystem: to reveal the full costs of the seemingly intangible information society by interrogating the entire life history of paraphernalia from smartphones through servers to underground/undersea cables; another approach is demonstrating the corporeality of commonplace phrases and Nature-inspired terms such as artificial intelligence, social media, Big Data, smart cities/farming, the Internet, the Cloud, and the Web. We sketch routes to realising three interlinked aims: cap annual power consumption and greenhouse gas emissions, become a zero waste institution, and rejuvenate and (re)integrate the natural and built environments.

Town-scale microbial sewer community and H2S emissions response to common chemical and biological dosing treatments

Controlling hydrogen sulfide (H₂S) odors and emissions using a single, effective treatment across a town-scale sewer network is a challenge faced by many water utilities. Implementation of a sewer diversion provided the opportunity to compare the effectiveness of magnesium hydroxide (Mg(OH)₂) and two biological dosing compounds (Bioproducts A and B), with different modes of action (MOA), in a field-test across a large sewer network. Mg(OH)₂ increases sewer pH allowing suppression of H₂S release into the sewer environment while Bioproduct A acts to disrupt microbial communication through quorum sensing (QS), reducing biofilm integrity. Bioproduct B reduces H₂S odors by scouring the sewer of fats, oils and grease (FOGs), which provide adhesion points for the microbial biofilm. Results revealed that only Mg(OH)₂ altered the microbial community structure and reduced H₂S emissions in a live sewer system, whilst Bioproducts A and B did not reduce H₂S emissions or have an observable effect on the composition of the microbial community at the dosed site. Study results recommend in situ testing of dosing treatments before implementation across an operational system.

Current status and future prospects of sewer biofilms: Their structure, influencing factors, and substance transformations

With rapid urbanization, sewer systems are extensively being constructed for the collection and transportation of sewage to minimize the severe environmental and health issues, especially relating to the spread diseases. The existence of abundant biofilms on the inner walls of sewers could lead to potential risks such as sewer explosions, poisonous gas leaks, and pipe corrosions with the transformations of various kinds of pollutants. Therefore, it is urgent to clarify their inner mechanisms to safely govern sewer systems. In this study, the characteristics of sewer biofilms including their structure, influencing factors, and substance transformations were analyzed in-depth. The results reveal that sewer biofilms (1.0 mm depth approximately) consist of large quantities of inorganic and some organic substances, while the abundant functional genus of the bacteria and archaea are summarized. Sewer biofilms influencing factors were determined to be sewer operation mode, sewage characteristics, and shear stress. Further, the transformation of organics, sulfur, and nitrogen as well as emerging micropollutants (such as, biomarkers, antibiotic resistance genes, and engineered nanoparticles) was investigated to guarantee sewer security and public health. Therefore, the current review could be considered as guidance for researchers and decision-makers.

Moulds on cementitious building materials-problems, prevention and future perspectives

Materials rich in organic and inorganic compounds, such as building materials or paints, represent an excellent substrate for the development of moulds. Several conditions affect mould's growth on cementitious materials, such as nutrient and water availability, temperature, pH and moisture. Microorganisms, and especially moulds, attack these surfaces and contribute to their erosion, thereby reducing the life of the structure itself and negatively affecting human health through inhalation, ingestion and dermal contact with spores. Interventions are based on The European Communities Council Directive 89/106/EEC, that obliges the use of materials, products and building elements that are resistant to fungi and other forms of degradation, and that do not constitute a health risk for users and the environment. This mini-review summarises the current state of problems related to mould growth on cementitious building materials, emphasising new innovative approaches for limiting or contrasting their growth. In particular, the use of nanoparticles and the related nanomaterials as well as the potential use of new "biocides" from natural sources is discussed.

Pilot scale cellulose recovery from sewage sludge and reuse in building and construction material

The recovery of cellulose in toilet paper from municipal wastewater is one of the most innovative actions in the circular economy context. In fact, fibres could address possible new uses in the building sector as reinforcing components in binder-based materials. In this paper, rotating belt filters were tested to enhance the recovery of sludge rich in cellulose fibres for possible valorisation in construction applications. Recovered cellulosic material reached value up to 26.6 gm^-3 with maximum solids removal of 74%. Content of cellulose, hemicellulose and lignin was found averagely equal to 87% of the total composition. Predictive equation of cellulosic material was further obtained. The addition of recovered cellulose fibres in mortars bring benefits in terms of lightness, microstructure and moisture buffering value (0.17 g/m²%UR). Concerning mechanical properties, flexural strength was improved with the addition of 20% of recovered cellulose fibres. In addition, a simplified economic assessment was reported for two possible pre-mixed blends with 5% and 20% of recovered fibres content.

Removal of micropollutants and cyanobacteria from drinking water using KMnO4 pre-oxidation coupled with bioaugmentation

Increasing micropollutant and cyanobacterial contamination of drinking water threatens human health worldwide. However, these contaminates are not efficiently removed by common drinking water treatment processes, and thus additional treatments are frequently required. Recent investigations have demonstrated that KMnO₄ pre-oxidation can efficiently remove some micropollutants and cyanobacteria but the release of cyanobacterial toxins and Mn²⁺ limit its use. To overcome these problems, we proposed a KMnO₄ pre-oxidation coupled with bioaugmentation (e.g., sand filtration) method to treat micropollutant- and cyanobacteria-laden water. We used 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (BP-4, a common micropollutant in drinking water sources) and Microcystis aeruginosa (a widely distributed cyanobacterial species) as model pollutants to verify the feasibility of the proposed method. Results revealed that KMnO₄ pre-oxidation efficiently removed existing natural organic matter and Microcystis aeruginosa but failed to remove BP-4 and released Mn²⁺ and microcystin-LR (MC-LR) during treatment. Following the addition of a manganese-oxidizing bacterial strain (Pseudomonas sp. QJX-1) to the KMnO₄-treated solution, we found that the bacteria could transform Mn²⁺ to Mn(III&IV) oxides, with the formed Mn oxides then able to remove BP-4 and MC-LR. Overall, the proposed method exhibited advantages in the removal of natural organic matter (i.e., decreasing disinfection byproduct formation), micropollutants, and cyanobacteria as well as preventing the release of Mn²⁺, and thus may be considered a good alternative for treating polluted drinking water.

Metabolic Activity of Micromycetes Affecting Urban Concrete Constructions

Concrete resistance to the destructive action of microorganisms is considered as a measure of its durability and is increasingly being raised as an important issue. We focused our study on the biodeterioration of concrete specimens widely used as a building material of urban houses by micromycetes isolated from the inner wall surface of the former military hospital in Kazan city, Tatarstan, Russia. Fungal community consists of 9 Penicillium isolates, 6 Aspergillus, 2 Trichoderma, and 1 isolate of Alternaria. First, we have identified two dominant isolates, Aspergillus fumigatus and Penicillium brevicompactum, and characterized their destructive properties according to the radial growth rate, antagonistic activity towards bacterial habitants of concrete, and production of organic acids. Then, we have demonstrated that five tested brands of high-strength concrete differ in bioreceptivity. The alterations in concrete resistances to compression and flexure after fungal attack were recorded at the trend level, mainly due to a short exposure time of concrete to fungal destructors in tests recommended by national Russian standard. Finally, using scanning electron microscopy we have shown that colonization of concrete by the dominant fungi includes their penetration into the thickness of concrete and germination in cracks. Elementary analysis revealed the decrease of calcium content on about 41% after fungal growth on the concrete in liquid phase and on 32% by superficial growth in comparison with the samples without fungal treatment.

A new paper sensor method for field analysis of acid volatile sulfides in soils

Monitoring of biogenic sulfide is important because acid volatile sulfides (AVS) represent a reactive pool responsible for immobilization of toxic metals. We propose a new sulfide paper sensor method for semiquantitative determination of AVS in which developed color is compared to a reference chart. The method was validated against the ion-selective microelectrode and the purge-and-trap methods. For fieldwork, readings should fall within 1 to 10 μmoles S^2- . Considering that the volume of soil used ranged between 1 and 16 cm³ , the corresponding soil sulfides concentration range spans from 0.06 to 10 mmoles S^2- cm^-3 . The sulfide paper sensor method is highly suitable for field screening and has sensitivity levels comparable to laboratory methods. Environ Toxicol Chem 2018;37:3025-3031. © 2018 SETAC.

Dust at Various Workplaces-Microbiological and Toxicological Threats

The aim of the present study was to evaluate the relation between the chemical (analysis of elements and pH) and microbiological composition (culture and metagenomics analysis) of the dust at various workplaces (cement plant, composting plant, poultry farm, and cultivated area) and the cytotoxicity effect on the human adenocarcinoma lung epithelial adherent cell line A-549 (MTT assay test). Analysis of the Particulate Matter (PM) fraction showed that the dust concentration in cultivated areas exceeded the OELs. For the remaining workplaces examined, the dust concentration was lower than OELs limits. The number of microorganisms in the dust samples was 3.8 × 10²–1.6 × 10⁸ CFU/g bacteria and 1.5 × 10²–6.5 × 10⁶ CFU/g fungi. The highest number of microorganisms was noted for dust from cultivated areas (total number of bacteria, actinomycetes, P. fluorescens) and composting plants (xerophilic fungi and staphylococci), while the least number of microorganisms was observed for dust from cement plants. Many types of potentially pathogenic microorganisms have been identified, including bacteria, such as Bacillus, Actinomyces, Corynebacterium, Prevotella, Clostridium, and Rickettsia, and fungi, such as Alternaria, Cladosporium, Penicillium, and Aspergillus. The most cytotoxic to the human lung cell line A-549 was dust from cultivated areas (IC₅₀ = 3.8 mg/mL after 72 h). The cytotoxicity of the tested dust samples depends on the PM concentration, the number of microorganisms, including potentially pathogenic genera, and the exposure time.

Biocorrosion of materials and sick building syndrome

The problem of biological damage of mineral building materials and structures based on them is multifaceted and covers all types of industry. The most destructive biocorrosion impacts are on building materials in cities with a large water area. Various types of microorganisms, including pathogens, and especially the filamentous fungi of the genera Aspergillus, Penicillium, Trichoderma, etc., occupy the surfaces of mineral building materials, cause their destruction, disturb the ecological balance of cities and endanger the human health. The term ‘sick building syndrome' (SBS) is used to describe a situation when the residents of a building experience acute health- or comfort-related effects that seem to be linked directly to the time spent in the building wherein no specific illness or cause can be identified. Biological contaminants, in particular micromycetes, can present one of the possible causes of SBS. Here, we assessed the biodeterioration level of structural materials on the basis of fine-grained concrete widely used in construction practice and architecture. First, we determined the strength characteristics of the material that has been biologically damaged; second, we identified the damaging micromycetes and analysed their metabolic activity related both to the induction of biocorrosion and to the impacts of fungi on human health. Applying a new integrated approach, which combines methods of molecular microbiology and genetic toxicology with standard methods for determining the strength of building structures, we confirmed the relation between biodestructive and pathogenic properties of micromycete isolates.

Characterization of sulfur oxidizing bacteria related to biogenic sulfuric acid corrosion in sludge digesters

BACKGROUND

Biogenic sulfuric acid (BSA) corrosion damages sewerage and wastewater treatment facilities but is not well investigated in sludge digesters. Sulfur/sulfide oxidizing bacteria (SOB) oxidize sulfur compounds to sulfuric acid, inducing BSA corrosion. To obtain more information on BSA corrosion in sludge digesters, microbial communities from six different, BSA-damaged, digesters were analyzed using culture dependent methods and subsequent polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE). BSA production was determined in laboratory scale systems with mixed and pure cultures, and in-situ with concrete specimens from the digester headspace and sludge zones.

RESULTS

The SOB Acidithiobacillus thiooxidans, Thiomonas intermedia, and Thiomonas perometabolis were cultivated and compared to PCR-DGGE results, revealing the presence of additional acidophilic and neutrophilic SOB. Sulfate concentrations of 10-87 mmol/L after 6-21 days of incubation (final pH 1.0-2.0) in mixed cultures, and up to 433 mmol/L after 42 days (final pH <1.0) in pure A. thiooxidans cultures showed huge sulfuric acid production potentials. Additionally, elevated sulfate concentrations in the corroded concrete of the digester headspace in contrast to the concrete of the sludge zone indicated biological sulfur/sulfide oxidation.

CONCLUSIONS

The presence of SOB and confirmation of their sulfuric acid production under laboratory conditions reveal that these organisms might contribute to BSA corrosion within sludge digesters. Elevated sulfate concentrations on the corroded concrete wall in the digester headspace (compared to the sludge zone) further indicate biological sulfur/sulfide oxidation in-situ. For the first time, SOB presence and activity is directly relatable to BSA corrosion in sludge digesters.

Testing Silica Fume-Based Concrete Composites under Chemical and Microbiological Sulfate Attacks

Current design practices based on descriptive approaches to concrete specification may not be appropriate for the management of aggressive environments. In this study, the durability of cement-based materials with and without the addition of silica fume, subjected to conditions that leach calcium and silicon, were investigated. Chemical corrosion was simulated by employing various H₂SO₄ and MgSO₄ solutions, and biological corrosion was simulated using Acidithiobacillus sp. bacterial inoculation, leading to disrupted and damaged surfaces; the samples’ mass changes were studied following both chemical and biological attacks. Different leaching trends were observed via X-ray fluorescence when comparing chemical with biological leaching. Lower leaching rates were found for concrete samples fortified with silica fume than those without silica fume. X-ray diffraction and scanning electron microscopy confirmed a massive sulfate precipitate formation on the concrete surface due to bacterial exposure.

Predicting concrete corrosion of sewers using artificial neural network

Corrosion is often a major failure mechanism for concrete sewers and under such circumstances the sewer service life is largely determined by the progression of microbially induced concrete corrosion. The modelling of sewer processes has become possible due to the improved understanding of in-sewer transformation. Recent systematic studies about the correlation between the corrosion processes and sewer environment factors should be utilized to improve the prediction capability of service life by sewer models. This paper presents an artificial neural network (ANN)-based approach for modelling the concrete corrosion processes in sewers. The approach included predicting the time for the corrosion to initiate and then predicting the corrosion rate after the initiation period. The ANN model was trained and validated with long-term (4.5 years) corrosion data obtained in laboratory corrosion chambers, and further verified with field measurements in real sewers across Australia. The trained model estimated the corrosion initiation time and corrosion rates very close to those measured in Australian sewers. The ANN model performed better than a multiple regression model also developed on the same dataset. Additionally, the ANN model can serve as a prediction framework for sewer service life, which can be progressively improved and expanded by including corrosion rates measured in different sewer conditions. Furthermore, the proposed methodology holds promise to facilitate the construction of analytical models associated with corrosion processes of concrete sewers.

Potential of pure and mixed cultures of Cladosporium cladosporioides and Geotrichum candidum for application in bioremediation and detergent industry

The effect of ethoxylated oleyl–cetyl alcohol (Henkel, “Merima”, Serbia) on the growth and metabolic activity of Cladosporium cladosporioides, Geotrichum candidum and their mixed culture was in the focus of this paper. The cultures were grown in Czapek-Dox liquid nutrient medium with the addition of 0.5% pollutant and without it. The physico-chemical and biochemical changes of pH, the total biomass dry weight, the quantity of free and total organic acids, proteolytic activity and the quality of carbohydrates were evaluated from 4th to 19th day of fungal growth. The pollutant caused an inhibitory effect on biomass dry weight of C. cladosporioides and G. candidum for 10.36% and 4.65% respectively, and stimulatory effect on biomass of mixed culture for 3.80%. The pollutant had influence on the decrease in pH value of the media in the phase of culture growth, and pH changes were correlated with the amount of excreted total organic acids. The highest quantity of free and total organic acids was noted in media with pollutant of mixed culture and C. cladosporioides, respectively. The alkaline protease activities of C. cladosporioides, G. candidum and mixed culture were enhanced by addition of pollutant for 56.88%, 55.84% and 30.94% respectively. The obtained results indicate the potential of both pure and mixed cultures in mycoremediation environment contaminated by alcohol ethoxylated and detergent industry.

KMnO4-Fe(II) pretreatment to enhance Microcystis aeruginosa removal by aluminum coagulation: Does it work after long distance transportation?

KMnO4-Fe(II) pretreatment was proposed to enhance Microcystis aeruginosa (M. aeruginosa) removal by aluminum (Al) coagulation in drinking water treatment plants (DWTPs) in our previous study. This study aims to optimize this process and evaluate the feasibility of using the process at water sources, which are usually far away from DWTPs. The optimum molar ratio of KMnO4 to Fe(II) [Formula: see text] is observed to be 1:3 with respect to algae removal and residual manganese (Mn) control. As indicated from flow cytometer analysis, KMnO4 at <20 μM promisingly maintains cell integrity, with damaged cell ratios of below 10%. KMnO4 at 30 and 60 μM damages M. aeruginosa cells more significantly and the damaged cell ratios increase to 21% and 34% after 480 min. The intracellular organic matter (IOM) release can be controlled by the subsequent introduction of Fe(II) to quench residual KMnO4. KMnO4-Fe(II) pretreatment at the KMnO4 dose of 10 μM dramatically enhances the algae removal by over 70% compared to that by Al coagulation, even if KMnO4 and Fe(II) are introduced 480 min prior to the addition of Al2(SO4)3. The Al doses can be reduced by more than half to achieve the same algae removal. Furthermore, the deposition of the tiny Fe-Mn precipitates formed rarely occurs, as indicated by a settleability evaluation prior to Al addition. The KMnO4-Fe(II) process can be sequentially dosed at intake points in water sources to achieve moderate inactivation of algae cells and to enhance algae removal in DWTPs thereafter.

A Post-Genomic View of the Ecophysiology, Catabolism and Biotechnological Relevance of Sulphate-Reducing Prokaryotes

Dissimilatory sulphate reduction is the unifying and defining trait of sulphate-reducing prokaryotes (SRP). In their predominant habitats, sulphate-rich marine sediments, SRP have long been recognized to be major players in the carbon and sulphur cycles. Other, more recently appreciated, ecophysiological roles include activity in the deep biosphere, symbiotic relations, syntrophic associations, human microbiome/health and long-distance electron transfer. SRP include a high diversity of organisms, with large nutritional versatility and broad metabolic capacities, including anaerobic degradation of aromatic compounds and hydrocarbons. Elucidation of novel catabolic capacities as well as progress in the understanding of metabolic and regulatory networks, energy metabolism, evolutionary processes and adaptation to changing environmental conditions has greatly benefited from genomics, functional OMICS approaches and advances in genetic accessibility and biochemical studies. Important biotechnological roles of SRP range from (i) wastewater and off gas treatment, (ii) bioremediation of metals and hydrocarbons and (iii) bioelectrochemistry, to undesired impacts such as (iv) souring in oil reservoirs and other environments, and (v) corrosion of iron and concrete. Here we review recent advances in our understanding of SRPs focusing mainly on works published after 2000. The wealth of publications in this period, covering many diverse areas, is a testimony to the large environmental, biogeochemical and technological relevance of these organisms and how much the field has progressed in these years, although many important questions and applications remain to be explored.

Determining the long-term effects of H₂S concentration, relative humidity and air temperature on concrete sewer corrosion

Many studies of sewer corrosion are performed in accelerated conditions that are not representing the actual corrosion processes. This study investigated the effects of various factors over 3.5 years under controlled conditions simulating the sewer environment. Concrete coupons prepared from precorroded sewers were exposed, both in the gas phase and partially submerged in wastewater, in laboratory controlled corrosion chambers. Over the 45 month exposure period, three environmental factors of H2S concentration, relative humidity and air temperature were controlled at different levels in the corrosion chambers. A total of 36 exposure conditions were investigated to determine the long term effects of these factors by regular retrieval of concrete coupons for detailed analysis of surface pH, corrosion layer sulfate levels and concrete loss. Corrosion rates were also determined for different exposure periods. It was found that the corrosion rate of both gas-phase and partially-submerged coupons was positively correlated with the H2S concentration in the gas phase. Relative humidity played also a role for the corrosion activity of the gas-phase coupons. However, the partially-submerged coupons were not affected by humidity as the surfaces of these coupons were saturated due to capillary suction of sewage on the coupon surface. The effect of temperature on corrosion activity varied and possibly the acclimation of corrosion-inducing microbes to temperature mitigated effects of that factor. It was apparent that biological sulfide oxidation was not the limiting step of the overall corrosion process. These findings provide real insights into the long-term effects of these key environmental factors on the sewer corrosion processes.