A long-term passive sampling approach for wastewater-based monitoring of SARS-CoV-2 in Leipzig, Germany.

Wastewater-based monitoring of SARS-CoV-2 has become a promising and useful tool in tracking the potential spread or dynamics of the virus. Its recording can be used to predict how the potential number of infections in a population will develop. Recent studies have shown that the use of passive samplers is also suitable for the detection of SARS-CoV-2 genome copies (GC) in wastewater. They can be used at any site, provide timely data and may collect SARS-CoV-2 GC missed by traditional sampling methods. Therefore, the aim of this study was to evaluate the suitability of passive samplers for the detection of SARS-CoV-2 GC in wastewater in the long-term at two different scales. Polyethylene-based plastic passive samplers were deployed at the city-scale level of Leipzig at 13 different locations, with samples being taken from March 2021 to August 2022. At the smaller city district level, three types of passive samplers (cotton-cloth, unravelled polypropylene plastic rope and polyethylene-based plastic strips) were used and sampled on a weekly basis from March to August 2022. The results are discussed in relation to wastewater samples taken at the individual passive sampling point. Our results show that passive samplers can indicate at a city-scale level an accurate level of positive infections in the population (positive-rate: 86 %). On a small-scale level, the use of passive samplers was also feasible and effective to detect SARS-CoV-2 GC easily and cost-effectively, mirroring a similar trend to that at a city-scale level. Thus, this study demonstrated that passive samplers provide reproducible SARS-CoV-2 GC signals from wastewater and a time-integrated measurement of the sampled matrix with greater sensitivity compared to wastewater. We thus recommend the use of passive samplers as an alternative method for wastewater-based epidemiology. Passive samplers can in particular be considered for a better estimation of infections compared to incidence levels.

Anaerobic co-digestion of waste yeast biomass from citric acid production and waste frying fat.

The application of spent yeast for biogas production has been studied only in the context of breweries so far. This study is focused on the anaerobic digestion of concentrated yeast biomass (CYB), being a by-product of citric acid biosynthesis. Two experimental set-ups were used in order to test CYB as a mono-substrate and co-substrate for closing the loop in accordance with the 'bioeconomy' approach. The results show that CYB allows for obtaining a high biogas yield, with a maximum of 1.45 m3 N/kgVS produced when CYB was used as a mono-substrate. The average methane concentration was 66 ± 4%. However, anaerobic digestion of CYB alone was difficult to perform because of a tendency for over-acidification, meaning that the maximum possible organic loading rate was 1 kg/(m3*d). Repeated clogging of tubes with coagulated biomass also disturbed continuous feeding. In contrast, the co-digestion of CYB with waste frying fat at a ratio of 1:20 showed stable operation during a 70-day fermentation period. The biogas yield using the substrate mixture was 1.42 m3/kgVS at an organic loading rate of 2 kg/(m3*d). The methane concentration reached 67 ± 4% and the acetate concentration did not exceed 30 mg/L during the entire fermentation.

Community-Level Physiological Profiling of Microbial Communities in Constructed Wetlands: Effects of Sample Preparation.

Community-level physiological profiling (CLPP) using BIOLOG® EcoPlates™ has become a popular method for characterizing and comparing the functional diversity, functional potential, and metabolic activity of heterotrophic microbial communities. The method was originally developed for profiling soil communities; however, its usage has expanded into the fields of ecotoxicology, agronomy, and the monitoring and profiling of microbial communities in various wastewater treatment systems, including constructed wetlands for water pollution control. When performing CLPP on aqueous samples from constructed wetlands, a wide variety of sample characteristics can be encountered and challenges may arise due to excessive solids, color, or turbidity. The aim of this study was to investigate the impacts of different sample preparation methods on CLPP performed on a variety of aqueous samples covering a broad range of physical and chemical characteristics. The results show that using filter paper, centrifugation, or settling helped clarify samples for subsequent CLPP analysis, however did not do so as effectively as dilution for the darkest samples. Dilution was able to provide suitable clarity for the darkest samples; however, 100-fold dilution significantly affected the carbon source utilization patterns (CSUPs), particularly with samples that were already partially or fully clear. Ten-fold dilution also had some effect on the CSUPs of samples which were originally clear; however, the effect was minimal. Based on these findings, for this specific set of samples, a 10-fold dilution provided a good balance between ease of use, sufficient clarity (for dark samples), and limited effect on CSUPs. The process and findings outlined here can hopefully serve future studies looking to utilize CLPP for functional analysis of microbial communities and also assist in comparing data from studies where different sample preparation methods were utilized.

The influence of oxygen limitation for the production of succinic acid with recombinant strains of Yarrowia lipolytica.

The yeast Yarrowia lipolytica is able to produce high amounts of several organic acids such as pyruvic, citric, isocitric, alpha-ketoglutaric, and succinic acid. Here we report on the influence of the reduced activity of succinate dehydrogenase in Y. lipolytica on its ability to produce succinate. The recombinant strains Y. lipolytica H222-AZ1 and H222-AZ2 were created by exchange of the native promoter of the succinate dehydrogenase subunit 2 encoding gene by inducible promoters. During the cultivation of the strain Y. lipolytica H222-AZ1 in shaking flask experiments, it was found that the promoter exchange resulted in an increase in succinic acid (SA) production. Moreover, it was found that the production of SA depends on an additional limitation of oxygen. Fed-batch cultivations in 1-l bioreactors confirmed this fundamental finding. Y. lipolytica H222-AZ1 produced 2 g l(-1) of SA with oxygen supply and 9.2 g l(-1) under the limitation of oxygen after 165 h. By using a less active promoter in Y. lipolytica H222-AZ2, the production of SA was increased to 25 g l(-1) with a productivity of 0.152 g (l*h)(-1) and a selectivity of 67 % after 165 h. Yields of 2.39 g SA per gram biomass and 0.26 g SA per gram glycerol were found.

Hydraulic characterization and optimization of total nitrogen removal in an aerated vertical subsurface flow treatment wetland.

In this study, a side-by-side comparison of two pilot-scale vertical subsurface flow constructed wetlands (6.2 m(2)×0.85 m, q(i)=95 L/m(2) d, τ(n)=3.5 d) handling primary treated domestic sewage was conducted. One system (VA-i) was set to intermittent aeration while the other was aerated continuously (VAp-c). Intermittent aeration was provided to VA-i in an 8 h on/4 h off pattern. The intermittently aerated wetland, VA-i, was observed to have 70% less nitrate nitrogen mass outflow than the continuously aerated wetland, VAp-c. Intermittent aeration was shown to increase treatment performance for TN while saving 33% of running energy cost for aeration. Parallel tracer experiments in the two wetlands showed hydraulic characteristics similar to one Continuously Stirred Tank Reactor (CSTR). Intermittent aeration did not significantly affect the hydraulic functioning of the system. Hydraulic efficiencies were 78% for VAp-c and 76% for VA-i.

Correlation of community dynamics and process parameters as a tool for the prediction of the stability of wastewater treatment.

Wastewater treatment often suffers from instabilities and the failure of specific functions such as biological phosphorus removal by polyphosphate accumulating organisms. Since most of the microorganisms involved in water clarification are unknown it is challenging to operate the process accounting for the permanent varying abiotic parameters and the complex composition and unrevealed metabolic capacity of a wastewater microbial community. Fulfilling the demands for water quality irrespective of substrate inflow conditions may emit severe problems if the limited management resources of municipal wastewater treatment plants are regarded. We used flow cytometric analyses of cellular DNA and polyphosphate to create patterns mirroring dynamics in community structure. These patterns were resolved in up to 15 subclusters, the presence and abundances of which correlated with abiotic data. The study used biostatistics to determine the kind and strength of the correlation. Samples investigated were obtained from a primary clarifier and two activated sludge basins. The stability of microbial community structure was found to be high in the basins and low in the primary clarifier. Despite major abiotic changes certain subcommunities were dominantly present (up to 80% stability), whereas others emerged only sporadically (down to 3% stability, both according to equivalence testing). Additionally, subcommunities of diagnostic value were detected showing positive correlation with substrate influxes. For instance blackwater (r(s) = 0.5) and brewery inflow (both r(s) = 0.6) were mirrored by increases in cell abundances in subclusters 1 and 6 as well as 4 and 8, respectively. Phosphate accumulation was obviously positively correlated with nitrate (r(s) = 0.4) and the presence of denitrifying organisms (Rhodacyclaceae). Various other correlations between community structure and abiotic parameters were apparent. The bacterial composition of certain subcommunities was determined by cell sorting and phylogenetic tools like T-RFLP. In essence, we developed a monitoring tool which is quick, cheap and causal in its interpretation. It will make laborious PCR based technique less obligatory as it allows reliable process monitoring and control in wastewater treatment plants.

Batch methanogenic fermentation experiments of wastewater from a brown coal low-temperature coke plant.

Coke plant effluents with high contents of organic compounds are mainly treated by biological aerobic fermentation after physical pre-treatment. In this study, a brown coal condensate wastewater from a low temperature coking process was fermented under methanogenic conditions in discontinuous experiments. By this fermentation, acetate, propionate, and the main polyphenolic compounds (catechol, resorcinol and hydroquinone) were degraded to a level below the detection limit. The COD was reduced by 72% with a residual concentration of 2.1 g/L. This anaerobic fermented wastewater had a residual BOD5 of 0.66 g/L and 2.2 L CH4 were formed per litre of wastewater. An abiotic pre-treatment for this wastewater with air had a negative effect on the COD reduction and decrease of colour on the methanogenic fermentation due to the autoxidation of polyphenolic compounds to humic-like compounds. This study showed that methanogenic fermentations in the treatment sequence of brown coal coking wastewaters could reduce energy consumption for aeration in further treatment processes and had the potential for a better effluent quality due to a less formation of recalcitrant humic-like compounds.