Lucie Moeller

Wrong content There was a mistake in Figure 7 as published. The R script used to calculate the correlation plot was not correctly executed, as the CLR transformation was skipped. The corrected Figure 7 appears below.Use the fields below to provide their contact information, and specific reasons for your suggestion in the comments box for each person. This information is not displayed to any of the reviewers. Please note that the journal1 may not follow your suggestions, but your help is appreciated and may speed up the selection of appropriate reviewers.There was a mistake in Figure 8 as published. The R script used to calculate the correlation plot was not correctly executed, as the CLR transformation was skipped. The corrected Figure 8 appears below.The correlations as shown in Figure 7 and 8 were not correctly described in the corresponding results section. A correction has been made to the section 3.4, Paragraphs 2-12:"Correlations between ASV relative abundance and process parameters before the VOA/TIC ratio surpassed 1 are shown in Figure 7. Both OLR and VOA/TIC values had positive correlations with the abundance of Oscillospiraceae HN-HF0106 (ASV24), Sedimentibacter (ASV6 and ASV19), Erysipeloclostridiaceae UCG-004 (ASV13), Fastidiosipila (ASV1), Bacteroidales UCG-001 (ASV3), Acholeplasma (ASV18), and Methanosarcina (ASV215, ASV216, ASV217, and ASV218). OLR and VOA/TIC values correlated negatively with the abundance of Tissierella (ASV15), Ruminiclostridium (ASV10), Erysipeloclostridiaceae UCG-004 (ASV20), Caldicoprobacter (ASV4), Rikenellaceae DMER64 (ASV12), and Rikenellaceae (ASV16).HRT, inversely to OLR and VOA/TIC, had positive correlations with Tissierella (ASV15), Ruminiclostridium (ASV10), Caldicoprobacter (ASV4), Rikenellaceae DMER64 (ASV12), and Rikenellaceae (ASV16). HRT was negatively correlated to the abundance of Oscillospiraceae HN-HF0106 (ASV24), Sedimentibacter (ASV6 and ASV19), Erysipeloclostridiaceae UCG-004 (ASV13), Fastidiosipila (ASV1), Bacteroidales UCG-001 (ASV3), Acholeplasma (ASV18), and Methanosarcina (ASV215, ASV216, ASV217, and ASV218).Hydrogen sulfide (H2S) production shows positive correlations with the relative abundance of Paludibacteraceae (ASV7 and ASV8) and Sedimentibacter (ASV9). H2S production correlated negatively with Rikenellaceae RC9 gut group (ASV5 and ASV11), Sedimentibacter (ASV19), Fermentimonas (ASV23), and Cloacimonadales W27 (ASV21 and ASV25). Specific methane production had positive correlations with the relative abundance of Rikenellaceae (ASV16) and Rikenellaceae DMER64 (ASV12), but negative correlations with Oscillospiraceae HN-HF0106 (ASV24), Fermentimonas (ASV2 and ASV23), and Erysipelatoclostridiaceae UCG-004 (ASV13).Concentrations of organic acids (propionate, n-butyrate, n-valerate, caproate, and enanthate) showed strong positive correlations with the abundances of Oscillospiraceae HN-HF0106 (ASV24), Sedimentibacter (ASV6 and ASV19), Fastidiosipila (ASV1), and Erysipeloclostridiaceae UCG-004 (ASV13). Negative correlations between organic acid concentrations and abundance included Tissierella (ASV15), Ruminiclostridium (ASV10), Caldicoprobacter (ASV4), Rikenellaceae DMER64 (ASV12), and Rikenellaceae (ASV16).Phenylacetate and phenylpropionate concentrations showed many correlations with the same ASVs. Among them were positive correlations with Sedimentibacter (ASV6), Oscillospiraceae HN-HF0106 (ASV24), Fastidiosipila (ASV1), and Erysipeloclostridiaceae UCG-004 (ASV13). They correlated negatively with the abundances of Ruminiclostridium (ASV10), Rikenellaceae DMER64 (ASV12), Rikenellaceae (ASV16), and Caldicoprobacter (ASV4).Amylase activity had strong and significant correlations with the relative abundance of several ASVs. The positive correlations include Sedimentibacter (ASV6 and ASV19), Paludibacteraceae (ASV7, ASV8), difference between the two reactors was a steady increase in relative abundance of ASVs associated with the Rikenellaceae RC9 gut group in R2. This taxon represents non-cultured fermentative bacteria, which have been found in mammalian gut microbiomes and discussed to be associated with VFA regulation in swine gut communities (Wu et al., 2024). At VOA/TIC >1, Rikenellaceae RC9 gut group (ASV5) abundance had a strong positive correlation with esterase activitiy. It is possible that this ASV represents fast reproducing hydrolytic microbes."The discussion contained redundant and partially incorrect statements on the correlations between process parameters and ASV abundances. A correction has been made to the section 4., Paragraph 20: "Overall, stepwise increase in OLR and corresponding decrease in HRT initially resulted in a slight increase in specific methane production, coinciding with elevated hydrolytic enzyme activities. This was followed by distinct responses in the two reactors, induced by changing operational conditions. R1 underwent over-acidification, accompanied by a shift towards chain elongation as the prevailing community function, while R2 maintained methanogenesis as the dominant community function under more severe operational conditions. Correlation analysis between hydrolytic enzyme activities and the VOA/TIC ratio (used as an indicator for process stability) showed that only protease activity exhibited a negative relationship. While all enzyme activities declined during over-acidification, with esterase becoming undetectable, whereas amylase and protease remained at low activity levels. Changes in microbial community composition reflected increasing operational stress. Higher bacterial diversity appeared to enhance process stability, preventing AD process failure for a longer time in one reactor than in the other. Our results show that maintaining a diverse microbial community is important for resilient AD processes. In conclusion, the diverging reactor responses despite identical operational changes highlight that even small differences in community composition or stochastic effects...

Introduction: Efficiency and stability of anaerobic digestion (AD) processes strongly depend on maintaining a balance between microbial conversion steps. Operational stress can disrupt this balance, leading to shifts in the microbial community, accumulation of intermediate metabolites, and changes in overall process performance. Therefore, the objective of the study was to better understand the role of hydrolysis and its interplay with subsequent conversion steps in the destabilization of the AD process during increasing organic loading rate (OLR). Methods: To systematically investigate the response of an AD process to operational stress, a stepwise increase in OLR until 15 g volatile solids (VS)/(L d) along with stepwise decrease of the hydraulic retention time (HRT) was applied in two parallel operated mesophilic lab-scale anaerobic digesters loaded with maize silage, cow manure and coarse-ground grain. The duplicate systems were comprehensively monitored, including key process parameters such as biogas production and composition, pH, buffer capacity, and volatile fatty acid (VFA) concentrations. Hydrolytic enzyme activities (amylase, protease, esterase) were measured to quantify key microbial functions, and microbial communities were analyzed via amplicon sequencing of 16S rRNA and mcrA genes to monitor compositional changes of the bacterial and methanogenic populations, respectively. Results and discussion: Both reactors showed similar trends in process performance until OLR was 2.5-fold increased, characterized by increasing hydrolytic enzyme activities and minor VFA accumulation. At higher OLR, VFA accumulation increased, and the process performance and microbial communities of the two reactors diverged. While methane production in one reactor collapsed due to over-acidification and was replaced by chain elongation as the predominant microbial process, the other reactor maintained methanogenic activity until 3-fold increase in OLR. These changes were also reflected in declining enzyme activities, where protease activity decreased first. Bacterial diversity in the reactor shifting to chain elongation decreased dramatically, indicating a loss of AD functionality under elevated OLR. These findings highlight the importance of microbial community composition and diversity for maintaining AD stability under increasing operational stress. Contrasting reactor responses suggest that even small differences in microbial communities or stochastic effects can influence process resilience.

Lactic acid fermentation (LAF) is a promising low-tech approach for the stabilization and hygienization of human feces from dry toilets. However, practical implementation remains limited due to a lack of application-relevant knowledge. This study systematically evaluated the influence of a series of practical process parameters on the performance of LAF under standardized laboratory conditions. Feces obtained from different types of dry toilets were physicochemically characterized and subsequently fermented under varying process conditions, using pH and lactic acid production as key indicators of fermentation performance. The results indicate that LAF is feasible across a broad range of process conditions, including temperatures between 8 and 30 °C, and is largely independent of carbon source type, air intrusion, and extended storage periods (>1 year), provided that a sufficient carbon supply is ensured. The investigated parameters exhibited varying degrees of influence on process performance, with carbon source dosage (≥10 w/w-% sugar beet molasses equivalent) and feces type emerging as the most influential factors. While ferrous iron addition (≤5 w/w-%) enhanced pH reduction, biochar, bentonite, and rock flour (≤10 w/w-%) showed negligible effects. Maximum lactic acid production was limited to ≤4.5 w/w-%, irrespective of carbon source dosage, resulting in minimum pH values ranging from 4.1 to 5.2. These values varied primarily with fecal type, suggesting a strong influence of intrinsic buffering capacity. Under conditions supporting stable LAF, i.e., rapid acidification followed by sustained low pH, E. coli was consistently reduced below the detection limit in the investigated samples. Overall, the findings suggest that LAF is a comparatively robust treatment approach and highlight operational parameters that are likely to be important for its practical implementation as a sanitation technology.

Water scarcity is an increasingly urgent global challenge, prompting the development of new water purification technologies that surpass conventional solutions. Decentralized greywater treatment is emerging as a viable option for enhancing water reuse in multifunctional systems that contribute to microclimate regulation, cooling, and urban climate adaptation. In this context, water-storage mats have been identified as a form of decentralized, roof-based biofilter for greywater treatment. The aim of this study was to assess the performance of newly developed, innovative, bio-based textile mats and assess their effectiveness in treating pre-treated greywater from a canteen (CGW) with a high organic content, in both laboratory- and pilot-scale experiments. The findings from the lab-scale testing revealed that the mats made from polyethylene terephthalate (PET) nonwoven fabric materials had the highest water storage capacity and dried out more slowly in outdoor conditions than mats made from polylactide (PLA) spunbonded fabric and polyhydroxyalkanoate (PHA) spunbonded nonwoven fabric. The PET hydroentangled nonwoven fabric mat (PET-WS) performed better than the other sample mats in the lab-scale experiment, and also outperformed the PHA mat consistently in the pilot-scale experiment when treating CGW. Apparent reductions in the concentration of the macro-pollutant parameters were observed at the outflow of the PET-WS mat compared to the inflow (p < 0.05) at the pilot-scale. Mean concentration reductions were comparatively higher for the five-day biochemical oxygen demand (BOD₅), chemical oxygen demand (COD), total nitrogen (TN), and total suspended solids (TSS), with mean reductions of 64%, 54%, 39% and 60%, respectively. This indicated the superior treatment performance of the PET-WS mat compared to the PHA mat, with mean reductions of only 36%, 25%, 6%, and 32%, respectively. However, the lower E. coli counts of 1.1 and 0.5 log reduction for the PET-WS and PHA mats, respectively, indicated that an additional disinfection unit was necessary. The findings of this study may help to determine the performance, stability and reliability of using lightweight, nonwoven fabric mats to treat high-strength GW, which is currently considered as an intermediate treatment step. The study also provides recommendations for process optimization. Additional post-treatment steps are required to produce high-quality treated effluent for non-potable reuse, particularly in urban areas facing high water scarcity, provided that the relevant reuse regulations or discharge criteria are met.

The aim of this study was to evaluate the treatment efficiency and applicability of using textile-based mats as roof biofilters on urban buildings for purifying preliminary treated wastewater (PTW) collected from a three-chamber septic tank. Therefore, a pilot plant with a 15° pitched wooden roof and two tracks for laying two mats made of different materials—polypropylene (PP), designated as Mat 1, and polyethylene terephthalate (PET), designated as Mat 2—was constructed at ground level under outdoor conditions. The plant was operated in parallel for a period of 455 days. Significant differences (p < 0.05) were observed in the results of the mass removal efficiencies between the two mats, with Mat 1 achieving mean removals of five-day biochemical oxygen demand (BOD₅), chemical oxygen demand (COD), ammonium-nitrogen (NH₄-N), and total nitrogen (TN) of 85%, 73%, 75%, and 38%, respectively, and Mat 2 achieving comparatively higher removals of 97%, 84%, 90%, and 57%, respectively. The mean concentrations of BOD₅ and COD at the outflow of both mats met the minimum water quality requirements for discharge and successfully met the minimum water quality class B for agricultural reuse. However, the comparatively low mean E. coli removal efficiencies of 2.0 and 2.4 log-units in Mat 1 and Mat 2, respectively, demonstrate the need for an effluent disinfection system. Highly efficient mass removal efficiencies were observed in the presence of dense vegetation on the mats, which may lead to a potential improvement in the urban climate through high daily evapotranspiration. Overall, this study demonstrates the potential for using lightweight, textile-based mats on rooftops to efficiently treat PTW from urban buildings, offering a promising decentralized wastewater management approach for climate-resilient cities.

Increasing climate change requires cities to adapt to changing weather conditions. New elements for decentralized stormwater management must be installed to protect the sewer system from overloading during heavy rainfall events and to keep water in the city for irrigation use. A pilot project was implemented in Leipzig in 2020, in which infiltration tree trench systems with three different designs were installed and equipped with measuring technology during a road renovation project. The catchment areas of these three tree trenches are between 215 and 300 m² each. In two of the systems, water retention was included to supply the tree with water during drought periods. The retention elements are sealed with clay in tree trench TT1 and bentonite in tree trench TT3. For tree trench TT2, no retention capacity was provided. This article presents the design, construction, and scientific monitoring of the three tree infiltration trenches. The conclusions after four years of operation from the perspective of two departments of the City of Leipzig are summarized. The tree trench TT1 with the clay pan for water storage shows the best performance in terms of water retention and tree fitness. For the next generation of such infiltration systems, improvements in the design of the street runoff inlets and the surface of the tree trench system’s interior are discussed.

Rapid urbanisation and climate change have intensified extreme rainfall events, exacerbating stormwater runoff and overwhelming urban drainage systems. Nature-based solutions, such as green roofs with integrated retention capacity, offer promising strategies to mitigate these challenges. This study investigates the influence of substrate thickness and retention volume on the stormwater retention and evapotranspiration (ET) performance of three green roof variants under extreme rainfall scenarios (natural and 5-, 30- and 100-year events). Using lysimeter-based experimental setups, we show that the overall retention capacity is highly dependent on the filling status of the retention layer. Near full capacity, retention performance decreases significantly, resulting in runoff behaviour similar to that of conventional green roofs, while empty systems store up to 99% of rainfall. In addition, ET rates tend to decrease in systems with higher substrate layers and larger retention spaces due to reduced surface evaporation and greater thermal insulation. However, higher substrate layers store more water, allowing plants to maintain transpiration during dry periods, potentially increasing total cumulative ET over time. Overall, this study highlights the importance of designing intensive retention green roofs with dynamic water management to optimise both rainwater retention and ET, thereby increasing urban resilience to increasing rainfall extremes caused by climate change.

To solve the upcoming environmental problems, sponge city concepts as well as new technologies are being developed these days. One of the future challenges is to reduce drinking water demand by using decentralized water recycling systems. This study aimed to investigate the performance of a specially designed pilot wetland roof (PWR) treating domestic greywater (GW) at ground level under outdoor conditions and to evaluate the effects of different hydraulic loading rates (HLRs) for a period of two years. The results showed highly efficient removal of typical greywater pollutants from the system, e.g., five-day biochemical oxygen demand (BOD₅) > 96%, chemical oxygen demand (COD) > 93%, total suspended solids (TSS) >94%, anionic surfactants (AS) > 94%, ammonium-nitrogen (NH₄-N) > 84%, total nitrogen (TN) > 71%, total phosphorous (TP) > 87%, and E. coli (1.86 ± 1.54 log-removal). The mean concentrations of the targeted parameters at the outflow were in compliance with the requirements for discharge to the environment and met reclaimed water quality standards for agricultural irrigation, except for E. coli. Statistically significant (p < 0.05) results of pollutant mass removal rate across different HLRs indicated the potential effect of HLR on treatment performance, and HLR in a range of 67–80 L m^–2 d^–1 contributed to a higher removal efficiency without compromising the limit values. A comparatively low HLR of 45 L m^–2 d^–1 should be applicable if pathogen removal is the most important requirement. Plant species showed good plant vitality and adapted well to the water storage mat. The higher the mean ambient air temperature, the greater runoff reduction (>50%) was observed due to high evapotranspiration. The results showed the system is a promising green technology for GW recycling and can be scaled up for application to urban buildings.