Effective chloramine management without "burn" in biofilm affected nitrifying tanks using a low dose of copper

This paper highlights the potential to effectively inhibit nitrification and restore chloramine levels using a low copper concentration in a biofilm-affected (surface-to-volume ratio 16 m-1) continuous-flow laboratory-scale chloraminated system. High nitrite and low chloramine containing tanks are always recovered with chlorine "burn" by water utilities. The "burn" is not only costly and operationally complex, but also compromises the water quality, public health, and customer relations. A laboratory system comprising five reactors connected in series was operated. Each reactor simulated conditions typically encountered in full-scale systems. Low amount of copper (0.1-0.2 mg-Cu L-1) was dosed once per day into nitrified reactors. At any given time, only one reactor was dosed with copper. Not only inhibition of nitrification, chloramine decay associated with bulk water, biofilm and sediments also improved. However, the improvement was quicker and more significant when the influent to the reactor contained a high chloramine and a low nitrite concentration. Ammonia oxidising microbes exhibited resilience when exposed to low copper and chloramine concentrations for an extended period. Chloramine decay due to planktonic microbes and chemical reactions in bulk water decreased more rapidly than decay attributed to biofilm and sediments. The concept "biostable residual chlorine" explained how copper and chloramine can inhibit nitrification. Once nitrification was inhibited, the chloramine supplied from upstream effectively continued to suppress downstream nitrification, and this effect lasted more than 50 days even at 22 °C. The findings could be used to develop short-term copper dosing strategies and prevent negative impacts of nitrification and breakpoint chlorination.

Efficacy and safety of topically applied therapeutic ammonia oxidising bacteria in adults with mild-to-moderate atopic dermatitis and moderate-to-severe pruritus: a randomised, double-blind, placebo-controlled, dose-ranging, phase 2b trial

Background

Topical anti-inflammatory therapy is a cornerstone of treatment for atopic dermatitis (AD). However, many unmet needs remain with existing therapies. B244 is a live topical biotherapeutic being tested for the reduction of pruritus and improvement of eczema signs in patients with AD. We aimed to assess the safety and efficacy of B244, compared to vehicle, for patients with mild-to-moderate AD and moderate-to-severe pruritus.

Methods

In this randomised, placebo-controlled, double-blind phase 2b trial, adults aged 18-65 years with mild-to-moderate AD and moderate-to-severe pruritus were enrolled across 56 sites in the USA. Patients were randomised 1:1:1 into a low-dose (optical density at 600 nm [OD] 5.0), high-dose (OD 20.0), or vehicle group for the 4-week treatment period and a 4 week follow-up period. Patients were instructed to apply the topical spray twice daily throughout the treatment period. Randomisation was centrally based (random alternating blocks of 6 and 3) and stratified by site. All participants, investigators, and those assessing outcomes were blinded to the treatment group assignments. The primary endpoint was the mean change in pruritus as measured by the Worst Itch Numeric Rating Scale (WI-NRS) at 4 weeks. Safety was tracked throughout the study. Primary efficacy analyses included the modified intent-to-treat (mITT) population, encompassing those who received at least one dose of study drug and attended at least one post-baseline visit. The safety population included all participants who received at least one does of study drug. This study is registered with ClinicalTrials.gov, NCT04490109.

Findings

Between June 4, 2020 and October 22, 2021, 547 eligible patients were enrolled. All study endpoints were meaningfully improved with B244 compared to vehicle. The WI-NRS score was reduced by 34% (-2.8 B244 vs -2.1 placebo, p = 0.014 and p = 0.015 for OD 20.0 and OD 5.0), from a baseline score of >8. B244 was well tolerated with no serious adverse events (SAEs); treatment-emergent adverse events (TEAEs) and treatment related TEAEs were low in incidence, mild in severity, and transient. 33 (18%) of 180 patients given B244 OD 5.0, 29 (16%) of 180 patients given B244 OD 20.0, and 17 (9%) of 186 patients given placebo reported treatment-emergent adverse events; headache was the most frequent (3%, 2%, and 1%, respectively).

Interpretation

B244 was well tolerated and demonstrated improved efficacy compared to vehicle in all primary, secondary, and exploratory endpoints and should be further developed as a novel, natural, fast-acting topical spray treatment option for AD and associated pruritus.

Funding

AOBiome Therapeutics.

The interaction between ionic liquids (ILs) and an enriched ammonia oxidising bacteria (AOB) culture

Ionic liquids (ILs) have attracted attention in recent years due to their "greener" properties compared to conventional organic solvents. However, they may still pose a risk to the environment as their toxicity is not fully understood. Bioremediation of such ILs can be an economically and environmentally friendly approach. Therefore, this study aims to examine the interaction of three ILs (1-dodecylpyridnium chloride [DPy]⁺Cl, 1-Butyl-3-methylimidazolium chloride [BMIm]⁺Cl, and 1-Carbamoylmethyl pyridinium chloride [CMPy]⁺Cl) at different concentrations with an enriched ammonia oxidising bacteria (AOB) culture, and investigate their effects on the ammonia oxidation rate (AOR) as well as their removal and transformation. The results indicated that the longer chain IL [DPy]⁺Cl had a negative effect on the AOR while [BMIm]⁺Cl and [CMPy]⁺Cl enhanced the AOR. However, the IL removal rates displayed the opposite results as [DPy]⁺Cl was observed with the highest removal. It was found that biosorption played a major role in [DPy]⁺Cl removal. Biotransformation products for each IL were identified and their pathways were proposed. This study demonstrated that although longer chain ILs have a greater degree of removal, and they are also more toxic to AOB at higher concentration.

The role of ammonium oxidising bacteria (AOB) in ionic liquid 1-dodecylpyridinium chloride removal

Ionic liquids (IL) have emerged as the next-generation "green" solvent that can replace traditional organic solvent due to properties such as high thermal stability and no vapour pressure. However, their increased usage inevitably allows them to find their way into the environment. The objective of this study was to evaluate the role of autotrophic ammonia-oxidising bacteria (AOB) in the potential removal of 1-dodecylpyridinium chloride ([DPy]⁺Cl) in both short- and long-term studies. In short-term batch experiments, it was observed that a notable amount of [DPy]⁺ can be removed by the AOB culture with the removal mechanism being biodegradation and absorption, with the latter playing a greater role. It was also found that [DPy]⁺ can be released back into the liquid phase when AOB's preferred substrate, NH₃, was present. In the long-term study, [DPy]⁺Cl was successfully biodegraded and a total of nine transformation products were identified. The biodegradation pathway was also proposed. This study demonstrated that [DPy]⁺Cl can be biological transformed by enriched AOB culture and the accumulation of the by-product did not show long-term negative impact on AOB activities.

Comparison of nitrous oxide emission between a partial and full nitrification enriched ammonia-oxidising culture

Nitrification systems are known to be a source of nitrous oxide (N₂O) emission, however, the contribution from partial and full nitrification systems remains controversial. In this study, N₂O emission from a partial and full nitrification culture was investigated. In all tests, nitrite, dissolved oxygen concentration and pH levels were controlled within a similar range limiting ammonium concentration to be the only variable. The results reveal with the same amount of ammonium removed, the full nitrification culture produced far greater N₂O than the partial nitrification culture for both pulse (25-36 times) and continuous feeding modes (2-110 times). The relative gene expression data indicate that under pulse feeding there is a decreasing trend of nirK and norB genes for the partial and full nitrification culture respectively while under continuous feeding, increasing norB trends were observed for both. This possibly indicated the hydroxylamine pathway was favoured for the partial nitrification culture while the hybrid N-nitrosation pathway maybe the major contributor for the full nitrification culture. These findings improve our understanding on N₂O production pathways and enable researchers to propose better mitigation strategies.

Long- and short-chain AHLs affect AOA and AOB microbial community composition and ammonia oxidation rate in activated sludge

Quorum sensing (QS) regulation of the composition of ammonia-oxidising archaea (AOA) and ammonia-oxidising bacteria (AOB) communities and functions in wastewater treatment was investigated. Specifically, we explored the role of N-acyl-l-homoserine lactones (AHLs) in microbial community dynamics in activated sludge. On average, the specific ammonia-oxidising-rate increased from 1.6 to 2.8 mg NH₄⁺-N/g MLSS/hr after treatment with long-chain AHLs for 16 days, and the addition of AHLs to sludge resulted in an increased number of AOA/AOB amoA genes. Significant differences were observed in the AOA communities of control and AHL-treated cultures, but not the AOB community. Furthermore, the dominant functional AOA strains of the Crenarchaeota altered their ecological niche in response to AHL addition. These results provide evidence that AHLs play an important role in mediating AOA/AOB microbial community parameters and demonstrate the potential for application of QS to the regulation of nitrogen compound metabolism in wastewater treatment.

N2O emission characteristics and its affecting factors in rain-fed potato fields in Wuchuan County, China

Representing an important greenhouse gas, nitrous oxide (N₂O) emission from cultivated land is a hot topic in current climate change research. This study examined the influences of nitrogen fertilisation, temperature and soil moisture on the ammonia monooxygenase subunit A (amoA) gene copy numbers and N₂O emission characteristics. The experimental observation of N₂O fluxes was based on the static chamber-gas chromatographic method. The ammonia-oxidising bacteria (AOB) and ammonia-oxidising archaea (AOA) gene copy numbers in different periods were measured by real-time polymerase chain reaction (PCR). The results indicated that rain-fed potato field was a N₂O source, and the average annual N₂O emission was approximately 0.46 ± 0.06 kgN₂O-N/ha/year. N₂O emissions increased significantly with increase in fertilisation, temperatures below 19.6 °C and soil volumetric water content under 15%. Crop rotation appreciably decreases N₂O emissions by 34.4 to 52.4% compared to continuous cropping in rain-fed potato fields. The significant correlation between N₂O fluxes and AOB copy numbers implied that N₂O emissions were primarily controlled by AOB in rain-fed potato fields. The research has important theoretical and practical value for understanding N₂O emissions from rain-fed dry farmland fields.

Effects of digestate on soil chemical and microbiological properties: A comparative study with compost and vermicompost

Anaerobic digestion has become increasingly popular as an alternative for recycling wastes from different origins. Consequently, biogas residues, most of them with unknown chemical and biological composition, accrue in large quantities and their application into soil has become a widespread agricultural practise. The aim of this study was to evaluate the effects of digestate application on the chemical and microbiological properties of an arable soil in comparison with untreated manure, compost and vermicompost. Once in the soil matrix either the addition of compost or digestate led to an increased nitrification rate, relative to unamended and manure-treated soil, after 15 and 60 days of incubation. Faecal coliform and E. coli colony forming units (CFUs) were not detected in any of the amended soils after 60 days. The highest number of Clostridium perfringens CFUs was recorded in manure-amended soil at the beginning of the experiment and after 15 days; whilst after 60 days the lowest CFU number was registered in digestate-treated soil. Denaturing gradient gel electrophoresis patterns also showed that besides the treatment the date of sampling could have contributed to modifications in the soil ammonia-oxidising bacteria community, thereby indicating that the soil itself may influence the community diversity more strongly than the treatments.